Docs & translations

Merge branch 'master' into v0.12
* master: Report versioning usage in usage report Swap the corsMiddleware and the csrfMiddleware to the unauthenticated OPTIONS requests are first processed. Return "No such object in the index" when /rest/db/file gets called on something that doesn't exist Revert "Add .arcconfig to project root" Add .arcconfig to project root
2016-02-14 20:26:33 +01:00 · 2016-02-14 19:39:59 +01:00 · 2016-02-14 19:39:34 +01:00 · 2016-02-13 08:19:30 +01:00 · 2016-02-12 21:29:45 +00:00 · 2016-02-12 22:10:08 +01:00
827 changed files with 124647 additions and 8826 deletions
@@ -0,0 +1,9 @@
+# Text files use LF line endings in this repository
+*   text=auto
+
+# Except the dependencies, which we leave alone
+Godeps/**   -text=auto
+
+# Diffs on these files are meaningless
+gui.files.go    -diff
+*.svg           -diff
@@ -1,3 +1,16 @@
 syncthing
+!gui/syncthing
+!Godeps/_workspace/src/github.com/syncthing
+syncthing.exe
 *.tar.gz
-build
+*.zip
+*.asc
+.jshintrc
+coverage.out
+files/pidx
+bin
+perfstats*.csv
+coverage.xml
+syncthing.sig
+RELEASE
+deb
@@ -0,0 +1 @@
+NICKS
@@ -0,0 +1,83 @@
+# This is the official list of Syncthing authors for copyright purposes.
+
+Aaron Bieber <qbit@deftly.net>
+Adam Piggott <aD@simplypeachy.co.uk> <simplypeachy@users.noreply.github.com>
+Alessandro G. <alessandro.g89@gmail.com>
+Alexander Graf <register-github@alex-graf.de>
+Anderson Mesquita <andersonvom@gmail.com>
+Andrew Dunham <andrew@du.nham.ca>
+Antony Male <antony.male@gmail.com>
+Arthur Axel fREW Schmidt <frew@afoolishmanifesto.com> <frioux@gmail.com>
+Audrius Butkevicius <audrius.butkevicius@gmail.com>
+Bart De Vries <devriesb@gmail.com>
+Ben Curthoys <ben@bencurthoys.com>
+Ben Schulz <ueomkail@gmail.com> <uok@users.noreply.github.com>
+Ben Sidhom <bsidhom@gmail.com>
+Benny Ng <benny.tpng@gmail.com>
+Brandon Philips <brandon@ifup.org>
+Brendan Long <self@brendanlong.com>
+Brian R. Becker <brbecker@gmail.com>
+Caleb Callaway <enlightened.despot@gmail.com>
+Carsten Hagemann <moter8@gmail.com>
+Cathryne Linenweaver <cathryne.linenweaver@gmail.com> <Cathryne@users.noreply.github.com>
+Chris Howie <me@chrishowie.com>
+Chris Joel <chris@scriptolo.gy>
+Colin Kennedy <moshen.colin@gmail.com>
+Daniel Bergmann <dan.arne.bergmann@gmail.com> <brgmnn@users.noreply.github.com>
+Daniel Martí <mvdan@mvdan.cc>
+Denis A. <denisva@gmail.com>
+Dennis Wilson <dw@risu.io>
+Dominik Heidler <dominik@heidler.eu>
+Elias Jarlebring <jarlebring@gmail.com>
+Emil Hessman <emil@hessman.se>
+Erik Meitner <e.meitner@willystreet.coop>
+Federico Castagnini <federico.castagnini@gmail.com>
+Felix Ableitner <me@nutomic.com>
+Felix Unterpaintner <bigbear2nd@gmail.com>
+Francois-Xavier Gsell <fxgsell@gmail.com>
+Frank Isemann <frank@isemann.name>
+Gilli Sigurdsson <gilli@vx.is>
+Jaakko Hannikainen <jgke@jgke.fi>
+Jacek Szafarkiewicz <szafar@linux.pl>
+Jake Peterson <jake@acogdev.com>
+Jakob Borg <jakob@nym.se>
+James Patterson <jamespatterson@operamail.com> <jpjp@users.noreply.github.com>
+Jaroslav Malec <dzardacz@gmail.com>
+Jens Diemer <github.com@jensdiemer.de> <git@jensdiemer.de>
+Jochen Voss <voss@seehuhn.de>
+Johan Vromans <jvromans@squirrel.nl>
+Karol Różycki <rozycki.karol@gmail.com>
+Ken'ichi Kamada <kamada@nanohz.org>
+Kevin Allen <kma1660@gmail.com>
+Laurent Etiemble <laurent.etiemble@gmail.com> <laurent.etiemble@monobjc.net>
+Lode Hoste <zillode@zillode.be>
+Lord Landon Agahnim <lordlandon@gmail.com>
+Marc Laporte <marc@marclaporte.com> <marc@laporte.name>
+Marc Pujol <kilburn@la3.org>
+Marcin Dziadus <dziadus.marcin@gmail.com>
+Mateusz Naściszewski <matin1111@wp.pl>
+Matt Burke <mburke@amplify.com> <burkemw3@gmail.com>
+Michael Jephcote <rewt0r@gmx.com> <Rewt0r@users.noreply.github.com>
+Michael Ploujnikov <ploujj@gmail.com>
+Michael Tilli <pyfisch@gmail.com>
+Nate Morrison <natemorrison@gmail.com>
+Pascal Jungblut <github@pascalj.com> <mail@pascal-jungblut.com>
+Peter Hoeg <peter@speartail.com>
+Philippe Schommers <philippe@schommers.be>
+Phill Luby <phill.luby@newredo.com>
+Piotr Bejda <piotrb10@gmail.com>
+Ryan Sullivan <kayoticsully@gmail.com>
+Scott Klupfel <kluppy@going2blue.com>
+Sergey Mishin <ralder@yandex.ru>
+Stefan Kuntz <stefan.github@gmail.com> <Stefan.github@gmail.com>
+Stefan Tatschner <stefan@sevenbyte.org> <rumpelsepp@sevenbyte.org>
+Tim Abell <tim@timwise.co.uk>
+Tobias Nygren <tnn@nygren.pp.se>
+Tomas Cerveny <kozec@kozec.com>
+Tully Robinson <tully@tojr.org>
+Tyler Brazier <tyler@tylerbrazier.com>
+Veeti Paananen <veeti.paananen@rojekti.fi>
+Victor Buinsky <vix_booja@tut.by>
+Vil Brekin <vilbrekin@gmail.com>
+William A. Kennington III <william@wkennington.com>
+Yannic A. <eipiminusone+github@gmail.com> <eipiminus1@users.noreply.github.com>
@@ -0,0 +1,92 @@
+## Conduct
+
+* We are committed to providing a friendly, safe and welcoming
+  environment for all, regardless of gender, sexual orientation,
+  disability, ethnicity, religion, or similar personal characteristic.
+
+* On IRC, please avoid using overtly sexual nicknames or other nicknames
+  that might detract from a friendly, safe and welcoming environment for
+  all.
+
+* Please be kind and courteous. There's no need to be mean or rude.
+
+* Respect that people have differences of opinion and that every design
+  or implementation choice carries a trade-off and numerous costs. There
+  is seldom a right answer.
+
+* Please keep unstructured critique to a minimum. If you have solid
+  ideas you want to experiment with, make a fork and see how it works.
+
+* We will exclude you from interaction if you insult, demean or harass
+  anyone. That is not welcome behaviour. We interpret the term
+  "harassment" as including the definition in the <a
+  href="http://citizencodeofconduct.org/">Citizen Code of Conduct</a>;
+  if you have any lack of clarity about what might be included in that
+  concept, please read their definition. In particular, we don't
+  tolerate behavior that excludes people in socially marginalized
+  groups.
+
+* Private harassment is also unacceptable. No matter who you are, if you
+  feel you have been or are being harassed or made uncomfortable by a
+  community member, please contact one of the channel ops or any of the
+  Syncthing core team immediately. Whether you're a regular  contributor
+  or a newcomer, we care about making this community a safe place for
+  you and we've got your back.
+
+* Likewise any spamming, trolling, flaming, baiting or other
+  attention-stealing behaviour is not welcome.
+
+## Moderation
+
+These are the policies for upholding our community's standards of
+conduct in our communication channels, most notably in Syncthing-related
+IRC channels and on the web forum.
+
+1. Remarks that violate the Syncthing standards of conduct, including
+   hateful, hurtful, oppressive, or exclusionary remarks, are not
+   allowed. (Cursing is allowed, but never targeting another user, and
+   never in a hateful manner.)
+
+2. Remarks that moderators find inappropriate, whether listed in the
+   code of conduct or not, are also not allowed.
+
+3. Moderators will first respond to such remarks with a warning.
+
+4. If the warning is unheeded, the user will be "kicked," i.e., kicked
+   out of the communication channel to cool off.
+
+5. If the user comes back and continues to make trouble, they will be
+   banned, i.e., indefinitely excluded.
+
+6. Moderators may choose at their discretion to un-ban the user if it
+   was a first offense and they offer the offended party a genuine
+   apology.
+
+7. If a moderator bans someone and you think it was unjustified, please
+   take it up with that moderator, or with a different moderator, **in
+   private**. Complaints about bans in-channel are not allowed.
+
+8. Moderators are held to a higher standard than other community
+   members. If a moderator creates an inappropriate situation, they
+   should expect less leeway than others.
+
+In the Syncthing community we strive to go the extra step to look out
+for each other. Don't just aim to be technically unimpeachable, try to
+be your best self. In particular, avoid flirting with offensive or
+sensitive issues, particularly if they're off-topic; this all too
+often leads to unnecessary fights, hurt feelings, and damaged trust;
+worse, it can drive people away from the community entirely.
+
+And if someone takes issue with something you said or did, resist the
+urge to be defensive. Just stop doing what it was they complained about
+and apologize. Even if you feel you were misinterpreted or unfairly
+accused, chances are good there was something you could've communicated
+better — remember that it's your responsibility to make your fellow
+community members comfortable. Everyone wants to get along and we are
+all here first and foremost because we want to talk about cool
+technology. You will find that people will be eager to assume good
+intent and forgive as long as you earn their trust.
+
+*Adapted from the [Rust Code of Conduct](https://github.com/rust-lang/rust/wiki/Note-development-policy#conduct)*
+
+*Adapted from the [Node.js Policy on Trolling](http://blog.izs.me/post/30036893703/policy-on-trolling)*
@@ -0,0 +1,52 @@
+## Reporting Bugs
+
+Please file bugs in the [Github Issue
+Tracker](https://github.com/syncthing/syncthing/issues). Include at
+least the following:
+
+ - What happened
+
+ - What did you expect to happen instead of what *did* happen, if it's
+   not crazy obvious
+
+ - What operating system, operating system version and version of
+   Syncthing you are running
+
+ - The same for other connected devices, where relevant
+
+ - Screenshot if the issue concerns something visible in the GUI
+
+ - Console log entries, where possible and relevant
+
+If you're not sure whether something is relevant, erring on the side of
+too much information will never get you yelled at. :)
+
+## Contributing Translations
+
+All translations are done via
+[Transifex](https://www.transifex.com/projects/p/syncthing/). If you
+wish to contribute to a translation, just head over there and sign up.
+Before every release, the language resources are updated from the
+latest info on Transifex.
+
+## Contributing Code
+
+Every contribution is welcome. If you want to contribute but are unsure
+where to start, any open issues are fair game! See the [Contribution
+Guidelines](http://docs.syncthing.net/dev/contributing.html) for the full
+story on committing code.
+
+## Contributing Documentation
+
+Updates to the [documentation site](http://docs.syncthing.net/) can be
+made as pull requests on the [documentation
+repository](https://github.com/syncthing/docs).
+
+## Licensing
+
+All contributions are made under the same MPLv2 license as the rest of
+the project, except documentation, user interface text and translation
+strings which are licensed under the Creative Commons Attribution 4.0
+International License. You retain the copyright to code you have
+written.
+
@@ -0,0 +1,90 @@
+{
+	"ImportPath": "github.com/syncthing/syncthing",
+	"GoVersion": "go1.5.2",
+	"Packages": [
+		"./cmd/..."
+	],
+	"Deps": [
+		{
+			"ImportPath": "github.com/bkaradzic/go-lz4",
+			"Rev": "74ddf82598bc4745b965729e9c6a463bedd33049"
+		},
+		{
+			"ImportPath": "github.com/calmh/du",
+			"Rev": "3c0690cca16228b97741327b1b6781397afbdb24"
+		},
+		{
+			"ImportPath": "github.com/calmh/luhn",
+			"Rev": "0c8388ff95fa92d4094011e5a04fc99dea3d1632"
+		},
+		{
+			"ImportPath": "github.com/calmh/xdr",
+			"Rev": "9eb3e1a622d9364deb39c831f7e5f164393d7e37"
+		},
+		{
+			"ImportPath": "github.com/golang/snappy",
+			"Rev": "723cc1e459b8eea2dea4583200fd60757d40097a"
+		},
+		{
+			"ImportPath": "github.com/juju/ratelimit",
+			"Rev": "772f5c38e468398c4511514f4f6aa9a4185bc0a0"
+		},
+		{
+			"ImportPath": "github.com/kardianos/osext",
+			"Rev": "29ae4ffbc9a6fe9fb2bc5029050ce6996ea1d3bc"
+		},
+		{
+			"ImportPath": "github.com/rcrowley/go-metrics",
+			"Rev": "1ce93efbc8f9c568886b2ef85ce305b2217b3de3"
+		},
+		{
+			"ImportPath": "github.com/syndtr/goleveldb/leveldb",
+			"Rev": "1a9d62f03ea92815b46fcaab357cfd4df264b1a0"
+		},
+		{
+			"ImportPath": "github.com/thejerf/suture",
+			"Comment": "v1.0.1",
+			"Rev": "99c1f2d613756768fc4299acd9dc621e11ed3fd7"
+		},
+		{
+			"ImportPath": "github.com/vitrun/qart/coding",
+			"Rev": "ccb109cf25f0cd24474da73b9fee4e7a3e8a8ce0"
+		},
+		{
+			"ImportPath": "github.com/vitrun/qart/gf256",
+			"Rev": "ccb109cf25f0cd24474da73b9fee4e7a3e8a8ce0"
+		},
+		{
+			"ImportPath": "github.com/vitrun/qart/qr",
+			"Rev": "ccb109cf25f0cd24474da73b9fee4e7a3e8a8ce0"
+		},
+		{
+			"ImportPath": "golang.org/x/crypto/bcrypt",
+			"Rev": "575fdbe86e5dd89229707ebec0575ce7d088a4a6"
+		},
+		{
+			"ImportPath": "golang.org/x/crypto/blowfish",
+			"Rev": "575fdbe86e5dd89229707ebec0575ce7d088a4a6"
+		},
+		{
+			"ImportPath": "golang.org/x/net/internal/iana",
+			"Rev": "042ba42fa6633b34205efc66ba5719cd3afd8d38"
+		},
+		{
+			"ImportPath": "golang.org/x/net/ipv6",
+			"Rev": "042ba42fa6633b34205efc66ba5719cd3afd8d38"
+		},
+		{
+			"ImportPath": "golang.org/x/net/proxy",
+			"Rev": "042ba42fa6633b34205efc66ba5719cd3afd8d38"
+		},
+		{
+			"ImportPath": "golang.org/x/text/transform",
+			"Rev": "5eb8d4684c4796dd36c74f6452f2c0fa6c79597e"
+		},
+		{
+			"ImportPath": "golang.org/x/text/unicode/norm",
+			"Rev": "5eb8d4684c4796dd36c74f6452f2c0fa6c79597e"
+		}
+	]
+}
@@ -0,0 +1,5 @@
+This directory tree is generated automatically by godep.
+
+Please do not edit.
+
+See https://github.com/tools/godep for more information.
@@ -0,0 +1,2 @@
+/pkg
+/bin
@@ -0,0 +1 @@
+/lz4-example/lz4-example
@@ -0,0 +1,9 @@
+language: go
+
+go:
+  - 1.1
+  - 1.2
+  - 1.3
+  - 1.4
+  - 1.5
+  - tip
@@ -0,0 +1,24 @@
+Copyright 2011-2012 Branimir Karadzic. All rights reserved.
+Copyright 2013 Damian Gryski. All rights reserved.
+
+Redistribution and use in source and binary forms, with or without modification,
+are permitted provided that the following conditions are met:
+
+   1. Redistributions of source code must retain the above copyright notice, this
+      list of conditions and the following disclaimer.
+
+   2. Redistributions in binary form must reproduce the above copyright notice,
+      this list of conditions and the following disclaimer in the documentation
+      and/or other materials provided with the distribution.
+
+THIS SOFTWARE IS PROVIDED BY COPYRIGHT HOLDER ``AS IS'' AND ANY EXPRESS OR
+IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
+SHALL COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
+OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
+THE POSSIBILITY OF SUCH DAMAGE.
+
@@ -0,0 +1,71 @@
+go-lz4
+======
+
+go-lz4 is port of LZ4 lossless compression algorithm to Go. The original C code
+is located at:
+
+https://github.com/Cyan4973/lz4
+
+Status
+------
+[![Build Status](https://secure.travis-ci.org/bkaradzic/go-lz4.png)](http://travis-ci.org/bkaradzic/go-lz4)  
+[![GoDoc](https://godoc.org/github.com/bkaradzic/go-lz4?status.png)](https://godoc.org/github.com/bkaradzic/go-lz4)
+
+Usage
+-----
+
+    go get github.com/bkaradzic/go-lz4
+
+    import "github.com/bkaradzic/go-lz4"
+
+The package name is `lz4`
+
+Notes
+-----
+
+* go-lz4 saves a uint32 with the original uncompressed length at the beginning
+  of the encoded buffer.  They may get in the way of interoperability with
+  other implementations.
+
+Contributors
+------------
+
+Damian Gryski ([@dgryski](https://github.com/dgryski))  
+Dustin Sallings ([@dustin](https://github.com/dustin))
+
+Contact
+-------
+
+[@bkaradzic](https://twitter.com/bkaradzic)  
+http://www.stuckingeometry.com
+
+Project page  
+https://github.com/bkaradzic/go-lz4
+
+License
+-------
+
+Copyright 2011-2012 Branimir Karadzic. All rights reserved.  
+Copyright 2013 Damian Gryski. All rights reserved.
+
+Redistribution and use in source and binary forms, with or without modification,
+are permitted provided that the following conditions are met:
+
+   1. Redistributions of source code must retain the above copyright notice, this
+      list of conditions and the following disclaimer.
+
+   2. Redistributions in binary form must reproduce the above copyright notice,
+      this list of conditions and the following disclaimer in the documentation
+      and/or other materials provided with the distribution.
+
+THIS SOFTWARE IS PROVIDED BY COPYRIGHT HOLDER ``AS IS'' AND ANY EXPRESS OR
+IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
+SHALL COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
+OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
+THE POSSIBILITY OF SUCH DAMAGE.
+
@@ -0,0 +1,23 @@
+// +build gofuzz
+
+package lz4
+
+import "encoding/binary"
+
+func Fuzz(data []byte) int {
+
+	if len(data) < 4 {
+		return 0
+	}
+
+	ln := binary.LittleEndian.Uint32(data)
+	if ln > (1 << 21) {
+		return 0
+	}
+
+	if _, err := Decode(nil, data); err != nil {
+		return 0
+	}
+
+	return 1
+}
@@ -0,0 +1,74 @@
+package main
+
+import (
+	"math/rand"
+
+	"github.com/bkaradzic/go-lz4"
+
+	// lz4's API matches snappy's, so we can easily see how it performs
+	// lz4 "code.google.com/p/snappy-go/snappy"
+)
+
+var input = `
+ADVENTURE I. A SCANDAL IN BOHEMIA
+
+I.
+
+To Sherlock Holmes she is always THE woman. I have seldom heard
+him mention her under any other name. In his eyes she eclipses
+and predominates the whole of her sex. It was not that he felt
+any emotion akin to love for Irene Adler. All emotions, and that
+one particularly, were abhorrent to his cold, precise but
+admirably balanced mind. He was, I take it, the most perfect
+reasoning and observing machine that the world has seen, but as a
+lover he would have placed himself in a false position. He never
+spoke of the softer passions, save with a gibe and a sneer. They
+were admirable things for the observer--excellent for drawing the
+veil from men's motives and actions. But for the trained reasoner
+to admit such intrusions into his own delicate and finely
+adjusted temperament was to introduce a distracting factor which
+might throw a doubt upon all his mental results. Grit in a
+sensitive instrument, or a crack in one of his own high-power
+lenses, would not be more disturbing than a strong emotion in a
+nature such as his. And yet there was but one woman to him, and
+that woman was the late Irene Adler, of dubious and questionable
+memory.
+
+I had seen little of Holmes lately. My marriage had drifted us
+away from each other. My own complete happiness, and the
+home-centred interests which rise up around the man who first
+finds himself master of his own establishment, were sufficient to
+absorb all my attention, while Holmes, who loathed every form of
+society with his whole Bohemian soul, remained in our lodgings in
+Baker Street, buried among his old books, and alternating from
+week to week between cocaine and ambition, the drowsiness of the
+drug, and the fierce energy of his own keen nature. He was still,
+as ever, deeply attracted by the study of crime, and occupied his
+immense faculties and extraordinary powers of observation in
+following out those clues, and clearing up those mysteries which
+had been abandoned as hopeless by the official police. From time
+to time I heard some vague account of his doings: of his summons
+to Odessa in the case of the Trepoff murder, of his clearing up
+of the singular tragedy of the Atkinson brothers at Trincomalee,
+and finally of the mission which he had accomplished so
+delicately and successfully for the reigning family of Holland.
+Beyond these signs of his activity, however, which I merely
+shared with all the readers of the daily press, I knew little of
+my former friend and companion.
+`
+
+func main() {
+
+	compressed, _ := lz4.Encode(nil, []byte(input))
+
+	modified := make([]byte, len(compressed))
+
+	for {
+		copy(modified, compressed)
+		for i := 0; i < 100; i++ {
+			modified[rand.Intn(len(compressed)-4)+4] = byte(rand.Intn(256))
+		}
+		lz4.Decode(nil, modified)
+	}
+
+}
@@ -0,0 +1,94 @@
+/*
+ * Copyright 2011 Branimir Karadzic. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without modification,
+ * are permitted provided that the following conditions are met:
+ *
+ *    1. Redistributions of source code must retain the above copyright notice, this
+ *       list of conditions and the following disclaimer.
+ *
+ *    2. Redistributions in binary form must reproduce the above copyright notice,
+ *       this list of conditions and the following disclaimer in the documentation
+ *       and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY COPYRIGHT HOLDER ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
+ * SHALL COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+ * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
+ * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
+ * THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+package main
+
+import (
+	"flag"
+	"fmt"
+	"io/ioutil"
+	"log"
+	"os"
+	"runtime/pprof"
+
+	lz4 "github.com/bkaradzic/go-lz4"
+)
+
+var (
+	decompress = flag.Bool("d", false, "decompress")
+)
+
+func main() {
+
+	var optCPUProfile = flag.String("cpuprofile", "", "profile")
+	flag.Parse()
+
+	if *optCPUProfile != "" {
+		f, err := os.Create(*optCPUProfile)
+		if err != nil {
+			log.Fatal(err)
+		}
+		pprof.StartCPUProfile(f)
+		defer pprof.StopCPUProfile()
+	}
+
+	args := flag.Args()
+
+	var data []byte
+
+	if len(args) < 2 {
+		fmt.Print("Usage: lz4 [-d] <input> <output>\n")
+		os.Exit(1)
+	}
+
+	input, err := os.OpenFile(args[0], os.O_RDONLY, 0644)
+	if err != nil {
+		fmt.Printf("Failed to open input file %s\n", args[0])
+		os.Exit(1)
+	}
+	defer input.Close()
+
+	if *decompress {
+		data, _ = ioutil.ReadAll(input)
+		data, err = lz4.Decode(nil, data)
+		if err != nil {
+			fmt.Println("Failed to decode:", err)
+			return
+		}
+	} else {
+		data, _ = ioutil.ReadAll(input)
+		data, err = lz4.Encode(nil, data)
+		if err != nil {
+			fmt.Println("Failed to encode:", err)
+			return
+		}
+	}
+
+	err = ioutil.WriteFile(args[1], data, 0644)
+	if err != nil {
+		fmt.Printf("Failed to open output file %s\n", args[1])
+		os.Exit(1)
+	}
+}
@@ -0,0 +1,199 @@
+/*
+ * Copyright 2011-2012 Branimir Karadzic. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without modification,
+ * are permitted provided that the following conditions are met:
+ *
+ *    1. Redistributions of source code must retain the above copyright notice, this
+ *       list of conditions and the following disclaimer.
+ *
+ *    2. Redistributions in binary form must reproduce the above copyright notice,
+ *       this list of conditions and the following disclaimer in the documentation
+ *       and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY COPYRIGHT HOLDER ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
+ * SHALL COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+ * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
+ * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
+ * THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+package lz4
+
+import (
+	"encoding/binary"
+	"errors"
+	"io"
+)
+
+var (
+	// ErrCorrupt indicates the input was corrupt
+	ErrCorrupt = errors.New("corrupt input")
+)
+
+const (
+	mlBits  = 4
+	mlMask  = (1 << mlBits) - 1
+	runBits = 8 - mlBits
+	runMask = (1 << runBits) - 1
+)
+
+type decoder struct {
+	src  []byte
+	dst  []byte
+	spos uint32
+	dpos uint32
+	ref  uint32
+}
+
+func (d *decoder) readByte() (uint8, error) {
+	if int(d.spos) == len(d.src) {
+		return 0, io.EOF
+	}
+	b := d.src[d.spos]
+	d.spos++
+	return b, nil
+}
+
+func (d *decoder) getLen() (uint32, error) {
+
+	length := uint32(0)
+	ln, err := d.readByte()
+	if err != nil {
+		return 0, ErrCorrupt
+	}
+	for ln == 255 {
+		length += 255
+		ln, err = d.readByte()
+		if err != nil {
+			return 0, ErrCorrupt
+		}
+	}
+	length += uint32(ln)
+
+	return length, nil
+}
+
+func (d *decoder) cp(length, decr uint32) {
+
+	if int(d.ref+length) < int(d.dpos) {
+		copy(d.dst[d.dpos:], d.dst[d.ref:d.ref+length])
+	} else {
+		for ii := uint32(0); ii < length; ii++ {
+			d.dst[d.dpos+ii] = d.dst[d.ref+ii]
+		}
+	}
+	d.dpos += length
+	d.ref += length - decr
+}
+
+func (d *decoder) finish(err error) error {
+	if err == io.EOF {
+		return nil
+	}
+
+	return err
+}
+
+// Decode returns the decoded form of src.  The returned slice may be a
+// subslice of dst if it was large enough to hold the entire decoded block.
+func Decode(dst, src []byte) ([]byte, error) {
+
+	if len(src) < 4 {
+		return nil, ErrCorrupt
+	}
+
+	uncompressedLen := binary.LittleEndian.Uint32(src)
+
+	if uncompressedLen == 0 {
+		return nil, nil
+	}
+
+	if uncompressedLen > MaxInputSize {
+		return nil, ErrTooLarge
+	}
+
+	if dst == nil || len(dst) < int(uncompressedLen) {
+		dst = make([]byte, uncompressedLen)
+	}
+
+	d := decoder{src: src, dst: dst[:uncompressedLen], spos: 4}
+
+	decr := []uint32{0, 3, 2, 3}
+
+	for {
+		code, err := d.readByte()
+		if err != nil {
+			return d.dst, d.finish(err)
+		}
+
+		length := uint32(code >> mlBits)
+		if length == runMask {
+			ln, err := d.getLen()
+			if err != nil {
+				return nil, ErrCorrupt
+			}
+			length += ln
+		}
+
+		if int(d.spos+length) > len(d.src) || int(d.dpos+length) > len(d.dst) {
+			return nil, ErrCorrupt
+		}
+
+		for ii := uint32(0); ii < length; ii++ {
+			d.dst[d.dpos+ii] = d.src[d.spos+ii]
+		}
+
+		d.spos += length
+		d.dpos += length
+
+		if int(d.spos) == len(d.src) {
+			return d.dst, nil
+		}
+
+		if int(d.spos+2) >= len(d.src) {
+			return nil, ErrCorrupt
+		}
+
+		back := uint32(d.src[d.spos]) | uint32(d.src[d.spos+1])<<8
+
+		if back > d.dpos {
+			return nil, ErrCorrupt
+		}
+
+		d.spos += 2
+		d.ref = d.dpos - back
+
+		length = uint32(code & mlMask)
+		if length == mlMask {
+			ln, err := d.getLen()
+			if err != nil {
+				return nil, ErrCorrupt
+			}
+			length += ln
+		}
+
+		literal := d.dpos - d.ref
+
+		if literal < 4 {
+			if int(d.dpos+4) > len(d.dst) {
+				return nil, ErrCorrupt
+			}
+
+			d.cp(4, decr[literal])
+		} else {
+			length += 4
+		}
+
+		if d.dpos+length > uncompressedLen {
+			return nil, ErrCorrupt
+		}
+
+		d.cp(length, 0)
+	}
+}
@@ -0,0 +1,190 @@
+/*
+ * Copyright 2011-2012 Branimir Karadzic. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without modification,
+ * are permitted provided that the following conditions are met:
+ *
+ *    1. Redistributions of source code must retain the above copyright notice, this
+ *       list of conditions and the following disclaimer.
+ *
+ *    2. Redistributions in binary form must reproduce the above copyright notice,
+ *       this list of conditions and the following disclaimer in the documentation
+ *       and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY COPYRIGHT HOLDER ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
+ * SHALL COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+ * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
+ * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
+ * THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+package lz4
+
+import (
+	"encoding/binary"
+	"errors"
+)
+
+const (
+	minMatch              = 4
+	hashLog               = 17
+	hashTableSize         = 1 << hashLog
+	hashShift             = (minMatch * 8) - hashLog
+	incompressible uint32 = 128
+	uninitHash            = 0x88888888
+
+	// MaxInputSize is the largest buffer than can be compressed in a single block
+	MaxInputSize = 0x7E000000
+)
+
+var (
+	// ErrTooLarge indicates the input buffer was too large
+	ErrTooLarge = errors.New("input too large")
+)
+
+type encoder struct {
+	src       []byte
+	dst       []byte
+	hashTable []uint32
+	pos       uint32
+	anchor    uint32
+	dpos      uint32
+}
+
+// CompressBound returns the maximum length of a lz4 block, given it's uncompressed length
+func CompressBound(isize int) int {
+	if isize > MaxInputSize {
+		return 0
+	}
+	return isize + ((isize) / 255) + 16 + 4
+}
+
+func (e *encoder) writeLiterals(length, mlLen, pos uint32) {
+
+	ln := length
+
+	var code byte
+	if ln > runMask-1 {
+		code = runMask
+	} else {
+		code = byte(ln)
+	}
+
+	if mlLen > mlMask-1 {
+		e.dst[e.dpos] = (code << mlBits) + byte(mlMask)
+	} else {
+		e.dst[e.dpos] = (code << mlBits) + byte(mlLen)
+	}
+	e.dpos++
+
+	if code == runMask {
+		ln -= runMask
+		for ; ln > 254; ln -= 255 {
+			e.dst[e.dpos] = 255
+			e.dpos++
+		}
+
+		e.dst[e.dpos] = byte(ln)
+		e.dpos++
+	}
+
+	for ii := uint32(0); ii < length; ii++ {
+		e.dst[e.dpos+ii] = e.src[pos+ii]
+	}
+
+	e.dpos += length
+}
+
+// Encode returns the encoded form of src.  The returned array may be a
+// sub-slice of dst if it was large enough to hold the entire output.
+func Encode(dst, src []byte) ([]byte, error) {
+
+	if len(src) >= MaxInputSize {
+		return nil, ErrTooLarge
+	}
+
+	if n := CompressBound(len(src)); len(dst) < n {
+		dst = make([]byte, n)
+	}
+
+	e := encoder{src: src, dst: dst, hashTable: make([]uint32, hashTableSize)}
+
+	binary.LittleEndian.PutUint32(dst, uint32(len(src)))
+	e.dpos = 4
+
+	var (
+		step  uint32 = 1
+		limit        = incompressible
+	)
+
+	for {
+		if int(e.pos)+12 >= len(e.src) {
+			e.writeLiterals(uint32(len(e.src))-e.anchor, 0, e.anchor)
+			return e.dst[:e.dpos], nil
+		}
+
+		sequence := uint32(e.src[e.pos+3])<<24 | uint32(e.src[e.pos+2])<<16 | uint32(e.src[e.pos+1])<<8 | uint32(e.src[e.pos+0])
+
+		hash := (sequence * 2654435761) >> hashShift
+		ref := e.hashTable[hash] + uninitHash
+		e.hashTable[hash] = e.pos - uninitHash
+
+		if ((e.pos-ref)>>16) != 0 || uint32(e.src[ref+3])<<24|uint32(e.src[ref+2])<<16|uint32(e.src[ref+1])<<8|uint32(e.src[ref+0]) != sequence {
+			if e.pos-e.anchor > limit {
+				limit <<= 1
+				step += 1 + (step >> 2)
+			}
+			e.pos += step
+			continue
+		}
+
+		if step > 1 {
+			e.hashTable[hash] = ref - uninitHash
+			e.pos -= step - 1
+			step = 1
+			continue
+		}
+		limit = incompressible
+
+		ln := e.pos - e.anchor
+		back := e.pos - ref
+
+		anchor := e.anchor
+
+		e.pos += minMatch
+		ref += minMatch
+		e.anchor = e.pos
+
+		for int(e.pos) < len(e.src)-5 && e.src[e.pos] == e.src[ref] {
+			e.pos++
+			ref++
+		}
+
+		mlLen := e.pos - e.anchor
+
+		e.writeLiterals(ln, mlLen, anchor)
+		e.dst[e.dpos] = uint8(back)
+		e.dst[e.dpos+1] = uint8(back >> 8)
+		e.dpos += 2
+
+		if mlLen > mlMask-1 {
+			mlLen -= mlMask
+			for mlLen > 254 {
+				mlLen -= 255
+
+				e.dst[e.dpos] = 255
+				e.dpos++
+			}
+
+			e.dst[e.dpos] = byte(mlLen)
+			e.dpos++
+		}
+
+		e.anchor = e.pos
+	}
+}
@@ -0,0 +1,24 @@
+This is free and unencumbered software released into the public domain.
+
+Anyone is free to copy, modify, publish, use, compile, sell, or
+distribute this software, either in source code form or as a compiled
+binary, for any purpose, commercial or non-commercial, and by any
+means.
+
+In jurisdictions that recognize copyright laws, the author or authors
+of this software dedicate any and all copyright interest in the
+software to the public domain. We make this dedication for the benefit
+of the public at large and to the detriment of our heirs and
+successors. We intend this dedication to be an overt act of
+relinquishment in perpetuity of all present and future rights to this
+software under copyright law.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
+OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
+ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+OTHER DEALINGS IN THE SOFTWARE.
+
+For more information, please refer to <http://unlicense.org>
@@ -0,0 +1,14 @@
+du
+==
+
+Get total and available disk space on a given volume.
+
+Documentation
+-------------
+
+http://godoc.org/github.com/calmh/du
+
+License
+-------
+
+Public Domain
@@ -0,0 +1,21 @@
+package main
+
+import (
+	"fmt"
+	"log"
+	"os"
+
+	"github.com/calmh/du"
+)
+
+var KB = int64(1024)
+
+func main() {
+	usage, err := du.Get(os.Args[1])
+	if err != nil {
+		log.Fatal(err)
+	}
+	fmt.Println("Free:", usage.FreeBytes/(KB*KB), "MiB")
+	fmt.Println("Available:", usage.AvailBytes/(KB*KB), "MiB")
+	fmt.Println("Size:", usage.TotalBytes/(KB*KB), "MiB")
+}
@@ -0,0 +1,8 @@
+package du
+
+// Usage holds information about total and available storage on a volume.
+type Usage struct {
+	TotalBytes int64 // Size of volume
+	FreeBytes  int64 // Unused size
+	AvailBytes int64 // Available to a non-privileged user
+}
@@ -0,0 +1,24 @@
+// +build !windows,!netbsd,!openbsd,!solaris
+
+package du
+
+import (
+	"path/filepath"
+	"syscall"
+)
+
+// Get returns the Usage of a given path, or an error if usage data is
+// unavailable.
+func Get(path string) (Usage, error) {
+	var stat syscall.Statfs_t
+	err := syscall.Statfs(filepath.Clean(path), &stat)
+	if err != nil {
+		return Usage{}, err
+	}
+	u := Usage{
+		FreeBytes:  int64(stat.Bfree) * int64(stat.Bsize),
+		TotalBytes: int64(stat.Blocks) * int64(stat.Bsize),
+		AvailBytes: int64(stat.Bavail) * int64(stat.Bsize),
+	}
+	return u, nil
+}
@@ -0,0 +1,13 @@
+// +build netbsd openbsd solaris
+
+package du
+
+import "errors"
+
+var ErrUnsupported = errors.New("unsupported platform")
+
+// Get returns the Usage of a given path, or an error if usage data is
+// unavailable.
+func Get(path string) (Usage, error) {
+	return Usage{}, ErrUnsupported
+}
@@ -0,0 +1,27 @@
+package du
+
+import (
+	"syscall"
+	"unsafe"
+)
+
+// Get returns the Usage of a given path, or an error if usage data is
+// unavailable.
+func Get(path string) (Usage, error) {
+	h := syscall.MustLoadDLL("kernel32.dll")
+	c := h.MustFindProc("GetDiskFreeSpaceExW")
+
+	var u Usage
+
+	ret, _, err := c.Call(
+		uintptr(unsafe.Pointer(syscall.StringToUTF16Ptr(path))),
+		uintptr(unsafe.Pointer(&u.FreeBytes)),
+		uintptr(unsafe.Pointer(&u.TotalBytes)),
+		uintptr(unsafe.Pointer(&u.AvailBytes)))
+
+	if ret == 0 {
+		return u, err
+	}
+
+	return u, nil
+}
@@ -0,0 +1,19 @@
+Copyright (C) 2014 Jakob Borg
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal in
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
+of the Software, and to permit persons to whom the Software is furnished to do
+so, subject to the following conditions:
+
+- The above copyright notice and this permission notice shall be included in
+  all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
@@ -0,0 +1,70 @@
+// Copyright (C) 2014 Jakob Borg
+
+// Package luhn generates and validates Luhn mod N check digits.
+package luhn
+
+import (
+	"fmt"
+	"strings"
+)
+
+// An alphabet is a string of N characters, representing the digits of a given
+// base N.
+type Alphabet string
+
+var (
+	Base32 Alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567"
+)
+
+// Generate returns a check digit for the string s, which should be composed
+// of characters from the Alphabet a.
+func (a Alphabet) Generate(s string) (rune, error) {
+	if err := a.check(); err != nil {
+		return 0, err
+	}
+
+	factor := 1
+	sum := 0
+	n := len(a)
+
+	for i := range s {
+		codepoint := strings.IndexByte(string(a), s[i])
+		if codepoint == -1 {
+			return 0, fmt.Errorf("Digit %q not valid in alphabet %q", s[i], a)
+		}
+		addend := factor * codepoint
+		if factor == 2 {
+			factor = 1
+		} else {
+			factor = 2
+		}
+		addend = (addend / n) + (addend % n)
+		sum += addend
+	}
+	remainder := sum % n
+	checkCodepoint := (n - remainder) % n
+	return rune(a[checkCodepoint]), nil
+}
+
+// Validate returns true if the last character of the string s is correct, for
+// a string s composed of characters in the alphabet a.
+func (a Alphabet) Validate(s string) bool {
+	t := s[:len(s)-1]
+	c, err := a.Generate(t)
+	if err != nil {
+		return false
+	}
+	return rune(s[len(s)-1]) == c
+}
+
+// check returns an error if the given alphabet does not consist of unique characters
+func (a Alphabet) check() error {
+	cm := make(map[byte]bool, len(a))
+	for i := range a {
+		if cm[a[i]] {
+			return fmt.Errorf("Digit %q non-unique in alphabet %q", a[i], a)
+		}
+		cm[a[i]] = true
+	}
+	return nil
+}
@@ -0,0 +1 @@
+coverage.out
@@ -0,0 +1,19 @@
+language: go
+go:
+- tip
+
+install:
+- export PATH=$PATH:$HOME/gopath/bin
+- go get golang.org/x/tools/cover
+- go get github.com/mattn/goveralls
+
+script:
+- ./generate.sh
+- go test -coverprofile=coverage.out
+
+after_success:
+- goveralls -coverprofile=coverage.out -service=travis-ci -package=calmh/xdr -repotoken="$COVERALLS_TOKEN"
+
+env:
+  global:
+    secure: SmgnrGfp2zLrA44ChRMpjPeujubt9veZ8Fx/OseMWECmacyV5N/TuDhzIbwo6QwV4xB0sBacoPzvxQbJRVjNKsPiSu72UbcQmQ7flN4Tf7nW09tSh1iW8NgrpBCq/3UYLoBu2iPBEBKm93IK0aGNAKs6oEkB0fU27iTVBwiTXOY=
@@ -0,0 +1,19 @@
+Copyright (C) 2014 Jakob Borg.
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to
+deal in the Software without restriction, including without limitation the
+rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+sell copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+- The above copyright notice and this permission notice shall be included in
+  all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+IN THE SOFTWARE.
@@ -0,0 +1,12 @@
+xdr
+===
+
+[![Build Status](https://img.shields.io/circleci/project/calmh/xdr.svg?style=flat-square)](https://circleci.com/gh/calmh/xdr)
+[![Coverage Status](https://img.shields.io/coveralls/calmh/xdr.svg?style=flat)](https://coveralls.io/r/calmh/xdr?branch=master)
+[![API Documentation](http://img.shields.io/badge/api-Godoc-blue.svg?style=flat)](http://godoc.org/github.com/calmh/xdr)
+[![MIT License](http://img.shields.io/badge/license-MIT-blue.svg?style=flat)](http://opensource.org/licenses/MIT)
+
+This is an XDR encoding/decoding library. It uses code generation and
+not reflection. It supports the IPDR bastardized XDR format when built
+with `-tags ipdr`.
+
@@ -0,0 +1,3 @@
+dependencies:
+  post:
+      - ./generate.sh
@@ -0,0 +1,530 @@
+// Copyright (C) 2014 Jakob Borg. All rights reserved. Use of this source code
+// is governed by an MIT-style license that can be found in the LICENSE file.
+
+package main
+
+import (
+	"bytes"
+	"flag"
+	"fmt"
+	"go/ast"
+	"go/format"
+	"go/parser"
+	"go/token"
+	"io"
+	"log"
+	"os"
+	"regexp"
+	"strconv"
+	"strings"
+	"text/template"
+)
+
+type fieldInfo struct {
+	Name      string
+	IsBasic   bool   // handled by one the native Read/WriteUint64 etc functions
+	IsSlice   bool   // field is a slice of FieldType
+	FieldType string // original type of field, i.e. "int"
+	Encoder   string // the encoder name, i.e. "Uint64" for Read/WriteUint64
+	Convert   string // what to convert to when encoding, i.e. "uint64"
+	Max       int    // max size for slices and strings
+	Submax    int    // max size for strings inside slices
+}
+
+type structInfo struct {
+	Name   string
+	Fields []fieldInfo
+}
+
+var headerTpl = template.Must(template.New("header").Parse(`// ************************************************************
+// This file is automatically generated by genxdr. Do not edit.
+// ************************************************************
+
+package {{.Package}}
+
+import (
+	"bytes"
+	"io"
+
+	"github.com/calmh/xdr"
+)
+`))
+
+var encodeTpl = template.Must(template.New("encoder").Parse(`
+func (o {{.TypeName}}) EncodeXDR(w io.Writer) (int, error) {
+	var xw = xdr.NewWriter(w)
+	return o.EncodeXDRInto(xw)
+}//+n
+
+func (o {{.TypeName}}) MarshalXDR() ([]byte, error) {
+	return o.AppendXDR(make([]byte, 0, 128))
+}//+n
+
+func (o {{.TypeName}}) MustMarshalXDR() []byte {
+	bs, err := o.MarshalXDR()
+	if err != nil {
+		panic(err)
+	}
+	return bs
+}//+n
+
+func (o {{.TypeName}}) AppendXDR(bs []byte) ([]byte, error) {
+	var aw = xdr.AppendWriter(bs)
+	var xw = xdr.NewWriter(&aw)
+	_, err := o.EncodeXDRInto(xw)
+	return []byte(aw), err
+}//+n
+
+func (o {{.TypeName}}) EncodeXDRInto(xw *xdr.Writer) (int, error) {
+	{{range $fieldInfo := .Fields}}
+		{{if not $fieldInfo.IsSlice}}
+			{{if ne $fieldInfo.Convert ""}}
+				xw.Write{{$fieldInfo.Encoder}}({{$fieldInfo.Convert}}(o.{{$fieldInfo.Name}}))
+			{{else if $fieldInfo.IsBasic}}
+				{{if ge $fieldInfo.Max 1}}
+					if l := len(o.{{$fieldInfo.Name}}); l > {{$fieldInfo.Max}} {
+						return xw.Tot(), xdr.ElementSizeExceeded("{{$fieldInfo.Name}}", l, {{$fieldInfo.Max}})
+					}
+				{{end}}
+				xw.Write{{$fieldInfo.Encoder}}(o.{{$fieldInfo.Name}})
+			{{else}}
+				_, err := o.{{$fieldInfo.Name}}.EncodeXDRInto(xw)
+				if err != nil {
+					return xw.Tot(), err
+				}
+			{{end}}
+		{{else}}
+			{{if ge $fieldInfo.Max 1}}
+				if l := len(o.{{$fieldInfo.Name}}); l > {{$fieldInfo.Max}} {
+					return xw.Tot(), xdr.ElementSizeExceeded("{{$fieldInfo.Name}}", l, {{$fieldInfo.Max}})
+				}
+			{{end}}
+			xw.WriteUint32(uint32(len(o.{{$fieldInfo.Name}})))
+			for i := range o.{{$fieldInfo.Name}} {
+			{{if ne $fieldInfo.Convert ""}}
+				xw.Write{{$fieldInfo.Encoder}}({{$fieldInfo.Convert}}(o.{{$fieldInfo.Name}}[i]))
+			{{else if $fieldInfo.IsBasic}}
+				xw.Write{{$fieldInfo.Encoder}}(o.{{$fieldInfo.Name}}[i])
+			{{else}}
+				_, err := o.{{$fieldInfo.Name}}[i].EncodeXDRInto(xw)
+				if err != nil {
+					return xw.Tot(), err
+				}
+			{{end}}
+			}
+		{{end}}
+	{{end}}
+	return xw.Tot(), xw.Error()
+}//+n
+
+func (o *{{.TypeName}}) DecodeXDR(r io.Reader) error {
+	xr := xdr.NewReader(r)
+	return o.DecodeXDRFrom(xr)
+}//+n
+
+func (o *{{.TypeName}}) UnmarshalXDR(bs []byte) error {
+	var br = bytes.NewReader(bs)
+	var xr = xdr.NewReader(br)
+	return o.DecodeXDRFrom(xr)
+}//+n
+
+func (o *{{.TypeName}}) DecodeXDRFrom(xr *xdr.Reader) error {
+	{{range $fieldInfo := .Fields}}
+		{{if not $fieldInfo.IsSlice}}
+			{{if ne $fieldInfo.Convert ""}}
+				o.{{$fieldInfo.Name}} = {{$fieldInfo.FieldType}}(xr.Read{{$fieldInfo.Encoder}}())
+			{{else if $fieldInfo.IsBasic}}
+				{{if ge $fieldInfo.Max 1}}
+					o.{{$fieldInfo.Name}} = xr.Read{{$fieldInfo.Encoder}}Max({{$fieldInfo.Max}})
+				{{else}}
+					o.{{$fieldInfo.Name}} = xr.Read{{$fieldInfo.Encoder}}()
+				{{end}}
+			{{else}}
+				(&o.{{$fieldInfo.Name}}).DecodeXDRFrom(xr)
+			{{end}}
+		{{else}}
+			_{{$fieldInfo.Name}}Size := int(xr.ReadUint32())
+			if _{{$fieldInfo.Name}}Size < 0 {
+				return xdr.ElementSizeExceeded("{{$fieldInfo.Name}}", _{{$fieldInfo.Name}}Size, {{$fieldInfo.Max}})
+			}
+			{{if ge $fieldInfo.Max 1}}
+				if _{{$fieldInfo.Name}}Size > {{$fieldInfo.Max}} {
+					return xdr.ElementSizeExceeded("{{$fieldInfo.Name}}", _{{$fieldInfo.Name}}Size, {{$fieldInfo.Max}})
+				}
+			{{end}}
+			o.{{$fieldInfo.Name}} = make([]{{$fieldInfo.FieldType}}, _{{$fieldInfo.Name}}Size)
+			for i := range o.{{$fieldInfo.Name}} {
+				{{if ne $fieldInfo.Convert ""}}
+					o.{{$fieldInfo.Name}}[i] = {{$fieldInfo.FieldType}}(xr.Read{{$fieldInfo.Encoder}}())
+				{{else if $fieldInfo.IsBasic}}
+					{{if ge $fieldInfo.Submax 1}}
+						o.{{$fieldInfo.Name}}[i] = xr.Read{{$fieldInfo.Encoder}}Max({{$fieldInfo.Submax}})
+					{{else}}
+						o.{{$fieldInfo.Name}}[i] = xr.Read{{$fieldInfo.Encoder}}()
+					{{end}}
+				{{else}}
+					(&o.{{$fieldInfo.Name}}[i]).DecodeXDRFrom(xr)
+				{{end}}
+			}
+		{{end}}
+	{{end}}
+	return xr.Error()
+}`))
+
+var emptyTypeTpl = template.Must(template.New("encoder").Parse(`
+func (o {{.TypeName}}) EncodeXDR(w io.Writer) (int, error) {
+	return 0, nil
+}//+n
+
+func (o {{.TypeName}}) MarshalXDR() ([]byte, error) {
+	return nil, nil
+}//+n
+
+func (o {{.TypeName}}) MustMarshalXDR() []byte {
+	return nil
+}//+n
+
+func (o {{.TypeName}}) AppendXDR(bs []byte) ([]byte, error) {
+	return bs, nil
+}//+n
+
+func (o {{.TypeName}}) EncodeXDRInto(xw *xdr.Writer) (int, error) {
+	return xw.Tot(), xw.Error()
+}//+n
+
+func (o *{{.TypeName}}) DecodeXDR(r io.Reader) error {
+	return nil
+}//+n
+
+func (o *{{.TypeName}}) UnmarshalXDR(bs []byte) error {
+	return nil
+}//+n
+
+func (o *{{.TypeName}}) DecodeXDRFrom(xr *xdr.Reader) error {
+	return xr.Error()
+}`))
+
+var maxRe = regexp.MustCompile(`(?:\Wmax:)(\d+)(?:\s*,\s*(\d+))?`)
+
+type typeSet struct {
+	Type    string
+	Encoder string
+}
+
+var xdrEncoders = map[string]typeSet{
+	"int8":   typeSet{"uint8", "Uint8"},
+	"uint8":  typeSet{"", "Uint8"},
+	"int16":  typeSet{"uint16", "Uint16"},
+	"uint16": typeSet{"", "Uint16"},
+	"int32":  typeSet{"uint32", "Uint32"},
+	"uint32": typeSet{"", "Uint32"},
+	"int64":  typeSet{"uint64", "Uint64"},
+	"uint64": typeSet{"", "Uint64"},
+	"int":    typeSet{"uint64", "Uint64"},
+	"string": typeSet{"", "String"},
+	"[]byte": typeSet{"", "Bytes"},
+	"bool":   typeSet{"", "Bool"},
+}
+
+func handleStruct(t *ast.StructType) []fieldInfo {
+	var fs []fieldInfo
+
+	for _, sf := range t.Fields.List {
+		if len(sf.Names) == 0 {
+			// We don't handle anonymous fields
+			continue
+		}
+
+		fn := sf.Names[0].Name
+		var max1, max2 int
+		if sf.Comment != nil {
+			c := sf.Comment.List[0].Text
+			m := maxRe.FindStringSubmatch(c)
+			if len(m) >= 2 {
+				max1, _ = strconv.Atoi(m[1])
+			}
+			if len(m) >= 3 {
+				max2, _ = strconv.Atoi(m[2])
+			}
+			if strings.Contains(c, "noencode") {
+				continue
+			}
+		}
+
+		var f fieldInfo
+		switch ft := sf.Type.(type) {
+		case *ast.Ident:
+			tn := ft.Name
+			if enc, ok := xdrEncoders[tn]; ok {
+				f = fieldInfo{
+					Name:      fn,
+					IsBasic:   true,
+					FieldType: tn,
+					Encoder:   enc.Encoder,
+					Convert:   enc.Type,
+					Max:       max1,
+					Submax:    max2,
+				}
+			} else {
+				f = fieldInfo{
+					Name:      fn,
+					IsBasic:   false,
+					FieldType: tn,
+					Max:       max1,
+					Submax:    max2,
+				}
+			}
+
+		case *ast.ArrayType:
+			if ft.Len != nil {
+				// We don't handle arrays
+				continue
+			}
+
+			tn := ft.Elt.(*ast.Ident).Name
+			if enc, ok := xdrEncoders["[]"+tn]; ok {
+				f = fieldInfo{
+					Name:      fn,
+					IsBasic:   true,
+					FieldType: tn,
+					Encoder:   enc.Encoder,
+					Convert:   enc.Type,
+					Max:       max1,
+					Submax:    max2,
+				}
+			} else if enc, ok := xdrEncoders[tn]; ok {
+				f = fieldInfo{
+					Name:      fn,
+					IsBasic:   true,
+					IsSlice:   true,
+					FieldType: tn,
+					Encoder:   enc.Encoder,
+					Convert:   enc.Type,
+					Max:       max1,
+					Submax:    max2,
+				}
+			} else {
+				f = fieldInfo{
+					Name:      fn,
+					IsSlice:   true,
+					FieldType: tn,
+					Max:       max1,
+					Submax:    max2,
+				}
+			}
+
+		case *ast.SelectorExpr:
+			f = fieldInfo{
+				Name:      fn,
+				FieldType: ft.Sel.Name,
+				Max:       max1,
+				Submax:    max2,
+			}
+		}
+
+		fs = append(fs, f)
+	}
+
+	return fs
+}
+
+func generateCode(output io.Writer, s structInfo) {
+	name := s.Name
+	fs := s.Fields
+
+	var buf bytes.Buffer
+	var err error
+	if len(fs) == 0 {
+		// This is an empty type. We can create a quite simple codec for it.
+		err = emptyTypeTpl.Execute(&buf, map[string]interface{}{"TypeName": name})
+	} else {
+		// Generate with the default template.
+		err = encodeTpl.Execute(&buf, map[string]interface{}{"TypeName": name, "Fields": fs})
+	}
+	if err != nil {
+		panic(err)
+	}
+
+	bs := regexp.MustCompile(`(\s*\n)+`).ReplaceAll(buf.Bytes(), []byte("\n"))
+	bs = bytes.Replace(bs, []byte("//+n"), []byte("\n"), -1)
+
+	bs, err = format.Source(bs)
+	if err != nil {
+		panic(err)
+	}
+	fmt.Fprintln(output, string(bs))
+}
+
+func uncamelize(s string) string {
+	return regexp.MustCompile("[a-z][A-Z]").ReplaceAllStringFunc(s, func(camel string) string {
+		return camel[:1] + " " + camel[1:]
+	})
+}
+
+func generateDiagram(output io.Writer, s structInfo) {
+	sn := s.Name
+	fs := s.Fields
+
+	fmt.Fprintln(output, sn+" Structure:")
+
+	if len(fs) == 0 {
+		fmt.Fprintln(output, "(contains no fields)")
+		fmt.Fprintln(output)
+		fmt.Fprintln(output)
+		return
+	}
+
+	fmt.Fprintln(output)
+	fmt.Fprintln(output, " 0                   1                   2                   3")
+	fmt.Fprintln(output, " 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1")
+	line := "+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+"
+	fmt.Fprintln(output, line)
+
+	for _, f := range fs {
+		tn := f.FieldType
+		name := uncamelize(f.Name)
+
+		if f.IsSlice {
+			fmt.Fprintf(output, "| %s |\n", center("Number of "+name, 61))
+			fmt.Fprintln(output, line)
+		}
+		switch tn {
+		case "bool":
+			fmt.Fprintf(output, "| %s |V|\n", center(name+" (V=0 or 1)", 59))
+			fmt.Fprintln(output, line)
+		case "int16", "uint16":
+			fmt.Fprintf(output, "| %s | %s |\n", center("0x0000", 29), center(name, 29))
+			fmt.Fprintln(output, line)
+		case "int32", "uint32":
+			fmt.Fprintf(output, "| %s |\n", center(name, 61))
+			fmt.Fprintln(output, line)
+		case "int64", "uint64":
+			fmt.Fprintf(output, "| %-61s |\n", "")
+			fmt.Fprintf(output, "+ %s +\n", center(name+" (64 bits)", 61))
+			fmt.Fprintf(output, "| %-61s |\n", "")
+			fmt.Fprintln(output, line)
+		case "string", "byte": // XXX We assume slice of byte!
+			fmt.Fprintf(output, "| %s |\n", center("Length of "+name, 61))
+			fmt.Fprintln(output, line)
+			fmt.Fprintf(output, "/ %61s /\n", "")
+			fmt.Fprintf(output, "\\ %s \\\n", center(name+" (variable length)", 61))
+			fmt.Fprintf(output, "/ %61s /\n", "")
+			fmt.Fprintln(output, line)
+		default:
+			if f.IsSlice {
+				tn = "Zero or more " + tn + " Structures"
+				fmt.Fprintf(output, "/ %s /\n", center("", 61))
+				fmt.Fprintf(output, "\\ %s \\\n", center(tn, 61))
+				fmt.Fprintf(output, "/ %s /\n", center("", 61))
+			} else {
+				tn = tn + " Structure"
+				fmt.Fprintf(output, "/ %s /\n", center("", 61))
+				fmt.Fprintf(output, "\\ %s \\\n", center(tn, 61))
+				fmt.Fprintf(output, "/ %s /\n", center("", 61))
+			}
+			fmt.Fprintln(output, line)
+		}
+	}
+	fmt.Fprintln(output)
+	fmt.Fprintln(output)
+}
+
+func generateXdr(output io.Writer, s structInfo) {
+	sn := s.Name
+	fs := s.Fields
+
+	fmt.Fprintf(output, "struct %s {\n", sn)
+
+	for _, f := range fs {
+		tn := f.FieldType
+		fn := f.Name
+		suf := ""
+		l := ""
+		if f.Max > 0 {
+			l = strconv.Itoa(f.Max)
+		}
+		if f.IsSlice {
+			suf = "<" + l + ">"
+		}
+
+		switch tn {
+		case "int16", "int32":
+			fmt.Fprintf(output, "\tint %s%s;\n", fn, suf)
+		case "uint16", "uint32":
+			fmt.Fprintf(output, "\tunsigned int %s%s;\n", fn, suf)
+		case "int64":
+			fmt.Fprintf(output, "\thyper %s%s;\n", fn, suf)
+		case "uint64":
+			fmt.Fprintf(output, "\tunsigned hyper %s%s;\n", fn, suf)
+		case "string":
+			fmt.Fprintf(output, "\tstring %s<%s>;\n", fn, l)
+		case "byte":
+			fmt.Fprintf(output, "\topaque %s<%s>;\n", fn, l)
+		default:
+			fmt.Fprintf(output, "\t%s %s%s;\n", tn, fn, suf)
+		}
+	}
+	fmt.Fprintln(output, "}")
+	fmt.Fprintln(output)
+}
+
+func center(s string, w int) string {
+	w -= len(s)
+	l := w / 2
+	r := l
+	if l+r < w {
+		r++
+	}
+	return strings.Repeat(" ", l) + s + strings.Repeat(" ", r)
+}
+
+func inspector(structs *[]structInfo) func(ast.Node) bool {
+	return func(n ast.Node) bool {
+		switch n := n.(type) {
+		case *ast.TypeSpec:
+			switch t := n.Type.(type) {
+			case *ast.StructType:
+				name := n.Name.Name
+				fs := handleStruct(t)
+				*structs = append(*structs, structInfo{name, fs})
+			}
+			return false
+		default:
+			return true
+		}
+	}
+}
+
+func main() {
+	outputFile := flag.String("o", "", "Output file, blank for stdout")
+	flag.Parse()
+	fname := flag.Arg(0)
+
+	fset := token.NewFileSet()
+	f, err := parser.ParseFile(fset, fname, nil, parser.ParseComments)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	var structs []structInfo
+	i := inspector(&structs)
+	ast.Inspect(f, i)
+
+	var output io.Writer = os.Stdout
+	if *outputFile != "" {
+		fd, err := os.Create(*outputFile)
+		if err != nil {
+			log.Fatal(err)
+		}
+		output = fd
+	}
+
+	headerTpl.Execute(output, map[string]string{"Package": f.Name.Name})
+	for _, s := range structs {
+		fmt.Fprintf(output, "\n/*\n\n")
+		generateDiagram(output, s)
+		generateXdr(output, s)
+		fmt.Fprintf(output, "*/\n")
+		generateCode(output, s)
+	}
+}
@@ -0,0 +1,16 @@
+// Copyright (C) 2014 Jakob Borg. All rights reserved. Use of this source code
+// is governed by an MIT-style license that can be found in the LICENSE file.
+
+package xdr
+
+import (
+	"log"
+	"os"
+)
+
+var (
+	debug = len(os.Getenv("XDRTRACE")) > 0
+	dl    = log.New(os.Stdout, "xdr: ", log.Lshortfile|log.Ltime|log.Lmicroseconds)
+)
+
+const maxDebugBytes = 32
@@ -0,0 +1,5 @@
+// Copyright (C) 2014 Jakob Borg. All rights reserved. Use of this source code
+// is governed by an MIT-style license that can be found in the LICENSE file.
+
+// Package xdr implements an XDR (RFC 4506) encoder/decoder.
+package xdr
@@ -0,0 +1,4 @@
+#!/bin/sh
+
+go run cmd/genxdr/main.go -- bench_test.go > bench_xdr_test.go
+go run cmd/genxdr/main.go -- encdec_test.go > encdec_xdr_test.go
@@ -0,0 +1,10 @@
+// Copyright (C) 2014 Jakob Borg. All rights reserved. Use of this source code
+// is governed by an MIT-style license that can be found in the LICENSE file.
+
+// +build ipdr
+
+package xdr
+
+func pad(l int) int {
+	return 0
+}
@@ -0,0 +1,14 @@
+// Copyright (C) 2014 Jakob Borg. All rights reserved. Use of this source code
+// is governed by an MIT-style license that can be found in the LICENSE file.
+
+// +build !ipdr
+
+package xdr
+
+func pad(l int) int {
+	d := l % 4
+	if d == 0 {
+		return 0
+	}
+	return 4 - d
+}
@@ -0,0 +1,171 @@
+// Copyright (C) 2014 Jakob Borg and Contributors (see the CONTRIBUTORS file).
+// All rights reserved. Use of this source code is governed by an MIT-style
+// license that can be found in the LICENSE file.
+
+package xdr
+
+import (
+	"fmt"
+	"io"
+	"reflect"
+	"unsafe"
+)
+
+type Reader struct {
+	r   io.Reader
+	err error
+	b   [8]byte
+}
+
+func NewReader(r io.Reader) *Reader {
+	return &Reader{
+		r: r,
+	}
+}
+
+func (r *Reader) ReadRaw(bs []byte) (int, error) {
+	if r.err != nil {
+		return 0, r.err
+	}
+
+	var n int
+	n, r.err = io.ReadFull(r.r, bs)
+	return n, r.err
+}
+
+func (r *Reader) ReadString() string {
+	return r.ReadStringMax(0)
+}
+
+func (r *Reader) ReadStringMax(max int) string {
+	buf := r.ReadBytesMaxInto(max, nil)
+	bh := (*reflect.SliceHeader)(unsafe.Pointer(&buf))
+	sh := reflect.StringHeader{
+		Data: bh.Data,
+		Len:  bh.Len,
+	}
+	return *((*string)(unsafe.Pointer(&sh)))
+}
+
+func (r *Reader) ReadBytes() []byte {
+	return r.ReadBytesInto(nil)
+}
+
+func (r *Reader) ReadBytesMax(max int) []byte {
+	return r.ReadBytesMaxInto(max, nil)
+}
+
+func (r *Reader) ReadBytesInto(dst []byte) []byte {
+	return r.ReadBytesMaxInto(0, dst)
+}
+
+func (r *Reader) ReadBytesMaxInto(max int, dst []byte) []byte {
+	if r.err != nil {
+		return nil
+	}
+
+	l := int(r.ReadUint32())
+	if r.err != nil {
+		return nil
+	}
+	if l < 0 || max > 0 && l > max {
+		// l may be negative on 32 bit builds
+		r.err = ElementSizeExceeded("bytes field", l, max)
+		return nil
+	}
+
+	if fullLen := l + pad(l); fullLen > len(dst) {
+		dst = make([]byte, fullLen)
+	} else {
+		dst = dst[:fullLen]
+	}
+
+	var n int
+	n, r.err = io.ReadFull(r.r, dst)
+	if r.err != nil {
+		if debug {
+			dl.Printf("rd bytes (%d): %v", len(dst), r.err)
+		}
+		return nil
+	}
+
+	if debug {
+		if n > maxDebugBytes {
+			dl.Printf("rd bytes (%d): %x...", len(dst), dst[:maxDebugBytes])
+		} else {
+			dl.Printf("rd bytes (%d): %x", len(dst), dst)
+		}
+	}
+	return dst[:l]
+}
+
+func (r *Reader) ReadBool() bool {
+	return r.ReadUint8() != 0
+}
+
+func (r *Reader) ReadUint32() uint32 {
+	if r.err != nil {
+		return 0
+	}
+
+	_, r.err = io.ReadFull(r.r, r.b[:4])
+	if r.err != nil {
+		if debug {
+			dl.Printf("rd uint32: %v", r.err)
+		}
+		return 0
+	}
+
+	v := uint32(r.b[3]) | uint32(r.b[2])<<8 | uint32(r.b[1])<<16 | uint32(r.b[0])<<24
+
+	if debug {
+		dl.Printf("rd uint32=%d (0x%08x)", v, v)
+	}
+	return v
+}
+
+func (r *Reader) ReadUint64() uint64 {
+	if r.err != nil {
+		return 0
+	}
+
+	_, r.err = io.ReadFull(r.r, r.b[:8])
+	if r.err != nil {
+		if debug {
+			dl.Printf("rd uint64: %v", r.err)
+		}
+		return 0
+	}
+
+	v := uint64(r.b[7]) | uint64(r.b[6])<<8 | uint64(r.b[5])<<16 | uint64(r.b[4])<<24 |
+		uint64(r.b[3])<<32 | uint64(r.b[2])<<40 | uint64(r.b[1])<<48 | uint64(r.b[0])<<56
+
+	if debug {
+		dl.Printf("rd uint64=%d (0x%016x)", v, v)
+	}
+	return v
+}
+
+type XDRError struct {
+	op  string
+	err error
+}
+
+func (e XDRError) Error() string {
+	return "xdr " + e.op + ": " + e.err.Error()
+}
+
+func (e XDRError) IsEOF() bool {
+	return e.err == io.EOF
+}
+
+func (r *Reader) Error() error {
+	if r.err == nil {
+		return nil
+	}
+	return XDRError{"read", r.err}
+}
+
+func ElementSizeExceeded(field string, size, limit int) error {
+	return fmt.Errorf("%s exceeds size limit; %d > %d", field, size, limit)
+}
@@ -0,0 +1,49 @@
+// Copyright (C) 2014 Jakob Borg and Contributors (see the CONTRIBUTORS file).
+// All rights reserved. Use of this source code is governed by an MIT-style
+// license that can be found in the LICENSE file.
+
+// +build ipdr
+
+package xdr
+
+import "io"
+
+func (r *Reader) ReadUint8() uint8 {
+	if r.err != nil {
+		return 0
+	}
+
+	_, r.err = io.ReadFull(r.r, r.b[:1])
+	if r.err != nil {
+		if debug {
+			dl.Printf("rd uint8: %v", r.err)
+		}
+		return 0
+	}
+
+	if debug {
+		dl.Printf("rd uint8=%d (0x%02x)", r.b[0], r.b[0])
+	}
+	return r.b[0]
+}
+
+func (r *Reader) ReadUint16() uint16 {
+	if r.err != nil {
+		return 0
+	}
+
+	_, r.err = io.ReadFull(r.r, r.b[:2])
+	if r.err != nil {
+		if debug {
+			dl.Printf("rd uint16: %v", r.err)
+		}
+		return 0
+	}
+
+	v := uint16(r.b[1]) | uint16(r.b[0])<<8
+
+	if debug {
+		dl.Printf("rd uint16=%d (0x%04x)", v, v)
+	}
+	return v
+}
@@ -0,0 +1,15 @@
+// Copyright (C) 2014 Jakob Borg and Contributors (see the CONTRIBUTORS file).
+// All rights reserved. Use of this source code is governed by an MIT-style
+// license that can be found in the LICENSE file.
+
+// +build !ipdr
+
+package xdr
+
+func (r *Reader) ReadUint8() uint8 {
+	return uint8(r.ReadUint32())
+}
+
+func (r *Reader) ReadUint16() uint16 {
+	return uint16(r.ReadUint32())
+}
@@ -0,0 +1,146 @@
+// Copyright (C) 2014 Jakob Borg. All rights reserved. Use of this source code
+// is governed by an MIT-style license that can be found in the LICENSE file.
+
+package xdr
+
+import (
+	"io"
+	"reflect"
+	"unsafe"
+)
+
+var padBytes = []byte{0, 0, 0}
+
+type Writer struct {
+	w   io.Writer
+	tot int
+	err error
+	b   [8]byte
+}
+
+type AppendWriter []byte
+
+func (w *AppendWriter) Write(bs []byte) (int, error) {
+	*w = append(*w, bs...)
+	return len(bs), nil
+}
+
+func NewWriter(w io.Writer) *Writer {
+	return &Writer{
+		w: w,
+	}
+}
+
+func (w *Writer) WriteRaw(bs []byte) (int, error) {
+	if w.err != nil {
+		return 0, w.err
+	}
+
+	var n int
+	n, w.err = w.w.Write(bs)
+	return n, w.err
+}
+
+func (w *Writer) WriteString(s string) (int, error) {
+	sh := *((*reflect.StringHeader)(unsafe.Pointer(&s)))
+	bh := reflect.SliceHeader{
+		Data: sh.Data,
+		Len:  sh.Len,
+		Cap:  sh.Len,
+	}
+	return w.WriteBytes(*(*[]byte)(unsafe.Pointer(&bh)))
+}
+
+func (w *Writer) WriteBytes(bs []byte) (int, error) {
+	if w.err != nil {
+		return 0, w.err
+	}
+
+	w.WriteUint32(uint32(len(bs)))
+	if w.err != nil {
+		return 0, w.err
+	}
+
+	if debug {
+		if len(bs) > maxDebugBytes {
+			dl.Printf("wr bytes (%d): %x...", len(bs), bs[:maxDebugBytes])
+		} else {
+			dl.Printf("wr bytes (%d): %x", len(bs), bs)
+		}
+	}
+
+	var l, n int
+	n, w.err = w.w.Write(bs)
+	l += n
+
+	if p := pad(len(bs)); w.err == nil && p > 0 {
+		n, w.err = w.w.Write(padBytes[:p])
+		l += n
+	}
+
+	w.tot += l
+	return l, w.err
+}
+
+func (w *Writer) WriteBool(v bool) (int, error) {
+	if v {
+		return w.WriteUint8(1)
+	} else {
+		return w.WriteUint8(0)
+	}
+}
+
+func (w *Writer) WriteUint32(v uint32) (int, error) {
+	if w.err != nil {
+		return 0, w.err
+	}
+
+	if debug {
+		dl.Printf("wr uint32=%d", v)
+	}
+
+	w.b[0] = byte(v >> 24)
+	w.b[1] = byte(v >> 16)
+	w.b[2] = byte(v >> 8)
+	w.b[3] = byte(v)
+
+	var l int
+	l, w.err = w.w.Write(w.b[:4])
+	w.tot += l
+	return l, w.err
+}
+
+func (w *Writer) WriteUint64(v uint64) (int, error) {
+	if w.err != nil {
+		return 0, w.err
+	}
+
+	if debug {
+		dl.Printf("wr uint64=%d", v)
+	}
+
+	w.b[0] = byte(v >> 56)
+	w.b[1] = byte(v >> 48)
+	w.b[2] = byte(v >> 40)
+	w.b[3] = byte(v >> 32)
+	w.b[4] = byte(v >> 24)
+	w.b[5] = byte(v >> 16)
+	w.b[6] = byte(v >> 8)
+	w.b[7] = byte(v)
+
+	var l int
+	l, w.err = w.w.Write(w.b[:8])
+	w.tot += l
+	return l, w.err
+}
+
+func (w *Writer) Tot() int {
+	return w.tot
+}
+
+func (w *Writer) Error() error {
+	if w.err == nil {
+		return nil
+	}
+	return XDRError{"write", w.err}
+}
@@ -0,0 +1,41 @@
+// Copyright (C) 2014 Jakob Borg. All rights reserved. Use of this source code
+// is governed by an MIT-style license that can be found in the LICENSE file.
+
+// +build ipdr
+
+package xdr
+
+func (w *Writer) WriteUint8(v uint8) (int, error) {
+	if w.err != nil {
+		return 0, w.err
+	}
+
+	if debug {
+		dl.Printf("wr uint8=%d", v)
+	}
+
+	w.b[0] = byte(v)
+
+	var l int
+	l, w.err = w.w.Write(w.b[:1])
+	w.tot += l
+	return l, w.err
+}
+
+func (w *Writer) WriteUint16(v uint16) (int, error) {
+	if w.err != nil {
+		return 0, w.err
+	}
+
+	if debug {
+		dl.Printf("wr uint8=%d", v)
+	}
+
+	w.b[0] = byte(v >> 8)
+	w.b[1] = byte(v)
+
+	var l int
+	l, w.err = w.w.Write(w.b[:2])
+	w.tot += l
+	return l, w.err
+}
@@ -0,0 +1,14 @@
+// Copyright (C) 2014 Jakob Borg. All rights reserved. Use of this source code
+// is governed by an MIT-style license that can be found in the LICENSE file.
+
+// +build !ipdr
+
+package xdr
+
+func (w *Writer) WriteUint8(v uint8) (int, error) {
+	return w.WriteUint32(uint32(v))
+}
+
+func (w *Writer) WriteUint16(v uint16) (int, error) {
+	return w.WriteUint32(uint32(v))
+}
@@ -0,0 +1,14 @@
+# This is the official list of Snappy-Go authors for copyright purposes.
+# This file is distinct from the CONTRIBUTORS files.
+# See the latter for an explanation.
+
+# Names should be added to this file as
+#	Name or Organization <email address>
+# The email address is not required for organizations.
+
+# Please keep the list sorted.
+
+Damian Gryski <dgryski@gmail.com>
+Google Inc.
+Jan Mercl <0xjnml@gmail.com>
+Sebastien Binet <seb.binet@gmail.com>
@@ -0,0 +1,36 @@
+# This is the official list of people who can contribute
+# (and typically have contributed) code to the Snappy-Go repository.
+# The AUTHORS file lists the copyright holders; this file
+# lists people.  For example, Google employees are listed here
+# but not in AUTHORS, because Google holds the copyright.
+#
+# The submission process automatically checks to make sure
+# that people submitting code are listed in this file (by email address).
+#
+# Names should be added to this file only after verifying that
+# the individual or the individual's organization has agreed to
+# the appropriate Contributor License Agreement, found here:
+#
+#     http://code.google.com/legal/individual-cla-v1.0.html
+#     http://code.google.com/legal/corporate-cla-v1.0.html
+#
+# The agreement for individuals can be filled out on the web.
+#
+# When adding J Random Contributor's name to this file,
+# either J's name or J's organization's name should be
+# added to the AUTHORS file, depending on whether the
+# individual or corporate CLA was used.
+
+# Names should be added to this file like so:
+#     Name <email address>
+
+# Please keep the list sorted.
+
+Damian Gryski <dgryski@gmail.com>
+Jan Mercl <0xjnml@gmail.com>
+Kai Backman <kaib@golang.org>
+Marc-Antoine Ruel <maruel@chromium.org>
+Nigel Tao <nigeltao@golang.org>
+Rob Pike <r@golang.org>
+Russ Cox <rsc@golang.org>
+Sebastien Binet <seb.binet@gmail.com>
@@ -1,17 +1,18 @@
-Copyright (c) 2012 Jesse van den Kieboom. All rights reserved.
+Copyright (c) 2011 The Snappy-Go Authors. All rights reserved.
+
 Redistribution and use in source and binary forms, with or without
 modification, are permitted provided that the following conditions are
 met:

   * Redistributions of source code must retain the above copyright
-     notice, this list of conditions and the following disclaimer.
+notice, this list of conditions and the following disclaimer.
   * Redistributions in binary form must reproduce the above
-     copyright notice, this list of conditions and the following disclaimer
-     in the documentation and/or other materials provided with the
-     distribution.
+copyright notice, this list of conditions and the following disclaimer
+in the documentation and/or other materials provided with the
+distribution.
   * Neither the name of Google Inc. nor the names of its
-     contributors may be used to endorse or promote products derived from
-     this software without specific prior written permission.
+contributors may be used to endorse or promote products derived from
+this software without specific prior written permission.

 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
@@ -0,0 +1,7 @@
+The Snappy compression format in the Go programming language.
+
+To download and install from source:
+$ go get github.com/golang/snappy
+
+Unless otherwise noted, the Snappy-Go source files are distributed
+under the BSD-style license found in the LICENSE file.
@@ -0,0 +1,294 @@
+// Copyright 2011 The Snappy-Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package snappy
+
+import (
+	"encoding/binary"
+	"errors"
+	"io"
+)
+
+var (
+	// ErrCorrupt reports that the input is invalid.
+	ErrCorrupt = errors.New("snappy: corrupt input")
+	// ErrTooLarge reports that the uncompressed length is too large.
+	ErrTooLarge = errors.New("snappy: decoded block is too large")
+	// ErrUnsupported reports that the input isn't supported.
+	ErrUnsupported = errors.New("snappy: unsupported input")
+)
+
+// DecodedLen returns the length of the decoded block.
+func DecodedLen(src []byte) (int, error) {
+	v, _, err := decodedLen(src)
+	return v, err
+}
+
+// decodedLen returns the length of the decoded block and the number of bytes
+// that the length header occupied.
+func decodedLen(src []byte) (blockLen, headerLen int, err error) {
+	v, n := binary.Uvarint(src)
+	if n <= 0 || v > 0xffffffff {
+		return 0, 0, ErrCorrupt
+	}
+
+	const wordSize = 32 << (^uint(0) >> 32 & 1)
+	if wordSize == 32 && v > 0x7fffffff {
+		return 0, 0, ErrTooLarge
+	}
+	return int(v), n, nil
+}
+
+// Decode returns the decoded form of src. The returned slice may be a sub-
+// slice of dst if dst was large enough to hold the entire decoded block.
+// Otherwise, a newly allocated slice will be returned.
+// It is valid to pass a nil dst.
+func Decode(dst, src []byte) ([]byte, error) {
+	dLen, s, err := decodedLen(src)
+	if err != nil {
+		return nil, err
+	}
+	if len(dst) < dLen {
+		dst = make([]byte, dLen)
+	}
+
+	var d, offset, length int
+	for s < len(src) {
+		switch src[s] & 0x03 {
+		case tagLiteral:
+			x := uint(src[s] >> 2)
+			switch {
+			case x < 60:
+				s++
+			case x == 60:
+				s += 2
+				if s > len(src) {
+					return nil, ErrCorrupt
+				}
+				x = uint(src[s-1])
+			case x == 61:
+				s += 3
+				if s > len(src) {
+					return nil, ErrCorrupt
+				}
+				x = uint(src[s-2]) | uint(src[s-1])<<8
+			case x == 62:
+				s += 4
+				if s > len(src) {
+					return nil, ErrCorrupt
+				}
+				x = uint(src[s-3]) | uint(src[s-2])<<8 | uint(src[s-1])<<16
+			case x == 63:
+				s += 5
+				if s > len(src) {
+					return nil, ErrCorrupt
+				}
+				x = uint(src[s-4]) | uint(src[s-3])<<8 | uint(src[s-2])<<16 | uint(src[s-1])<<24
+			}
+			length = int(x + 1)
+			if length <= 0 {
+				return nil, errors.New("snappy: unsupported literal length")
+			}
+			if length > len(dst)-d || length > len(src)-s {
+				return nil, ErrCorrupt
+			}
+			copy(dst[d:], src[s:s+length])
+			d += length
+			s += length
+			continue
+
+		case tagCopy1:
+			s += 2
+			if s > len(src) {
+				return nil, ErrCorrupt
+			}
+			length = 4 + int(src[s-2])>>2&0x7
+			offset = int(src[s-2])&0xe0<<3 | int(src[s-1])
+
+		case tagCopy2:
+			s += 3
+			if s > len(src) {
+				return nil, ErrCorrupt
+			}
+			length = 1 + int(src[s-3])>>2
+			offset = int(src[s-2]) | int(src[s-1])<<8
+
+		case tagCopy4:
+			return nil, errors.New("snappy: unsupported COPY_4 tag")
+		}
+
+		end := d + length
+		if offset > d || end > len(dst) {
+			return nil, ErrCorrupt
+		}
+		for ; d < end; d++ {
+			dst[d] = dst[d-offset]
+		}
+	}
+	if d != dLen {
+		return nil, ErrCorrupt
+	}
+	return dst[:d], nil
+}
+
+// NewReader returns a new Reader that decompresses from r, using the framing
+// format described at
+// https://github.com/google/snappy/blob/master/framing_format.txt
+func NewReader(r io.Reader) *Reader {
+	return &Reader{
+		r:       r,
+		decoded: make([]byte, maxUncompressedChunkLen),
+		buf:     make([]byte, MaxEncodedLen(maxUncompressedChunkLen)+checksumSize),
+	}
+}
+
+// Reader is an io.Reader than can read Snappy-compressed bytes.
+type Reader struct {
+	r       io.Reader
+	err     error
+	decoded []byte
+	buf     []byte
+	// decoded[i:j] contains decoded bytes that have not yet been passed on.
+	i, j       int
+	readHeader bool
+}
+
+// Reset discards any buffered data, resets all state, and switches the Snappy
+// reader to read from r. This permits reusing a Reader rather than allocating
+// a new one.
+func (r *Reader) Reset(reader io.Reader) {
+	r.r = reader
+	r.err = nil
+	r.i = 0
+	r.j = 0
+	r.readHeader = false
+}
+
+func (r *Reader) readFull(p []byte) (ok bool) {
+	if _, r.err = io.ReadFull(r.r, p); r.err != nil {
+		if r.err == io.ErrUnexpectedEOF {
+			r.err = ErrCorrupt
+		}
+		return false
+	}
+	return true
+}
+
+// Read satisfies the io.Reader interface.
+func (r *Reader) Read(p []byte) (int, error) {
+	if r.err != nil {
+		return 0, r.err
+	}
+	for {
+		if r.i < r.j {
+			n := copy(p, r.decoded[r.i:r.j])
+			r.i += n
+			return n, nil
+		}
+		if !r.readFull(r.buf[:4]) {
+			return 0, r.err
+		}
+		chunkType := r.buf[0]
+		if !r.readHeader {
+			if chunkType != chunkTypeStreamIdentifier {
+				r.err = ErrCorrupt
+				return 0, r.err
+			}
+			r.readHeader = true
+		}
+		chunkLen := int(r.buf[1]) | int(r.buf[2])<<8 | int(r.buf[3])<<16
+		if chunkLen > len(r.buf) {
+			r.err = ErrUnsupported
+			return 0, r.err
+		}
+
+		// The chunk types are specified at
+		// https://github.com/google/snappy/blob/master/framing_format.txt
+		switch chunkType {
+		case chunkTypeCompressedData:
+			// Section 4.2. Compressed data (chunk type 0x00).
+			if chunkLen < checksumSize {
+				r.err = ErrCorrupt
+				return 0, r.err
+			}
+			buf := r.buf[:chunkLen]
+			if !r.readFull(buf) {
+				return 0, r.err
+			}
+			checksum := uint32(buf[0]) | uint32(buf[1])<<8 | uint32(buf[2])<<16 | uint32(buf[3])<<24
+			buf = buf[checksumSize:]
+
+			n, err := DecodedLen(buf)
+			if err != nil {
+				r.err = err
+				return 0, r.err
+			}
+			if n > len(r.decoded) {
+				r.err = ErrCorrupt
+				return 0, r.err
+			}
+			if _, err := Decode(r.decoded, buf); err != nil {
+				r.err = err
+				return 0, r.err
+			}
+			if crc(r.decoded[:n]) != checksum {
+				r.err = ErrCorrupt
+				return 0, r.err
+			}
+			r.i, r.j = 0, n
+			continue
+
+		case chunkTypeUncompressedData:
+			// Section 4.3. Uncompressed data (chunk type 0x01).
+			if chunkLen < checksumSize {
+				r.err = ErrCorrupt
+				return 0, r.err
+			}
+			buf := r.buf[:checksumSize]
+			if !r.readFull(buf) {
+				return 0, r.err
+			}
+			checksum := uint32(buf[0]) | uint32(buf[1])<<8 | uint32(buf[2])<<16 | uint32(buf[3])<<24
+			// Read directly into r.decoded instead of via r.buf.
+			n := chunkLen - checksumSize
+			if !r.readFull(r.decoded[:n]) {
+				return 0, r.err
+			}
+			if crc(r.decoded[:n]) != checksum {
+				r.err = ErrCorrupt
+				return 0, r.err
+			}
+			r.i, r.j = 0, n
+			continue
+
+		case chunkTypeStreamIdentifier:
+			// Section 4.1. Stream identifier (chunk type 0xff).
+			if chunkLen != len(magicBody) {
+				r.err = ErrCorrupt
+				return 0, r.err
+			}
+			if !r.readFull(r.buf[:len(magicBody)]) {
+				return 0, r.err
+			}
+			for i := 0; i < len(magicBody); i++ {
+				if r.buf[i] != magicBody[i] {
+					r.err = ErrCorrupt
+					return 0, r.err
+				}
+			}
+			continue
+		}
+
+		if chunkType <= 0x7f {
+			// Section 4.5. Reserved unskippable chunks (chunk types 0x02-0x7f).
+			r.err = ErrUnsupported
+			return 0, r.err
+		}
+		// Section 4.4 Padding (chunk type 0xfe).
+		// Section 4.6. Reserved skippable chunks (chunk types 0x80-0xfd).
+		if !r.readFull(r.buf[:chunkLen]) {
+			return 0, r.err
+		}
+	}
+}
@@ -0,0 +1,254 @@
+// Copyright 2011 The Snappy-Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package snappy
+
+import (
+	"encoding/binary"
+	"io"
+)
+
+// We limit how far copy back-references can go, the same as the C++ code.
+const maxOffset = 1 << 15
+
+// emitLiteral writes a literal chunk and returns the number of bytes written.
+func emitLiteral(dst, lit []byte) int {
+	i, n := 0, uint(len(lit)-1)
+	switch {
+	case n < 60:
+		dst[0] = uint8(n)<<2 | tagLiteral
+		i = 1
+	case n < 1<<8:
+		dst[0] = 60<<2 | tagLiteral
+		dst[1] = uint8(n)
+		i = 2
+	case n < 1<<16:
+		dst[0] = 61<<2 | tagLiteral
+		dst[1] = uint8(n)
+		dst[2] = uint8(n >> 8)
+		i = 3
+	case n < 1<<24:
+		dst[0] = 62<<2 | tagLiteral
+		dst[1] = uint8(n)
+		dst[2] = uint8(n >> 8)
+		dst[3] = uint8(n >> 16)
+		i = 4
+	case int64(n) < 1<<32:
+		dst[0] = 63<<2 | tagLiteral
+		dst[1] = uint8(n)
+		dst[2] = uint8(n >> 8)
+		dst[3] = uint8(n >> 16)
+		dst[4] = uint8(n >> 24)
+		i = 5
+	default:
+		panic("snappy: source buffer is too long")
+	}
+	if copy(dst[i:], lit) != len(lit) {
+		panic("snappy: destination buffer is too short")
+	}
+	return i + len(lit)
+}
+
+// emitCopy writes a copy chunk and returns the number of bytes written.
+func emitCopy(dst []byte, offset, length int) int {
+	i := 0
+	for length > 0 {
+		x := length - 4
+		if 0 <= x && x < 1<<3 && offset < 1<<11 {
+			dst[i+0] = uint8(offset>>8)&0x07<<5 | uint8(x)<<2 | tagCopy1
+			dst[i+1] = uint8(offset)
+			i += 2
+			break
+		}
+
+		x = length
+		if x > 1<<6 {
+			x = 1 << 6
+		}
+		dst[i+0] = uint8(x-1)<<2 | tagCopy2
+		dst[i+1] = uint8(offset)
+		dst[i+2] = uint8(offset >> 8)
+		i += 3
+		length -= x
+	}
+	return i
+}
+
+// Encode returns the encoded form of src. The returned slice may be a sub-
+// slice of dst if dst was large enough to hold the entire encoded block.
+// Otherwise, a newly allocated slice will be returned.
+// It is valid to pass a nil dst.
+func Encode(dst, src []byte) []byte {
+	if n := MaxEncodedLen(len(src)); len(dst) < n {
+		dst = make([]byte, n)
+	}
+
+	// The block starts with the varint-encoded length of the decompressed bytes.
+	d := binary.PutUvarint(dst, uint64(len(src)))
+
+	// Return early if src is short.
+	if len(src) <= 4 {
+		if len(src) != 0 {
+			d += emitLiteral(dst[d:], src)
+		}
+		return dst[:d]
+	}
+
+	// Initialize the hash table. Its size ranges from 1<<8 to 1<<14 inclusive.
+	const maxTableSize = 1 << 14
+	shift, tableSize := uint(32-8), 1<<8
+	for tableSize < maxTableSize && tableSize < len(src) {
+		shift--
+		tableSize *= 2
+	}
+	var table [maxTableSize]int
+
+	// Iterate over the source bytes.
+	var (
+		s   int // The iterator position.
+		t   int // The last position with the same hash as s.
+		lit int // The start position of any pending literal bytes.
+	)
+	for s+3 < len(src) {
+		// Update the hash table.
+		b0, b1, b2, b3 := src[s], src[s+1], src[s+2], src[s+3]
+		h := uint32(b0) | uint32(b1)<<8 | uint32(b2)<<16 | uint32(b3)<<24
+		p := &table[(h*0x1e35a7bd)>>shift]
+		// We need to to store values in [-1, inf) in table. To save
+		// some initialization time, (re)use the table's zero value
+		// and shift the values against this zero: add 1 on writes,
+		// subtract 1 on reads.
+		t, *p = *p-1, s+1
+		// If t is invalid or src[s:s+4] differs from src[t:t+4], accumulate a literal byte.
+		if t < 0 || s-t >= maxOffset || b0 != src[t] || b1 != src[t+1] || b2 != src[t+2] || b3 != src[t+3] {
+			s++
+			continue
+		}
+		// Otherwise, we have a match. First, emit any pending literal bytes.
+		if lit != s {
+			d += emitLiteral(dst[d:], src[lit:s])
+		}
+		// Extend the match to be as long as possible.
+		s0 := s
+		s, t = s+4, t+4
+		for s < len(src) && src[s] == src[t] {
+			s++
+			t++
+		}
+		// Emit the copied bytes.
+		d += emitCopy(dst[d:], s-t, s-s0)
+		lit = s
+	}
+
+	// Emit any final pending literal bytes and return.
+	if lit != len(src) {
+		d += emitLiteral(dst[d:], src[lit:])
+	}
+	return dst[:d]
+}
+
+// MaxEncodedLen returns the maximum length of a snappy block, given its
+// uncompressed length.
+func MaxEncodedLen(srcLen int) int {
+	// Compressed data can be defined as:
+	//    compressed := item* literal*
+	//    item       := literal* copy
+	//
+	// The trailing literal sequence has a space blowup of at most 62/60
+	// since a literal of length 60 needs one tag byte + one extra byte
+	// for length information.
+	//
+	// Item blowup is trickier to measure. Suppose the "copy" op copies
+	// 4 bytes of data. Because of a special check in the encoding code,
+	// we produce a 4-byte copy only if the offset is < 65536. Therefore
+	// the copy op takes 3 bytes to encode, and this type of item leads
+	// to at most the 62/60 blowup for representing literals.
+	//
+	// Suppose the "copy" op copies 5 bytes of data. If the offset is big
+	// enough, it will take 5 bytes to encode the copy op. Therefore the
+	// worst case here is a one-byte literal followed by a five-byte copy.
+	// That is, 6 bytes of input turn into 7 bytes of "compressed" data.
+	//
+	// This last factor dominates the blowup, so the final estimate is:
+	return 32 + srcLen + srcLen/6
+}
+
+// NewWriter returns a new Writer that compresses to w, using the framing
+// format described at
+// https://github.com/google/snappy/blob/master/framing_format.txt
+func NewWriter(w io.Writer) *Writer {
+	return &Writer{
+		w:   w,
+		enc: make([]byte, MaxEncodedLen(maxUncompressedChunkLen)),
+	}
+}
+
+// Writer is an io.Writer than can write Snappy-compressed bytes.
+type Writer struct {
+	w           io.Writer
+	err         error
+	enc         []byte
+	buf         [checksumSize + chunkHeaderSize]byte
+	wroteHeader bool
+}
+
+// Reset discards the writer's state and switches the Snappy writer to write to
+// w. This permits reusing a Writer rather than allocating a new one.
+func (w *Writer) Reset(writer io.Writer) {
+	w.w = writer
+	w.err = nil
+	w.wroteHeader = false
+}
+
+// Write satisfies the io.Writer interface.
+func (w *Writer) Write(p []byte) (n int, errRet error) {
+	if w.err != nil {
+		return 0, w.err
+	}
+	if !w.wroteHeader {
+		copy(w.enc, magicChunk)
+		if _, err := w.w.Write(w.enc[:len(magicChunk)]); err != nil {
+			w.err = err
+			return n, err
+		}
+		w.wroteHeader = true
+	}
+	for len(p) > 0 {
+		var uncompressed []byte
+		if len(p) > maxUncompressedChunkLen {
+			uncompressed, p = p[:maxUncompressedChunkLen], p[maxUncompressedChunkLen:]
+		} else {
+			uncompressed, p = p, nil
+		}
+		checksum := crc(uncompressed)
+
+		// Compress the buffer, discarding the result if the improvement
+		// isn't at least 12.5%.
+		chunkType := uint8(chunkTypeCompressedData)
+		chunkBody := Encode(w.enc, uncompressed)
+		if len(chunkBody) >= len(uncompressed)-len(uncompressed)/8 {
+			chunkType, chunkBody = chunkTypeUncompressedData, uncompressed
+		}
+
+		chunkLen := 4 + len(chunkBody)
+		w.buf[0] = chunkType
+		w.buf[1] = uint8(chunkLen >> 0)
+		w.buf[2] = uint8(chunkLen >> 8)
+		w.buf[3] = uint8(chunkLen >> 16)
+		w.buf[4] = uint8(checksum >> 0)
+		w.buf[5] = uint8(checksum >> 8)
+		w.buf[6] = uint8(checksum >> 16)
+		w.buf[7] = uint8(checksum >> 24)
+		if _, err := w.w.Write(w.buf[:]); err != nil {
+			w.err = err
+			return n, err
+		}
+		if _, err := w.w.Write(chunkBody); err != nil {
+			w.err = err
+			return n, err
+		}
+		n += len(uncompressed)
+	}
+	return n, nil
+}
@@ -0,0 +1,68 @@
+// Copyright 2011 The Snappy-Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package snappy implements the snappy block-based compression format.
+// It aims for very high speeds and reasonable compression.
+//
+// The C++ snappy implementation is at https://github.com/google/snappy
+package snappy
+
+import (
+	"hash/crc32"
+)
+
+/*
+Each encoded block begins with the varint-encoded length of the decoded data,
+followed by a sequence of chunks. Chunks begin and end on byte boundaries. The
+first byte of each chunk is broken into its 2 least and 6 most significant bits
+called l and m: l ranges in [0, 4) and m ranges in [0, 64). l is the chunk tag.
+Zero means a literal tag. All other values mean a copy tag.
+
+For literal tags:
+  - If m < 60, the next 1 + m bytes are literal bytes.
+  - Otherwise, let n be the little-endian unsigned integer denoted by the next
+    m - 59 bytes. The next 1 + n bytes after that are literal bytes.
+
+For copy tags, length bytes are copied from offset bytes ago, in the style of
+Lempel-Ziv compression algorithms. In particular:
+  - For l == 1, the offset ranges in [0, 1<<11) and the length in [4, 12).
+    The length is 4 + the low 3 bits of m. The high 3 bits of m form bits 8-10
+    of the offset. The next byte is bits 0-7 of the offset.
+  - For l == 2, the offset ranges in [0, 1<<16) and the length in [1, 65).
+    The length is 1 + m. The offset is the little-endian unsigned integer
+    denoted by the next 2 bytes.
+  - For l == 3, this tag is a legacy format that is no longer supported.
+*/
+const (
+	tagLiteral = 0x00
+	tagCopy1   = 0x01
+	tagCopy2   = 0x02
+	tagCopy4   = 0x03
+)
+
+const (
+	checksumSize    = 4
+	chunkHeaderSize = 4
+	magicChunk      = "\xff\x06\x00\x00" + magicBody
+	magicBody       = "sNaPpY"
+	// https://github.com/google/snappy/blob/master/framing_format.txt says
+	// that "the uncompressed data in a chunk must be no longer than 65536 bytes".
+	maxUncompressedChunkLen = 65536
+)
+
+const (
+	chunkTypeCompressedData   = 0x00
+	chunkTypeUncompressedData = 0x01
+	chunkTypePadding          = 0xfe
+	chunkTypeStreamIdentifier = 0xff
+)
+
+var crcTable = crc32.MakeTable(crc32.Castagnoli)
+
+// crc implements the checksum specified in section 3 of
+// https://github.com/google/snappy/blob/master/framing_format.txt
+func crc(b []byte) uint32 {
+	c := crc32.Update(0, crcTable, b)
+	return uint32(c>>15|c<<17) + 0xa282ead8
+}
@@ -0,0 +1,191 @@
+All files in this repository are licensed as follows. If you contribute
+to this repository, it is assumed that you license your contribution
+under the same license unless you state otherwise.
+
+All files Copyright (C) 2015 Canonical Ltd. unless otherwise specified in the file.
+
+This software is licensed under the LGPLv3, included below.
+
+As a special exception to the GNU Lesser General Public License version 3
+("LGPL3"), the copyright holders of this Library give you permission to
+convey to a third party a Combined Work that links statically or dynamically
+to this Library without providing any Minimal Corresponding Source or
+Minimal Application Code as set out in 4d or providing the installation
+information set out in section 4e, provided that you comply with the other
+provisions of LGPL3 and provided that you meet, for the Application the
+terms and conditions of the license(s) which apply to the Application.
+
+Except as stated in this special exception, the provisions of LGPL3 will
+continue to comply in full to this Library. If you modify this Library, you
+may apply this exception to your version of this Library, but you are not
+obliged to do so. If you do not wish to do so, delete this exception
+statement from your version. This exception does not (and cannot) modify any
+license terms which apply to the Application, with which you must still
+comply.
+
+
+                   GNU LESSER GENERAL PUBLIC LICENSE
+                       Version 3, 29 June 2007
+
+ Copyright (C) 2007 Free Software Foundation, Inc. <http://fsf.org/>
+ Everyone is permitted to copy and distribute verbatim copies
+ of this license document, but changing it is not allowed.
+
+
+  This version of the GNU Lesser General Public License incorporates
+the terms and conditions of version 3 of the GNU General Public
+License, supplemented by the additional permissions listed below.
+
+  0. Additional Definitions.
+
+  As used herein, "this License" refers to version 3 of the GNU Lesser
+General Public License, and the "GNU GPL" refers to version 3 of the GNU
+General Public License.
+
+  "The Library" refers to a covered work governed by this License,
+other than an Application or a Combined Work as defined below.
+
+  An "Application" is any work that makes use of an interface provided
+by the Library, but which is not otherwise based on the Library.
+Defining a subclass of a class defined by the Library is deemed a mode
+of using an interface provided by the Library.
+
+  A "Combined Work" is a work produced by combining or linking an
+Application with the Library.  The particular version of the Library
+with which the Combined Work was made is also called the "Linked
+Version".
+
+  The "Minimal Corresponding Source" for a Combined Work means the
+Corresponding Source for the Combined Work, excluding any source code
+for portions of the Combined Work that, considered in isolation, are
+based on the Application, and not on the Linked Version.
+
+  The "Corresponding Application Code" for a Combined Work means the
+object code and/or source code for the Application, including any data
+and utility programs needed for reproducing the Combined Work from the
+Application, but excluding the System Libraries of the Combined Work.
+
+  1. Exception to Section 3 of the GNU GPL.
+
+  You may convey a covered work under sections 3 and 4 of this License
+without being bound by section 3 of the GNU GPL.
+
+  2. Conveying Modified Versions.
+
+  If you modify a copy of the Library, and, in your modifications, a
+facility refers to a function or data to be supplied by an Application
+that uses the facility (other than as an argument passed when the
+facility is invoked), then you may convey a copy of the modified
+version:
+
+   a) under this License, provided that you make a good faith effort to
+   ensure that, in the event an Application does not supply the
+   function or data, the facility still operates, and performs
+   whatever part of its purpose remains meaningful, or
+
+   b) under the GNU GPL, with none of the additional permissions of
+   this License applicable to that copy.
+
+  3. Object Code Incorporating Material from Library Header Files.
+
+  The object code form of an Application may incorporate material from
+a header file that is part of the Library.  You may convey such object
+code under terms of your choice, provided that, if the incorporated
+material is not limited to numerical parameters, data structure
+layouts and accessors, or small macros, inline functions and templates
+(ten or fewer lines in length), you do both of the following:
+
+   a) Give prominent notice with each copy of the object code that the
+   Library is used in it and that the Library and its use are
+   covered by this License.
+
+   b) Accompany the object code with a copy of the GNU GPL and this license
+   document.
+
+  4. Combined Works.
+
+  You may convey a Combined Work under terms of your choice that,
+taken together, effectively do not restrict modification of the
+portions of the Library contained in the Combined Work and reverse
+engineering for debugging such modifications, if you also do each of
+the following:
+
+   a) Give prominent notice with each copy of the Combined Work that
+   the Library is used in it and that the Library and its use are
+   covered by this License.
+
+   b) Accompany the Combined Work with a copy of the GNU GPL and this license
+   document.
+
+   c) For a Combined Work that displays copyright notices during
+   execution, include the copyright notice for the Library among
+   these notices, as well as a reference directing the user to the
+   copies of the GNU GPL and this license document.
+
+   d) Do one of the following:
+
+       0) Convey the Minimal Corresponding Source under the terms of this
+       License, and the Corresponding Application Code in a form
+       suitable for, and under terms that permit, the user to
+       recombine or relink the Application with a modified version of
+       the Linked Version to produce a modified Combined Work, in the
+       manner specified by section 6 of the GNU GPL for conveying
+       Corresponding Source.
+
+       1) Use a suitable shared library mechanism for linking with the
+       Library.  A suitable mechanism is one that (a) uses at run time
+       a copy of the Library already present on the user's computer
+       system, and (b) will operate properly with a modified version
+       of the Library that is interface-compatible with the Linked
+       Version.
+
+   e) Provide Installation Information, but only if you would otherwise
+   be required to provide such information under section 6 of the
+   GNU GPL, and only to the extent that such information is
+   necessary to install and execute a modified version of the
+   Combined Work produced by recombining or relinking the
+   Application with a modified version of the Linked Version. (If
+   you use option 4d0, the Installation Information must accompany
+   the Minimal Corresponding Source and Corresponding Application
+   Code. If you use option 4d1, you must provide the Installation
+   Information in the manner specified by section 6 of the GNU GPL
+   for conveying Corresponding Source.)
+
+  5. Combined Libraries.
+
+  You may place library facilities that are a work based on the
+Library side by side in a single library together with other library
+facilities that are not Applications and are not covered by this
+License, and convey such a combined library under terms of your
+choice, if you do both of the following:
+
+   a) Accompany the combined library with a copy of the same work based
+   on the Library, uncombined with any other library facilities,
+   conveyed under the terms of this License.
+
+   b) Give prominent notice with the combined library that part of it
+   is a work based on the Library, and explaining where to find the
+   accompanying uncombined form of the same work.
+
+  6. Revised Versions of the GNU Lesser General Public License.
+
+  The Free Software Foundation may publish revised and/or new versions
+of the GNU Lesser General Public License from time to time. Such new
+versions will be similar in spirit to the present version, but may
+differ in detail to address new problems or concerns.
+
+  Each version is given a distinguishing version number. If the
+Library as you received it specifies that a certain numbered version
+of the GNU Lesser General Public License "or any later version"
+applies to it, you have the option of following the terms and
+conditions either of that published version or of any later version
+published by the Free Software Foundation. If the Library as you
+received it does not specify a version number of the GNU Lesser
+General Public License, you may choose any version of the GNU Lesser
+General Public License ever published by the Free Software Foundation.
+
+  If the Library as you received it specifies that a proxy can decide
+whether future versions of the GNU Lesser General Public License shall
+apply, that proxy's public statement of acceptance of any version is
+permanent authorization for you to choose that version for the
+Library.
@@ -0,0 +1,117 @@
+# ratelimit
+--
+    import "github.com/juju/ratelimit"
+
+The ratelimit package provides an efficient token bucket implementation. See
+http://en.wikipedia.org/wiki/Token_bucket.
+
+## Usage
+
+#### func  Reader
+
+```go
+func Reader(r io.Reader, bucket *Bucket) io.Reader
+```
+Reader returns a reader that is rate limited by the given token bucket. Each
+token in the bucket represents one byte.
+
+#### func  Writer
+
+```go
+func Writer(w io.Writer, bucket *Bucket) io.Writer
+```
+Writer returns a writer that is rate limited by the given token bucket. Each
+token in the bucket represents one byte.
+
+#### type Bucket
+
+```go
+type Bucket struct {
+}
+```
+
+Bucket represents a token bucket that fills at a predetermined rate. Methods on
+Bucket may be called concurrently.
+
+#### func  NewBucket
+
+```go
+func NewBucket(fillInterval time.Duration, capacity int64) *Bucket
+```
+NewBucket returns a new token bucket that fills at the rate of one token every
+fillInterval, up to the given maximum capacity. Both arguments must be positive.
+The bucket is initially full.
+
+#### func  NewBucketWithQuantum
+
+```go
+func NewBucketWithQuantum(fillInterval time.Duration, capacity, quantum int64) *Bucket
+```
+NewBucketWithQuantum is similar to NewBucket, but allows the specification of
+the quantum size - quantum tokens are added every fillInterval.
+
+#### func  NewBucketWithRate
+
+```go
+func NewBucketWithRate(rate float64, capacity int64) *Bucket
+```
+NewBucketWithRate returns a token bucket that fills the bucket at the rate of
+rate tokens per second up to the given maximum capacity. Because of limited
+clock resolution, at high rates, the actual rate may be up to 1% different from
+the specified rate.
+
+#### func (*Bucket) Rate
+
+```go
+func (tb *Bucket) Rate() float64
+```
+Rate returns the fill rate of the bucket, in tokens per second.
+
+#### func (*Bucket) Take
+
+```go
+func (tb *Bucket) Take(count int64) time.Duration
+```
+Take takes count tokens from the bucket without blocking. It returns the time
+that the caller should wait until the tokens are actually available.
+
+Note that if the request is irrevocable - there is no way to return tokens to
+the bucket once this method commits us to taking them.
+
+#### func (*Bucket) TakeAvailable
+
+```go
+func (tb *Bucket) TakeAvailable(count int64) int64
+```
+TakeAvailable takes up to count immediately available tokens from the bucket. It
+returns the number of tokens removed, or zero if there are no available tokens.
+It does not block.
+
+#### func (*Bucket) TakeMaxDuration
+
+```go
+func (tb *Bucket) TakeMaxDuration(count int64, maxWait time.Duration) (time.Duration, bool)
+```
+TakeMaxDuration is like Take, except that it will only take tokens from the
+bucket if the wait time for the tokens is no greater than maxWait.
+
+If it would take longer than maxWait for the tokens to become available, it does
+nothing and reports false, otherwise it returns the time that the caller should
+wait until the tokens are actually available, and reports true.
+
+#### func (*Bucket) Wait
+
+```go
+func (tb *Bucket) Wait(count int64)
+```
+Wait takes count tokens from the bucket, waiting until they are available.
+
+#### func (*Bucket) WaitMaxDuration
+
+```go
+func (tb *Bucket) WaitMaxDuration(count int64, maxWait time.Duration) bool
+```
+WaitMaxDuration is like Wait except that it will only take tokens from the
+bucket if it needs to wait for no greater than maxWait. It reports whether any
+tokens have been removed from the bucket If no tokens have been removed, it
+returns immediately.
@@ -0,0 +1,221 @@
+// Copyright 2014 Canonical Ltd.
+// Licensed under the LGPLv3 with static-linking exception.
+// See LICENCE file for details.
+
+// The ratelimit package provides an efficient token bucket implementation
+// that can be used to limit the rate of arbitrary things.
+// See http://en.wikipedia.org/wiki/Token_bucket.
+package ratelimit
+
+import (
+	"strconv"
+	"sync"
+	"time"
+	"math"
+)
+
+// Bucket represents a token bucket that fills at a predetermined rate.
+// Methods on Bucket may be called concurrently.
+type Bucket struct {
+	startTime    time.Time
+	capacity     int64
+	quantum      int64
+	fillInterval time.Duration
+
+	// The mutex guards the fields following it.
+	mu sync.Mutex
+
+	// avail holds the number of available tokens
+	// in the bucket, as of availTick ticks from startTime.
+	// It will be negative when there are consumers
+	// waiting for tokens.
+	avail     int64
+	availTick int64
+}
+
+// NewBucket returns a new token bucket that fills at the
+// rate of one token every fillInterval, up to the given
+// maximum capacity. Both arguments must be
+// positive. The bucket is initially full.
+func NewBucket(fillInterval time.Duration, capacity int64) *Bucket {
+	return NewBucketWithQuantum(fillInterval, capacity, 1)
+}
+
+// rateMargin specifes the allowed variance of actual
+// rate from specified rate. 1% seems reasonable.
+const rateMargin = 0.01
+
+// NewBucketWithRate returns a token bucket that fills the bucket
+// at the rate of rate tokens per second up to the given
+// maximum capacity. Because of limited clock resolution,
+// at high rates, the actual rate may be up to 1% different from the
+// specified rate.
+func NewBucketWithRate(rate float64, capacity int64) *Bucket {
+	for quantum := int64(1); quantum < 1<<50; quantum = nextQuantum(quantum) {
+		fillInterval := time.Duration(1e9 * float64(quantum) / rate)
+		if fillInterval <= 0 {
+			continue
+		}
+		tb := NewBucketWithQuantum(fillInterval, capacity, quantum)
+		if diff := math.Abs(tb.Rate() - rate); diff/rate <= rateMargin {
+			return tb
+		}
+	}
+	panic("cannot find suitable quantum for " + strconv.FormatFloat(rate, 'g', -1, 64))
+}
+
+// nextQuantum returns the next quantum to try after q.
+// We grow the quantum exponentially, but slowly, so we
+// get a good fit in the lower numbers.
+func nextQuantum(q int64) int64 {
+	q1 := q * 11 / 10
+	if q1 == q {
+		q1++
+	}
+	return q1
+}
+
+// NewBucketWithQuantum is similar to NewBucket, but allows
+// the specification of the quantum size - quantum tokens
+// are added every fillInterval.
+func NewBucketWithQuantum(fillInterval time.Duration, capacity, quantum int64) *Bucket {
+	if fillInterval <= 0 {
+		panic("token bucket fill interval is not > 0")
+	}
+	if capacity <= 0 {
+		panic("token bucket capacity is not > 0")
+	}
+	if quantum <= 0 {
+		panic("token bucket quantum is not > 0")
+	}
+	return &Bucket{
+		startTime:    time.Now(),
+		capacity:     capacity,
+		quantum:      quantum,
+		avail:        capacity,
+		fillInterval: fillInterval,
+	}
+}
+
+// Wait takes count tokens from the bucket, waiting until they are
+// available.
+func (tb *Bucket) Wait(count int64) {
+	if d := tb.Take(count); d > 0 {
+		time.Sleep(d)
+	}
+}
+
+// WaitMaxDuration is like Wait except that it will
+// only take tokens from the bucket if it needs to wait
+// for no greater than maxWait. It reports whether
+// any tokens have been removed from the bucket
+// If no tokens have been removed, it returns immediately.
+func (tb *Bucket) WaitMaxDuration(count int64, maxWait time.Duration) bool {
+	d, ok := tb.TakeMaxDuration(count, maxWait)
+	if d > 0 {
+		time.Sleep(d)
+	}
+	return ok
+}
+
+const infinityDuration time.Duration = 0x7fffffffffffffff
+
+// Take takes count tokens from the bucket without blocking. It returns
+// the time that the caller should wait until the tokens are actually
+// available.
+//
+// Note that if the request is irrevocable - there is no way to return
+// tokens to the bucket once this method commits us to taking them.
+func (tb *Bucket) Take(count int64) time.Duration {
+	d, _ := tb.take(time.Now(), count, infinityDuration)
+	return d
+}
+
+// TakeMaxDuration is like Take, except that
+// it will only take tokens from the bucket if the wait
+// time for the tokens is no greater than maxWait.
+//
+// If it would take longer than maxWait for the tokens
+// to become available, it does nothing and reports false,
+// otherwise it returns the time that the caller should
+// wait until the tokens are actually available, and reports
+// true.
+func (tb *Bucket) TakeMaxDuration(count int64, maxWait time.Duration) (time.Duration, bool) {
+	return tb.take(time.Now(), count, maxWait)
+}
+
+// TakeAvailable takes up to count immediately available tokens from the
+// bucket. It returns the number of tokens removed, or zero if there are
+// no available tokens. It does not block.
+func (tb *Bucket) TakeAvailable(count int64) int64 {
+	return tb.takeAvailable(time.Now(), count)
+}
+
+// takeAvailable is the internal version of TakeAvailable - it takes the
+// current time as an argument to enable easy testing.
+func (tb *Bucket) takeAvailable(now time.Time, count int64) int64 {
+	if count <= 0 {
+		return 0
+	}
+	tb.mu.Lock()
+	defer tb.mu.Unlock()
+
+	tb.adjust(now)
+	if tb.avail <= 0 {
+		return 0
+	}
+	if count > tb.avail {
+		count = tb.avail
+	}
+	tb.avail -= count
+	return count
+}
+
+// Rate returns the fill rate of the bucket, in tokens per second.
+func (tb *Bucket) Rate() float64 {
+	return 1e9 * float64(tb.quantum) / float64(tb.fillInterval)
+}
+
+// take is the internal version of Take - it takes the current time as
+// an argument to enable easy testing.
+func (tb *Bucket) take(now time.Time, count int64, maxWait time.Duration) (time.Duration, bool) {
+	if count <= 0 {
+		return 0, true
+	}
+	tb.mu.Lock()
+	defer tb.mu.Unlock()
+
+	currentTick := tb.adjust(now)
+	avail := tb.avail - count
+	if avail >= 0 {
+		tb.avail = avail
+		return 0, true
+	}
+	// Round up the missing tokens to the nearest multiple
+	// of quantum - the tokens won't be available until
+	// that tick.
+	endTick := currentTick + (-avail+tb.quantum-1)/tb.quantum
+	endTime := tb.startTime.Add(time.Duration(endTick) * tb.fillInterval)
+	waitTime := endTime.Sub(now)
+	if waitTime > maxWait {
+		return 0, false
+	}
+	tb.avail = avail
+	return waitTime, true
+}
+
+// adjust adjusts the current bucket capacity based on the current time.
+// It returns the current tick.
+func (tb *Bucket) adjust(now time.Time) (currentTick int64) {
+	currentTick = int64(now.Sub(tb.startTime) / tb.fillInterval)
+
+	if tb.avail >= tb.capacity {
+		return
+	}
+	tb.avail += (currentTick - tb.availTick) * tb.quantum
+	if tb.avail > tb.capacity {
+		tb.avail = tb.capacity
+	}
+	tb.availTick = currentTick
+	return
+}
@@ -0,0 +1,51 @@
+// Copyright 2014 Canonical Ltd.
+// Licensed under the LGPLv3 with static-linking exception.
+// See LICENCE file for details.
+
+package ratelimit
+
+import "io"
+
+type reader struct {
+	r      io.Reader
+	bucket *Bucket
+}
+
+// Reader returns a reader that is rate limited by
+// the given token bucket. Each token in the bucket
+// represents one byte.
+func Reader(r io.Reader, bucket *Bucket) io.Reader {
+	return &reader{
+		r:      r,
+		bucket: bucket,
+	}
+}
+
+func (r *reader) Read(buf []byte) (int, error) {
+	n, err := r.r.Read(buf)
+	if n <= 0 {
+		return n, err
+	}
+	r.bucket.Wait(int64(n))
+	return n, err
+}
+
+type writer struct {
+	w      io.Writer
+	bucket *Bucket
+}
+
+// Writer returns a reader that is rate limited by
+// the given token bucket. Each token in the bucket
+// represents one byte.
+func Writer(w io.Writer, bucket *Bucket) io.Writer {
+	return &writer{
+		w:      w,
+		bucket: bucket,
+	}
+}
+
+func (w *writer) Write(buf []byte) (int, error) {
+	w.bucket.Wait(int64(len(buf)))
+	return w.w.Write(buf)
+}
@@ -0,0 +1,27 @@
+Copyright (c) 2012 The Go Authors. All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+
+   * Redistributions of source code must retain the above copyright
+notice, this list of conditions and the following disclaimer.
+   * Redistributions in binary form must reproduce the above
+copyright notice, this list of conditions and the following disclaimer
+in the documentation and/or other materials provided with the
+distribution.
+   * Neither the name of Google Inc. nor the names of its
+contributors may be used to endorse or promote products derived from
+this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
@@ -0,0 +1,16 @@
+### Extensions to the "os" package.
+
+## Find the current Executable and ExecutableFolder.
+
+There is sometimes utility in finding the current executable file
+that is running. This can be used for upgrading the current executable
+or finding resources located relative to the executable file. Both
+working directory and the os.Args[0] value are arbitrary and cannot
+be relied on; os.Args[0] can be "faked".
+
+Multi-platform and supports:
+ * Linux
+ * OS X
+ * Windows
+ * Plan 9
+ * BSDs.
@@ -0,0 +1,33 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Extensions to the standard "os" package.
+package osext
+
+import "path/filepath"
+
+var cx, ce = executableClean()
+
+func executableClean() (string, error) {
+	p, err := executable()
+	return filepath.Clean(p), err
+}
+
+// Executable returns an absolute path that can be used to
+// re-invoke the current program.
+// It may not be valid after the current program exits.
+func Executable() (string, error) {
+	return cx, ce
+}
+
+// Returns same path as Executable, returns just the folder
+// path. Excludes the executable name and any trailing slash.
+func ExecutableFolder() (string, error) {
+	p, err := Executable()
+	if err != nil {
+		return "", err
+	}
+
+	return filepath.Dir(p), nil
+}
@@ -0,0 +1,20 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package osext
+
+import (
+	"os"
+	"strconv"
+	"syscall"
+)
+
+func executable() (string, error) {
+	f, err := os.Open("/proc/" + strconv.Itoa(os.Getpid()) + "/text")
+	if err != nil {
+		return "", err
+	}
+	defer f.Close()
+	return syscall.Fd2path(int(f.Fd()))
+}
@@ -0,0 +1,36 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build linux netbsd solaris dragonfly
+
+package osext
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"runtime"
+	"strings"
+)
+
+func executable() (string, error) {
+	switch runtime.GOOS {
+	case "linux":
+		const deletedTag = " (deleted)"
+		execpath, err := os.Readlink("/proc/self/exe")
+		if err != nil {
+			return execpath, err
+		}
+		execpath = strings.TrimSuffix(execpath, deletedTag)
+		execpath = strings.TrimPrefix(execpath, deletedTag)
+		return execpath, nil
+	case "netbsd":
+		return os.Readlink("/proc/curproc/exe")
+	case "dragonfly":
+		return os.Readlink("/proc/curproc/file")
+	case "solaris":
+		return os.Readlink(fmt.Sprintf("/proc/%d/path/a.out", os.Getpid()))
+	}
+	return "", errors.New("ExecPath not implemented for " + runtime.GOOS)
+}
@@ -0,0 +1,126 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build darwin freebsd openbsd
+
+package osext
+
+import (
+	"os"
+	"os/exec"
+	"path/filepath"
+	"runtime"
+	"syscall"
+	"unsafe"
+)
+
+var initCwd, initCwdErr = os.Getwd()
+
+func executable() (string, error) {
+	var mib [4]int32
+	switch runtime.GOOS {
+	case "freebsd":
+		mib = [4]int32{1 /* CTL_KERN */, 14 /* KERN_PROC */, 12 /* KERN_PROC_PATHNAME */, -1}
+	case "darwin":
+		mib = [4]int32{1 /* CTL_KERN */, 38 /* KERN_PROCARGS */, int32(os.Getpid()), -1}
+	case "openbsd":
+		mib = [4]int32{1 /* CTL_KERN */, 55 /* KERN_PROC_ARGS */, int32(os.Getpid()), 1 /* KERN_PROC_ARGV */}
+	}
+
+	n := uintptr(0)
+	// Get length.
+	_, _, errNum := syscall.Syscall6(syscall.SYS___SYSCTL, uintptr(unsafe.Pointer(&mib[0])), 4, 0, uintptr(unsafe.Pointer(&n)), 0, 0)
+	if errNum != 0 {
+		return "", errNum
+	}
+	if n == 0 { // This shouldn't happen.
+		return "", nil
+	}
+	buf := make([]byte, n)
+	_, _, errNum = syscall.Syscall6(syscall.SYS___SYSCTL, uintptr(unsafe.Pointer(&mib[0])), 4, uintptr(unsafe.Pointer(&buf[0])), uintptr(unsafe.Pointer(&n)), 0, 0)
+	if errNum != 0 {
+		return "", errNum
+	}
+	if n == 0 { // This shouldn't happen.
+		return "", nil
+	}
+
+	var execPath string
+	switch runtime.GOOS {
+	case "openbsd":
+		// buf now contains **argv, with pointers to each of the C-style
+		// NULL terminated arguments.
+		var args []string
+		argv := uintptr(unsafe.Pointer(&buf[0]))
+	Loop:
+		for {
+			argp := *(**[1 << 20]byte)(unsafe.Pointer(argv))
+			if argp == nil {
+				break
+			}
+			for i := 0; uintptr(i) < n; i++ {
+				// we don't want the full arguments list
+				if string(argp[i]) == " " {
+					break Loop
+				}
+				if argp[i] != 0 {
+					continue
+				}
+				args = append(args, string(argp[:i]))
+				n -= uintptr(i)
+				break
+			}
+			if n < unsafe.Sizeof(argv) {
+				break
+			}
+			argv += unsafe.Sizeof(argv)
+			n -= unsafe.Sizeof(argv)
+		}
+		execPath = args[0]
+		// There is no canonical way to get an executable path on
+		// OpenBSD, so check PATH in case we are called directly
+		if execPath[0] != '/' && execPath[0] != '.' {
+			execIsInPath, err := exec.LookPath(execPath)
+			if err == nil {
+				execPath = execIsInPath
+			}
+		}
+	default:
+		for i, v := range buf {
+			if v == 0 {
+				buf = buf[:i]
+				break
+			}
+		}
+		execPath = string(buf)
+	}
+
+	var err error
+	// execPath will not be empty due to above checks.
+	// Try to get the absolute path if the execPath is not rooted.
+	if execPath[0] != '/' {
+		execPath, err = getAbs(execPath)
+		if err != nil {
+			return execPath, err
+		}
+	}
+	// For darwin KERN_PROCARGS may return the path to a symlink rather than the
+	// actual executable.
+	if runtime.GOOS == "darwin" {
+		if execPath, err = filepath.EvalSymlinks(execPath); err != nil {
+			return execPath, err
+		}
+	}
+	return execPath, nil
+}
+
+func getAbs(execPath string) (string, error) {
+	if initCwdErr != nil {
+		return execPath, initCwdErr
+	}
+	// The execPath may begin with a "../" or a "./" so clean it first.
+	// Join the two paths, trailing and starting slashes undetermined, so use
+	// the generic Join function.
+	return filepath.Join(initCwd, filepath.Clean(execPath)), nil
+}
@@ -0,0 +1,34 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package osext
+
+import (
+	"syscall"
+	"unicode/utf16"
+	"unsafe"
+)
+
+var (
+	kernel                = syscall.MustLoadDLL("kernel32.dll")
+	getModuleFileNameProc = kernel.MustFindProc("GetModuleFileNameW")
+)
+
+// GetModuleFileName() with hModule = NULL
+func executable() (exePath string, err error) {
+	return getModuleFileName()
+}
+
+func getModuleFileName() (string, error) {
+	var n uint32
+	b := make([]uint16, syscall.MAX_PATH)
+	size := uint32(len(b))
+
+	r0, _, e1 := getModuleFileNameProc.Call(0, uintptr(unsafe.Pointer(&b[0])), uintptr(size))
+	n = uint32(r0)
+	if n == 0 {
+		return "", e1
+	}
+	return string(utf16.Decode(b[0:n])), nil
+}
@@ -0,0 +1,9 @@
+*.[68]
+*.a
+*.out
+*.swp
+_obj
+_testmain.go
+cmd/metrics-bench/metrics-bench
+cmd/metrics-example/metrics-example
+cmd/never-read/never-read
@@ -0,0 +1,13 @@
+language: go
+
+go:
+    - 1.2
+    - 1.3
+    - 1.4
+
+script:
+    - ./validate.sh
+
+# this should give us faster builds according to 
+# http://docs.travis-ci.com/user/migrating-from-legacy/
+sudo: false
@@ -0,0 +1,29 @@
+Copyright 2012 Richard Crowley. All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+
+    1.  Redistributions of source code must retain the above copyright
+        notice, this list of conditions and the following disclaimer.
+
+    2.  Redistributions in binary form must reproduce the above
+        copyright notice, this list of conditions and the following
+        disclaimer in the documentation and/or other materials provided
+        with the distribution.
+
+THIS SOFTWARE IS PROVIDED BY RICHARD CROWLEY ``AS IS'' AND ANY EXPRESS
+OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL RICHARD CROWLEY OR CONTRIBUTORS BE LIABLE
+FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
+THE POSSIBILITY OF SUCH DAMAGE.
+
+The views and conclusions contained in the software and documentation
+are those of the authors and should not be interpreted as representing
+official policies, either expressed or implied, of Richard Crowley.
@@ -0,0 +1,126 @@
+go-metrics
+==========
+
+![travis build status](https://travis-ci.org/rcrowley/go-metrics.svg?branch=master)
+
+Go port of Coda Hale's Metrics library: <https://github.com/dropwizard/metrics>.
+
+Documentation: <http://godoc.org/github.com/rcrowley/go-metrics>.
+
+Usage
+-----
+
+Create and update metrics:
+
+```go
+c := metrics.NewCounter()
+metrics.Register("foo", c)
+c.Inc(47)
+
+g := metrics.NewGauge()
+metrics.Register("bar", g)
+g.Update(47)
+
+s := metrics.NewExpDecaySample(1028, 0.015) // or metrics.NewUniformSample(1028)
+h := metrics.NewHistogram(s)
+metrics.Register("baz", h)
+h.Update(47)
+
+m := metrics.NewMeter()
+metrics.Register("quux", m)
+m.Mark(47)
+
+t := metrics.NewTimer()
+metrics.Register("bang", t)
+t.Time(func() {})
+t.Update(47)
+```
+
+Periodically log every metric in human-readable form to standard error:
+
+```go
+go metrics.Log(metrics.DefaultRegistry, 60e9, log.New(os.Stderr, "metrics: ", log.Lmicroseconds))
+```
+
+Periodically log every metric in slightly-more-parseable form to syslog:
+
+```go
+w, _ := syslog.Dial("unixgram", "/dev/log", syslog.LOG_INFO, "metrics")
+go metrics.Syslog(metrics.DefaultRegistry, 60e9, w)
+```
+
+Periodically emit every metric to Graphite using the [Graphite client](https://github.com/cyberdelia/go-metrics-graphite):
+
+```go
+
+import "github.com/cyberdelia/go-metrics-graphite"
+
+addr, _ := net.ResolveTCPAddr("tcp", "127.0.0.1:2003")
+go graphite.Graphite(metrics.DefaultRegistry, 10e9, "metrics", addr)
+```
+
+Periodically emit every metric into InfluxDB:
+
+**NOTE:** this has been pulled out of the library due to constant fluctuations
+in the InfluxDB API. In fact, all client libraries are on their way out. see
+issues [#121](https://github.com/rcrowley/go-metrics/issues/121) and
+[#124](https://github.com/rcrowley/go-metrics/issues/124) for progress and details.
+
+```go
+import "github.com/rcrowley/go-metrics/influxdb"
+
+go influxdb.Influxdb(metrics.DefaultRegistry, 10e9, &influxdb.Config{
+    Host:     "127.0.0.1:8086",
+    Database: "metrics",
+    Username: "test",
+    Password: "test",
+})
+```
+
+Periodically upload every metric to Librato using the [Librato client](https://github.com/mihasya/go-metrics-librato):
+
+**Note**: the client included with this repository under the `librato` package
+has been deprecated and moved to the repository linked above.
+
+```go
+import "github.com/mihasya/go-metrics-librato"
+
+go librato.Librato(metrics.DefaultRegistry,
+    10e9,                  // interval
+    "example@example.com", // account owner email address
+    "token",               // Librato API token
+    "hostname",            // source
+    []float64{0.95},       // percentiles to send
+    time.Millisecond,      // time unit
+)
+```
+
+Periodically emit every metric to StatHat:
+
+```go
+import "github.com/rcrowley/go-metrics/stathat"
+
+go stathat.Stathat(metrics.DefaultRegistry, 10e9, "example@example.com")
+```
+
+Installation
+------------
+
+```sh
+go get github.com/rcrowley/go-metrics
+```
+
+StatHat support additionally requires their Go client:
+
+```sh
+go get github.com/stathat/go
+```
+
+Publishing Metrics
+------------------
+
+Clients are available for the following destinations:
+
+* Librato - [https://github.com/mihasya/go-metrics-librato](https://github.com/mihasya/go-metrics-librato)
+* Graphite - [https://github.com/cyberdelia/go-metrics-graphite](https://github.com/cyberdelia/go-metrics-graphite)
+* InfluxDB - [https://github.com/vrischmann/go-metrics-influxdb](https://github.com/vrischmann/go-metrics-influxdb)
@@ -0,0 +1,20 @@
+package main
+
+import (
+	"fmt"
+	"github.com/rcrowley/go-metrics"
+	"time"
+)
+
+func main() {
+	r := metrics.NewRegistry()
+	for i := 0; i < 10000; i++ {
+		r.Register(fmt.Sprintf("counter-%d", i), metrics.NewCounter())
+		r.Register(fmt.Sprintf("gauge-%d", i), metrics.NewGauge())
+		r.Register(fmt.Sprintf("gaugefloat64-%d", i), metrics.NewGaugeFloat64())
+		r.Register(fmt.Sprintf("histogram-uniform-%d", i), metrics.NewHistogram(metrics.NewUniformSample(1028)))
+		r.Register(fmt.Sprintf("histogram-exp-%d", i), metrics.NewHistogram(metrics.NewExpDecaySample(1028, 0.015)))
+		r.Register(fmt.Sprintf("meter-%d", i), metrics.NewMeter())
+	}
+	time.Sleep(600e9)
+}
@@ -0,0 +1,154 @@
+package main
+
+import (
+	"errors"
+	"github.com/rcrowley/go-metrics"
+	// "github.com/rcrowley/go-metrics/stathat"
+	"log"
+	"math/rand"
+	"os"
+	// "syslog"
+	"time"
+)
+
+const fanout = 10
+
+func main() {
+
+	r := metrics.NewRegistry()
+
+	c := metrics.NewCounter()
+	r.Register("foo", c)
+	for i := 0; i < fanout; i++ {
+		go func() {
+			for {
+				c.Dec(19)
+				time.Sleep(300e6)
+			}
+		}()
+		go func() {
+			for {
+				c.Inc(47)
+				time.Sleep(400e6)
+			}
+		}()
+	}
+
+	g := metrics.NewGauge()
+	r.Register("bar", g)
+	for i := 0; i < fanout; i++ {
+		go func() {
+			for {
+				g.Update(19)
+				time.Sleep(300e6)
+			}
+		}()
+		go func() {
+			for {
+				g.Update(47)
+				time.Sleep(400e6)
+			}
+		}()
+	}
+
+	gf := metrics.NewGaugeFloat64()
+	r.Register("barfloat64", gf)
+	for i := 0; i < fanout; i++ {
+		go func() {
+			for {
+				g.Update(19.0)
+				time.Sleep(300e6)
+			}
+		}()
+		go func() {
+			for {
+				g.Update(47.0)
+				time.Sleep(400e6)
+			}
+		}()
+	}
+
+	hc := metrics.NewHealthcheck(func(h metrics.Healthcheck) {
+		if 0 < rand.Intn(2) {
+			h.Healthy()
+		} else {
+			h.Unhealthy(errors.New("baz"))
+		}
+	})
+	r.Register("baz", hc)
+
+	s := metrics.NewExpDecaySample(1028, 0.015)
+	//s := metrics.NewUniformSample(1028)
+	h := metrics.NewHistogram(s)
+	r.Register("bang", h)
+	for i := 0; i < fanout; i++ {
+		go func() {
+			for {
+				h.Update(19)
+				time.Sleep(300e6)
+			}
+		}()
+		go func() {
+			for {
+				h.Update(47)
+				time.Sleep(400e6)
+			}
+		}()
+	}
+
+	m := metrics.NewMeter()
+	r.Register("quux", m)
+	for i := 0; i < fanout; i++ {
+		go func() {
+			for {
+				m.Mark(19)
+				time.Sleep(300e6)
+			}
+		}()
+		go func() {
+			for {
+				m.Mark(47)
+				time.Sleep(400e6)
+			}
+		}()
+	}
+
+	t := metrics.NewTimer()
+	r.Register("hooah", t)
+	for i := 0; i < fanout; i++ {
+		go func() {
+			for {
+				t.Time(func() { time.Sleep(300e6) })
+			}
+		}()
+		go func() {
+			for {
+				t.Time(func() { time.Sleep(400e6) })
+			}
+		}()
+	}
+
+	metrics.RegisterDebugGCStats(r)
+	go metrics.CaptureDebugGCStats(r, 5e9)
+
+	metrics.RegisterRuntimeMemStats(r)
+	go metrics.CaptureRuntimeMemStats(r, 5e9)
+
+	metrics.Log(r, 60e9, log.New(os.Stderr, "metrics: ", log.Lmicroseconds))
+
+	/*
+		w, err := syslog.Dial("unixgram", "/dev/log", syslog.LOG_INFO, "metrics")
+		if nil != err { log.Fatalln(err) }
+		metrics.Syslog(r, 60e9, w)
+	*/
+
+	/*
+		addr, _ := net.ResolveTCPAddr("tcp", "127.0.0.1:2003")
+		metrics.Graphite(r, 10e9, "metrics", addr)
+	*/
+
+	/*
+		stathat.Stathat(r, 10e9, "example@example.com")
+	*/
+
+}
@@ -0,0 +1,22 @@
+package main
+
+import (
+	"log"
+	"net"
+)
+
+func main() {
+	addr, _ := net.ResolveTCPAddr("tcp", "127.0.0.1:2003")
+	l, err := net.ListenTCP("tcp", addr)
+	if nil != err {
+		log.Fatalln(err)
+	}
+	log.Println("listening", l.Addr())
+	for {
+		c, err := l.AcceptTCP()
+		if nil != err {
+			log.Fatalln(err)
+		}
+		log.Println("accepted", c.RemoteAddr())
+	}
+}
@@ -0,0 +1,112 @@
+package metrics
+
+import "sync/atomic"
+
+// Counters hold an int64 value that can be incremented and decremented.
+type Counter interface {
+	Clear()
+	Count() int64
+	Dec(int64)
+	Inc(int64)
+	Snapshot() Counter
+}
+
+// GetOrRegisterCounter returns an existing Counter or constructs and registers
+// a new StandardCounter.
+func GetOrRegisterCounter(name string, r Registry) Counter {
+	if nil == r {
+		r = DefaultRegistry
+	}
+	return r.GetOrRegister(name, NewCounter).(Counter)
+}
+
+// NewCounter constructs a new StandardCounter.
+func NewCounter() Counter {
+	if UseNilMetrics {
+		return NilCounter{}
+	}
+	return &StandardCounter{0}
+}
+
+// NewRegisteredCounter constructs and registers a new StandardCounter.
+func NewRegisteredCounter(name string, r Registry) Counter {
+	c := NewCounter()
+	if nil == r {
+		r = DefaultRegistry
+	}
+	r.Register(name, c)
+	return c
+}
+
+// CounterSnapshot is a read-only copy of another Counter.
+type CounterSnapshot int64
+
+// Clear panics.
+func (CounterSnapshot) Clear() {
+	panic("Clear called on a CounterSnapshot")
+}
+
+// Count returns the count at the time the snapshot was taken.
+func (c CounterSnapshot) Count() int64 { return int64(c) }
+
+// Dec panics.
+func (CounterSnapshot) Dec(int64) {
+	panic("Dec called on a CounterSnapshot")
+}
+
+// Inc panics.
+func (CounterSnapshot) Inc(int64) {
+	panic("Inc called on a CounterSnapshot")
+}
+
+// Snapshot returns the snapshot.
+func (c CounterSnapshot) Snapshot() Counter { return c }
+
+// NilCounter is a no-op Counter.
+type NilCounter struct{}
+
+// Clear is a no-op.
+func (NilCounter) Clear() {}
+
+// Count is a no-op.
+func (NilCounter) Count() int64 { return 0 }
+
+// Dec is a no-op.
+func (NilCounter) Dec(i int64) {}
+
+// Inc is a no-op.
+func (NilCounter) Inc(i int64) {}
+
+// Snapshot is a no-op.
+func (NilCounter) Snapshot() Counter { return NilCounter{} }
+
+// StandardCounter is the standard implementation of a Counter and uses the
+// sync/atomic package to manage a single int64 value.
+type StandardCounter struct {
+	count int64
+}
+
+// Clear sets the counter to zero.
+func (c *StandardCounter) Clear() {
+	atomic.StoreInt64(&c.count, 0)
+}
+
+// Count returns the current count.
+func (c *StandardCounter) Count() int64 {
+	return atomic.LoadInt64(&c.count)
+}
+
+// Dec decrements the counter by the given amount.
+func (c *StandardCounter) Dec(i int64) {
+	atomic.AddInt64(&c.count, -i)
+}
+
+// Inc increments the counter by the given amount.
+func (c *StandardCounter) Inc(i int64) {
+	atomic.AddInt64(&c.count, i)
+}
+
+// Snapshot returns a read-only copy of the counter.
+func (c *StandardCounter) Snapshot() Counter {
+	return CounterSnapshot(c.Count())
+}
@@ -0,0 +1,76 @@
+package metrics
+
+import (
+	"runtime/debug"
+	"time"
+)
+
+var (
+	debugMetrics struct {
+		GCStats struct {
+			LastGC Gauge
+			NumGC  Gauge
+			Pause  Histogram
+			//PauseQuantiles Histogram
+			PauseTotal Gauge
+		}
+		ReadGCStats Timer
+	}
+	gcStats debug.GCStats
+)
+
+// Capture new values for the Go garbage collector statistics exported in
+// debug.GCStats.  This is designed to be called as a goroutine.
+func CaptureDebugGCStats(r Registry, d time.Duration) {
+	for _ = range time.Tick(d) {
+		CaptureDebugGCStatsOnce(r)
+	}
+}
+
+// Capture new values for the Go garbage collector statistics exported in
+// debug.GCStats.  This is designed to be called in a background goroutine.
+// Giving a registry which has not been given to RegisterDebugGCStats will
+// panic.
+//
+// Be careful (but much less so) with this because debug.ReadGCStats calls
+// the C function runtime·lock(runtime·mheap) which, while not a stop-the-world
+// operation, isn't something you want to be doing all the time.
+func CaptureDebugGCStatsOnce(r Registry) {
+	lastGC := gcStats.LastGC
+	t := time.Now()
+	debug.ReadGCStats(&gcStats)
+	debugMetrics.ReadGCStats.UpdateSince(t)
+
+	debugMetrics.GCStats.LastGC.Update(int64(gcStats.LastGC.UnixNano()))
+	debugMetrics.GCStats.NumGC.Update(int64(gcStats.NumGC))
+	if lastGC != gcStats.LastGC && 0 < len(gcStats.Pause) {
+		debugMetrics.GCStats.Pause.Update(int64(gcStats.Pause[0]))
+	}
+	//debugMetrics.GCStats.PauseQuantiles.Update(gcStats.PauseQuantiles)
+	debugMetrics.GCStats.PauseTotal.Update(int64(gcStats.PauseTotal))
+}
+
+// Register metrics for the Go garbage collector statistics exported in
+// debug.GCStats.  The metrics are named by their fully-qualified Go symbols,
+// i.e. debug.GCStats.PauseTotal.
+func RegisterDebugGCStats(r Registry) {
+	debugMetrics.GCStats.LastGC = NewGauge()
+	debugMetrics.GCStats.NumGC = NewGauge()
+	debugMetrics.GCStats.Pause = NewHistogram(NewExpDecaySample(1028, 0.015))
+	//debugMetrics.GCStats.PauseQuantiles = NewHistogram(NewExpDecaySample(1028, 0.015))
+	debugMetrics.GCStats.PauseTotal = NewGauge()
+	debugMetrics.ReadGCStats = NewTimer()
+
+	r.Register("debug.GCStats.LastGC", debugMetrics.GCStats.LastGC)
+	r.Register("debug.GCStats.NumGC", debugMetrics.GCStats.NumGC)
+	r.Register("debug.GCStats.Pause", debugMetrics.GCStats.Pause)
+	//r.Register("debug.GCStats.PauseQuantiles", debugMetrics.GCStats.PauseQuantiles)
+	r.Register("debug.GCStats.PauseTotal", debugMetrics.GCStats.PauseTotal)
+	r.Register("debug.ReadGCStats", debugMetrics.ReadGCStats)
+}
+
+// Allocate an initial slice for gcStats.Pause to avoid allocations during
+// normal operation.
+func init() {
+	gcStats.Pause = make([]time.Duration, 11)
+}
@@ -0,0 +1,118 @@
+package metrics
+
+import (
+	"math"
+	"sync"
+	"sync/atomic"
+)
+
+// EWMAs continuously calculate an exponentially-weighted moving average
+// based on an outside source of clock ticks.
+type EWMA interface {
+	Rate() float64
+	Snapshot() EWMA
+	Tick()
+	Update(int64)
+}
+
+// NewEWMA constructs a new EWMA with the given alpha.
+func NewEWMA(alpha float64) EWMA {
+	if UseNilMetrics {
+		return NilEWMA{}
+	}
+	return &StandardEWMA{alpha: alpha}
+}
+
+// NewEWMA1 constructs a new EWMA for a one-minute moving average.
+func NewEWMA1() EWMA {
+	return NewEWMA(1 - math.Exp(-5.0/60.0/1))
+}
+
+// NewEWMA5 constructs a new EWMA for a five-minute moving average.
+func NewEWMA5() EWMA {
+	return NewEWMA(1 - math.Exp(-5.0/60.0/5))
+}
+
+// NewEWMA15 constructs a new EWMA for a fifteen-minute moving average.
+func NewEWMA15() EWMA {
+	return NewEWMA(1 - math.Exp(-5.0/60.0/15))
+}
+
+// EWMASnapshot is a read-only copy of another EWMA.
+type EWMASnapshot float64
+
+// Rate returns the rate of events per second at the time the snapshot was
+// taken.
+func (a EWMASnapshot) Rate() float64 { return float64(a) }
+
+// Snapshot returns the snapshot.
+func (a EWMASnapshot) Snapshot() EWMA { return a }
+
+// Tick panics.
+func (EWMASnapshot) Tick() {
+	panic("Tick called on an EWMASnapshot")
+}
+
+// Update panics.
+func (EWMASnapshot) Update(int64) {
+	panic("Update called on an EWMASnapshot")
+}
+
+// NilEWMA is a no-op EWMA.
+type NilEWMA struct{}
+
+// Rate is a no-op.
+func (NilEWMA) Rate() float64 { return 0.0 }
+
+// Snapshot is a no-op.
+func (NilEWMA) Snapshot() EWMA { return NilEWMA{} }
+
+// Tick is a no-op.
+func (NilEWMA) Tick() {}
+
+// Update is a no-op.
+func (NilEWMA) Update(n int64) {}
+
+// StandardEWMA is the standard implementation of an EWMA and tracks the number
+// of uncounted events and processes them on each tick.  It uses the
+// sync/atomic package to manage uncounted events.
+type StandardEWMA struct {
+	uncounted int64 // /!\ this should be the first member to ensure 64-bit alignment
+	alpha     float64
+	rate      float64
+	init      bool
+	mutex     sync.Mutex
+}
+
+// Rate returns the moving average rate of events per second.
+func (a *StandardEWMA) Rate() float64 {
+	a.mutex.Lock()
+	defer a.mutex.Unlock()
+	return a.rate * float64(1e9)
+}
+
+// Snapshot returns a read-only copy of the EWMA.
+func (a *StandardEWMA) Snapshot() EWMA {
+	return EWMASnapshot(a.Rate())
+}
+
+// Tick ticks the clock to update the moving average.  It assumes it is called
+// every five seconds.
+func (a *StandardEWMA) Tick() {
+	count := atomic.LoadInt64(&a.uncounted)
+	atomic.AddInt64(&a.uncounted, -count)
+	instantRate := float64(count) / float64(5e9)
+	a.mutex.Lock()
+	defer a.mutex.Unlock()
+	if a.init {
+		a.rate += a.alpha * (instantRate - a.rate)
+	} else {
+		a.init = true
+		a.rate = instantRate
+	}
+}
+
+// Update adds n uncounted events.
+func (a *StandardEWMA) Update(n int64) {
+	atomic.AddInt64(&a.uncounted, n)
+}
@@ -0,0 +1,84 @@
+package metrics
+
+import "sync/atomic"
+
+// Gauges hold an int64 value that can be set arbitrarily.
+type Gauge interface {
+	Snapshot() Gauge
+	Update(int64)
+	Value() int64
+}
+
+// GetOrRegisterGauge returns an existing Gauge or constructs and registers a
+// new StandardGauge.
+func GetOrRegisterGauge(name string, r Registry) Gauge {
+	if nil == r {
+		r = DefaultRegistry
+	}
+	return r.GetOrRegister(name, NewGauge).(Gauge)
+}
+
+// NewGauge constructs a new StandardGauge.
+func NewGauge() Gauge {
+	if UseNilMetrics {
+		return NilGauge{}
+	}
+	return &StandardGauge{0}
+}
+
+// NewRegisteredGauge constructs and registers a new StandardGauge.
+func NewRegisteredGauge(name string, r Registry) Gauge {
+	c := NewGauge()
+	if nil == r {
+		r = DefaultRegistry
+	}
+	r.Register(name, c)
+	return c
+}
+
+// GaugeSnapshot is a read-only copy of another Gauge.
+type GaugeSnapshot int64
+
+// Snapshot returns the snapshot.
+func (g GaugeSnapshot) Snapshot() Gauge { return g }
+
+// Update panics.
+func (GaugeSnapshot) Update(int64) {
+	panic("Update called on a GaugeSnapshot")
+}
+
+// Value returns the value at the time the snapshot was taken.
+func (g GaugeSnapshot) Value() int64 { return int64(g) }
+
+// NilGauge is a no-op Gauge.
+type NilGauge struct{}
+
+// Snapshot is a no-op.
+func (NilGauge) Snapshot() Gauge { return NilGauge{} }
+
+// Update is a no-op.
+func (NilGauge) Update(v int64) {}
+
+// Value is a no-op.
+func (NilGauge) Value() int64 { return 0 }
+
+// StandardGauge is the standard implementation of a Gauge and uses the
+// sync/atomic package to manage a single int64 value.
+type StandardGauge struct {
+	value int64
+}
+
+// Snapshot returns a read-only copy of the gauge.
+func (g *StandardGauge) Snapshot() Gauge {
+	return GaugeSnapshot(g.Value())
+}
+
+// Update updates the gauge's value.
+func (g *StandardGauge) Update(v int64) {
+	atomic.StoreInt64(&g.value, v)
+}
+
+// Value returns the gauge's current value.
+func (g *StandardGauge) Value() int64 {
+	return atomic.LoadInt64(&g.value)
+}
@@ -0,0 +1,91 @@
+package metrics
+
+import "sync"
+
+// GaugeFloat64s hold a float64 value that can be set arbitrarily.
+type GaugeFloat64 interface {
+	Snapshot() GaugeFloat64
+	Update(float64)
+	Value() float64
+}
+
+// GetOrRegisterGaugeFloat64 returns an existing GaugeFloat64 or constructs and registers a
+// new StandardGaugeFloat64.
+func GetOrRegisterGaugeFloat64(name string, r Registry) GaugeFloat64 {
+	if nil == r {
+		r = DefaultRegistry
+	}
+	return r.GetOrRegister(name, NewGaugeFloat64()).(GaugeFloat64)
+}
+
+// NewGaugeFloat64 constructs a new StandardGaugeFloat64.
+func NewGaugeFloat64() GaugeFloat64 {
+	if UseNilMetrics {
+		return NilGaugeFloat64{}
+	}
+	return &StandardGaugeFloat64{
+		value: 0.0,
+	}
+}
+
+// NewRegisteredGaugeFloat64 constructs and registers a new StandardGaugeFloat64.
+func NewRegisteredGaugeFloat64(name string, r Registry) GaugeFloat64 {
+	c := NewGaugeFloat64()
+	if nil == r {
+		r = DefaultRegistry
+	}
+	r.Register(name, c)
+	return c
+}
+
+// GaugeFloat64Snapshot is a read-only copy of another GaugeFloat64.
+type GaugeFloat64Snapshot float64
+
+// Snapshot returns the snapshot.
+func (g GaugeFloat64Snapshot) Snapshot() GaugeFloat64 { return g }
+
+// Update panics.
+func (GaugeFloat64Snapshot) Update(float64) {
+	panic("Update called on a GaugeFloat64Snapshot")
+}
+
+// Value returns the value at the time the snapshot was taken.
+func (g GaugeFloat64Snapshot) Value() float64 { return float64(g) }
+
+// NilGauge is a no-op Gauge.
+type NilGaugeFloat64 struct{}
+
+// Snapshot is a no-op.
+func (NilGaugeFloat64) Snapshot() GaugeFloat64 { return NilGaugeFloat64{} }
+
+// Update is a no-op.
+func (NilGaugeFloat64) Update(v float64) {}
+
+// Value is a no-op.
+func (NilGaugeFloat64) Value() float64 { return 0.0 }
+
+// StandardGaugeFloat64 is the standard implementation of a GaugeFloat64 and uses
+// sync.Mutex to manage a single float64 value.
+type StandardGaugeFloat64 struct {
+	mutex sync.Mutex
+	value float64
+}
+
+// Snapshot returns a read-only copy of the gauge.
+func (g *StandardGaugeFloat64) Snapshot() GaugeFloat64 {
+	return GaugeFloat64Snapshot(g.Value())
+}
+
+// Update updates the gauge's value.
+func (g *StandardGaugeFloat64) Update(v float64) {
+	g.mutex.Lock()
+	defer g.mutex.Unlock()
+	g.value = v
+}
+
+// Value returns the gauge's current value.
+func (g *StandardGaugeFloat64) Value() float64 {
+	g.mutex.Lock()
+	defer g.mutex.Unlock()
+	return g.value
+}
@@ -0,0 +1,113 @@
+package metrics
+
+import (
+	"bufio"
+	"fmt"
+	"log"
+	"net"
+	"strconv"
+	"strings"
+	"time"
+)
+
+// GraphiteConfig provides a container with configuration parameters for
+// the Graphite exporter
+type GraphiteConfig struct {
+	Addr          *net.TCPAddr  // Network address to connect to
+	Registry      Registry      // Registry to be exported
+	FlushInterval time.Duration // Flush interval
+	DurationUnit  time.Duration // Time conversion unit for durations
+	Prefix        string        // Prefix to be prepended to metric names
+	Percentiles   []float64     // Percentiles to export from timers and histograms
+}
+
+// Graphite is a blocking exporter function which reports metrics in r
+// to a graphite server located at addr, flushing them every d duration
+// and prepending metric names with prefix.
+func Graphite(r Registry, d time.Duration, prefix string, addr *net.TCPAddr) {
+	GraphiteWithConfig(GraphiteConfig{
+		Addr:          addr,
+		Registry:      r,
+		FlushInterval: d,
+		DurationUnit:  time.Nanosecond,
+		Prefix:        prefix,
+		Percentiles:   []float64{0.5, 0.75, 0.95, 0.99, 0.999},
+	})
+}
+
+// GraphiteWithConfig is a blocking exporter function just like Graphite,
+// but it takes a GraphiteConfig instead.
+func GraphiteWithConfig(c GraphiteConfig) {
+	log.Printf("WARNING: This go-metrics client has been DEPRECATED! It has been moved to https://github.com/cyberdelia/go-metrics-graphite and will be removed from rcrowley/go-metrics on August 12th 2015")
+	for _ = range time.Tick(c.FlushInterval) {
+		if err := graphite(&c); nil != err {
+			log.Println(err)
+		}
+	}
+}
+
+// GraphiteOnce performs a single submission to Graphite, returning a
+// non-nil error on failed connections. This can be used in a loop
+// similar to GraphiteWithConfig for custom error handling.
+func GraphiteOnce(c GraphiteConfig) error {
+	log.Printf("WARNING: This go-metrics client has been DEPRECATED! It has been moved to https://github.com/cyberdelia/go-metrics-graphite and will be removed from rcrowley/go-metrics on August 12th 2015")
+	return graphite(&c)
+}
+
+func graphite(c *GraphiteConfig) error {
+	now := time.Now().Unix()
+	du := float64(c.DurationUnit)
+	conn, err := net.DialTCP("tcp", nil, c.Addr)
+	if nil != err {
+		return err
+	}
+	defer conn.Close()
+	w := bufio.NewWriter(conn)
+	c.Registry.Each(func(name string, i interface{}) {
+		switch metric := i.(type) {
+		case Counter:
+			fmt.Fprintf(w, "%s.%s.count %d %d\n", c.Prefix, name, metric.Count(), now)
+		case Gauge:
+			fmt.Fprintf(w, "%s.%s.value %d %d\n", c.Prefix, name, metric.Value(), now)
+		case GaugeFloat64:
+			fmt.Fprintf(w, "%s.%s.value %f %d\n", c.Prefix, name, metric.Value(), now)
+		case Histogram:
+			h := metric.Snapshot()
+			ps := h.Percentiles(c.Percentiles)
+			fmt.Fprintf(w, "%s.%s.count %d %d\n", c.Prefix, name, h.Count(), now)
+			fmt.Fprintf(w, "%s.%s.min %d %d\n", c.Prefix, name, h.Min(), now)
+			fmt.Fprintf(w, "%s.%s.max %d %d\n", c.Prefix, name, h.Max(), now)
+			fmt.Fprintf(w, "%s.%s.mean %.2f %d\n", c.Prefix, name, h.Mean(), now)
+			fmt.Fprintf(w, "%s.%s.std-dev %.2f %d\n", c.Prefix, name, h.StdDev(), now)
+			for psIdx, psKey := range c.Percentiles {
+				key := strings.Replace(strconv.FormatFloat(psKey*100.0, 'f', -1, 64), ".", "", 1)
+				fmt.Fprintf(w, "%s.%s.%s-percentile %.2f %d\n", c.Prefix, name, key, ps[psIdx], now)
+			}
+		case Meter:
+			m := metric.Snapshot()
+			fmt.Fprintf(w, "%s.%s.count %d %d\n", c.Prefix, name, m.Count(), now)
+			fmt.Fprintf(w, "%s.%s.one-minute %.2f %d\n", c.Prefix, name, m.Rate1(), now)
+			fmt.Fprintf(w, "%s.%s.five-minute %.2f %d\n", c.Prefix, name, m.Rate5(), now)
+			fmt.Fprintf(w, "%s.%s.fifteen-minute %.2f %d\n", c.Prefix, name, m.Rate15(), now)
+			fmt.Fprintf(w, "%s.%s.mean %.2f %d\n", c.Prefix, name, m.RateMean(), now)
+		case Timer:
+			t := metric.Snapshot()
+			ps := t.Percentiles(c.Percentiles)
+			fmt.Fprintf(w, "%s.%s.count %d %d\n", c.Prefix, name, t.Count(), now)
+			fmt.Fprintf(w, "%s.%s.min %d %d\n", c.Prefix, name, t.Min()/int64(du), now)
+			fmt.Fprintf(w, "%s.%s.max %d %d\n", c.Prefix, name, t.Max()/int64(du), now)
+			fmt.Fprintf(w, "%s.%s.mean %.2f %d\n", c.Prefix, name, t.Mean()/du, now)
+			fmt.Fprintf(w, "%s.%s.std-dev %.2f %d\n", c.Prefix, name, t.StdDev()/du, now)
+			for psIdx, psKey := range c.Percentiles {
+				key := strings.Replace(strconv.FormatFloat(psKey*100.0, 'f', -1, 64), ".", "", 1)
+				fmt.Fprintf(w, "%s.%s.%s-percentile %.2f %d\n", c.Prefix, name, key, ps[psIdx], now)
+			}
+			fmt.Fprintf(w, "%s.%s.one-minute %.2f %d\n", c.Prefix, name, t.Rate1(), now)
+			fmt.Fprintf(w, "%s.%s.five-minute %.2f %d\n", c.Prefix, name, t.Rate5(), now)
+			fmt.Fprintf(w, "%s.%s.fifteen-minute %.2f %d\n", c.Prefix, name, t.Rate15(), now)
+			fmt.Fprintf(w, "%s.%s.mean-rate %.2f %d\n", c.Prefix, name, t.RateMean(), now)
+		}
+		w.Flush()
+	})
+	return nil
+}
@@ -0,0 +1,61 @@
+package metrics
+
+// Healthchecks hold an error value describing an arbitrary up/down status.
+type Healthcheck interface {
+	Check()
+	Error() error
+	Healthy()
+	Unhealthy(error)
+}
+
+// NewHealthcheck constructs a new Healthcheck which will use the given
+// function to update its status.
+func NewHealthcheck(f func(Healthcheck)) Healthcheck {
+	if UseNilMetrics {
+		return NilHealthcheck{}
+	}
+	return &StandardHealthcheck{nil, f}
+}
+
+// NilHealthcheck is a no-op.
+type NilHealthcheck struct{}
+
+// Check is a no-op.
+func (NilHealthcheck) Check() {}
+
+// Error is a no-op.
+func (NilHealthcheck) Error() error { return nil }
+
+// Healthy is a no-op.
+func (NilHealthcheck) Healthy() {}
+
+// Unhealthy is a no-op.
+func (NilHealthcheck) Unhealthy(error) {}
+
+// StandardHealthcheck is the standard implementation of a Healthcheck and
+// stores the status and a function to call to update the status.
+type StandardHealthcheck struct {
+	err error
+	f   func(Healthcheck)
+}
+
+// Check runs the healthcheck function to update the healthcheck's status.
+func (h *StandardHealthcheck) Check() {
+	h.f(h)
+}
+
+// Error returns the healthcheck's status, which will be nil if it is healthy.
+func (h *StandardHealthcheck) Error() error {
+	return h.err
+}
+
+// Healthy marks the healthcheck as healthy.
+func (h *StandardHealthcheck) Healthy() {
+	h.err = nil
+}
+
+// Unhealthy marks the healthcheck as unhealthy.  The error is stored and
+// may be retrieved by the Error method.
+func (h *StandardHealthcheck) Unhealthy(err error) {
+	h.err = err
+}
@@ -0,0 +1,202 @@
+package metrics
+
+// Histograms calculate distribution statistics from a series of int64 values.
+type Histogram interface {
+	Clear()
+	Count() int64
+	Max() int64
+	Mean() float64
+	Min() int64
+	Percentile(float64) float64
+	Percentiles([]float64) []float64
+	Sample() Sample
+	Snapshot() Histogram
+	StdDev() float64
+	Sum() int64
+	Update(int64)
+	Variance() float64
+}
+
+// GetOrRegisterHistogram returns an existing Histogram or constructs and
+// registers a new StandardHistogram.
+func GetOrRegisterHistogram(name string, r Registry, s Sample) Histogram {
+	if nil == r {
+		r = DefaultRegistry
+	}
+	return r.GetOrRegister(name, func() Histogram { return NewHistogram(s) }).(Histogram)
+}
+
+// NewHistogram constructs a new StandardHistogram from a Sample.
+func NewHistogram(s Sample) Histogram {
+	if UseNilMetrics {
+		return NilHistogram{}
+	}
+	return &StandardHistogram{sample: s}
+}
+
+// NewRegisteredHistogram constructs and registers a new StandardHistogram from
+// a Sample.
+func NewRegisteredHistogram(name string, r Registry, s Sample) Histogram {
+	c := NewHistogram(s)
+	if nil == r {
+		r = DefaultRegistry
+	}
+	r.Register(name, c)
+	return c
+}
+
+// HistogramSnapshot is a read-only copy of another Histogram.
+type HistogramSnapshot struct {
+	sample *SampleSnapshot
+}
+
+// Clear panics.
+func (*HistogramSnapshot) Clear() {
+	panic("Clear called on a HistogramSnapshot")
+}
+
+// Count returns the number of samples recorded at the time the snapshot was
+// taken.
+func (h *HistogramSnapshot) Count() int64 { return h.sample.Count() }
+
+// Max returns the maximum value in the sample at the time the snapshot was
+// taken.
+func (h *HistogramSnapshot) Max() int64 { return h.sample.Max() }
+
+// Mean returns the mean of the values in the sample at the time the snapshot
+// was taken.
+func (h *HistogramSnapshot) Mean() float64 { return h.sample.Mean() }
+
+// Min returns the minimum value in the sample at the time the snapshot was
+// taken.
+func (h *HistogramSnapshot) Min() int64 { return h.sample.Min() }
+
+// Percentile returns an arbitrary percentile of values in the sample at the
+// time the snapshot was taken.
+func (h *HistogramSnapshot) Percentile(p float64) float64 {
+	return h.sample.Percentile(p)
+}
+
+// Percentiles returns a slice of arbitrary percentiles of values in the sample
+// at the time the snapshot was taken.
+func (h *HistogramSnapshot) Percentiles(ps []float64) []float64 {
+	return h.sample.Percentiles(ps)
+}
+
+// Sample returns the Sample underlying the histogram.
+func (h *HistogramSnapshot) Sample() Sample { return h.sample }
+
+// Snapshot returns the snapshot.
+func (h *HistogramSnapshot) Snapshot() Histogram { return h }
+
+// StdDev returns the standard deviation of the values in the sample at the
+// time the snapshot was taken.
+func (h *HistogramSnapshot) StdDev() float64 { return h.sample.StdDev() }
+
+// Sum returns the sum in the sample at the time the snapshot was taken.
+func (h *HistogramSnapshot) Sum() int64 { return h.sample.Sum() }
+
+// Update panics.
+func (*HistogramSnapshot) Update(int64) {
+	panic("Update called on a HistogramSnapshot")
+}
+
+// Variance returns the variance of inputs at the time the snapshot was taken.
+func (h *HistogramSnapshot) Variance() float64 { return h.sample.Variance() }
+
+// NilHistogram is a no-op Histogram.
+type NilHistogram struct{}
+
+// Clear is a no-op.
+func (NilHistogram) Clear() {}
+
+// Count is a no-op.
+func (NilHistogram) Count() int64 { return 0 }
+
+// Max is a no-op.
+func (NilHistogram) Max() int64 { return 0 }
+
+// Mean is a no-op.
+func (NilHistogram) Mean() float64 { return 0.0 }
+
+// Min is a no-op.
+func (NilHistogram) Min() int64 { return 0 }
+
+// Percentile is a no-op.
+func (NilHistogram) Percentile(p float64) float64 { return 0.0 }
+
+// Percentiles is a no-op.
+func (NilHistogram) Percentiles(ps []float64) []float64 {
+	return make([]float64, len(ps))
+}
+
+// Sample is a no-op.
+func (NilHistogram) Sample() Sample { return NilSample{} }
+
+// Snapshot is a no-op.
+func (NilHistogram) Snapshot() Histogram { return NilHistogram{} }
+
+// StdDev is a no-op.
+func (NilHistogram) StdDev() float64 { return 0.0 }
+
+// Sum is a no-op.
+func (NilHistogram) Sum() int64 { return 0 }
+
+// Update is a no-op.
+func (NilHistogram) Update(v int64) {}
+
+// Variance is a no-op.
+func (NilHistogram) Variance() float64 { return 0.0 }
+
+// StandardHistogram is the standard implementation of a Histogram and uses a
+// Sample to bound its memory use.
+type StandardHistogram struct {
+	sample Sample
+}
+
+// Clear clears the histogram and its sample.
+func (h *StandardHistogram) Clear() { h.sample.Clear() }
+
+// Count returns the number of samples recorded since the histogram was last
+// cleared.
+func (h *StandardHistogram) Count() int64 { return h.sample.Count() }
+
+// Max returns the maximum value in the sample.
+func (h *StandardHistogram) Max() int64 { return h.sample.Max() }
+
+// Mean returns the mean of the values in the sample.
+func (h *StandardHistogram) Mean() float64 { return h.sample.Mean() }
+
+// Min returns the minimum value in the sample.
+func (h *StandardHistogram) Min() int64 { return h.sample.Min() }
+
+// Percentile returns an arbitrary percentile of the values in the sample.
+func (h *StandardHistogram) Percentile(p float64) float64 {
+	return h.sample.Percentile(p)
+}
+
+// Percentiles returns a slice of arbitrary percentiles of the values in the
+// sample.
+func (h *StandardHistogram) Percentiles(ps []float64) []float64 {
+	return h.sample.Percentiles(ps)
+}
+
+// Sample returns the Sample underlying the histogram.
+func (h *StandardHistogram) Sample() Sample { return h.sample }
+
+// Snapshot returns a read-only copy of the histogram.
+func (h *StandardHistogram) Snapshot() Histogram {
+	return &HistogramSnapshot{sample: h.sample.Snapshot().(*SampleSnapshot)}
+}
+
+// StdDev returns the standard deviation of the values in the sample.
+func (h *StandardHistogram) StdDev() float64 { return h.sample.StdDev() }
+
+// Sum returns the sum in the sample.
+func (h *StandardHistogram) Sum() int64 { return h.sample.Sum() }
+
+// Update samples a new value.
+func (h *StandardHistogram) Update(v int64) { h.sample.Update(v) }
+
+// Variance returns the variance of the values in the sample.
+func (h *StandardHistogram) Variance() float64 { return h.sample.Variance() }
@@ -0,0 +1,83 @@
+package metrics
+
+import (
+	"encoding/json"
+	"io"
+	"time"
+)
+
+// MarshalJSON returns a byte slice containing a JSON representation of all
+// the metrics in the Registry.
+func (r *StandardRegistry) MarshalJSON() ([]byte, error) {
+	data := make(map[string]map[string]interface{})
+	r.Each(func(name string, i interface{}) {
+		values := make(map[string]interface{})
+		switch metric := i.(type) {
+		case Counter:
+			values["count"] = metric.Count()
+		case Gauge:
+			values["value"] = metric.Value()
+		case GaugeFloat64:
+			values["value"] = metric.Value()
+		case Healthcheck:
+			values["error"] = nil
+			metric.Check()
+			if err := metric.Error(); nil != err {
+				values["error"] = metric.Error().Error()
+			}
+		case Histogram:
+			h := metric.Snapshot()
+			ps := h.Percentiles([]float64{0.5, 0.75, 0.95, 0.99, 0.999})
+			values["count"] = h.Count()
+			values["min"] = h.Min()
+			values["max"] = h.Max()
+			values["mean"] = h.Mean()
+			values["stddev"] = h.StdDev()
+			values["median"] = ps[0]
+			values["75%"] = ps[1]
+			values["95%"] = ps[2]
+			values["99%"] = ps[3]
+			values["99.9%"] = ps[4]
+		case Meter:
+			m := metric.Snapshot()
+			values["count"] = m.Count()
+			values["1m.rate"] = m.Rate1()
+			values["5m.rate"] = m.Rate5()
+			values["15m.rate"] = m.Rate15()
+			values["mean.rate"] = m.RateMean()
+		case Timer:
+			t := metric.Snapshot()
+			ps := t.Percentiles([]float64{0.5, 0.75, 0.95, 0.99, 0.999})
+			values["count"] = t.Count()
+			values["min"] = t.Min()
+			values["max"] = t.Max()
+			values["mean"] = t.Mean()
+			values["stddev"] = t.StdDev()
+			values["median"] = ps[0]
+			values["75%"] = ps[1]
+			values["95%"] = ps[2]
+			values["99%"] = ps[3]
+			values["99.9%"] = ps[4]
+			values["1m.rate"] = t.Rate1()
+			values["5m.rate"] = t.Rate5()
+			values["15m.rate"] = t.Rate15()
+			values["mean.rate"] = t.RateMean()
+		}
+		data[name] = values
+	})
+	return json.Marshal(data)
+}
+
+// WriteJSON writes metrics from the given registry  periodically to the
+// specified io.Writer as JSON.
+func WriteJSON(r Registry, d time.Duration, w io.Writer) {
+	for _ = range time.Tick(d) {
+		WriteJSONOnce(r, w)
+	}
+}
+
+// WriteJSONOnce writes metrics from the given registry to the specified
+// io.Writer as JSON.
+func WriteJSONOnce(r Registry, w io.Writer) {
+	json.NewEncoder(w).Encode(r)
+}
@@ -0,0 +1,102 @@
+package librato
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"io/ioutil"
+	"net/http"
+)
+
+const Operations = "operations"
+const OperationsShort = "ops"
+
+type LibratoClient struct {
+	Email, Token string
+}
+
+// property strings
+const (
+	// display attributes
+	Color             = "color"
+	DisplayMax        = "display_max"
+	DisplayMin        = "display_min"
+	DisplayUnitsLong  = "display_units_long"
+	DisplayUnitsShort = "display_units_short"
+	DisplayStacked    = "display_stacked"
+	DisplayTransform  = "display_transform"
+	// special gauge display attributes
+	SummarizeFunction = "summarize_function"
+	Aggregate         = "aggregate"
+
+	// metric keys
+	Name        = "name"
+	Period      = "period"
+	Description = "description"
+	DisplayName = "display_name"
+	Attributes  = "attributes"
+
+	// measurement keys
+	MeasureTime = "measure_time"
+	Source      = "source"
+	Value       = "value"
+
+	// special gauge keys
+	Count      = "count"
+	Sum        = "sum"
+	Max        = "max"
+	Min        = "min"
+	SumSquares = "sum_squares"
+
+	// batch keys
+	Counters = "counters"
+	Gauges   = "gauges"
+
+	MetricsPostUrl = "https://metrics-api.librato.com/v1/metrics"
+)
+
+type Measurement map[string]interface{}
+type Metric map[string]interface{}
+
+type Batch struct {
+	Gauges      []Measurement `json:"gauges,omitempty"`
+	Counters    []Measurement `json:"counters,omitempty"`
+	MeasureTime int64         `json:"measure_time"`
+	Source      string        `json:"source"`
+}
+
+func (self *LibratoClient) PostMetrics(batch Batch) (err error) {
+	var (
+		js   []byte
+		req  *http.Request
+		resp *http.Response
+	)
+
+	if len(batch.Counters) == 0 && len(batch.Gauges) == 0 {
+		return nil
+	}
+
+	if js, err = json.Marshal(batch); err != nil {
+		return
+	}
+
+	if req, err = http.NewRequest("POST", MetricsPostUrl, bytes.NewBuffer(js)); err != nil {
+		return
+	}
+
+	req.Header.Set("Content-Type", "application/json")
+	req.SetBasicAuth(self.Email, self.Token)
+
+	if resp, err = http.DefaultClient.Do(req); err != nil {
+		return
+	}
+
+	if resp.StatusCode != http.StatusOK {
+		var body []byte
+		if body, err = ioutil.ReadAll(resp.Body); err != nil {
+			body = []byte(fmt.Sprintf("(could not fetch response body for error: %s)", err))
+		}
+		err = fmt.Errorf("Unable to post to Librato: %d %s %s", resp.StatusCode, resp.Status, string(body))
+	}
+	return
+}
@@ -0,0 +1,231 @@
+package librato
+
+import (
+	"fmt"
+	"log"
+	"math"
+	"regexp"
+	"time"
+
+	"github.com/rcrowley/go-metrics"
+)
+
+// a regexp for extracting the unit from time.Duration.String
+var unitRegexp = regexp.MustCompile("[^\\d]+$")
+
+// a helper that turns a time.Duration into librato display attributes for timer metrics
+func translateTimerAttributes(d time.Duration) (attrs map[string]interface{}) {
+	attrs = make(map[string]interface{})
+	attrs[DisplayTransform] = fmt.Sprintf("x/%d", int64(d))
+	attrs[DisplayUnitsShort] = string(unitRegexp.Find([]byte(d.String())))
+	return
+}
+
+type Reporter struct {
+	Email, Token    string
+	Source          string
+	Interval        time.Duration
+	Registry        metrics.Registry
+	Percentiles     []float64              // percentiles to report on histogram metrics
+	TimerAttributes map[string]interface{} // units in which timers will be displayed
+	intervalSec     int64
+}
+
+func NewReporter(r metrics.Registry, d time.Duration, e string, t string, s string, p []float64, u time.Duration) *Reporter {
+	return &Reporter{e, t, s, d, r, p, translateTimerAttributes(u), int64(d / time.Second)}
+}
+
+func Librato(r metrics.Registry, d time.Duration, e string, t string, s string, p []float64, u time.Duration) {
+	NewReporter(r, d, e, t, s, p, u).Run()
+}
+
+func (self *Reporter) Run() {
+	log.Printf("WARNING: This client has been DEPRECATED! It has been moved to https://github.com/mihasya/go-metrics-librato and will be removed from rcrowley/go-metrics on August 5th 2015")
+	ticker := time.Tick(self.Interval)
+	metricsApi := &LibratoClient{self.Email, self.Token}
+	for now := range ticker {
+		var metrics Batch
+		var err error
+		if metrics, err = self.BuildRequest(now, self.Registry); err != nil {
+			log.Printf("ERROR constructing librato request body %s", err)
+			continue
+		}
+		if err := metricsApi.PostMetrics(metrics); err != nil {
+			log.Printf("ERROR sending metrics to librato %s", err)
+			continue
+		}
+	}
+}
+
+// calculate sum of squares from data provided by metrics.Histogram
+// see http://en.wikipedia.org/wiki/Standard_deviation#Rapid_calculation_methods
+func sumSquares(s metrics.Sample) float64 {
+	count := float64(s.Count())
+	sumSquared := math.Pow(count*s.Mean(), 2)
+	sumSquares := math.Pow(count*s.StdDev(), 2) + sumSquared/count
+	if math.IsNaN(sumSquares) {
+		return 0.0
+	}
+	return sumSquares
+}
+func sumSquaresTimer(t metrics.Timer) float64 {
+	count := float64(t.Count())
+	sumSquared := math.Pow(count*t.Mean(), 2)
+	sumSquares := math.Pow(count*t.StdDev(), 2) + sumSquared/count
+	if math.IsNaN(sumSquares) {
+		return 0.0
+	}
+	return sumSquares
+}
+
+func (self *Reporter) BuildRequest(now time.Time, r metrics.Registry) (snapshot Batch, err error) {
+	snapshot = Batch{
+		// coerce timestamps to a stepping fn so that they line up in Librato graphs
+		MeasureTime: (now.Unix() / self.intervalSec) * self.intervalSec,
+		Source:      self.Source,
+	}
+	snapshot.Gauges = make([]Measurement, 0)
+	snapshot.Counters = make([]Measurement, 0)
+	histogramGaugeCount := 1 + len(self.Percentiles)
+	r.Each(func(name string, metric interface{}) {
+		measurement := Measurement{}
+		measurement[Period] = self.Interval.Seconds()
+		switch m := metric.(type) {
+		case metrics.Counter:
+			if m.Count() > 0 {
+				measurement[Name] = fmt.Sprintf("%s.%s", name, "count")
+				measurement[Value] = float64(m.Count())
+				measurement[Attributes] = map[string]interface{}{
+					DisplayUnitsLong:  Operations,
+					DisplayUnitsShort: OperationsShort,
+					DisplayMin:        "0",
+				}
+				snapshot.Counters = append(snapshot.Counters, measurement)
+			}
+		case metrics.Gauge:
+			measurement[Name] = name
+			measurement[Value] = float64(m.Value())
+			snapshot.Gauges = append(snapshot.Gauges, measurement)
+		case metrics.GaugeFloat64:
+			measurement[Name] = name
+			measurement[Value] = float64(m.Value())
+			snapshot.Gauges = append(snapshot.Gauges, measurement)
+		case metrics.Histogram:
+			if m.Count() > 0 {
+				gauges := make([]Measurement, histogramGaugeCount, histogramGaugeCount)
+				s := m.Sample()
+				measurement[Name] = fmt.Sprintf("%s.%s", name, "hist")
+				measurement[Count] = uint64(s.Count())
+				measurement[Max] = float64(s.Max())
+				measurement[Min] = float64(s.Min())
+				measurement[Sum] = float64(s.Sum())
+				measurement[SumSquares] = sumSquares(s)
+				gauges[0] = measurement
+				for i, p := range self.Percentiles {
+					gauges[i+1] = Measurement{
+						Name:   fmt.Sprintf("%s.%.2f", measurement[Name], p),
+						Value:  s.Percentile(p),
+						Period: measurement[Period],
+					}
+				}
+				snapshot.Gauges = append(snapshot.Gauges, gauges...)
+			}
+		case metrics.Meter:
+			measurement[Name] = name
+			measurement[Value] = float64(m.Count())
+			snapshot.Counters = append(snapshot.Counters, measurement)
+			snapshot.Gauges = append(snapshot.Gauges,
+				Measurement{
+					Name:   fmt.Sprintf("%s.%s", name, "1min"),
+					Value:  m.Rate1(),
+					Period: int64(self.Interval.Seconds()),
+					Attributes: map[string]interface{}{
+						DisplayUnitsLong:  Operations,
+						DisplayUnitsShort: OperationsShort,
+						DisplayMin:        "0",
+					},
+				},
+				Measurement{
+					Name:   fmt.Sprintf("%s.%s", name, "5min"),
+					Value:  m.Rate5(),
+					Period: int64(self.Interval.Seconds()),
+					Attributes: map[string]interface{}{
+						DisplayUnitsLong:  Operations,
+						DisplayUnitsShort: OperationsShort,
+						DisplayMin:        "0",
+					},
+				},
+				Measurement{
+					Name:   fmt.Sprintf("%s.%s", name, "15min"),
+					Value:  m.Rate15(),
+					Period: int64(self.Interval.Seconds()),
+					Attributes: map[string]interface{}{
+						DisplayUnitsLong:  Operations,
+						DisplayUnitsShort: OperationsShort,
+						DisplayMin:        "0",
+					},
+				},
+			)
+		case metrics.Timer:
+			measurement[Name] = name
+			measurement[Value] = float64(m.Count())
+			snapshot.Counters = append(snapshot.Counters, measurement)
+			if m.Count() > 0 {
+				libratoName := fmt.Sprintf("%s.%s", name, "timer.mean")
+				gauges := make([]Measurement, histogramGaugeCount, histogramGaugeCount)
+				gauges[0] = Measurement{
+					Name:       libratoName,
+					Count:      uint64(m.Count()),
+					Sum:        m.Mean() * float64(m.Count()),
+					Max:        float64(m.Max()),
+					Min:        float64(m.Min()),
+					SumSquares: sumSquaresTimer(m),
+					Period:     int64(self.Interval.Seconds()),
+					Attributes: self.TimerAttributes,
+				}
+				for i, p := range self.Percentiles {
+					gauges[i+1] = Measurement{
+						Name:       fmt.Sprintf("%s.timer.%2.0f", name, p*100),
+						Value:      m.Percentile(p),
+						Period:     int64(self.Interval.Seconds()),
+						Attributes: self.TimerAttributes,
+					}
+				}
+				snapshot.Gauges = append(snapshot.Gauges, gauges...)
+				snapshot.Gauges = append(snapshot.Gauges,
+					Measurement{
+						Name:   fmt.Sprintf("%s.%s", name, "rate.1min"),
+						Value:  m.Rate1(),
+						Period: int64(self.Interval.Seconds()),
+						Attributes: map[string]interface{}{
+							DisplayUnitsLong:  Operations,
+							DisplayUnitsShort: OperationsShort,
+							DisplayMin:        "0",
+						},
+					},
+					Measurement{
+						Name:   fmt.Sprintf("%s.%s", name, "rate.5min"),
+						Value:  m.Rate5(),
+						Period: int64(self.Interval.Seconds()),
+						Attributes: map[string]interface{}{
+							DisplayUnitsLong:  Operations,
+							DisplayUnitsShort: OperationsShort,
+							DisplayMin:        "0",
+						},
+					},
+					Measurement{
+						Name:   fmt.Sprintf("%s.%s", name, "rate.15min"),
+						Value:  m.Rate15(),
+						Period: int64(self.Interval.Seconds()),
+						Attributes: map[string]interface{}{
+							DisplayUnitsLong:  Operations,
+							DisplayUnitsShort: OperationsShort,
+							DisplayMin:        "0",
+						},
+					},
+				)
+			}
+		}
+	})
+	return
+}
@@ -0,0 +1,70 @@
+package metrics
+
+import (
+	"log"
+	"time"
+)
+
+// Output each metric in the given registry periodically using the given
+// logger.
+func Log(r Registry, d time.Duration, l *log.Logger) {
+	for _ = range time.Tick(d) {
+		r.Each(func(name string, i interface{}) {
+			switch metric := i.(type) {
+			case Counter:
+				l.Printf("counter %s\n", name)
+				l.Printf("  count:       %9d\n", metric.Count())
+			case Gauge:
+				l.Printf("gauge %s\n", name)
+				l.Printf("  value:       %9d\n", metric.Value())
+			case GaugeFloat64:
+				l.Printf("gauge %s\n", name)
+				l.Printf("  value:       %f\n", metric.Value())
+			case Healthcheck:
+				metric.Check()
+				l.Printf("healthcheck %s\n", name)
+				l.Printf("  error:       %v\n", metric.Error())
+			case Histogram:
+				h := metric.Snapshot()
+				ps := h.Percentiles([]float64{0.5, 0.75, 0.95, 0.99, 0.999})
+				l.Printf("histogram %s\n", name)
+				l.Printf("  count:       %9d\n", h.Count())
+				l.Printf("  min:         %9d\n", h.Min())
+				l.Printf("  max:         %9d\n", h.Max())
+				l.Printf("  mean:        %12.2f\n", h.Mean())
+				l.Printf("  stddev:      %12.2f\n", h.StdDev())
+				l.Printf("  median:      %12.2f\n", ps[0])
+				l.Printf("  75%%:         %12.2f\n", ps[1])
+				l.Printf("  95%%:         %12.2f\n", ps[2])
+				l.Printf("  99%%:         %12.2f\n", ps[3])
+				l.Printf("  99.9%%:       %12.2f\n", ps[4])
+			case Meter:
+				m := metric.Snapshot()
+				l.Printf("meter %s\n", name)
+				l.Printf("  count:       %9d\n", m.Count())
+				l.Printf("  1-min rate:  %12.2f\n", m.Rate1())
+				l.Printf("  5-min rate:  %12.2f\n", m.Rate5())
+				l.Printf("  15-min rate: %12.2f\n", m.Rate15())
+				l.Printf("  mean rate:   %12.2f\n", m.RateMean())
+			case Timer:
+				t := metric.Snapshot()
+				ps := t.Percentiles([]float64{0.5, 0.75, 0.95, 0.99, 0.999})
+				l.Printf("timer %s\n", name)
+				l.Printf("  count:       %9d\n", t.Count())
+				l.Printf("  min:         %9d\n", t.Min())
+				l.Printf("  max:         %9d\n", t.Max())
+				l.Printf("  mean:        %12.2f\n", t.Mean())
+				l.Printf("  stddev:      %12.2f\n", t.StdDev())
+				l.Printf("  median:      %12.2f\n", ps[0])
+				l.Printf("  75%%:         %12.2f\n", ps[1])
+				l.Printf("  95%%:         %12.2f\n", ps[2])
+				l.Printf("  99%%:         %12.2f\n", ps[3])
+				l.Printf("  99.9%%:       %12.2f\n", ps[4])
+				l.Printf("  1-min rate:  %12.2f\n", t.Rate1())
+				l.Printf("  5-min rate:  %12.2f\n", t.Rate5())
+				l.Printf("  15-min rate: %12.2f\n", t.Rate15())
+				l.Printf("  mean rate:   %12.2f\n", t.RateMean())
+			}
+		})
+	}
+}
@@ -0,0 +1,285 @@
+Memory usage
+============
+
+(Highly unscientific.)
+
+Command used to gather static memory usage:
+
+```sh
+grep ^Vm "/proc/$(ps fax | grep [m]etrics-bench | awk '{print $1}')/status"
+```
+
+Program used to gather baseline memory usage:
+
+```go
+package main
+
+import "time"
+
+func main() {
+	time.Sleep(600e9)
+}
+```
+
+Baseline
+--------
+
+```
+VmPeak:    42604 kB
+VmSize:    42604 kB
+VmLck:         0 kB
+VmHWM:      1120 kB
+VmRSS:      1120 kB
+VmData:    35460 kB
+VmStk:       136 kB
+VmExe:      1020 kB
+VmLib:      1848 kB
+VmPTE:        36 kB
+VmSwap:        0 kB
+```
+
+Program used to gather metric memory usage (with other metrics being similar):
+
+```go
+package main
+
+import (
+	"fmt"
+	"metrics"
+	"time"
+)
+
+func main() {
+	fmt.Sprintf("foo")
+	metrics.NewRegistry()
+	time.Sleep(600e9)
+}
+```
+
+1000 counters registered
+------------------------
+
+```
+VmPeak:    44016 kB
+VmSize:    44016 kB
+VmLck:         0 kB
+VmHWM:      1928 kB
+VmRSS:      1928 kB
+VmData:    36868 kB
+VmStk:       136 kB
+VmExe:      1024 kB
+VmLib:      1848 kB
+VmPTE:        40 kB
+VmSwap:        0 kB
+```
+
+**1.412 kB virtual, TODO 0.808 kB resident per counter.**
+
+100000 counters registered
+--------------------------
+
+```
+VmPeak:    55024 kB
+VmSize:    55024 kB
+VmLck:         0 kB
+VmHWM:     12440 kB
+VmRSS:     12440 kB
+VmData:    47876 kB
+VmStk:       136 kB
+VmExe:      1024 kB
+VmLib:      1848 kB
+VmPTE:        64 kB
+VmSwap:        0 kB
+```
+
+**0.1242 kB virtual, 0.1132 kB resident per counter.**
+
+1000 gauges registered
+----------------------
+
+```
+VmPeak:    44012 kB
+VmSize:    44012 kB
+VmLck:         0 kB
+VmHWM:      1928 kB
+VmRSS:      1928 kB
+VmData:    36868 kB
+VmStk:       136 kB
+VmExe:      1020 kB
+VmLib:      1848 kB
+VmPTE:        40 kB
+VmSwap:        0 kB
+```
+
+**1.408 kB virtual, 0.808 kB resident per counter.**
+
+100000 gauges registered
+------------------------
+
+```
+VmPeak:    55020 kB
+VmSize:    55020 kB
+VmLck:         0 kB
+VmHWM:     12432 kB
+VmRSS:     12432 kB
+VmData:    47876 kB
+VmStk:       136 kB
+VmExe:      1020 kB
+VmLib:      1848 kB
+VmPTE:        60 kB
+VmSwap:        0 kB
+```
+
+**0.12416 kB virtual, 0.11312 resident per gauge.**
+
+1000 histograms with a uniform sample size of 1028
+--------------------------------------------------
+
+```
+VmPeak:    72272 kB
+VmSize:    72272 kB
+VmLck:         0 kB
+VmHWM:     16204 kB
+VmRSS:     16204 kB
+VmData:    65100 kB
+VmStk:       136 kB
+VmExe:      1048 kB
+VmLib:      1848 kB
+VmPTE:        80 kB
+VmSwap:        0 kB
+```
+
+**29.668 kB virtual, TODO 15.084 resident per histogram.**
+
+10000 histograms with a uniform sample size of 1028
+---------------------------------------------------
+
+```
+VmPeak:   256912 kB
+VmSize:   256912 kB
+VmLck:         0 kB
+VmHWM:    146204 kB
+VmRSS:    146204 kB
+VmData:   249740 kB
+VmStk:       136 kB
+VmExe:      1048 kB
+VmLib:      1848 kB
+VmPTE:       448 kB
+VmSwap:        0 kB
+```
+
+**21.4308 kB virtual, 14.5084 kB resident per histogram.**
+
+50000 histograms with a uniform sample size of 1028
+---------------------------------------------------
+
+```
+VmPeak:   908112 kB
+VmSize:   908112 kB
+VmLck:         0 kB
+VmHWM:    645832 kB
+VmRSS:    645588 kB
+VmData:   900940 kB
+VmStk:       136 kB
+VmExe:      1048 kB
+VmLib:      1848 kB
+VmPTE:      1716 kB
+VmSwap:     1544 kB
+```
+
+**17.31016 kB virtual, 12.88936 kB resident per histogram.**
+
+1000 histograms with an exponentially-decaying sample size of 1028 and alpha of 0.015
+-------------------------------------------------------------------------------------
+
+```
+VmPeak:    62480 kB
+VmSize:    62480 kB
+VmLck:         0 kB
+VmHWM:     11572 kB
+VmRSS:     11572 kB
+VmData:    55308 kB
+VmStk:       136 kB
+VmExe:      1048 kB
+VmLib:      1848 kB
+VmPTE:        64 kB
+VmSwap:        0 kB
+```
+
+**19.876 kB virtual, 10.452 kB resident per histogram.**
+
+10000 histograms with an exponentially-decaying sample size of 1028 and alpha of 0.015
+--------------------------------------------------------------------------------------
+
+```
+VmPeak:   153296 kB
+VmSize:   153296 kB
+VmLck:         0 kB
+VmHWM:    101176 kB
+VmRSS:    101176 kB
+VmData:   146124 kB
+VmStk:       136 kB
+VmExe:      1048 kB
+VmLib:      1848 kB
+VmPTE:       240 kB
+VmSwap:        0 kB
+```
+
+**11.0692 kB virtual, 10.0056 kB resident per histogram.**
+
+50000 histograms with an exponentially-decaying sample size of 1028 and alpha of 0.015
+--------------------------------------------------------------------------------------
+
+```
+VmPeak:   557264 kB
+VmSize:   557264 kB
+VmLck:         0 kB
+VmHWM:    501056 kB
+VmRSS:    501056 kB
+VmData:   550092 kB
+VmStk:       136 kB
+VmExe:      1048 kB
+VmLib:      1848 kB
+VmPTE:      1032 kB
+VmSwap:        0 kB
+```
+
+**10.2932 kB virtual, 9.99872 kB resident per histogram.**
+
+1000 meters
+-----------
+
+```
+VmPeak:    74504 kB
+VmSize:    74504 kB
+VmLck:         0 kB
+VmHWM:     24124 kB
+VmRSS:     24124 kB
+VmData:    67340 kB
+VmStk:       136 kB
+VmExe:      1040 kB
+VmLib:      1848 kB
+VmPTE:        92 kB
+VmSwap:        0 kB
+```
+
+**31.9 kB virtual, 23.004 kB resident per meter.**
+
+10000 meters
+------------
+
+```
+VmPeak:   278920 kB
+VmSize:   278920 kB
+VmLck:         0 kB
+VmHWM:    227300 kB
+VmRSS:    227300 kB
+VmData:   271756 kB
+VmStk:       136 kB
+VmExe:      1040 kB
+VmLib:      1848 kB
+VmPTE:       488 kB
+VmSwap:        0 kB
+```
+
+**23.6316 kB virtual, 22.618 kB resident per meter.**
@@ -0,0 +1,233 @@
+package metrics
+
+import (
+	"sync"
+	"time"
+)
+
+// Meters count events to produce exponentially-weighted moving average rates
+// at one-, five-, and fifteen-minutes and a mean rate.
+type Meter interface {
+	Count() int64
+	Mark(int64)
+	Rate1() float64
+	Rate5() float64
+	Rate15() float64
+	RateMean() float64
+	Snapshot() Meter
+}
+
+// GetOrRegisterMeter returns an existing Meter or constructs and registers a
+// new StandardMeter.
+func GetOrRegisterMeter(name string, r Registry) Meter {
+	if nil == r {
+		r = DefaultRegistry
+	}
+	return r.GetOrRegister(name, NewMeter).(Meter)
+}
+
+// NewMeter constructs a new StandardMeter and launches a goroutine.
+func NewMeter() Meter {
+	if UseNilMetrics {
+		return NilMeter{}
+	}
+	m := newStandardMeter()
+	arbiter.Lock()
+	defer arbiter.Unlock()
+	arbiter.meters = append(arbiter.meters, m)
+	if !arbiter.started {
+		arbiter.started = true
+		go arbiter.tick()
+	}
+	return m
+}
+
+// NewMeter constructs and registers a new StandardMeter and launches a
+// goroutine.
+func NewRegisteredMeter(name string, r Registry) Meter {
+	c := NewMeter()
+	if nil == r {
+		r = DefaultRegistry
+	}
+	r.Register(name, c)
+	return c
+}
+
+// MeterSnapshot is a read-only copy of another Meter.
+type MeterSnapshot struct {
+	count                          int64
+	rate1, rate5, rate15, rateMean float64
+}
+
+// Count returns the count of events at the time the snapshot was taken.
+func (m *MeterSnapshot) Count() int64 { return m.count }
+
+// Mark panics.
+func (*MeterSnapshot) Mark(n int64) {
+	panic("Mark called on a MeterSnapshot")
+}
+
+// Rate1 returns the one-minute moving average rate of events per second at the
+// time the snapshot was taken.
+func (m *MeterSnapshot) Rate1() float64 { return m.rate1 }
+
+// Rate5 returns the five-minute moving average rate of events per second at
+// the time the snapshot was taken.
+func (m *MeterSnapshot) Rate5() float64 { return m.rate5 }
+
+// Rate15 returns the fifteen-minute moving average rate of events per second
+// at the time the snapshot was taken.
+func (m *MeterSnapshot) Rate15() float64 { return m.rate15 }
+
+// RateMean returns the meter's mean rate of events per second at the time the
+// snapshot was taken.
+func (m *MeterSnapshot) RateMean() float64 { return m.rateMean }
+
+// Snapshot returns the snapshot.
+func (m *MeterSnapshot) Snapshot() Meter { return m }
+
+// NilMeter is a no-op Meter.
+type NilMeter struct{}
+
+// Count is a no-op.
+func (NilMeter) Count() int64 { return 0 }
+
+// Mark is a no-op.
+func (NilMeter) Mark(n int64) {}
+
+// Rate1 is a no-op.
+func (NilMeter) Rate1() float64 { return 0.0 }
+
+// Rate5 is a no-op.
+func (NilMeter) Rate5() float64 { return 0.0 }
+
+// Rate15is a no-op.
+func (NilMeter) Rate15() float64 { return 0.0 }
+
+// RateMean is a no-op.
+func (NilMeter) RateMean() float64 { return 0.0 }
+
+// Snapshot is a no-op.
+func (NilMeter) Snapshot() Meter { return NilMeter{} }
+
+// StandardMeter is the standard implementation of a Meter.
+type StandardMeter struct {
+	lock        sync.RWMutex
+	snapshot    *MeterSnapshot
+	a1, a5, a15 EWMA
+	startTime   time.Time
+}
+
+func newStandardMeter() *StandardMeter {
+	return &StandardMeter{
+		snapshot:  &MeterSnapshot{},
+		a1:        NewEWMA1(),
+		a5:        NewEWMA5(),
+		a15:       NewEWMA15(),
+		startTime: time.Now(),
+	}
+}
+
+// Count returns the number of events recorded.
+func (m *StandardMeter) Count() int64 {
+	m.lock.RLock()
+	count := m.snapshot.count
+	m.lock.RUnlock()
+	return count
+}
+
+// Mark records the occurance of n events.
+func (m *StandardMeter) Mark(n int64) {
+	m.lock.Lock()
+	defer m.lock.Unlock()
+	m.snapshot.count += n
+	m.a1.Update(n)
+	m.a5.Update(n)
+	m.a15.Update(n)
+	m.updateSnapshot()
+}
+
+// Rate1 returns the one-minute moving average rate of events per second.
+func (m *StandardMeter) Rate1() float64 {
+	m.lock.RLock()
+	rate1 := m.snapshot.rate1
+	m.lock.RUnlock()
+	return rate1
+}
+
+// Rate5 returns the five-minute moving average rate of events per second.
+func (m *StandardMeter) Rate5() float64 {
+	m.lock.RLock()
+	rate5 := m.snapshot.rate5
+	m.lock.RUnlock()
+	return rate5
+}
+
+// Rate15 returns the fifteen-minute moving average rate of events per second.
+func (m *StandardMeter) Rate15() float64 {
+	m.lock.RLock()
+	rate15 := m.snapshot.rate15
+	m.lock.RUnlock()
+	return rate15
+}
+
+// RateMean returns the meter's mean rate of events per second.
+func (m *StandardMeter) RateMean() float64 {
+	m.lock.RLock()
+	rateMean := m.snapshot.rateMean
+	m.lock.RUnlock()
+	return rateMean
+}
+
+// Snapshot returns a read-only copy of the meter.
+func (m *StandardMeter) Snapshot() Meter {
+	m.lock.RLock()
+	snapshot := *m.snapshot
+	m.lock.RUnlock()
+	return &snapshot
+}
+
+func (m *StandardMeter) updateSnapshot() {
+	// should run with write lock held on m.lock
+	snapshot := m.snapshot
+	snapshot.rate1 = m.a1.Rate()
+	snapshot.rate5 = m.a5.Rate()
+	snapshot.rate15 = m.a15.Rate()
+	snapshot.rateMean = float64(snapshot.count) / time.Since(m.startTime).Seconds()
+}
+
+func (m *StandardMeter) tick() {
+	m.lock.Lock()
+	defer m.lock.Unlock()
+	m.a1.Tick()
+	m.a5.Tick()
+	m.a15.Tick()
+	m.updateSnapshot()
+}
+
+type meterArbiter struct {
+	sync.RWMutex
+	started bool
+	meters  []*StandardMeter
+	ticker  *time.Ticker
+}
+
+var arbiter = meterArbiter{ticker: time.NewTicker(5e9)}
+
+// Ticks meters on the scheduled interval
+func (ma *meterArbiter) tick() {
+	for {
+		select {
+		case <-ma.ticker.C:
+			ma.tickMeters()
+		}
+	}
+}
+
+func (ma *meterArbiter) tickMeters() {
+	ma.RLock()
+	defer ma.RUnlock()
+	for _, meter := range ma.meters {
+		meter.tick()
+	}
+}
@@ -0,0 +1,13 @@
+// Go port of Coda Hale's Metrics library
+//
+// <https://github.com/rcrowley/go-metrics>
+//
+// Coda Hale's original work: <https://github.com/codahale/metrics>
+package metrics
+
+// UseNilMetrics is checked by the constructor functions for all of the
+// standard metrics.  If it is true, the metric returned is a stub.
+//
+// This global kill-switch helps quantify the observer effect and makes
+// for less cluttered pprof profiles.
+var UseNilMetrics bool = false
@@ -0,0 +1,119 @@
+package metrics
+
+import (
+	"bufio"
+	"fmt"
+	"log"
+	"net"
+	"os"
+	"strings"
+	"time"
+)
+
+var shortHostName string = ""
+
+// OpenTSDBConfig provides a container with configuration parameters for
+// the OpenTSDB exporter
+type OpenTSDBConfig struct {
+	Addr          *net.TCPAddr  // Network address to connect to
+	Registry      Registry      // Registry to be exported
+	FlushInterval time.Duration // Flush interval
+	DurationUnit  time.Duration // Time conversion unit for durations
+	Prefix        string        // Prefix to be prepended to metric names
+}
+
+// OpenTSDB is a blocking exporter function which reports metrics in r
+// to a TSDB server located at addr, flushing them every d duration
+// and prepending metric names with prefix.
+func OpenTSDB(r Registry, d time.Duration, prefix string, addr *net.TCPAddr) {
+	OpenTSDBWithConfig(OpenTSDBConfig{
+		Addr:          addr,
+		Registry:      r,
+		FlushInterval: d,
+		DurationUnit:  time.Nanosecond,
+		Prefix:        prefix,
+	})
+}
+
+// OpenTSDBWithConfig is a blocking exporter function just like OpenTSDB,
+// but it takes a OpenTSDBConfig instead.
+func OpenTSDBWithConfig(c OpenTSDBConfig) {
+	for _ = range time.Tick(c.FlushInterval) {
+		if err := openTSDB(&c); nil != err {
+			log.Println(err)
+		}
+	}
+}
+
+func getShortHostname() string {
+	if shortHostName == "" {
+		host, _ := os.Hostname()
+		if index := strings.Index(host, "."); index > 0 {
+			shortHostName = host[:index]
+		} else {
+			shortHostName = host
+		}
+	}
+	return shortHostName
+}
+
+func openTSDB(c *OpenTSDBConfig) error {
+	shortHostname := getShortHostname()
+	now := time.Now().Unix()
+	du := float64(c.DurationUnit)
+	conn, err := net.DialTCP("tcp", nil, c.Addr)
+	if nil != err {
+		return err
+	}
+	defer conn.Close()
+	w := bufio.NewWriter(conn)
+	c.Registry.Each(func(name string, i interface{}) {
+		switch metric := i.(type) {
+		case Counter:
+			fmt.Fprintf(w, "put %s.%s.count %d %d host=%s\n", c.Prefix, name, now, metric.Count(), shortHostname)
+		case Gauge:
+			fmt.Fprintf(w, "put %s.%s.value %d %d host=%s\n", c.Prefix, name, now, metric.Value(), shortHostname)
+		case GaugeFloat64:
+			fmt.Fprintf(w, "put %s.%s.value %d %f host=%s\n", c.Prefix, name, now, metric.Value(), shortHostname)
+		case Histogram:
+			h := metric.Snapshot()
+			ps := h.Percentiles([]float64{0.5, 0.75, 0.95, 0.99, 0.999})
+			fmt.Fprintf(w, "put %s.%s.count %d %d host=%s\n", c.Prefix, name, now, h.Count(), shortHostname)
+			fmt.Fprintf(w, "put %s.%s.min %d %d host=%s\n", c.Prefix, name, now, h.Min(), shortHostname)
+			fmt.Fprintf(w, "put %s.%s.max %d %d host=%s\n", c.Prefix, name, now, h.Max(), shortHostname)
+			fmt.Fprintf(w, "put %s.%s.mean %d %.2f host=%s\n", c.Prefix, name, now, h.Mean(), shortHostname)
+			fmt.Fprintf(w, "put %s.%s.std-dev %d %.2f host=%s\n", c.Prefix, name, now, h.StdDev(), shortHostname)
+			fmt.Fprintf(w, "put %s.%s.50-percentile %d %.2f host=%s\n", c.Prefix, name, now, ps[0], shortHostname)
+			fmt.Fprintf(w, "put %s.%s.75-percentile %d %.2f host=%s\n", c.Prefix, name, now, ps[1], shortHostname)
+			fmt.Fprintf(w, "put %s.%s.95-percentile %d %.2f host=%s\n", c.Prefix, name, now, ps[2], shortHostname)
+			fmt.Fprintf(w, "put %s.%s.99-percentile %d %.2f host=%s\n", c.Prefix, name, now, ps[3], shortHostname)
+			fmt.Fprintf(w, "put %s.%s.999-percentile %d %.2f host=%s\n", c.Prefix, name, now, ps[4], shortHostname)
+		case Meter:
+			m := metric.Snapshot()
+			fmt.Fprintf(w, "put %s.%s.count %d %d host=%s\n", c.Prefix, name, now, m.Count(), shortHostname)
+			fmt.Fprintf(w, "put %s.%s.one-minute %d %.2f host=%s\n", c.Prefix, name, now, m.Rate1(), shortHostname)
+			fmt.Fprintf(w, "put %s.%s.five-minute %d %.2f host=%s\n", c.Prefix, name, now, m.Rate5(), shortHostname)
+			fmt.Fprintf(w, "put %s.%s.fifteen-minute %d %.2f host=%s\n", c.Prefix, name, now, m.Rate15(), shortHostname)
+			fmt.Fprintf(w, "put %s.%s.mean %d %.2f host=%s\n", c.Prefix, name, now, m.RateMean(), shortHostname)
+		case Timer:
+			t := metric.Snapshot()
+			ps := t.Percentiles([]float64{0.5, 0.75, 0.95, 0.99, 0.999})
+			fmt.Fprintf(w, "put %s.%s.count %d %d host=%s\n", c.Prefix, name, now, t.Count(), shortHostname)
+			fmt.Fprintf(w, "put %s.%s.min %d %d host=%s\n", c.Prefix, name, now, t.Min()/int64(du), shortHostname)
+			fmt.Fprintf(w, "put %s.%s.max %d %d host=%s\n", c.Prefix, name, now, t.Max()/int64(du), shortHostname)
+			fmt.Fprintf(w, "put %s.%s.mean %d %.2f host=%s\n", c.Prefix, name, now, t.Mean()/du, shortHostname)
+			fmt.Fprintf(w, "put %s.%s.std-dev %d %.2f host=%s\n", c.Prefix, name, now, t.StdDev()/du, shortHostname)
+			fmt.Fprintf(w, "put %s.%s.50-percentile %d %.2f host=%s\n", c.Prefix, name, now, ps[0]/du, shortHostname)
+			fmt.Fprintf(w, "put %s.%s.75-percentile %d %.2f host=%s\n", c.Prefix, name, now, ps[1]/du, shortHostname)
+			fmt.Fprintf(w, "put %s.%s.95-percentile %d %.2f host=%s\n", c.Prefix, name, now, ps[2]/du, shortHostname)
+			fmt.Fprintf(w, "put %s.%s.99-percentile %d %.2f host=%s\n", c.Prefix, name, now, ps[3]/du, shortHostname)
+			fmt.Fprintf(w, "put %s.%s.999-percentile %d %.2f host=%s\n", c.Prefix, name, now, ps[4]/du, shortHostname)
+			fmt.Fprintf(w, "put %s.%s.one-minute %d %.2f host=%s\n", c.Prefix, name, now, t.Rate1(), shortHostname)
+			fmt.Fprintf(w, "put %s.%s.five-minute %d %.2f host=%s\n", c.Prefix, name, now, t.Rate5(), shortHostname)
+			fmt.Fprintf(w, "put %s.%s.fifteen-minute %d %.2f host=%s\n", c.Prefix, name, now, t.Rate15(), shortHostname)
+			fmt.Fprintf(w, "put %s.%s.mean-rate %d %.2f host=%s\n", c.Prefix, name, now, t.RateMean(), shortHostname)
+		}
+		w.Flush()
+	})
+	return nil
+}
@@ -0,0 +1,240 @@
+package metrics
+
+import (
+	"fmt"
+	"reflect"
+	"sync"
+)
+
+// DuplicateMetric is the error returned by Registry.Register when a metric
+// already exists.  If you mean to Register that metric you must first
+// Unregister the existing metric.
+type DuplicateMetric string
+
+func (err DuplicateMetric) Error() string {
+	return fmt.Sprintf("duplicate metric: %s", string(err))
+}
+
+// A Registry holds references to a set of metrics by name and can iterate
+// over them, calling callback functions provided by the user.
+//
+// This is an interface so as to encourage other structs to implement
+// the Registry API as appropriate.
+type Registry interface {
+
+	// Call the given function for each registered metric.
+	Each(func(string, interface{}))
+
+	// Get the metric by the given name or nil if none is registered.
+	Get(string) interface{}
+
+	// Gets an existing metric or registers the given one.
+	// The interface can be the metric to register if not found in registry,
+	// or a function returning the metric for lazy instantiation.
+	GetOrRegister(string, interface{}) interface{}
+
+	// Register the given metric under the given name.
+	Register(string, interface{}) error
+
+	// Run all registered healthchecks.
+	RunHealthchecks()
+
+	// Unregister the metric with the given name.
+	Unregister(string)
+
+	// Unregister all metrics.  (Mostly for testing.)
+	UnregisterAll()
+}
+
+// The standard implementation of a Registry is a mutex-protected map
+// of names to metrics.
+type StandardRegistry struct {
+	metrics map[string]interface{}
+	mutex   sync.Mutex
+}
+
+// Create a new registry.
+func NewRegistry() Registry {
+	return &StandardRegistry{metrics: make(map[string]interface{})}
+}
+
+// Call the given function for each registered metric.
+func (r *StandardRegistry) Each(f func(string, interface{})) {
+	for name, i := range r.registered() {
+		f(name, i)
+	}
+}
+
+// Get the metric by the given name or nil if none is registered.
+func (r *StandardRegistry) Get(name string) interface{} {
+	r.mutex.Lock()
+	defer r.mutex.Unlock()
+	return r.metrics[name]
+}
+
+// Gets an existing metric or creates and registers a new one. Threadsafe
+// alternative to calling Get and Register on failure.
+// The interface can be the metric to register if not found in registry,
+// or a function returning the metric for lazy instantiation.
+func (r *StandardRegistry) GetOrRegister(name string, i interface{}) interface{} {
+	r.mutex.Lock()
+	defer r.mutex.Unlock()
+	if metric, ok := r.metrics[name]; ok {
+		return metric
+	}
+	if v := reflect.ValueOf(i); v.Kind() == reflect.Func {
+		i = v.Call(nil)[0].Interface()
+	}
+	r.register(name, i)
+	return i
+}
+
+// Register the given metric under the given name.  Returns a DuplicateMetric
+// if a metric by the given name is already registered.
+func (r *StandardRegistry) Register(name string, i interface{}) error {
+	r.mutex.Lock()
+	defer r.mutex.Unlock()
+	return r.register(name, i)
+}
+
+// Run all registered healthchecks.
+func (r *StandardRegistry) RunHealthchecks() {
+	r.mutex.Lock()
+	defer r.mutex.Unlock()
+	for _, i := range r.metrics {
+		if h, ok := i.(Healthcheck); ok {
+			h.Check()
+		}
+	}
+}
+
+// Unregister the metric with the given name.
+func (r *StandardRegistry) Unregister(name string) {
+	r.mutex.Lock()
+	defer r.mutex.Unlock()
+	delete(r.metrics, name)
+}
+
+// Unregister all metrics.  (Mostly for testing.)
+func (r *StandardRegistry) UnregisterAll() {
+	r.mutex.Lock()
+	defer r.mutex.Unlock()
+	for name, _ := range r.metrics {
+		delete(r.metrics, name)
+	}
+}
+
+func (r *StandardRegistry) register(name string, i interface{}) error {
+	if _, ok := r.metrics[name]; ok {
+		return DuplicateMetric(name)
+	}
+	switch i.(type) {
+	case Counter, Gauge, GaugeFloat64, Healthcheck, Histogram, Meter, Timer:
+		r.metrics[name] = i
+	}
+	return nil
+}
+
+func (r *StandardRegistry) registered() map[string]interface{} {
+	r.mutex.Lock()
+	defer r.mutex.Unlock()
+	metrics := make(map[string]interface{}, len(r.metrics))
+	for name, i := range r.metrics {
+		metrics[name] = i
+	}
+	return metrics
+}
+
+type PrefixedRegistry struct {
+	underlying Registry
+	prefix     string
+}
+
+func NewPrefixedRegistry(prefix string) Registry {
+	return &PrefixedRegistry{
+		underlying: NewRegistry(),
+		prefix:     prefix,
+	}
+}
+
+// Call the given function for each registered metric.
+func (r *PrefixedRegistry) Each(fn func(string, interface{})) {
+	r.underlying.Each(fn)
+}
+
+// Get the metric by the given name or nil if none is registered.
+func (r *PrefixedRegistry) Get(name string) interface{} {
+	return r.underlying.Get(name)
+}
+
+// Gets an existing metric or registers the given one.
+// The interface can be the metric to register if not found in registry,
+// or a function returning the metric for lazy instantiation.
+func (r *PrefixedRegistry) GetOrRegister(name string, metric interface{}) interface{} {
+	realName := r.prefix + name
+	return r.underlying.GetOrRegister(realName, metric)
+}
+
+// Register the given metric under the given name. The name will be prefixed.
+func (r *PrefixedRegistry) Register(name string, metric interface{}) error {
+	realName := r.prefix + name
+	return r.underlying.Register(realName, metric)
+}
+
+// Run all registered healthchecks.
+func (r *PrefixedRegistry) RunHealthchecks() {
+	r.underlying.RunHealthchecks()
+}
+
+// Unregister the metric with the given name. The name will be prefixed.
+func (r *PrefixedRegistry) Unregister(name string) {
+	realName := r.prefix + name
+	r.underlying.Unregister(realName)
+}
+
+// Unregister all metrics.  (Mostly for testing.)
+func (r *PrefixedRegistry) UnregisterAll() {
+	r.underlying.UnregisterAll()
+}
+
+var DefaultRegistry Registry = NewRegistry()
+
+// Call the given function for each registered metric.
+func Each(f func(string, interface{})) {
+	DefaultRegistry.Each(f)
+}
+
+// Get the metric by the given name or nil if none is registered.
+func Get(name string) interface{} {
+	return DefaultRegistry.Get(name)
+}
+
+// Gets an existing metric or creates and registers a new one. Threadsafe
+// alternative to calling Get and Register on failure.
+func GetOrRegister(name string, i interface{}) interface{} {
+	return DefaultRegistry.GetOrRegister(name, i)
+}
+
+// Register the given metric under the given name.  Returns a DuplicateMetric
+// if a metric by the given name is already registered.
+func Register(name string, i interface{}) error {
+	return DefaultRegistry.Register(name, i)
+}
+
+// Register the given metric under the given name.  Panics if a metric by the
+// given name is already registered.
+func MustRegister(name string, i interface{}) {
+	if err := Register(name, i); err != nil {
+		panic(err)
+	}
+}
+
+// Run all registered healthchecks.
+func RunHealthchecks() {
+	DefaultRegistry.RunHealthchecks()
+}
+
+// Unregister the metric with the given name.
+func Unregister(name string) {
+	DefaultRegistry.Unregister(name)
+}
@@ -0,0 +1,200 @@
+package metrics
+
+import (
+	"runtime"
+	"time"
+)
+
+var (
+	memStats       runtime.MemStats
+	runtimeMetrics struct {
+		MemStats struct {
+			Alloc        Gauge
+			BuckHashSys  Gauge
+			DebugGC      Gauge
+			EnableGC     Gauge
+			Frees        Gauge
+			HeapAlloc    Gauge
+			HeapIdle     Gauge
+			HeapInuse    Gauge
+			HeapObjects  Gauge
+			HeapReleased Gauge
+			HeapSys      Gauge
+			LastGC       Gauge
+			Lookups      Gauge
+			Mallocs      Gauge
+			MCacheInuse  Gauge
+			MCacheSys    Gauge
+			MSpanInuse   Gauge
+			MSpanSys     Gauge
+			NextGC       Gauge
+			NumGC        Gauge
+			PauseNs      Histogram
+			PauseTotalNs Gauge
+			StackInuse   Gauge
+			StackSys     Gauge
+			Sys          Gauge
+			TotalAlloc   Gauge
+		}
+		NumCgoCall   Gauge
+		NumGoroutine Gauge
+		ReadMemStats Timer
+	}
+	frees       uint64
+	lookups     uint64
+	mallocs     uint64
+	numGC       uint32
+	numCgoCalls int64
+)
+
+// Capture new values for the Go runtime statistics exported in
+// runtime.MemStats.  This is designed to be called as a goroutine.
+func CaptureRuntimeMemStats(r Registry, d time.Duration) {
+	for _ = range time.Tick(d) {
+		CaptureRuntimeMemStatsOnce(r)
+	}
+}
+
+// Capture new values for the Go runtime statistics exported in
+// runtime.MemStats.  This is designed to be called in a background
+// goroutine.  Giving a registry which has not been given to
+// RegisterRuntimeMemStats will panic.
+//
+// Be very careful with this because runtime.ReadMemStats calls the C
+// functions runtime·semacquire(&runtime·worldsema) and runtime·stoptheworld()
+// and that last one does what it says on the tin.
+func CaptureRuntimeMemStatsOnce(r Registry) {
+	t := time.Now()
+	runtime.ReadMemStats(&memStats) // This takes 50-200us.
+	runtimeMetrics.ReadMemStats.UpdateSince(t)
+
+	runtimeMetrics.MemStats.Alloc.Update(int64(memStats.Alloc))
+	runtimeMetrics.MemStats.BuckHashSys.Update(int64(memStats.BuckHashSys))
+	if memStats.DebugGC {
+		runtimeMetrics.MemStats.DebugGC.Update(1)
+	} else {
+		runtimeMetrics.MemStats.DebugGC.Update(0)
+	}
+	if memStats.EnableGC {
+		runtimeMetrics.MemStats.EnableGC.Update(1)
+	} else {
+		runtimeMetrics.MemStats.EnableGC.Update(0)
+	}
+
+	runtimeMetrics.MemStats.Frees.Update(int64(memStats.Frees - frees))
+	runtimeMetrics.MemStats.HeapAlloc.Update(int64(memStats.HeapAlloc))
+	runtimeMetrics.MemStats.HeapIdle.Update(int64(memStats.HeapIdle))
+	runtimeMetrics.MemStats.HeapInuse.Update(int64(memStats.HeapInuse))
+	runtimeMetrics.MemStats.HeapObjects.Update(int64(memStats.HeapObjects))
+	runtimeMetrics.MemStats.HeapReleased.Update(int64(memStats.HeapReleased))
+	runtimeMetrics.MemStats.HeapSys.Update(int64(memStats.HeapSys))
+	runtimeMetrics.MemStats.LastGC.Update(int64(memStats.LastGC))
+	runtimeMetrics.MemStats.Lookups.Update(int64(memStats.Lookups - lookups))
+	runtimeMetrics.MemStats.Mallocs.Update(int64(memStats.Mallocs - mallocs))
+	runtimeMetrics.MemStats.MCacheInuse.Update(int64(memStats.MCacheInuse))
+	runtimeMetrics.MemStats.MCacheSys.Update(int64(memStats.MCacheSys))
+	runtimeMetrics.MemStats.MSpanInuse.Update(int64(memStats.MSpanInuse))
+	runtimeMetrics.MemStats.MSpanSys.Update(int64(memStats.MSpanSys))
+	runtimeMetrics.MemStats.NextGC.Update(int64(memStats.NextGC))
+	runtimeMetrics.MemStats.NumGC.Update(int64(memStats.NumGC - numGC))
+
+	// <https://code.google.com/p/go/source/browse/src/pkg/runtime/mgc0.c>
+	i := numGC % uint32(len(memStats.PauseNs))
+	ii := memStats.NumGC % uint32(len(memStats.PauseNs))
+	if memStats.NumGC-numGC >= uint32(len(memStats.PauseNs)) {
+		for i = 0; i < uint32(len(memStats.PauseNs)); i++ {
+			runtimeMetrics.MemStats.PauseNs.Update(int64(memStats.PauseNs[i]))
+		}
+	} else {
+		if i > ii {
+			for ; i < uint32(len(memStats.PauseNs)); i++ {
+				runtimeMetrics.MemStats.PauseNs.Update(int64(memStats.PauseNs[i]))
+			}
+			i = 0
+		}
+		for ; i < ii; i++ {
+			runtimeMetrics.MemStats.PauseNs.Update(int64(memStats.PauseNs[i]))
+		}
+	}
+	frees = memStats.Frees
+	lookups = memStats.Lookups
+	mallocs = memStats.Mallocs
+	numGC = memStats.NumGC
+
+	runtimeMetrics.MemStats.PauseTotalNs.Update(int64(memStats.PauseTotalNs))
+	runtimeMetrics.MemStats.StackInuse.Update(int64(memStats.StackInuse))
+	runtimeMetrics.MemStats.StackSys.Update(int64(memStats.StackSys))
+	runtimeMetrics.MemStats.Sys.Update(int64(memStats.Sys))
+	runtimeMetrics.MemStats.TotalAlloc.Update(int64(memStats.TotalAlloc))
+
+	currentNumCgoCalls := numCgoCall()
+	runtimeMetrics.NumCgoCall.Update(currentNumCgoCalls - numCgoCalls)
+	numCgoCalls = currentNumCgoCalls
+
+	runtimeMetrics.NumGoroutine.Update(int64(runtime.NumGoroutine()))
+}
+
+// Register runtimeMetrics for the Go runtime statistics exported in runtime and
+// specifically runtime.MemStats.  The runtimeMetrics are named by their
+// fully-qualified Go symbols, i.e. runtime.MemStats.Alloc.
+func RegisterRuntimeMemStats(r Registry) {
+	runtimeMetrics.MemStats.Alloc = NewGauge()
+	runtimeMetrics.MemStats.BuckHashSys = NewGauge()
+	runtimeMetrics.MemStats.DebugGC = NewGauge()
+	runtimeMetrics.MemStats.EnableGC = NewGauge()
+	runtimeMetrics.MemStats.Frees = NewGauge()
+	runtimeMetrics.MemStats.HeapAlloc = NewGauge()
+	runtimeMetrics.MemStats.HeapIdle = NewGauge()
+	runtimeMetrics.MemStats.HeapInuse = NewGauge()
+	runtimeMetrics.MemStats.HeapObjects = NewGauge()
+	runtimeMetrics.MemStats.HeapReleased = NewGauge()
+	runtimeMetrics.MemStats.HeapSys = NewGauge()
+	runtimeMetrics.MemStats.LastGC = NewGauge()
+	runtimeMetrics.MemStats.Lookups = NewGauge()
+	runtimeMetrics.MemStats.Mallocs = NewGauge()
+	runtimeMetrics.MemStats.MCacheInuse = NewGauge()
+	runtimeMetrics.MemStats.MCacheSys = NewGauge()
+	runtimeMetrics.MemStats.MSpanInuse = NewGauge()
+	runtimeMetrics.MemStats.MSpanSys = NewGauge()
+	runtimeMetrics.MemStats.NextGC = NewGauge()
+	runtimeMetrics.MemStats.NumGC = NewGauge()
+	runtimeMetrics.MemStats.PauseNs = NewHistogram(NewExpDecaySample(1028, 0.015))
+	runtimeMetrics.MemStats.PauseTotalNs = NewGauge()
+	runtimeMetrics.MemStats.StackInuse = NewGauge()
+	runtimeMetrics.MemStats.StackSys = NewGauge()
+	runtimeMetrics.MemStats.Sys = NewGauge()
+	runtimeMetrics.MemStats.TotalAlloc = NewGauge()
+	runtimeMetrics.NumCgoCall = NewGauge()
+	runtimeMetrics.NumGoroutine = NewGauge()
+	runtimeMetrics.ReadMemStats = NewTimer()
+
+	r.Register("runtime.MemStats.Alloc", runtimeMetrics.MemStats.Alloc)
+	r.Register("runtime.MemStats.BuckHashSys", runtimeMetrics.MemStats.BuckHashSys)
+	r.Register("runtime.MemStats.DebugGC", runtimeMetrics.MemStats.DebugGC)
+	r.Register("runtime.MemStats.EnableGC", runtimeMetrics.MemStats.EnableGC)
+	r.Register("runtime.MemStats.Frees", runtimeMetrics.MemStats.Frees)
+	r.Register("runtime.MemStats.HeapAlloc", runtimeMetrics.MemStats.HeapAlloc)
+	r.Register("runtime.MemStats.HeapIdle", runtimeMetrics.MemStats.HeapIdle)
+	r.Register("runtime.MemStats.HeapInuse", runtimeMetrics.MemStats.HeapInuse)
+	r.Register("runtime.MemStats.HeapObjects", runtimeMetrics.MemStats.HeapObjects)
+	r.Register("runtime.MemStats.HeapReleased", runtimeMetrics.MemStats.HeapReleased)
+	r.Register("runtime.MemStats.HeapSys", runtimeMetrics.MemStats.HeapSys)
+	r.Register("runtime.MemStats.LastGC", runtimeMetrics.MemStats.LastGC)
+	r.Register("runtime.MemStats.Lookups", runtimeMetrics.MemStats.Lookups)
+	r.Register("runtime.MemStats.Mallocs", runtimeMetrics.MemStats.Mallocs)
+	r.Register("runtime.MemStats.MCacheInuse", runtimeMetrics.MemStats.MCacheInuse)
+	r.Register("runtime.MemStats.MCacheSys", runtimeMetrics.MemStats.MCacheSys)
+	r.Register("runtime.MemStats.MSpanInuse", runtimeMetrics.MemStats.MSpanInuse)
+	r.Register("runtime.MemStats.MSpanSys", runtimeMetrics.MemStats.MSpanSys)
+	r.Register("runtime.MemStats.NextGC", runtimeMetrics.MemStats.NextGC)
+	r.Register("runtime.MemStats.NumGC", runtimeMetrics.MemStats.NumGC)
+	r.Register("runtime.MemStats.PauseNs", runtimeMetrics.MemStats.PauseNs)
+	r.Register("runtime.MemStats.PauseTotalNs", runtimeMetrics.MemStats.PauseTotalNs)
+	r.Register("runtime.MemStats.StackInuse", runtimeMetrics.MemStats.StackInuse)
+	r.Register("runtime.MemStats.StackSys", runtimeMetrics.MemStats.StackSys)
+	r.Register("runtime.MemStats.Sys", runtimeMetrics.MemStats.Sys)
+	r.Register("runtime.MemStats.TotalAlloc", runtimeMetrics.MemStats.TotalAlloc)
+	r.Register("runtime.NumCgoCall", runtimeMetrics.NumCgoCall)
+	r.Register("runtime.NumGoroutine", runtimeMetrics.NumGoroutine)
+	r.Register("runtime.ReadMemStats", runtimeMetrics.ReadMemStats)
+}
@@ -0,0 +1,10 @@
+// +build cgo
+// +build !appengine
+
+package metrics
+
+import "runtime"
+
+func numCgoCall() int64 {
+	return runtime.NumCgoCall()
+}
@@ -0,0 +1,7 @@
+// +build !cgo appengine
+
+package metrics
+
+func numCgoCall() int64 {
+	return 0
+}
@@ -0,0 +1,609 @@
+package metrics
+
+import (
+	"math"
+	"math/rand"
+	"sort"
+	"sync"
+	"time"
+)
+
+const rescaleThreshold = time.Hour
+
+// Samples maintain a statistically-significant selection of values from
+// a stream.
+type Sample interface {
+	Clear()
+	Count() int64
+	Max() int64
+	Mean() float64
+	Min() int64
+	Percentile(float64) float64
+	Percentiles([]float64) []float64
+	Size() int
+	Snapshot() Sample
+	StdDev() float64
+	Sum() int64
+	Update(int64)
+	Values() []int64
+	Variance() float64
+}
+
+// ExpDecaySample is an exponentially-decaying sample using a forward-decaying
+// priority reservoir.  See Cormode et al's "Forward Decay: A Practical Time
+// Decay Model for Streaming Systems".
+//
+// <http://www.research.att.com/people/Cormode_Graham/library/publications/CormodeShkapenyukSrivastavaXu09.pdf>
+type ExpDecaySample struct {
+	alpha         float64
+	count         int64
+	mutex         sync.Mutex
+	reservoirSize int
+	t0, t1        time.Time
+	values        *expDecaySampleHeap
+}
+
+// NewExpDecaySample constructs a new exponentially-decaying sample with the
+// given reservoir size and alpha.
+func NewExpDecaySample(reservoirSize int, alpha float64) Sample {
+	if UseNilMetrics {
+		return NilSample{}
+	}
+	s := &ExpDecaySample{
+		alpha:         alpha,
+		reservoirSize: reservoirSize,
+		t0:            time.Now(),
+		values:        newExpDecaySampleHeap(reservoirSize),
+	}
+	s.t1 = s.t0.Add(rescaleThreshold)
+	return s
+}
+
+// Clear clears all samples.
+func (s *ExpDecaySample) Clear() {
+	s.mutex.Lock()
+	defer s.mutex.Unlock()
+	s.count = 0
+	s.t0 = time.Now()
+	s.t1 = s.t0.Add(rescaleThreshold)
+	s.values.Clear()
+}
+
+// Count returns the number of samples recorded, which may exceed the
+// reservoir size.
+func (s *ExpDecaySample) Count() int64 {
+	s.mutex.Lock()
+	defer s.mutex.Unlock()
+	return s.count
+}
+
+// Max returns the maximum value in the sample, which may not be the maximum
+// value ever to be part of the sample.
+func (s *ExpDecaySample) Max() int64 {
+	return SampleMax(s.Values())
+}
+
+// Mean returns the mean of the values in the sample.
+func (s *ExpDecaySample) Mean() float64 {
+	return SampleMean(s.Values())
+}
+
+// Min returns the minimum value in the sample, which may not be the minimum
+// value ever to be part of the sample.
+func (s *ExpDecaySample) Min() int64 {
+	return SampleMin(s.Values())
+}
+
+// Percentile returns an arbitrary percentile of values in the sample.
+func (s *ExpDecaySample) Percentile(p float64) float64 {
+	return SamplePercentile(s.Values(), p)
+}
+
+// Percentiles returns a slice of arbitrary percentiles of values in the
+// sample.
+func (s *ExpDecaySample) Percentiles(ps []float64) []float64 {
+	return SamplePercentiles(s.Values(), ps)
+}
+
+// Size returns the size of the sample, which is at most the reservoir size.
+func (s *ExpDecaySample) Size() int {
+	s.mutex.Lock()
+	defer s.mutex.Unlock()
+	return s.values.Size()
+}
+
+// Snapshot returns a read-only copy of the sample.
+func (s *ExpDecaySample) Snapshot() Sample {
+	s.mutex.Lock()
+	defer s.mutex.Unlock()
+	vals := s.values.Values()
+	values := make([]int64, len(vals))
+	for i, v := range vals {
+		values[i] = v.v
+	}
+	return &SampleSnapshot{
+		count:  s.count,
+		values: values,
+	}
+}
+
+// StdDev returns the standard deviation of the values in the sample.
+func (s *ExpDecaySample) StdDev() float64 {
+	return SampleStdDev(s.Values())
+}
+
+// Sum returns the sum of the values in the sample.
+func (s *ExpDecaySample) Sum() int64 {
+	return SampleSum(s.Values())
+}
+
+// Update samples a new value.
+func (s *ExpDecaySample) Update(v int64) {
+	s.update(time.Now(), v)
+}
+
+// Values returns a copy of the values in the sample.
+func (s *ExpDecaySample) Values() []int64 {
+	s.mutex.Lock()
+	defer s.mutex.Unlock()
+	vals := s.values.Values()
+	values := make([]int64, len(vals))
+	for i, v := range vals {
+		values[i] = v.v
+	}
+	return values
+}
+
+// Variance returns the variance of the values in the sample.
+func (s *ExpDecaySample) Variance() float64 {
+	return SampleVariance(s.Values())
+}
+
+// update samples a new value at a particular timestamp.  This is a method all
+// its own to facilitate testing.
+func (s *ExpDecaySample) update(t time.Time, v int64) {
+	s.mutex.Lock()
+	defer s.mutex.Unlock()
+	s.count++
+	if s.values.Size() == s.reservoirSize {
+		s.values.Pop()
+	}
+	s.values.Push(expDecaySample{
+		k: math.Exp(t.Sub(s.t0).Seconds()*s.alpha) / rand.Float64(),
+		v: v,
+	})
+	if t.After(s.t1) {
+		values := s.values.Values()
+		t0 := s.t0
+		s.values.Clear()
+		s.t0 = t
+		s.t1 = s.t0.Add(rescaleThreshold)
+		for _, v := range values {
+			v.k = v.k * math.Exp(-s.alpha*s.t0.Sub(t0).Seconds())
+			s.values.Push(v)
+		}
+	}
+}
+
+// NilSample is a no-op Sample.
+type NilSample struct{}
+
+// Clear is a no-op.
+func (NilSample) Clear() {}
+
+// Count is a no-op.
+func (NilSample) Count() int64 { return 0 }
+
+// Max is a no-op.
+func (NilSample) Max() int64 { return 0 }
+
+// Mean is a no-op.
+func (NilSample) Mean() float64 { return 0.0 }
+
+// Min is a no-op.
+func (NilSample) Min() int64 { return 0 }
+
+// Percentile is a no-op.
+func (NilSample) Percentile(p float64) float64 { return 0.0 }
+
+// Percentiles is a no-op.
+func (NilSample) Percentiles(ps []float64) []float64 {
+	return make([]float64, len(ps))
+}
+
+// Size is a no-op.
+func (NilSample) Size() int { return 0 }
+
+// Sample is a no-op.
+func (NilSample) Snapshot() Sample { return NilSample{} }
+
+// StdDev is a no-op.
+func (NilSample) StdDev() float64 { return 0.0 }
+
+// Sum is a no-op.
+func (NilSample) Sum() int64 { return 0 }
+
+// Update is a no-op.
+func (NilSample) Update(v int64) {}
+
+// Values is a no-op.
+func (NilSample) Values() []int64 { return []int64{} }
+
+// Variance is a no-op.
+func (NilSample) Variance() float64 { return 0.0 }
+
+// SampleMax returns the maximum value of the slice of int64.
+func SampleMax(values []int64) int64 {
+	if 0 == len(values) {
+		return 0
+	}
+	var max int64 = math.MinInt64
+	for _, v := range values {
+		if max < v {
+			max = v
+		}
+	}
+	return max
+}
+
+// SampleMean returns the mean value of the slice of int64.
+func SampleMean(values []int64) float64 {
+	if 0 == len(values) {
+		return 0.0
+	}
+	return float64(SampleSum(values)) / float64(len(values))
+}
+
+// SampleMin returns the minimum value of the slice of int64.
+func SampleMin(values []int64) int64 {
+	if 0 == len(values) {
+		return 0
+	}
+	var min int64 = math.MaxInt64
+	for _, v := range values {
+		if min > v {
+			min = v
+		}
+	}
+	return min
+}
+
+// SamplePercentiles returns an arbitrary percentile of the slice of int64.
+func SamplePercentile(values int64Slice, p float64) float64 {
+	return SamplePercentiles(values, []float64{p})[0]
+}
+
+// SamplePercentiles returns a slice of arbitrary percentiles of the slice of
+// int64.
+func SamplePercentiles(values int64Slice, ps []float64) []float64 {
+	scores := make([]float64, len(ps))
+	size := len(values)
+	if size > 0 {
+		sort.Sort(values)
+		for i, p := range ps {
+			pos := p * float64(size+1)
+			if pos < 1.0 {
+				scores[i] = float64(values[0])
+			} else if pos >= float64(size) {
+				scores[i] = float64(values[size-1])
+			} else {
+				lower := float64(values[int(pos)-1])
+				upper := float64(values[int(pos)])
+				scores[i] = lower + (pos-math.Floor(pos))*(upper-lower)
+			}
+		}
+	}
+	return scores
+}
+
+// SampleSnapshot is a read-only copy of another Sample.
+type SampleSnapshot struct {
+	count  int64
+	values []int64
+}
+
+// Clear panics.
+func (*SampleSnapshot) Clear() {
+	panic("Clear called on a SampleSnapshot")
+}
+
+// Count returns the count of inputs at the time the snapshot was taken.
+func (s *SampleSnapshot) Count() int64 { return s.count }
+
+// Max returns the maximal value at the time the snapshot was taken.
+func (s *SampleSnapshot) Max() int64 { return SampleMax(s.values) }
+
+// Mean returns the mean value at the time the snapshot was taken.
+func (s *SampleSnapshot) Mean() float64 { return SampleMean(s.values) }
+
+// Min returns the minimal value at the time the snapshot was taken.
+func (s *SampleSnapshot) Min() int64 { return SampleMin(s.values) }
+
+// Percentile returns an arbitrary percentile of values at the time the
+// snapshot was taken.
+func (s *SampleSnapshot) Percentile(p float64) float64 {
+	return SamplePercentile(s.values, p)
+}
+
+// Percentiles returns a slice of arbitrary percentiles of values at the time
+// the snapshot was taken.
+func (s *SampleSnapshot) Percentiles(ps []float64) []float64 {
+	return SamplePercentiles(s.values, ps)
+}
+
+// Size returns the size of the sample at the time the snapshot was taken.
+func (s *SampleSnapshot) Size() int { return len(s.values) }
+
+// Snapshot returns the snapshot.
+func (s *SampleSnapshot) Snapshot() Sample { return s }
+
+// StdDev returns the standard deviation of values at the time the snapshot was
+// taken.
+func (s *SampleSnapshot) StdDev() float64 { return SampleStdDev(s.values) }
+
+// Sum returns the sum of values at the time the snapshot was taken.
+func (s *SampleSnapshot) Sum() int64 { return SampleSum(s.values) }
+
+// Update panics.
+func (*SampleSnapshot) Update(int64) {
+	panic("Update called on a SampleSnapshot")
+}
+
+// Values returns a copy of the values in the sample.
+func (s *SampleSnapshot) Values() []int64 {
+	values := make([]int64, len(s.values))
+	copy(values, s.values)
+	return values
+}
+
+// Variance returns the variance of values at the time the snapshot was taken.
+func (s *SampleSnapshot) Variance() float64 { return SampleVariance(s.values) }
+
+// SampleStdDev returns the standard deviation of the slice of int64.
+func SampleStdDev(values []int64) float64 {
+	return math.Sqrt(SampleVariance(values))
+}
+
+// SampleSum returns the sum of the slice of int64.
+func SampleSum(values []int64) int64 {
+	var sum int64
+	for _, v := range values {
+		sum += v
+	}
+	return sum
+}
+
+// SampleVariance returns the variance of the slice of int64.
+func SampleVariance(values []int64) float64 {
+	if 0 == len(values) {
+		return 0.0
+	}
+	m := SampleMean(values)
+	var sum float64
+	for _, v := range values {
+		d := float64(v) - m
+		sum += d * d
+	}
+	return sum / float64(len(values))
+}
+
+// A uniform sample using Vitter's Algorithm R.
+//
+// <http://www.cs.umd.edu/~samir/498/vitter.pdf>
+type UniformSample struct {
+	count         int64
+	mutex         sync.Mutex
+	reservoirSize int
+	values        []int64
+}
+
+// NewUniformSample constructs a new uniform sample with the given reservoir
+// size.
+func NewUniformSample(reservoirSize int) Sample {
+	if UseNilMetrics {
+		return NilSample{}
+	}
+	return &UniformSample{
+		reservoirSize: reservoirSize,
+		values:        make([]int64, 0, reservoirSize),
+	}
+}
+
+// Clear clears all samples.
+func (s *UniformSample) Clear() {
+	s.mutex.Lock()
+	defer s.mutex.Unlock()
+	s.count = 0
+	s.values = make([]int64, 0, s.reservoirSize)
+}
+
+// Count returns the number of samples recorded, which may exceed the
+// reservoir size.
+func (s *UniformSample) Count() int64 {
+	s.mutex.Lock()
+	defer s.mutex.Unlock()
+	return s.count
+}
+
+// Max returns the maximum value in the sample, which may not be the maximum
+// value ever to be part of the sample.
+func (s *UniformSample) Max() int64 {
+	s.mutex.Lock()
+	defer s.mutex.Unlock()
+	return SampleMax(s.values)
+}
+
+// Mean returns the mean of the values in the sample.
+func (s *UniformSample) Mean() float64 {
+	s.mutex.Lock()
+	defer s.mutex.Unlock()
+	return SampleMean(s.values)
+}
+
+// Min returns the minimum value in the sample, which may not be the minimum
+// value ever to be part of the sample.
+func (s *UniformSample) Min() int64 {
+	s.mutex.Lock()
+	defer s.mutex.Unlock()
+	return SampleMin(s.values)
+}
+
+// Percentile returns an arbitrary percentile of values in the sample.
+func (s *UniformSample) Percentile(p float64) float64 {
+	s.mutex.Lock()
+	defer s.mutex.Unlock()
+	return SamplePercentile(s.values, p)
+}
+
+// Percentiles returns a slice of arbitrary percentiles of values in the
+// sample.
+func (s *UniformSample) Percentiles(ps []float64) []float64 {
+	s.mutex.Lock()
+	defer s.mutex.Unlock()
+	return SamplePercentiles(s.values, ps)
+}
+
+// Size returns the size of the sample, which is at most the reservoir size.
+func (s *UniformSample) Size() int {
+	s.mutex.Lock()
+	defer s.mutex.Unlock()
+	return len(s.values)
+}
+
+// Snapshot returns a read-only copy of the sample.
+func (s *UniformSample) Snapshot() Sample {
+	s.mutex.Lock()
+	defer s.mutex.Unlock()
+	values := make([]int64, len(s.values))
+	copy(values, s.values)
+	return &SampleSnapshot{
+		count:  s.count,
+		values: values,
+	}
+}
+
+// StdDev returns the standard deviation of the values in the sample.
+func (s *UniformSample) StdDev() float64 {
+	s.mutex.Lock()
+	defer s.mutex.Unlock()
+	return SampleStdDev(s.values)
+}
+
+// Sum returns the sum of the values in the sample.
+func (s *UniformSample) Sum() int64 {
+	s.mutex.Lock()
+	defer s.mutex.Unlock()
+	return SampleSum(s.values)
+}
+
+// Update samples a new value.
+func (s *UniformSample) Update(v int64) {
+	s.mutex.Lock()
+	defer s.mutex.Unlock()
+	s.count++
+	if len(s.values) < s.reservoirSize {
+		s.values = append(s.values, v)
+	} else {
+		r := rand.Int63n(s.count)
+		if r < int64(len(s.values)) {
+			s.values[int(r)] = v
+		}
+	}
+}
+
+// Values returns a copy of the values in the sample.
+func (s *UniformSample) Values() []int64 {
+	s.mutex.Lock()
+	defer s.mutex.Unlock()
+	values := make([]int64, len(s.values))
+	copy(values, s.values)
+	return values
+}
+
+// Variance returns the variance of the values in the sample.
+func (s *UniformSample) Variance() float64 {
+	s.mutex.Lock()
+	defer s.mutex.Unlock()
+	return SampleVariance(s.values)
+}
+
+// expDecaySample represents an individual sample in a heap.
+type expDecaySample struct {
+	k float64
+	v int64
+}
+
+func newExpDecaySampleHeap(reservoirSize int) *expDecaySampleHeap {
+	return &expDecaySampleHeap{make([]expDecaySample, 0, reservoirSize)}
+}
+
+// expDecaySampleHeap is a min-heap of expDecaySamples.
+// The internal implementation is copied from the standard library's container/heap
+type expDecaySampleHeap struct {
+	s []expDecaySample
+}
+
+func (h *expDecaySampleHeap) Clear() {
+	h.s = h.s[:0]
+}
+
+func (h *expDecaySampleHeap) Push(s expDecaySample) {
+	n := len(h.s)
+	h.s = h.s[0 : n+1]
+	h.s[n] = s
+	h.up(n)
+}
+
+func (h *expDecaySampleHeap) Pop() expDecaySample {
+	n := len(h.s) - 1
+	h.s[0], h.s[n] = h.s[n], h.s[0]
+	h.down(0, n)
+
+	n = len(h.s)
+	s := h.s[n-1]
+	h.s = h.s[0 : n-1]
+	return s
+}
+
+func (h *expDecaySampleHeap) Size() int {
+	return len(h.s)
+}
+
+func (h *expDecaySampleHeap) Values() []expDecaySample {
+	return h.s
+}
+
+func (h *expDecaySampleHeap) up(j int) {
+	for {
+		i := (j - 1) / 2 // parent
+		if i == j || !(h.s[j].k < h.s[i].k) {
+			break
+		}
+		h.s[i], h.s[j] = h.s[j], h.s[i]
+		j = i
+	}
+}
+
+func (h *expDecaySampleHeap) down(i, n int) {
+	for {
+		j1 := 2*i + 1
+		if j1 >= n || j1 < 0 { // j1 < 0 after int overflow
+			break
+		}
+		j := j1 // left child
+		if j2 := j1 + 1; j2 < n && !(h.s[j1].k < h.s[j2].k) {
+			j = j2 // = 2*i + 2  // right child
+		}
+		if !(h.s[j].k < h.s[i].k) {
+			break
+		}
+		h.s[i], h.s[j] = h.s[j], h.s[i]
+		i = j
+	}
+}
+
+type int64Slice []int64
+
+func (p int64Slice) Len() int           { return len(p) }
+func (p int64Slice) Less(i, j int) bool { return p[i] < p[j] }
+func (p int64Slice) Swap(i, j int)      { p[i], p[j] = p[j], p[i] }
@@ -0,0 +1,69 @@
+// Metrics output to StatHat.
+package stathat
+
+import (
+	"github.com/rcrowley/go-metrics"
+	"github.com/stathat/go"
+	"log"
+	"time"
+)
+
+func Stathat(r metrics.Registry, d time.Duration, userkey string) {
+	for {
+		if err := sh(r, userkey); nil != err {
+			log.Println(err)
+		}
+		time.Sleep(d)
+	}
+}
+
+func sh(r metrics.Registry, userkey string) error {
+	r.Each(func(name string, i interface{}) {
+		switch metric := i.(type) {
+		case metrics.Counter:
+			stathat.PostEZCount(name, userkey, int(metric.Count()))
+		case metrics.Gauge:
+			stathat.PostEZValue(name, userkey, float64(metric.Value()))
+		case metrics.GaugeFloat64:
+			stathat.PostEZValue(name, userkey, float64(metric.Value()))
+		case metrics.Histogram:
+			h := metric.Snapshot()
+			ps := h.Percentiles([]float64{0.5, 0.75, 0.95, 0.99, 0.999})
+			stathat.PostEZCount(name+".count", userkey, int(h.Count()))
+			stathat.PostEZValue(name+".min", userkey, float64(h.Min()))
+			stathat.PostEZValue(name+".max", userkey, float64(h.Max()))
+			stathat.PostEZValue(name+".mean", userkey, float64(h.Mean()))
+			stathat.PostEZValue(name+".std-dev", userkey, float64(h.StdDev()))
+			stathat.PostEZValue(name+".50-percentile", userkey, float64(ps[0]))
+			stathat.PostEZValue(name+".75-percentile", userkey, float64(ps[1]))
+			stathat.PostEZValue(name+".95-percentile", userkey, float64(ps[2]))
+			stathat.PostEZValue(name+".99-percentile", userkey, float64(ps[3]))
+			stathat.PostEZValue(name+".999-percentile", userkey, float64(ps[4]))
+		case metrics.Meter:
+			m := metric.Snapshot()
+			stathat.PostEZCount(name+".count", userkey, int(m.Count()))
+			stathat.PostEZValue(name+".one-minute", userkey, float64(m.Rate1()))
+			stathat.PostEZValue(name+".five-minute", userkey, float64(m.Rate5()))
+			stathat.PostEZValue(name+".fifteen-minute", userkey, float64(m.Rate15()))
+			stathat.PostEZValue(name+".mean", userkey, float64(m.RateMean()))
+		case metrics.Timer:
+			t := metric.Snapshot()
+			ps := t.Percentiles([]float64{0.5, 0.75, 0.95, 0.99, 0.999})
+			stathat.PostEZCount(name+".count", userkey, int(t.Count()))
+			stathat.PostEZValue(name+".min", userkey, float64(t.Min()))
+			stathat.PostEZValue(name+".max", userkey, float64(t.Max()))
+			stathat.PostEZValue(name+".mean", userkey, float64(t.Mean()))
+			stathat.PostEZValue(name+".std-dev", userkey, float64(t.StdDev()))
+			stathat.PostEZValue(name+".50-percentile", userkey, float64(ps[0]))
+			stathat.PostEZValue(name+".75-percentile", userkey, float64(ps[1]))
+			stathat.PostEZValue(name+".95-percentile", userkey, float64(ps[2]))
+			stathat.PostEZValue(name+".99-percentile", userkey, float64(ps[3]))
+			stathat.PostEZValue(name+".999-percentile", userkey, float64(ps[4]))
+			stathat.PostEZValue(name+".one-minute", userkey, float64(t.Rate1()))
+			stathat.PostEZValue(name+".five-minute", userkey, float64(t.Rate5()))
+			stathat.PostEZValue(name+".fifteen-minute", userkey, float64(t.Rate15()))
+			stathat.PostEZValue(name+".mean-rate", userkey, float64(t.RateMean()))
+		}
+	})
+	return nil
+}
@@ -0,0 +1,78 @@
+// +build !windows
+
+package metrics
+
+import (
+	"fmt"
+	"log/syslog"
+	"time"
+)
+
+// Output each metric in the given registry to syslog periodically using
+// the given syslogger.
+func Syslog(r Registry, d time.Duration, w *syslog.Writer) {
+	for _ = range time.Tick(d) {
+		r.Each(func(name string, i interface{}) {
+			switch metric := i.(type) {
+			case Counter:
+				w.Info(fmt.Sprintf("counter %s: count: %d", name, metric.Count()))
+			case Gauge:
+				w.Info(fmt.Sprintf("gauge %s: value: %d", name, metric.Value()))
+			case GaugeFloat64:
+				w.Info(fmt.Sprintf("gauge %s: value: %f", name, metric.Value()))
+			case Healthcheck:
+				metric.Check()
+				w.Info(fmt.Sprintf("healthcheck %s: error: %v", name, metric.Error()))
+			case Histogram:
+				h := metric.Snapshot()
+				ps := h.Percentiles([]float64{0.5, 0.75, 0.95, 0.99, 0.999})
+				w.Info(fmt.Sprintf(
+					"histogram %s: count: %d min: %d max: %d mean: %.2f stddev: %.2f median: %.2f 75%%: %.2f 95%%: %.2f 99%%: %.2f 99.9%%: %.2f",
+					name,
+					h.Count(),
+					h.Min(),
+					h.Max(),
+					h.Mean(),
+					h.StdDev(),
+					ps[0],
+					ps[1],
+					ps[2],
+					ps[3],
+					ps[4],
+				))
+			case Meter:
+				m := metric.Snapshot()
+				w.Info(fmt.Sprintf(
+					"meter %s: count: %d 1-min: %.2f 5-min: %.2f 15-min: %.2f mean: %.2f",
+					name,
+					m.Count(),
+					m.Rate1(),
+					m.Rate5(),
+					m.Rate15(),
+					m.RateMean(),
+				))
+			case Timer:
+				t := metric.Snapshot()
+				ps := t.Percentiles([]float64{0.5, 0.75, 0.95, 0.99, 0.999})
+				w.Info(fmt.Sprintf(
+					"timer %s: count: %d min: %d max: %d mean: %.2f stddev: %.2f median: %.2f 75%%: %.2f 95%%: %.2f 99%%: %.2f 99.9%%: %.2f 1-min: %.2f 5-min: %.2f 15-min: %.2f mean-rate: %.2f",
+					name,
+					t.Count(),
+					t.Min(),
+					t.Max(),
+					t.Mean(),
+					t.StdDev(),
+					ps[0],
+					ps[1],
+					ps[2],
+					ps[3],
+					ps[4],
+					t.Rate1(),
+					t.Rate5(),
+					t.Rate15(),
+					t.RateMean(),
+				))
+			}
+		})
+	}
+}
@@ -0,0 +1,311 @@
+package metrics
+
+import (
+	"sync"
+	"time"
+)
+
+// Timers capture the duration and rate of events.
+type Timer interface {
+	Count() int64
+	Max() int64
+	Mean() float64
+	Min() int64
+	Percentile(float64) float64
+	Percentiles([]float64) []float64
+	Rate1() float64
+	Rate5() float64
+	Rate15() float64
+	RateMean() float64
+	Snapshot() Timer
+	StdDev() float64
+	Sum() int64
+	Time(func())
+	Update(time.Duration)
+	UpdateSince(time.Time)
+	Variance() float64
+}
+
+// GetOrRegisterTimer returns an existing Timer or constructs and registers a
+// new StandardTimer.
+func GetOrRegisterTimer(name string, r Registry) Timer {
+	if nil == r {
+		r = DefaultRegistry
+	}
+	return r.GetOrRegister(name, NewTimer).(Timer)
+}
+
+// NewCustomTimer constructs a new StandardTimer from a Histogram and a Meter.
+func NewCustomTimer(h Histogram, m Meter) Timer {
+	if UseNilMetrics {
+		return NilTimer{}
+	}
+	return &StandardTimer{
+		histogram: h,
+		meter:     m,
+	}
+}
+
+// NewRegisteredTimer constructs and registers a new StandardTimer.
+func NewRegisteredTimer(name string, r Registry) Timer {
+	c := NewTimer()
+	if nil == r {
+		r = DefaultRegistry
+	}
+	r.Register(name, c)
+	return c
+}
+
+// NewTimer constructs a new StandardTimer using an exponentially-decaying
+// sample with the same reservoir size and alpha as UNIX load averages.
+func NewTimer() Timer {
+	if UseNilMetrics {
+		return NilTimer{}
+	}
+	return &StandardTimer{
+		histogram: NewHistogram(NewExpDecaySample(1028, 0.015)),
+		meter:     NewMeter(),
+	}
+}
+
+// NilTimer is a no-op Timer.
+type NilTimer struct {
+	h Histogram
+	m Meter
+}
+
+// Count is a no-op.
+func (NilTimer) Count() int64 { return 0 }
+
+// Max is a no-op.
+func (NilTimer) Max() int64 { return 0 }
+
+// Mean is a no-op.
+func (NilTimer) Mean() float64 { return 0.0 }
+
+// Min is a no-op.
+func (NilTimer) Min() int64 { return 0 }
+
+// Percentile is a no-op.
+func (NilTimer) Percentile(p float64) float64 { return 0.0 }
+
+// Percentiles is a no-op.
+func (NilTimer) Percentiles(ps []float64) []float64 {
+	return make([]float64, len(ps))
+}
+
+// Rate1 is a no-op.
+func (NilTimer) Rate1() float64 { return 0.0 }
+
+// Rate5 is a no-op.
+func (NilTimer) Rate5() float64 { return 0.0 }
+
+// Rate15 is a no-op.
+func (NilTimer) Rate15() float64 { return 0.0 }
+
+// RateMean is a no-op.
+func (NilTimer) RateMean() float64 { return 0.0 }
+
+// Snapshot is a no-op.
+func (NilTimer) Snapshot() Timer { return NilTimer{} }
+
+// StdDev is a no-op.
+func (NilTimer) StdDev() float64 { return 0.0 }
+
+// Sum is a no-op.
+func (NilTimer) Sum() int64 { return 0 }
+
+// Time is a no-op.
+func (NilTimer) Time(func()) {}
+
+// Update is a no-op.
+func (NilTimer) Update(time.Duration) {}
+
+// UpdateSince is a no-op.
+func (NilTimer) UpdateSince(time.Time) {}
+
+// Variance is a no-op.
+func (NilTimer) Variance() float64 { return 0.0 }
+
+// StandardTimer is the standard implementation of a Timer and uses a Histogram
+// and Meter.
+type StandardTimer struct {
+	histogram Histogram
+	meter     Meter
+	mutex     sync.Mutex
+}
+
+// Count returns the number of events recorded.
+func (t *StandardTimer) Count() int64 {
+	return t.histogram.Count()
+}
+
+// Max returns the maximum value in the sample.
+func (t *StandardTimer) Max() int64 {
+	return t.histogram.Max()
+}
+
+// Mean returns the mean of the values in the sample.
+func (t *StandardTimer) Mean() float64 {
+	return t.histogram.Mean()
+}
+
+// Min returns the minimum value in the sample.
+func (t *StandardTimer) Min() int64 {
+	return t.histogram.Min()
+}
+
+// Percentile returns an arbitrary percentile of the values in the sample.
+func (t *StandardTimer) Percentile(p float64) float64 {
+	return t.histogram.Percentile(p)
+}
+
+// Percentiles returns a slice of arbitrary percentiles of the values in the
+// sample.
+func (t *StandardTimer) Percentiles(ps []float64) []float64 {
+	return t.histogram.Percentiles(ps)
+}
+
+// Rate1 returns the one-minute moving average rate of events per second.
+func (t *StandardTimer) Rate1() float64 {
+	return t.meter.Rate1()
+}
+
+// Rate5 returns the five-minute moving average rate of events per second.
+func (t *StandardTimer) Rate5() float64 {
+	return t.meter.Rate5()
+}
+
+// Rate15 returns the fifteen-minute moving average rate of events per second.
+func (t *StandardTimer) Rate15() float64 {
+	return t.meter.Rate15()
+}
+
+// RateMean returns the meter's mean rate of events per second.
+func (t *StandardTimer) RateMean() float64 {
+	return t.meter.RateMean()
+}
+
+// Snapshot returns a read-only copy of the timer.
+func (t *StandardTimer) Snapshot() Timer {
+	t.mutex.Lock()
+	defer t.mutex.Unlock()
+	return &TimerSnapshot{
+		histogram: t.histogram.Snapshot().(*HistogramSnapshot),
+		meter:     t.meter.Snapshot().(*MeterSnapshot),
+	}
+}
+
+// StdDev returns the standard deviation of the values in the sample.
+func (t *StandardTimer) StdDev() float64 {
+	return t.histogram.StdDev()
+}
+
+// Sum returns the sum in the sample.
+func (t *StandardTimer) Sum() int64 {
+	return t.histogram.Sum()
+}
+
+// Record the duration of the execution of the given function.
+func (t *StandardTimer) Time(f func()) {
+	ts := time.Now()
+	f()
+	t.Update(time.Since(ts))
+}
+
+// Record the duration of an event.
+func (t *StandardTimer) Update(d time.Duration) {
+	t.mutex.Lock()
+	defer t.mutex.Unlock()
+	t.histogram.Update(int64(d))
+	t.meter.Mark(1)
+}
+
+// Record the duration of an event that started at a time and ends now.
+func (t *StandardTimer) UpdateSince(ts time.Time) {
+	t.mutex.Lock()
+	defer t.mutex.Unlock()
+	t.histogram.Update(int64(time.Since(ts)))
+	t.meter.Mark(1)
+}
+
+// Variance returns the variance of the values in the sample.
+func (t *StandardTimer) Variance() float64 {
+	return t.histogram.Variance()
+}
+
+// TimerSnapshot is a read-only copy of another Timer.
+type TimerSnapshot struct {
+	histogram *HistogramSnapshot
+	meter     *MeterSnapshot
+}
+
+// Count returns the number of events recorded at the time the snapshot was
+// taken.
+func (t *TimerSnapshot) Count() int64 { return t.histogram.Count() }
+
+// Max returns the maximum value at the time the snapshot was taken.
+func (t *TimerSnapshot) Max() int64 { return t.histogram.Max() }
+
+// Mean returns the mean value at the time the snapshot was taken.
+func (t *TimerSnapshot) Mean() float64 { return t.histogram.Mean() }
+
+// Min returns the minimum value at the time the snapshot was taken.
+func (t *TimerSnapshot) Min() int64 { return t.histogram.Min() }
+
+// Percentile returns an arbitrary percentile of sampled values at the time the
+// snapshot was taken.
+func (t *TimerSnapshot) Percentile(p float64) float64 {
+	return t.histogram.Percentile(p)
+}
+
+// Percentiles returns a slice of arbitrary percentiles of sampled values at
+// the time the snapshot was taken.
+func (t *TimerSnapshot) Percentiles(ps []float64) []float64 {
+	return t.histogram.Percentiles(ps)
+}
+
+// Rate1 returns the one-minute moving average rate of events per second at the
+// time the snapshot was taken.
+func (t *TimerSnapshot) Rate1() float64 { return t.meter.Rate1() }
+
+// Rate5 returns the five-minute moving average rate of events per second at
+// the time the snapshot was taken.
+func (t *TimerSnapshot) Rate5() float64 { return t.meter.Rate5() }
+
+// Rate15 returns the fifteen-minute moving average rate of events per second
+// at the time the snapshot was taken.
+func (t *TimerSnapshot) Rate15() float64 { return t.meter.Rate15() }
+
+// RateMean returns the meter's mean rate of events per second at the time the
+// snapshot was taken.
+func (t *TimerSnapshot) RateMean() float64 { return t.meter.RateMean() }
+
+// Snapshot returns the snapshot.
+func (t *TimerSnapshot) Snapshot() Timer { return t }
+
+// StdDev returns the standard deviation of the values at the time the snapshot
+// was taken.
+func (t *TimerSnapshot) StdDev() float64 { return t.histogram.StdDev() }
+
+// Sum returns the sum at the time the snapshot was taken.
+func (t *TimerSnapshot) Sum() int64 { return t.histogram.Sum() }
+
+// Time panics.
+func (*TimerSnapshot) Time(func()) {
+	panic("Time called on a TimerSnapshot")
+}
+
+// Update panics.
+func (*TimerSnapshot) Update(time.Duration) {
+	panic("Update called on a TimerSnapshot")
+}
+
+// UpdateSince panics.
+func (*TimerSnapshot) UpdateSince(time.Time) {
+	panic("UpdateSince called on a TimerSnapshot")
+}
+
+// Variance returns the variance of the values at the time the snapshot was
+// taken.
+func (t *TimerSnapshot) Variance() float64 { return t.histogram.Variance() }
@@ -0,0 +1,10 @@
+#!/bin/bash
+
+set -e
+
+# check there are no formatting issues
+GOFMT_LINES=`gofmt -l . | wc -l | xargs`
+test $GOFMT_LINES -eq 0 || echo "gofmt needs to be run, ${GOFMT_LINES} files have issues"
+
+# run the tests for the root package
+go test .
@@ -0,0 +1,100 @@
+package metrics
+
+import (
+	"fmt"
+	"io"
+	"sort"
+	"time"
+)
+
+// Write sorts writes each metric in the given registry periodically to the
+// given io.Writer.
+func Write(r Registry, d time.Duration, w io.Writer) {
+	for _ = range time.Tick(d) {
+		WriteOnce(r, w)
+	}
+}
+
+// WriteOnce sorts and writes metrics in the given registry to the given
+// io.Writer.
+func WriteOnce(r Registry, w io.Writer) {
+	var namedMetrics namedMetricSlice
+	r.Each(func(name string, i interface{}) {
+		namedMetrics = append(namedMetrics, namedMetric{name, i})
+	})
+
+	sort.Sort(namedMetrics)
+	for _, namedMetric := range namedMetrics {
+		switch metric := namedMetric.m.(type) {
+		case Counter:
+			fmt.Fprintf(w, "counter %s\n", namedMetric.name)
+			fmt.Fprintf(w, "  count:       %9d\n", metric.Count())
+		case Gauge:
+			fmt.Fprintf(w, "gauge %s\n", namedMetric.name)
+			fmt.Fprintf(w, "  value:       %9d\n", metric.Value())
+		case GaugeFloat64:
+			fmt.Fprintf(w, "gauge %s\n", namedMetric.name)
+			fmt.Fprintf(w, "  value:       %f\n", metric.Value())
+		case Healthcheck:
+			metric.Check()
+			fmt.Fprintf(w, "healthcheck %s\n", namedMetric.name)
+			fmt.Fprintf(w, "  error:       %v\n", metric.Error())
+		case Histogram:
+			h := metric.Snapshot()
+			ps := h.Percentiles([]float64{0.5, 0.75, 0.95, 0.99, 0.999})
+			fmt.Fprintf(w, "histogram %s\n", namedMetric.name)
+			fmt.Fprintf(w, "  count:       %9d\n", h.Count())
+			fmt.Fprintf(w, "  min:         %9d\n", h.Min())
+			fmt.Fprintf(w, "  max:         %9d\n", h.Max())
+			fmt.Fprintf(w, "  mean:        %12.2f\n", h.Mean())
+			fmt.Fprintf(w, "  stddev:      %12.2f\n", h.StdDev())
+			fmt.Fprintf(w, "  median:      %12.2f\n", ps[0])
+			fmt.Fprintf(w, "  75%%:         %12.2f\n", ps[1])
+			fmt.Fprintf(w, "  95%%:         %12.2f\n", ps[2])
+			fmt.Fprintf(w, "  99%%:         %12.2f\n", ps[3])
+			fmt.Fprintf(w, "  99.9%%:       %12.2f\n", ps[4])
+		case Meter:
+			m := metric.Snapshot()
+			fmt.Fprintf(w, "meter %s\n", namedMetric.name)
+			fmt.Fprintf(w, "  count:       %9d\n", m.Count())
+			fmt.Fprintf(w, "  1-min rate:  %12.2f\n", m.Rate1())
+			fmt.Fprintf(w, "  5-min rate:  %12.2f\n", m.Rate5())
+			fmt.Fprintf(w, "  15-min rate: %12.2f\n", m.Rate15())
+			fmt.Fprintf(w, "  mean rate:   %12.2f\n", m.RateMean())
+		case Timer:
+			t := metric.Snapshot()
+			ps := t.Percentiles([]float64{0.5, 0.75, 0.95, 0.99, 0.999})
+			fmt.Fprintf(w, "timer %s\n", namedMetric.name)
+			fmt.Fprintf(w, "  count:       %9d\n", t.Count())
+			fmt.Fprintf(w, "  min:         %9d\n", t.Min())
+			fmt.Fprintf(w, "  max:         %9d\n", t.Max())
+			fmt.Fprintf(w, "  mean:        %12.2f\n", t.Mean())
+			fmt.Fprintf(w, "  stddev:      %12.2f\n", t.StdDev())
+			fmt.Fprintf(w, "  median:      %12.2f\n", ps[0])
+			fmt.Fprintf(w, "  75%%:         %12.2f\n", ps[1])
+			fmt.Fprintf(w, "  95%%:         %12.2f\n", ps[2])
+			fmt.Fprintf(w, "  99%%:         %12.2f\n", ps[3])
+			fmt.Fprintf(w, "  99.9%%:       %12.2f\n", ps[4])
+			fmt.Fprintf(w, "  1-min rate:  %12.2f\n", t.Rate1())
+			fmt.Fprintf(w, "  5-min rate:  %12.2f\n", t.Rate5())
+			fmt.Fprintf(w, "  15-min rate: %12.2f\n", t.Rate15())
+			fmt.Fprintf(w, "  mean rate:   %12.2f\n", t.RateMean())
+		}
+	}
+}
+
+type namedMetric struct {
+	name string
+	m    interface{}
+}
+
+// namedMetricSlice is a slice of namedMetrics that implements sort.Interface.
+type namedMetricSlice []namedMetric
+
+func (nms namedMetricSlice) Len() int { return len(nms) }
+
+func (nms namedMetricSlice) Swap(i, j int) { nms[i], nms[j] = nms[j], nms[i] }
+
+func (nms namedMetricSlice) Less(i, j int) bool {
+	return nms[i].name < nms[j].name
+}
@@ -0,0 +1,252 @@
+// Copyright (c) 2012, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package leveldb
+
+import (
+	"encoding/binary"
+	"fmt"
+
+	"github.com/syndtr/goleveldb/leveldb/errors"
+	"github.com/syndtr/goleveldb/leveldb/memdb"
+)
+
+type ErrBatchCorrupted struct {
+	Reason string
+}
+
+func (e *ErrBatchCorrupted) Error() string {
+	return fmt.Sprintf("leveldb: batch corrupted: %s", e.Reason)
+}
+
+func newErrBatchCorrupted(reason string) error {
+	return errors.NewErrCorrupted(nil, &ErrBatchCorrupted{reason})
+}
+
+const (
+	batchHdrLen  = 8 + 4
+	batchGrowRec = 3000
+)
+
+type BatchReplay interface {
+	Put(key, value []byte)
+	Delete(key []byte)
+}
+
+// Batch is a write batch.
+type Batch struct {
+	data       []byte
+	rLen, bLen int
+	seq        uint64
+	sync       bool
+}
+
+func (b *Batch) grow(n int) {
+	off := len(b.data)
+	if off == 0 {
+		off = batchHdrLen
+		if b.data != nil {
+			b.data = b.data[:off]
+		}
+	}
+	if cap(b.data)-off < n {
+		if b.data == nil {
+			b.data = make([]byte, off, off+n)
+		} else {
+			odata := b.data
+			div := 1
+			if b.rLen > batchGrowRec {
+				div = b.rLen / batchGrowRec
+			}
+			b.data = make([]byte, off, off+n+(off-batchHdrLen)/div)
+			copy(b.data, odata)
+		}
+	}
+}
+
+func (b *Batch) appendRec(kt kType, key, value []byte) {
+	n := 1 + binary.MaxVarintLen32 + len(key)
+	if kt == ktVal {
+		n += binary.MaxVarintLen32 + len(value)
+	}
+	b.grow(n)
+	off := len(b.data)
+	data := b.data[:off+n]
+	data[off] = byte(kt)
+	off += 1
+	off += binary.PutUvarint(data[off:], uint64(len(key)))
+	copy(data[off:], key)
+	off += len(key)
+	if kt == ktVal {
+		off += binary.PutUvarint(data[off:], uint64(len(value)))
+		copy(data[off:], value)
+		off += len(value)
+	}
+	b.data = data[:off]
+	b.rLen++
+	//  Include 8-byte ikey header
+	b.bLen += len(key) + len(value) + 8
+}
+
+// Put appends 'put operation' of the given key/value pair to the batch.
+// It is safe to modify the contents of the argument after Put returns.
+func (b *Batch) Put(key, value []byte) {
+	b.appendRec(ktVal, key, value)
+}
+
+// Delete appends 'delete operation' of the given key to the batch.
+// It is safe to modify the contents of the argument after Delete returns.
+func (b *Batch) Delete(key []byte) {
+	b.appendRec(ktDel, key, nil)
+}
+
+// Dump dumps batch contents. The returned slice can be loaded into the
+// batch using Load method.
+// The returned slice is not its own copy, so the contents should not be
+// modified.
+func (b *Batch) Dump() []byte {
+	return b.encode()
+}
+
+// Load loads given slice into the batch. Previous contents of the batch
+// will be discarded.
+// The given slice will not be copied and will be used as batch buffer, so
+// it is not safe to modify the contents of the slice.
+func (b *Batch) Load(data []byte) error {
+	return b.decode(0, data)
+}
+
+// Replay replays batch contents.
+func (b *Batch) Replay(r BatchReplay) error {
+	return b.decodeRec(func(i int, kt kType, key, value []byte) {
+		switch kt {
+		case ktVal:
+			r.Put(key, value)
+		case ktDel:
+			r.Delete(key)
+		}
+	})
+}
+
+// Len returns number of records in the batch.
+func (b *Batch) Len() int {
+	return b.rLen
+}
+
+// Reset resets the batch.
+func (b *Batch) Reset() {
+	b.data = b.data[:0]
+	b.seq = 0
+	b.rLen = 0
+	b.bLen = 0
+	b.sync = false
+}
+
+func (b *Batch) init(sync bool) {
+	b.sync = sync
+}
+
+func (b *Batch) append(p *Batch) {
+	if p.rLen > 0 {
+		b.grow(len(p.data) - batchHdrLen)
+		b.data = append(b.data, p.data[batchHdrLen:]...)
+		b.rLen += p.rLen
+	}
+	if p.sync {
+		b.sync = true
+	}
+}
+
+// size returns sums of key/value pair length plus 8-bytes ikey.
+func (b *Batch) size() int {
+	return b.bLen
+}
+
+func (b *Batch) encode() []byte {
+	b.grow(0)
+	binary.LittleEndian.PutUint64(b.data, b.seq)
+	binary.LittleEndian.PutUint32(b.data[8:], uint32(b.rLen))
+
+	return b.data
+}
+
+func (b *Batch) decode(prevSeq uint64, data []byte) error {
+	if len(data) < batchHdrLen {
+		return newErrBatchCorrupted("too short")
+	}
+
+	b.seq = binary.LittleEndian.Uint64(data)
+	if b.seq < prevSeq {
+		return newErrBatchCorrupted("invalid sequence number")
+	}
+	b.rLen = int(binary.LittleEndian.Uint32(data[8:]))
+	if b.rLen < 0 {
+		return newErrBatchCorrupted("invalid records length")
+	}
+	// No need to be precise at this point, it won't be used anyway
+	b.bLen = len(data) - batchHdrLen
+	b.data = data
+
+	return nil
+}
+
+func (b *Batch) decodeRec(f func(i int, kt kType, key, value []byte)) (err error) {
+	off := batchHdrLen
+	for i := 0; i < b.rLen; i++ {
+		if off >= len(b.data) {
+			return newErrBatchCorrupted("invalid records length")
+		}
+
+		kt := kType(b.data[off])
+		if kt > ktVal {
+			return newErrBatchCorrupted("bad record: invalid type")
+		}
+		off += 1
+
+		x, n := binary.Uvarint(b.data[off:])
+		off += n
+		if n <= 0 || off+int(x) > len(b.data) {
+			return newErrBatchCorrupted("bad record: invalid key length")
+		}
+		key := b.data[off : off+int(x)]
+		off += int(x)
+		var value []byte
+		if kt == ktVal {
+			x, n := binary.Uvarint(b.data[off:])
+			off += n
+			if n <= 0 || off+int(x) > len(b.data) {
+				return newErrBatchCorrupted("bad record: invalid value length")
+			}
+			value = b.data[off : off+int(x)]
+			off += int(x)
+		}
+
+		f(i, kt, key, value)
+	}
+
+	return nil
+}
+
+func (b *Batch) memReplay(to *memdb.DB) error {
+	return b.decodeRec(func(i int, kt kType, key, value []byte) {
+		ikey := newIkey(key, b.seq+uint64(i), kt)
+		to.Put(ikey, value)
+	})
+}
+
+func (b *Batch) memDecodeAndReplay(prevSeq uint64, data []byte, to *memdb.DB) error {
+	if err := b.decode(prevSeq, data); err != nil {
+		return err
+	}
+	return b.memReplay(to)
+}
+
+func (b *Batch) revertMemReplay(to *memdb.DB) error {
+	return b.decodeRec(func(i int, kt kType, key, value []byte) {
+		ikey := newIkey(key, b.seq+uint64(i), kt)
+		to.Delete(ikey)
+	})
+}
@@ -0,0 +1,676 @@
+// Copyright (c) 2012, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Package cache provides interface and implementation of a cache algorithms.
+package cache
+
+import (
+	"sync"
+	"sync/atomic"
+	"unsafe"
+
+	"github.com/syndtr/goleveldb/leveldb/util"
+)
+
+// Cacher provides interface to implements a caching functionality.
+// An implementation must be goroutine-safe.
+type Cacher interface {
+	// Capacity returns cache capacity.
+	Capacity() int
+
+	// SetCapacity sets cache capacity.
+	SetCapacity(capacity int)
+
+	// Promote promotes the 'cache node'.
+	Promote(n *Node)
+
+	// Ban evicts the 'cache node' and prevent subsequent 'promote'.
+	Ban(n *Node)
+
+	// Evict evicts the 'cache node'.
+	Evict(n *Node)
+
+	// EvictNS evicts 'cache node' with the given namespace.
+	EvictNS(ns uint64)
+
+	// EvictAll evicts all 'cache node'.
+	EvictAll()
+
+	// Close closes the 'cache tree'
+	Close() error
+}
+
+// Value is a 'cacheable object'. It may implements util.Releaser, if
+// so the the Release method will be called once object is released.
+type Value interface{}
+
+type CacheGetter struct {
+	Cache *Cache
+	NS    uint64
+}
+
+func (g *CacheGetter) Get(key uint64, setFunc func() (size int, value Value)) *Handle {
+	return g.Cache.Get(g.NS, key, setFunc)
+}
+
+// The hash tables implementation is based on:
+// "Dynamic-Sized Nonblocking Hash Tables", by Yujie Liu, Kunlong Zhang, and Michael Spear. ACM Symposium on Principles of Distributed Computing, Jul 2014.
+
+const (
+	mInitialSize           = 1 << 4
+	mOverflowThreshold     = 1 << 5
+	mOverflowGrowThreshold = 1 << 7
+)
+
+type mBucket struct {
+	mu     sync.Mutex
+	node   []*Node
+	frozen bool
+}
+
+func (b *mBucket) freeze() []*Node {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+	if !b.frozen {
+		b.frozen = true
+	}
+	return b.node
+}
+
+func (b *mBucket) get(r *Cache, h *mNode, hash uint32, ns, key uint64, noset bool) (done, added bool, n *Node) {
+	b.mu.Lock()
+
+	if b.frozen {
+		b.mu.Unlock()
+		return
+	}
+
+	// Scan the node.
+	for _, n := range b.node {
+		if n.hash == hash && n.ns == ns && n.key == key {
+			atomic.AddInt32(&n.ref, 1)
+			b.mu.Unlock()
+			return true, false, n
+		}
+	}
+
+	// Get only.
+	if noset {
+		b.mu.Unlock()
+		return true, false, nil
+	}
+
+	// Create node.
+	n = &Node{
+		r:    r,
+		hash: hash,
+		ns:   ns,
+		key:  key,
+		ref:  1,
+	}
+	// Add node to bucket.
+	b.node = append(b.node, n)
+	bLen := len(b.node)
+	b.mu.Unlock()
+
+	// Update counter.
+	grow := atomic.AddInt32(&r.nodes, 1) >= h.growThreshold
+	if bLen > mOverflowThreshold {
+		grow = grow || atomic.AddInt32(&h.overflow, 1) >= mOverflowGrowThreshold
+	}
+
+	// Grow.
+	if grow && atomic.CompareAndSwapInt32(&h.resizeInProgess, 0, 1) {
+		nhLen := len(h.buckets) << 1
+		nh := &mNode{
+			buckets:         make([]unsafe.Pointer, nhLen),
+			mask:            uint32(nhLen) - 1,
+			pred:            unsafe.Pointer(h),
+			growThreshold:   int32(nhLen * mOverflowThreshold),
+			shrinkThreshold: int32(nhLen >> 1),
+		}
+		ok := atomic.CompareAndSwapPointer(&r.mHead, unsafe.Pointer(h), unsafe.Pointer(nh))
+		if !ok {
+			panic("BUG: failed swapping head")
+		}
+		go nh.initBuckets()
+	}
+
+	return true, true, n
+}
+
+func (b *mBucket) delete(r *Cache, h *mNode, hash uint32, ns, key uint64) (done, deleted bool) {
+	b.mu.Lock()
+
+	if b.frozen {
+		b.mu.Unlock()
+		return
+	}
+
+	// Scan the node.
+	var (
+		n    *Node
+		bLen int
+	)
+	for i := range b.node {
+		n = b.node[i]
+		if n.ns == ns && n.key == key {
+			if atomic.LoadInt32(&n.ref) == 0 {
+				deleted = true
+
+				// Call releaser.
+				if n.value != nil {
+					if r, ok := n.value.(util.Releaser); ok {
+						r.Release()
+					}
+					n.value = nil
+				}
+
+				// Remove node from bucket.
+				b.node = append(b.node[:i], b.node[i+1:]...)
+				bLen = len(b.node)
+			}
+			break
+		}
+	}
+	b.mu.Unlock()
+
+	if deleted {
+		// Call OnDel.
+		for _, f := range n.onDel {
+			f()
+		}
+
+		// Update counter.
+		atomic.AddInt32(&r.size, int32(n.size)*-1)
+		shrink := atomic.AddInt32(&r.nodes, -1) < h.shrinkThreshold
+		if bLen >= mOverflowThreshold {
+			atomic.AddInt32(&h.overflow, -1)
+		}
+
+		// Shrink.
+		if shrink && len(h.buckets) > mInitialSize && atomic.CompareAndSwapInt32(&h.resizeInProgess, 0, 1) {
+			nhLen := len(h.buckets) >> 1
+			nh := &mNode{
+				buckets:         make([]unsafe.Pointer, nhLen),
+				mask:            uint32(nhLen) - 1,
+				pred:            unsafe.Pointer(h),
+				growThreshold:   int32(nhLen * mOverflowThreshold),
+				shrinkThreshold: int32(nhLen >> 1),
+			}
+			ok := atomic.CompareAndSwapPointer(&r.mHead, unsafe.Pointer(h), unsafe.Pointer(nh))
+			if !ok {
+				panic("BUG: failed swapping head")
+			}
+			go nh.initBuckets()
+		}
+	}
+
+	return true, deleted
+}
+
+type mNode struct {
+	buckets         []unsafe.Pointer // []*mBucket
+	mask            uint32
+	pred            unsafe.Pointer // *mNode
+	resizeInProgess int32
+
+	overflow        int32
+	growThreshold   int32
+	shrinkThreshold int32
+}
+
+func (n *mNode) initBucket(i uint32) *mBucket {
+	if b := (*mBucket)(atomic.LoadPointer(&n.buckets[i])); b != nil {
+		return b
+	}
+
+	p := (*mNode)(atomic.LoadPointer(&n.pred))
+	if p != nil {
+		var node []*Node
+		if n.mask > p.mask {
+			// Grow.
+			pb := (*mBucket)(atomic.LoadPointer(&p.buckets[i&p.mask]))
+			if pb == nil {
+				pb = p.initBucket(i & p.mask)
+			}
+			m := pb.freeze()
+			// Split nodes.
+			for _, x := range m {
+				if x.hash&n.mask == i {
+					node = append(node, x)
+				}
+			}
+		} else {
+			// Shrink.
+			pb0 := (*mBucket)(atomic.LoadPointer(&p.buckets[i]))
+			if pb0 == nil {
+				pb0 = p.initBucket(i)
+			}
+			pb1 := (*mBucket)(atomic.LoadPointer(&p.buckets[i+uint32(len(n.buckets))]))
+			if pb1 == nil {
+				pb1 = p.initBucket(i + uint32(len(n.buckets)))
+			}
+			m0 := pb0.freeze()
+			m1 := pb1.freeze()
+			// Merge nodes.
+			node = make([]*Node, 0, len(m0)+len(m1))
+			node = append(node, m0...)
+			node = append(node, m1...)
+		}
+		b := &mBucket{node: node}
+		if atomic.CompareAndSwapPointer(&n.buckets[i], nil, unsafe.Pointer(b)) {
+			if len(node) > mOverflowThreshold {
+				atomic.AddInt32(&n.overflow, int32(len(node)-mOverflowThreshold))
+			}
+			return b
+		}
+	}
+
+	return (*mBucket)(atomic.LoadPointer(&n.buckets[i]))
+}
+
+func (n *mNode) initBuckets() {
+	for i := range n.buckets {
+		n.initBucket(uint32(i))
+	}
+	atomic.StorePointer(&n.pred, nil)
+}
+
+// Cache is a 'cache map'.
+type Cache struct {
+	mu     sync.RWMutex
+	mHead  unsafe.Pointer // *mNode
+	nodes  int32
+	size   int32
+	cacher Cacher
+	closed bool
+}
+
+// NewCache creates a new 'cache map'. The cacher is optional and
+// may be nil.
+func NewCache(cacher Cacher) *Cache {
+	h := &mNode{
+		buckets:         make([]unsafe.Pointer, mInitialSize),
+		mask:            mInitialSize - 1,
+		growThreshold:   int32(mInitialSize * mOverflowThreshold),
+		shrinkThreshold: 0,
+	}
+	for i := range h.buckets {
+		h.buckets[i] = unsafe.Pointer(&mBucket{})
+	}
+	r := &Cache{
+		mHead:  unsafe.Pointer(h),
+		cacher: cacher,
+	}
+	return r
+}
+
+func (r *Cache) getBucket(hash uint32) (*mNode, *mBucket) {
+	h := (*mNode)(atomic.LoadPointer(&r.mHead))
+	i := hash & h.mask
+	b := (*mBucket)(atomic.LoadPointer(&h.buckets[i]))
+	if b == nil {
+		b = h.initBucket(i)
+	}
+	return h, b
+}
+
+func (r *Cache) delete(n *Node) bool {
+	for {
+		h, b := r.getBucket(n.hash)
+		done, deleted := b.delete(r, h, n.hash, n.ns, n.key)
+		if done {
+			return deleted
+		}
+	}
+	return false
+}
+
+// Nodes returns number of 'cache node' in the map.
+func (r *Cache) Nodes() int {
+	return int(atomic.LoadInt32(&r.nodes))
+}
+
+// Size returns sums of 'cache node' size in the map.
+func (r *Cache) Size() int {
+	return int(atomic.LoadInt32(&r.size))
+}
+
+// Capacity returns cache capacity.
+func (r *Cache) Capacity() int {
+	if r.cacher == nil {
+		return 0
+	}
+	return r.cacher.Capacity()
+}
+
+// SetCapacity sets cache capacity.
+func (r *Cache) SetCapacity(capacity int) {
+	if r.cacher != nil {
+		r.cacher.SetCapacity(capacity)
+	}
+}
+
+// Get gets 'cache node' with the given namespace and key.
+// If cache node is not found and setFunc is not nil, Get will atomically creates
+// the 'cache node' by calling setFunc. Otherwise Get will returns nil.
+//
+// The returned 'cache handle' should be released after use by calling Release
+// method.
+func (r *Cache) Get(ns, key uint64, setFunc func() (size int, value Value)) *Handle {
+	r.mu.RLock()
+	defer r.mu.RUnlock()
+	if r.closed {
+		return nil
+	}
+
+	hash := murmur32(ns, key, 0xf00)
+	for {
+		h, b := r.getBucket(hash)
+		done, _, n := b.get(r, h, hash, ns, key, setFunc == nil)
+		if done {
+			if n != nil {
+				n.mu.Lock()
+				if n.value == nil {
+					if setFunc == nil {
+						n.mu.Unlock()
+						n.unref()
+						return nil
+					}
+
+					n.size, n.value = setFunc()
+					if n.value == nil {
+						n.size = 0
+						n.mu.Unlock()
+						n.unref()
+						return nil
+					}
+					atomic.AddInt32(&r.size, int32(n.size))
+				}
+				n.mu.Unlock()
+				if r.cacher != nil {
+					r.cacher.Promote(n)
+				}
+				return &Handle{unsafe.Pointer(n)}
+			}
+
+			break
+		}
+	}
+	return nil
+}
+
+// Delete removes and ban 'cache node' with the given namespace and key.
+// A banned 'cache node' will never inserted into the 'cache tree'. Ban
+// only attributed to the particular 'cache node', so when a 'cache node'
+// is recreated it will not be banned.
+//
+// If onDel is not nil, then it will be executed if such 'cache node'
+// doesn't exist or once the 'cache node' is released.
+//
+// Delete return true is such 'cache node' exist.
+func (r *Cache) Delete(ns, key uint64, onDel func()) bool {
+	r.mu.RLock()
+	defer r.mu.RUnlock()
+	if r.closed {
+		return false
+	}
+
+	hash := murmur32(ns, key, 0xf00)
+	for {
+		h, b := r.getBucket(hash)
+		done, _, n := b.get(r, h, hash, ns, key, true)
+		if done {
+			if n != nil {
+				if onDel != nil {
+					n.mu.Lock()
+					n.onDel = append(n.onDel, onDel)
+					n.mu.Unlock()
+				}
+				if r.cacher != nil {
+					r.cacher.Ban(n)
+				}
+				n.unref()
+				return true
+			}
+
+			break
+		}
+	}
+
+	if onDel != nil {
+		onDel()
+	}
+
+	return false
+}
+
+// Evict evicts 'cache node' with the given namespace and key. This will
+// simply call Cacher.Evict.
+//
+// Evict return true is such 'cache node' exist.
+func (r *Cache) Evict(ns, key uint64) bool {
+	r.mu.RLock()
+	defer r.mu.RUnlock()
+	if r.closed {
+		return false
+	}
+
+	hash := murmur32(ns, key, 0xf00)
+	for {
+		h, b := r.getBucket(hash)
+		done, _, n := b.get(r, h, hash, ns, key, true)
+		if done {
+			if n != nil {
+				if r.cacher != nil {
+					r.cacher.Evict(n)
+				}
+				n.unref()
+				return true
+			}
+
+			break
+		}
+	}
+
+	return false
+}
+
+// EvictNS evicts 'cache node' with the given namespace. This will
+// simply call Cacher.EvictNS.
+func (r *Cache) EvictNS(ns uint64) {
+	r.mu.RLock()
+	defer r.mu.RUnlock()
+	if r.closed {
+		return
+	}
+
+	if r.cacher != nil {
+		r.cacher.EvictNS(ns)
+	}
+}
+
+// EvictAll evicts all 'cache node'. This will simply call Cacher.EvictAll.
+func (r *Cache) EvictAll() {
+	r.mu.RLock()
+	defer r.mu.RUnlock()
+	if r.closed {
+		return
+	}
+
+	if r.cacher != nil {
+		r.cacher.EvictAll()
+	}
+}
+
+// Close closes the 'cache map' and releases all 'cache node'.
+func (r *Cache) Close() error {
+	r.mu.Lock()
+	if !r.closed {
+		r.closed = true
+
+		if r.cacher != nil {
+			if err := r.cacher.Close(); err != nil {
+				return err
+			}
+		}
+
+		h := (*mNode)(r.mHead)
+		h.initBuckets()
+
+		for i := range h.buckets {
+			b := (*mBucket)(h.buckets[i])
+			for _, n := range b.node {
+				// Call releaser.
+				if n.value != nil {
+					if r, ok := n.value.(util.Releaser); ok {
+						r.Release()
+					}
+					n.value = nil
+				}
+
+				// Call OnDel.
+				for _, f := range n.onDel {
+					f()
+				}
+			}
+		}
+	}
+	r.mu.Unlock()
+	return nil
+}
+
+// Node is a 'cache node'.
+type Node struct {
+	r *Cache
+
+	hash    uint32
+	ns, key uint64
+
+	mu    sync.Mutex
+	size  int
+	value Value
+
+	ref   int32
+	onDel []func()
+
+	CacheData unsafe.Pointer
+}
+
+// NS returns this 'cache node' namespace.
+func (n *Node) NS() uint64 {
+	return n.ns
+}
+
+// Key returns this 'cache node' key.
+func (n *Node) Key() uint64 {
+	return n.key
+}
+
+// Size returns this 'cache node' size.
+func (n *Node) Size() int {
+	return n.size
+}
+
+// Value returns this 'cache node' value.
+func (n *Node) Value() Value {
+	return n.value
+}
+
+// Ref returns this 'cache node' ref counter.
+func (n *Node) Ref() int32 {
+	return atomic.LoadInt32(&n.ref)
+}
+
+// GetHandle returns an handle for this 'cache node'.
+func (n *Node) GetHandle() *Handle {
+	if atomic.AddInt32(&n.ref, 1) <= 1 {
+		panic("BUG: Node.GetHandle on zero ref")
+	}
+	return &Handle{unsafe.Pointer(n)}
+}
+
+func (n *Node) unref() {
+	if atomic.AddInt32(&n.ref, -1) == 0 {
+		n.r.delete(n)
+	}
+}
+
+func (n *Node) unrefLocked() {
+	if atomic.AddInt32(&n.ref, -1) == 0 {
+		n.r.mu.RLock()
+		if !n.r.closed {
+			n.r.delete(n)
+		}
+		n.r.mu.RUnlock()
+	}
+}
+
+type Handle struct {
+	n unsafe.Pointer // *Node
+}
+
+func (h *Handle) Value() Value {
+	n := (*Node)(atomic.LoadPointer(&h.n))
+	if n != nil {
+		return n.value
+	}
+	return nil
+}
+
+func (h *Handle) Release() {
+	nPtr := atomic.LoadPointer(&h.n)
+	if nPtr != nil && atomic.CompareAndSwapPointer(&h.n, nPtr, nil) {
+		n := (*Node)(nPtr)
+		n.unrefLocked()
+	}
+}
+
+func murmur32(ns, key uint64, seed uint32) uint32 {
+	const (
+		m = uint32(0x5bd1e995)
+		r = 24
+	)
+
+	k1 := uint32(ns >> 32)
+	k2 := uint32(ns)
+	k3 := uint32(key >> 32)
+	k4 := uint32(key)
+
+	k1 *= m
+	k1 ^= k1 >> r
+	k1 *= m
+
+	k2 *= m
+	k2 ^= k2 >> r
+	k2 *= m
+
+	k3 *= m
+	k3 ^= k3 >> r
+	k3 *= m
+
+	k4 *= m
+	k4 ^= k4 >> r
+	k4 *= m
+
+	h := seed
+
+	h *= m
+	h ^= k1
+	h *= m
+	h ^= k2
+	h *= m
+	h ^= k3
+	h *= m
+	h ^= k4
+
+	h ^= h >> 13
+	h *= m
+	h ^= h >> 15
+
+	return h
+}
@@ -0,0 +1,195 @@
+// Copyright (c) 2012, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package cache
+
+import (
+	"sync"
+	"unsafe"
+)
+
+type lruNode struct {
+	n   *Node
+	h   *Handle
+	ban bool
+
+	next, prev *lruNode
+}
+
+func (n *lruNode) insert(at *lruNode) {
+	x := at.next
+	at.next = n
+	n.prev = at
+	n.next = x
+	x.prev = n
+}
+
+func (n *lruNode) remove() {
+	if n.prev != nil {
+		n.prev.next = n.next
+		n.next.prev = n.prev
+		n.prev = nil
+		n.next = nil
+	} else {
+		panic("BUG: removing removed node")
+	}
+}
+
+type lru struct {
+	mu       sync.Mutex
+	capacity int
+	used     int
+	recent   lruNode
+}
+
+func (r *lru) reset() {
+	r.recent.next = &r.recent
+	r.recent.prev = &r.recent
+	r.used = 0
+}
+
+func (r *lru) Capacity() int {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	return r.capacity
+}
+
+func (r *lru) SetCapacity(capacity int) {
+	var evicted []*lruNode
+
+	r.mu.Lock()
+	r.capacity = capacity
+	for r.used > r.capacity {
+		rn := r.recent.prev
+		if rn == nil {
+			panic("BUG: invalid LRU used or capacity counter")
+		}
+		rn.remove()
+		rn.n.CacheData = nil
+		r.used -= rn.n.Size()
+		evicted = append(evicted, rn)
+	}
+	r.mu.Unlock()
+
+	for _, rn := range evicted {
+		rn.h.Release()
+	}
+}
+
+func (r *lru) Promote(n *Node) {
+	var evicted []*lruNode
+
+	r.mu.Lock()
+	if n.CacheData == nil {
+		if n.Size() <= r.capacity {
+			rn := &lruNode{n: n, h: n.GetHandle()}
+			rn.insert(&r.recent)
+			n.CacheData = unsafe.Pointer(rn)
+			r.used += n.Size()
+
+			for r.used > r.capacity {
+				rn := r.recent.prev
+				if rn == nil {
+					panic("BUG: invalid LRU used or capacity counter")
+				}
+				rn.remove()
+				rn.n.CacheData = nil
+				r.used -= rn.n.Size()
+				evicted = append(evicted, rn)
+			}
+		}
+	} else {
+		rn := (*lruNode)(n.CacheData)
+		if !rn.ban {
+			rn.remove()
+			rn.insert(&r.recent)
+		}
+	}
+	r.mu.Unlock()
+
+	for _, rn := range evicted {
+		rn.h.Release()
+	}
+}
+
+func (r *lru) Ban(n *Node) {
+	r.mu.Lock()
+	if n.CacheData == nil {
+		n.CacheData = unsafe.Pointer(&lruNode{n: n, ban: true})
+	} else {
+		rn := (*lruNode)(n.CacheData)
+		if !rn.ban {
+			rn.remove()
+			rn.ban = true
+			r.used -= rn.n.Size()
+			r.mu.Unlock()
+
+			rn.h.Release()
+			rn.h = nil
+			return
+		}
+	}
+	r.mu.Unlock()
+}
+
+func (r *lru) Evict(n *Node) {
+	r.mu.Lock()
+	rn := (*lruNode)(n.CacheData)
+	if rn == nil || rn.ban {
+		r.mu.Unlock()
+		return
+	}
+	n.CacheData = nil
+	r.mu.Unlock()
+
+	rn.h.Release()
+}
+
+func (r *lru) EvictNS(ns uint64) {
+	var evicted []*lruNode
+
+	r.mu.Lock()
+	for e := r.recent.prev; e != &r.recent; {
+		rn := e
+		e = e.prev
+		if rn.n.NS() == ns {
+			rn.remove()
+			rn.n.CacheData = nil
+			r.used -= rn.n.Size()
+			evicted = append(evicted, rn)
+		}
+	}
+	r.mu.Unlock()
+
+	for _, rn := range evicted {
+		rn.h.Release()
+	}
+}
+
+func (r *lru) EvictAll() {
+	r.mu.Lock()
+	back := r.recent.prev
+	for rn := back; rn != &r.recent; rn = rn.prev {
+		rn.n.CacheData = nil
+	}
+	r.reset()
+	r.mu.Unlock()
+
+	for rn := back; rn != &r.recent; rn = rn.prev {
+		rn.h.Release()
+	}
+}
+
+func (r *lru) Close() error {
+	return nil
+}
+
+// NewLRU create a new LRU-cache.
+func NewLRU(capacity int) Cacher {
+	r := &lru{capacity: capacity}
+	r.reset()
+	return r
+}
@@ -0,0 +1,75 @@
+// Copyright (c) 2012, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package leveldb
+
+import "github.com/syndtr/goleveldb/leveldb/comparer"
+
+type iComparer struct {
+	ucmp comparer.Comparer
+}
+
+func (icmp *iComparer) uName() string {
+	return icmp.ucmp.Name()
+}
+
+func (icmp *iComparer) uCompare(a, b []byte) int {
+	return icmp.ucmp.Compare(a, b)
+}
+
+func (icmp *iComparer) uSeparator(dst, a, b []byte) []byte {
+	return icmp.ucmp.Separator(dst, a, b)
+}
+
+func (icmp *iComparer) uSuccessor(dst, b []byte) []byte {
+	return icmp.ucmp.Successor(dst, b)
+}
+
+func (icmp *iComparer) Name() string {
+	return icmp.uName()
+}
+
+func (icmp *iComparer) Compare(a, b []byte) int {
+	x := icmp.ucmp.Compare(iKey(a).ukey(), iKey(b).ukey())
+	if x == 0 {
+		if m, n := iKey(a).num(), iKey(b).num(); m > n {
+			x = -1
+		} else if m < n {
+			x = 1
+		}
+	}
+	return x
+}
+
+func (icmp *iComparer) Separator(dst, a, b []byte) []byte {
+	ua, ub := iKey(a).ukey(), iKey(b).ukey()
+	dst = icmp.ucmp.Separator(dst, ua, ub)
+	if dst == nil {
+		return nil
+	}
+	if len(dst) < len(ua) && icmp.uCompare(ua, dst) < 0 {
+		dst = append(dst, kMaxNumBytes...)
+	} else {
+		// Did not close possibilities that n maybe longer than len(ub).
+		dst = append(dst, a[len(a)-8:]...)
+	}
+	return dst
+}
+
+func (icmp *iComparer) Successor(dst, b []byte) []byte {
+	ub := iKey(b).ukey()
+	dst = icmp.ucmp.Successor(dst, ub)
+	if dst == nil {
+		return nil
+	}
+	if len(dst) < len(ub) && icmp.uCompare(ub, dst) < 0 {
+		dst = append(dst, kMaxNumBytes...)
+	} else {
+		// Did not close possibilities that n maybe longer than len(ub).
+		dst = append(dst, b[len(b)-8:]...)
+	}
+	return dst
+}
@@ -0,0 +1,51 @@
+// Copyright (c) 2012, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package comparer
+
+import "bytes"
+
+type bytesComparer struct{}
+
+func (bytesComparer) Compare(a, b []byte) int {
+	return bytes.Compare(a, b)
+}
+
+func (bytesComparer) Name() string {
+	return "leveldb.BytewiseComparator"
+}
+
+func (bytesComparer) Separator(dst, a, b []byte) []byte {
+	i, n := 0, len(a)
+	if n > len(b) {
+		n = len(b)
+	}
+	for ; i < n && a[i] == b[i]; i++ {
+	}
+	if i >= n {
+		// Do not shorten if one string is a prefix of the other
+	} else if c := a[i]; c < 0xff && c+1 < b[i] {
+		dst = append(dst, a[:i+1]...)
+		dst[i]++
+		return dst
+	}
+	return nil
+}
+
+func (bytesComparer) Successor(dst, b []byte) []byte {
+	for i, c := range b {
+		if c != 0xff {
+			dst = append(dst, b[:i+1]...)
+			dst[i]++
+			return dst
+		}
+	}
+	return nil
+}
+
+// DefaultComparer are default implementation of the Comparer interface.
+// It uses the natural ordering, consistent with bytes.Compare.
+var DefaultComparer = bytesComparer{}
--- a/Show More
+++ b/Show More