lib/connections: Fix and optimize registry (#7996)

Registry.Get used a full sort to get the minimum of a list, and the sort
was broken because util.AddressUnspecifiedLess assumed it could find out
whether an address is IPv4 or IPv6 from its Network method. However,
net.(TCP|UDP)Addr.Network always returns "tcp"/"udp".

lib/connections/registry/registry_test.go

@@ -7,13 +7,18 @@
 package registry
 
 import (
+	"net"
 	"testing"
 )
 
 func TestRegistry(t *testing.T) {
 	r := New()
 
-	if res := r.Get("int", intLess); res != nil {
+	want := func(i int) func(interface{}) bool {
+		return func(x interface{}) bool { return x.(int) == i }
+	}
+
+	if res := r.Get("int", want(1)); res != nil {
 		t.Error("unexpected")
 	}
 
@@ -24,30 +29,28 @@ func TestRegistry(t *testing.T) {
 	r.Register("int6", 6)
 	r.Register("int6", 66)
 
-	if res := r.Get("int", intLess).(int); res != 1 {
+	if res := r.Get("int", want(1)).(int); res != 1 {
 		t.Error("unexpected", res)
 	}
 
 	// int is prefix of int4, so returns 1
-	if res := r.Get("int4", intLess).(int); res != 1 {
+	if res := r.Get("int4", want(1)).(int); res != 1 {
 		t.Error("unexpected", res)
 	}
 
 	r.Unregister("int", 1)
 
-	// Check that falls through to 11
-	if res := r.Get("int", intLess).(int); res != 11 {
+	if res := r.Get("int", want(1)).(int); res == 1 {
 		t.Error("unexpected", res)
 	}
 
-	// 6 is smaller than 11 available in int.
-	if res := r.Get("int6", intLess).(int); res != 6 {
+	if res := r.Get("int6", want(6)).(int); res != 6 {
 		t.Error("unexpected", res)
 	}
 
 	// Unregister 11, int should be impossible to find
 	r.Unregister("int", 11)
-	if res := r.Get("int", intLess); res != nil {
+	if res := r.Get("int", want(11)); res != nil {
 		t.Error("unexpected")
 	}
 
@@ -59,13 +62,35 @@ func TestRegistry(t *testing.T) {
 	r.Register("int", 1)
 	r.Unregister("int", 1)
 
-	if res := r.Get("int4", intLess).(int); res != 1 {
+	if res := r.Get("int4", want(1)).(int); res != 1 {
 		t.Error("unexpected", res)
 	}
 }
 
-func intLess(i, j interface{}) bool {
-	iInt := i.(int)
-	jInt := j.(int)
-	return iInt < jInt
+func TestShortSchemeFirst(t *testing.T) {
+	r := New()
+	r.Register("foo", 0)
+	r.Register("foobar", 1)
+
+	// If we don't care about the value, we should get the one with "foo".
+	res := r.Get("foo", func(interface{}) bool { return false })
+	if res != 0 {
+		t.Error("unexpected", res)
+	}
+}
+
+func BenchmarkGet(b *testing.B) {
+	r := New()
+	for _, addr := range []string{"192.168.1.1", "172.1.1.1", "10.1.1.1"} {
+		r.Register("tcp", &net.TCPAddr{IP: net.ParseIP(addr)})
+	}
+
+	b.ReportAllocs()
+	b.ResetTimer()
+
+	for i := 0; i < b.N; i++ {
+		r.Get("tcp", func(x interface{}) bool {
+			return x.(*net.TCPAddr).IP.IsUnspecified()
+		})
+	}
 }