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leveldb.go
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leveldb.go
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// Copyright 2014 The Prometheus Authors
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package index
import (
"encoding"
"github.com/syndtr/goleveldb/leveldb"
leveldb_filter "github.com/syndtr/goleveldb/leveldb/filter"
leveldb_iterator "github.com/syndtr/goleveldb/leveldb/iterator"
leveldb_opt "github.com/syndtr/goleveldb/leveldb/opt"
leveldb_util "github.com/syndtr/goleveldb/leveldb/util"
)
var (
keyspace = &leveldb_util.Range{
Start: nil,
Limit: nil,
}
iteratorOpts = &leveldb_opt.ReadOptions{
DontFillCache: true,
}
)
// LevelDB is a LevelDB-backed sorted KeyValueStore.
type LevelDB struct {
storage *leveldb.DB
readOpts *leveldb_opt.ReadOptions
writeOpts *leveldb_opt.WriteOptions
}
// LevelDBOptions provides options for a LevelDB.
type LevelDBOptions struct {
Path string // Base path to store files.
CacheSizeBytes int
}
// NewLevelDB returns a newly allocated LevelDB-backed KeyValueStore ready to
// use.
func NewLevelDB(o LevelDBOptions) (KeyValueStore, error) {
options := &leveldb_opt.Options{
BlockCacheCapacity: o.CacheSizeBytes,
Filter: leveldb_filter.NewBloomFilter(10),
}
storage, err := leveldb.OpenFile(o.Path, options)
if err != nil {
return nil, err
}
return &LevelDB{
storage: storage,
readOpts: &leveldb_opt.ReadOptions{},
writeOpts: &leveldb_opt.WriteOptions{},
}, nil
}
// NewBatch implements KeyValueStore.
func (l *LevelDB) NewBatch() Batch {
return &LevelDBBatch{
batch: &leveldb.Batch{},
}
}
// Close implements KeyValueStore.
func (l *LevelDB) Close() error {
return l.storage.Close()
}
// Get implements KeyValueStore.
func (l *LevelDB) Get(key encoding.BinaryMarshaler, value encoding.BinaryUnmarshaler) (bool, error) {
k, err := key.MarshalBinary()
if err != nil {
return false, err
}
raw, err := l.storage.Get(k, l.readOpts)
if err == leveldb.ErrNotFound {
return false, nil
}
if err != nil {
return false, err
}
if value == nil {
return true, nil
}
return true, value.UnmarshalBinary(raw)
}
// Has implements KeyValueStore.
func (l *LevelDB) Has(key encoding.BinaryMarshaler) (has bool, err error) {
return l.Get(key, nil)
}
// Delete implements KeyValueStore.
func (l *LevelDB) Delete(key encoding.BinaryMarshaler) (bool, error) {
k, err := key.MarshalBinary()
if err != nil {
return false, err
}
// Note that Delete returns nil if k does not exist. So we have to test
// for existence with Has first.
if has, err := l.storage.Has(k, l.readOpts); !has || err != nil {
return false, err
}
if err = l.storage.Delete(k, l.writeOpts); err != nil {
return false, err
}
return true, nil
}
// Put implements KeyValueStore.
func (l *LevelDB) Put(key, value encoding.BinaryMarshaler) error {
k, err := key.MarshalBinary()
if err != nil {
return err
}
v, err := value.MarshalBinary()
if err != nil {
return err
}
return l.storage.Put(k, v, l.writeOpts)
}
// Commit implements KeyValueStore.
func (l *LevelDB) Commit(b Batch) error {
return l.storage.Write(b.(*LevelDBBatch).batch, l.writeOpts)
}
// ForEach implements KeyValueStore.
func (l *LevelDB) ForEach(cb func(kv KeyValueAccessor) error) error {
snap, err := l.storage.GetSnapshot()
if err != nil {
return err
}
defer snap.Release()
iter := snap.NewIterator(keyspace, iteratorOpts)
kv := &levelDBKeyValueAccessor{it: iter}
for valid := iter.First(); valid; valid = iter.Next() {
if err = iter.Error(); err != nil {
return err
}
if err := cb(kv); err != nil {
return err
}
}
return nil
}
// LevelDBBatch is a Batch implementation for LevelDB.
type LevelDBBatch struct {
batch *leveldb.Batch
}
// Put implements Batch.
func (b *LevelDBBatch) Put(key, value encoding.BinaryMarshaler) error {
k, err := key.MarshalBinary()
if err != nil {
return err
}
v, err := value.MarshalBinary()
if err != nil {
return err
}
b.batch.Put(k, v)
return nil
}
// Delete implements Batch.
func (b *LevelDBBatch) Delete(key encoding.BinaryMarshaler) error {
k, err := key.MarshalBinary()
if err != nil {
return err
}
b.batch.Delete(k)
return nil
}
// Reset implements Batch.
func (b *LevelDBBatch) Reset() {
b.batch.Reset()
}
// levelDBKeyValueAccessor implements KeyValueAccessor.
type levelDBKeyValueAccessor struct {
it leveldb_iterator.Iterator
}
func (i *levelDBKeyValueAccessor) Key(key encoding.BinaryUnmarshaler) error {
return key.UnmarshalBinary(i.it.Key())
}
func (i *levelDBKeyValueAccessor) Value(value encoding.BinaryUnmarshaler) error {
return value.UnmarshalBinary(i.it.Value())
}