syncthing/lib/db/namespaced.go
2019-02-01 09:54:21 +01:00

178 lines
5.2 KiB
Go

// 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 (
"encoding/binary"
"time"
"github.com/syndtr/goleveldb/leveldb"
"github.com/syndtr/goleveldb/leveldb/util"
)
// NamespacedKV is a simple key-value store using a specific namespace within
// a leveldb.
type NamespacedKV struct {
db *Lowlevel
prefix []byte
}
// NewNamespacedKV returns a new NamespacedKV that lives in the namespace
// specified by the prefix.
func NewNamespacedKV(db *Lowlevel, prefix string) *NamespacedKV {
prefixBs := []byte(prefix)
// After the conversion from string the cap will be larger than the len (in Go 1.11.5,
// 32 bytes cap for small strings). We need to cut it down to ensure append() calls
// on the prefix make a new allocation.
prefixBs = prefixBs[:len(prefixBs):len(prefixBs)]
return &NamespacedKV{
db: db,
prefix: prefixBs,
}
}
// Reset removes all entries in this namespace.
func (n *NamespacedKV) Reset() {
it := n.db.NewIterator(util.BytesPrefix(n.prefix), nil)
defer it.Release()
batch := new(leveldb.Batch)
for it.Next() {
batch.Delete(it.Key())
if batch.Len() > batchFlushSize {
if err := n.db.Write(batch, nil); err != nil {
panic(err)
}
batch.Reset()
}
}
if batch.Len() > 0 {
if err := n.db.Write(batch, nil); err != nil {
panic(err)
}
}
}
// PutInt64 stores a new int64. Any existing value (even if of another type)
// is overwritten.
func (n *NamespacedKV) PutInt64(key string, val int64) {
var valBs [8]byte
binary.BigEndian.PutUint64(valBs[:], uint64(val))
n.db.Put(n.prefixedKey(key), valBs[:], nil)
}
// 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 *NamespacedKV) Int64(key string) (int64, bool) {
valBs, err := n.db.Get(n.prefixedKey(key), nil)
if err != nil {
return 0, false
}
val := binary.BigEndian.Uint64(valBs)
return int64(val), true
}
// PutTime stores a new time.Time. Any existing value (even if of another
// type) is overwritten.
func (n *NamespacedKV) PutTime(key string, val time.Time) {
valBs, _ := val.MarshalBinary() // never returns an error
n.db.Put(n.prefixedKey(key), valBs, nil)
}
// 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 NamespacedKV) Time(key string) (time.Time, bool) {
var t time.Time
valBs, err := n.db.Get(n.prefixedKey(key), nil)
if err != nil {
return t, false
}
err = t.UnmarshalBinary(valBs)
return t, err == nil
}
// PutString stores a new string. Any existing value (even if of another type)
// is overwritten.
func (n *NamespacedKV) PutString(key, val string) {
n.db.Put(n.prefixedKey(key), []byte(val), nil)
}
// 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 NamespacedKV) String(key string) (string, bool) {
valBs, err := n.db.Get(n.prefixedKey(key), nil)
if err != nil {
return "", false
}
return string(valBs), true
}
// PutBytes stores a new byte slice. Any existing value (even if of another type)
// is overwritten.
func (n *NamespacedKV) PutBytes(key string, val []byte) {
n.db.Put(n.prefixedKey(key), val, nil)
}
// 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 NamespacedKV) Bytes(key string) ([]byte, bool) {
valBs, err := n.db.Get(n.prefixedKey(key), nil)
if err != nil {
return nil, false
}
return valBs, true
}
// PutBool stores a new boolean. Any existing value (even if of another type)
// is overwritten.
func (n *NamespacedKV) PutBool(key string, val bool) {
if val {
n.db.Put(n.prefixedKey(key), []byte{0x0}, nil)
} else {
n.db.Put(n.prefixedKey(key), []byte{0x1}, nil)
}
}
// Bool returns the stored value as a boolean and a boolean that
// is false if no value was stored at the key.
func (n NamespacedKV) Bool(key string) (bool, bool) {
valBs, err := n.db.Get(n.prefixedKey(key), nil)
if err != nil {
return false, false
}
return valBs[0] == 0x0, true
}
// Delete deletes the specified key. It is allowed to delete a nonexistent
// key.
func (n NamespacedKV) Delete(key string) {
n.db.Delete(n.prefixedKey(key), nil)
}
func (n NamespacedKV) prefixedKey(key string) []byte {
return append(n.prefix, []byte(key)...)
}
// Well known namespaces that can be instantiated without knowing the key
// details.
// NewDeviceStatisticsNamespace creates a KV namespace for device statistics
// for the given device.
func NewDeviceStatisticsNamespace(db *Lowlevel, device string) *NamespacedKV {
return NewNamespacedKV(db, string(KeyTypeDeviceStatistic)+device)
}
// NewFolderStatisticsNamespace creates a KV namespace for folder statistics
// for the given folder.
func NewFolderStatisticsNamespace(db *Lowlevel, folder string) *NamespacedKV {
return NewNamespacedKV(db, string(KeyTypeFolderStatistic)+folder)
}
// NewMiscDateNamespace creates a KV namespace for miscellaneous metadata.
func NewMiscDataNamespace(db *Lowlevel) *NamespacedKV {
return NewNamespacedKV(db, string(KeyTypeMiscData))
}