mtsatellite/leveldb.go

120 lines
2.3 KiB
Go

// Copyright 2014 by Sascha L. Teichmann
// Use of this source code is governed by the MIT license
// that can be found in the LICENSE file.
package main
import (
"log"
leveldb "github.com/jmhodges/levigo"
)
type LevelDBBackend struct {
cache *leveldb.Cache
db *leveldb.DB
}
type LevelDBSession struct {
backend *LevelDBBackend
tx *leveldb.WriteBatch
}
func NewLeveDBBackend(path string, cacheSize int) (ldb *LevelDBBackend, err error) {
cache := leveldb.NewLRUCache(cacheSize * 1024 * 1024)
opts := leveldb.NewOptions()
opts.SetCache(cache)
opts.SetCreateIfMissing(true)
var db *leveldb.DB
if db, err = leveldb.Open(path, opts); err != nil {
cache.Close()
return
}
ldb = &LevelDBBackend{
cache: cache,
db: db}
return
}
func (ldb *LevelDBBackend) NewSession() (Session, error) {
return &LevelDBSession{ldb, nil}, nil
}
func (ldbs *LevelDBSession) Close() error {
if ldbs.tx != nil {
ldbs.tx.Close()
}
return nil
}
func (ldb *LevelDBBackend) Shutdown() error {
ldb.db.Close()
ldb.cache.Close()
return nil
}
func (ldbs *LevelDBSession) Fetch(hash, key []byte) (value []byte, err error) {
ro := leveldb.NewReadOptions()
value, err = ldbs.backend.db.Get(ro, key)
ro.Close()
return
}
func (ldbs *LevelDBSession) InTransaction() bool {
return ldbs.tx != nil
}
func (ldbs *LevelDBSession) keyExists(key []byte) (exists bool, err error) {
ro := leveldb.NewReadOptions()
defer ro.Close()
var data []byte
if data, err = ldbs.backend.db.Get(ro, key); err != nil {
return
}
exists = data != nil
return
}
func (ldbs *LevelDBSession) Store(hash, key, value []byte) (exists bool, err error) {
var pos int64
if pos, err = bytes2pos(key); err != nil {
return
}
// Re-code it to make LevelDB happy.
key = pos2bytes(pos)
if exists, err = ldbs.keyExists(key); err != nil {
return
}
if ldbs.tx != nil {
ldbs.tx.Put(key, value)
return
}
wo := leveldb.NewWriteOptions()
err = ldbs.backend.db.Put(wo, key, value)
wo.Close()
return
}
func (ldbs *LevelDBSession) BeginTransaction() error {
ldbs.tx = leveldb.NewWriteBatch()
return nil
}
func (ldbs *LevelDBSession) CommitTransaction() (err error) {
tx := ldbs.tx
if tx == nil {
log.Println("WARN: No transaction running.")
return
}
ldbs.tx = nil
wo := leveldb.NewWriteOptions()
err = ldbs.backend.db.Write(wo, tx)
wo.Close()
return
}