chore: switch database engine to sqlite (fixes #9954) (#9965)

Switch the database from LevelDB to SQLite, for greater stability and
simpler code.

Co-authored-by: Tommy van der Vorst <tommy@pixelspark.nl>
Co-authored-by: bt90 <btom1990@googlemail.com>

internal/db/typed.go

@@ -0,0 +1,140 @@
+// Copyright (C) 2014 The Syncthing Authors.
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this file,
+// You can obtain one at https://mozilla.org/MPL/2.0/.
+
+package db
+
+import (
+	"database/sql"
+	"encoding/binary"
+	"errors"
+	"time"
+)
+
+// Typed is a simple key-value store using a specific namespace within a
+// lower level KV.
+type Typed struct {
+	db     KV
+	prefix string
+}
+
+func NewMiscDB(db KV) *Typed {
+	return NewTyped(db, "misc")
+}
+
+// NewTyped returns a new typed key-value store that lives in the namespace
+// specified by the prefix.
+func NewTyped(db KV, prefix string) *Typed {
+	return &Typed{
+		db:     db,
+		prefix: prefix,
+	}
+}
+
+// PutInt64 stores a new int64. Any existing value (even if of another type)
+// is overwritten.
+func (n *Typed) PutInt64(key string, val int64) error {
+	var valBs [8]byte
+	binary.BigEndian.PutUint64(valBs[:], uint64(val))
+	return n.db.PutKV(n.prefixedKey(key), valBs[:])
+}
+
+// Int64 returns the stored value interpreted as an int64 and a boolean that
+// is false if no value was stored at the key.
+func (n *Typed) Int64(key string) (int64, bool, error) {
+	valBs, err := n.db.GetKV(n.prefixedKey(key))
+	if err != nil {
+		return 0, false, filterNotFound(err)
+	}
+	val := binary.BigEndian.Uint64(valBs)
+	return int64(val), true, nil
+}
+
+// PutTime stores a new time.Time. Any existing value (even if of another
+// type) is overwritten.
+func (n *Typed) PutTime(key string, val time.Time) error {
+	valBs, _ := val.MarshalBinary() // never returns an error
+	return n.db.PutKV(n.prefixedKey(key), valBs)
+}
+
+// Time returns the stored value interpreted as a time.Time and a boolean
+// that is false if no value was stored at the key.
+func (n *Typed) Time(key string) (time.Time, bool, error) {
+	var t time.Time
+	valBs, err := n.db.GetKV(n.prefixedKey(key))
+	if err != nil {
+		return t, false, filterNotFound(err)
+	}
+	err = t.UnmarshalBinary(valBs)
+	return t, err == nil, err
+}
+
+// PutString stores a new string. Any existing value (even if of another type)
+// is overwritten.
+func (n *Typed) PutString(key, val string) error {
+	return n.db.PutKV(n.prefixedKey(key), []byte(val))
+}
+
+// String returns the stored value interpreted as a string and a boolean that
+// is false if no value was stored at the key.
+func (n *Typed) String(key string) (string, bool, error) {
+	valBs, err := n.db.GetKV(n.prefixedKey(key))
+	if err != nil {
+		return "", false, filterNotFound(err)
+	}
+	return string(valBs), true, nil
+}
+
+// PutBytes stores a new byte slice. Any existing value (even if of another type)
+// is overwritten.
+func (n *Typed) PutBytes(key string, val []byte) error {
+	return n.db.PutKV(n.prefixedKey(key), val)
+}
+
+// Bytes returns the stored value as a raw byte slice and a boolean that
+// is false if no value was stored at the key.
+func (n *Typed) Bytes(key string) ([]byte, bool, error) {
+	valBs, err := n.db.GetKV(n.prefixedKey(key))
+	if err != nil {
+		return nil, false, filterNotFound(err)
+	}
+	return valBs, true, nil
+}
+
+// PutBool stores a new boolean. Any existing value (even if of another type)
+// is overwritten.
+func (n *Typed) PutBool(key string, val bool) error {
+	if val {
+		return n.db.PutKV(n.prefixedKey(key), []byte{0x0})
+	}
+	return n.db.PutKV(n.prefixedKey(key), []byte{0x1})
+}
+
+// Bool returns the stored value as a boolean and a boolean that
+// is false if no value was stored at the key.
+func (n *Typed) Bool(key string) (bool, bool, error) {
+	valBs, err := n.db.GetKV(n.prefixedKey(key))
+	if err != nil {
+		return false, false, filterNotFound(err)
+	}
+	return valBs[0] == 0x0, true, nil
+}
+
+// Delete deletes the specified key. It is allowed to delete a nonexistent
+// key.
+func (n *Typed) Delete(key string) error {
+	return n.db.DeleteKV(n.prefixedKey(key))
+}
+
+func (n *Typed) prefixedKey(key string) string {
+	return n.prefix + "/" + key
+}
+
+func filterNotFound(err error) error {
+	if errors.Is(err, sql.ErrNoRows) {
+		return nil
+	}
+	return err
+}