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leveldb.go
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/
leveldb.go
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// Package database provides KV database for meta-information
package database
import (
"bytes"
"errors"
"github.com/syndtr/goleveldb/leveldb"
"github.com/syndtr/goleveldb/leveldb/filter"
"github.com/syndtr/goleveldb/leveldb/opt"
"github.com/syndtr/goleveldb/leveldb/storage"
"github.com/syndtr/goleveldb/leveldb/util"
)
// Errors for Storage
var (
ErrNotFound = errors.New("key not found")
)
// Storage is an interface to KV storage
type Storage interface {
Get(key []byte) ([]byte, error)
Put(key []byte, value []byte) error
Delete(key []byte) error
KeysByPrefix(prefix []byte) [][]byte
FetchByPrefix(prefix []byte) [][]byte
Close() error
StartBatch()
FinishBatch() error
CompactDB() error
}
type levelDB struct {
db *leveldb.DB
batch *leveldb.Batch
}
// Check interface
var (
_ Storage = &levelDB{}
)
// OpenDB opens (creates) LevelDB database
func OpenDB(path string) (Storage, error) {
o := &opt.Options{
Filter: filter.NewBloomFilter(10),
}
db, err := leveldb.OpenFile(path, o)
if err != nil {
return nil, err
}
return &levelDB{db: db}, nil
}
// RecoverDB recovers LevelDB database from corruption
func RecoverDB(path string) error {
stor, err := storage.OpenFile(path)
if err != nil {
return err
}
db, err := leveldb.Recover(stor, nil)
if err != nil {
return err
}
db.Close()
stor.Close()
return nil
}
// Get key value from database
func (l *levelDB) Get(key []byte) ([]byte, error) {
value, err := l.db.Get(key, nil)
if err != nil {
if err == leveldb.ErrNotFound {
return nil, ErrNotFound
}
return nil, err
}
return value, nil
}
// Put saves key to database, if key has the same value in DB already, it is not saved
func (l *levelDB) Put(key []byte, value []byte) error {
if l.batch != nil {
l.batch.Put(key, value)
return nil
}
old, err := l.db.Get(key, nil)
if err != nil {
if err != leveldb.ErrNotFound {
return err
}
} else {
if bytes.Compare(old, value) == 0 {
return nil
}
}
return l.db.Put(key, value, nil)
}
// Delete removes key from DB
func (l *levelDB) Delete(key []byte) error {
if l.batch != nil {
l.batch.Delete(key)
return nil
}
return l.db.Delete(key, nil)
}
// KeysByPrefix returns all keys that start with prefix
func (l *levelDB) KeysByPrefix(prefix []byte) [][]byte {
result := make([][]byte, 0, 20)
iterator := l.db.NewIterator(nil, nil)
defer iterator.Release()
for ok := iterator.Seek(prefix); ok && bytes.HasPrefix(iterator.Key(), prefix); ok = iterator.Next() {
key := iterator.Key()
keyc := make([]byte, len(key))
copy(keyc, key)
result = append(result, keyc)
}
return result
}
// FetchByPrefix returns all values with keys that start with prefix
func (l *levelDB) FetchByPrefix(prefix []byte) [][]byte {
result := make([][]byte, 0, 20)
iterator := l.db.NewIterator(nil, nil)
defer iterator.Release()
for ok := iterator.Seek(prefix); ok && bytes.HasPrefix(iterator.Key(), prefix); ok = iterator.Next() {
val := iterator.Value()
valc := make([]byte, len(val))
copy(valc, val)
result = append(result, valc)
}
return result
}
// Close finishes DB work
func (l *levelDB) Close() error {
return l.db.Close()
}
// StartBatch starts batch processing of keys
//
// All subsequent Get, Put and Delete would work on batch
func (l *levelDB) StartBatch() {
if l.batch != nil {
panic("batch already started")
}
l.batch = new(leveldb.Batch)
}
// FinishBatch finalizes the batch, saving operations
func (l *levelDB) FinishBatch() error {
if l.batch == nil {
panic("no batch")
}
err := l.db.Write(l.batch, nil)
l.batch = nil
return err
}
// CompactDB compacts database by merging layers
func (l *levelDB) CompactDB() error {
return l.db.CompactRange(util.Range{})
}