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memstore.go
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memstore.go
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// Copyright 2014, Shuhei Tanuma. All rights reserved.
// Use of this source code is governed by a MIT license
// that can be found in the LICENSE file.
package datastore
import (
"bytes"
"errors"
"github.com/PYW1/momonga/skiplist"
"sync"
)
type MemstoreIterator struct {
Iterator *skiplist.SkipListIterator
}
func (self *MemstoreIterator) Seek(key []byte) {
self.Iterator.Seek(key)
}
func (self *MemstoreIterator) Key() []byte {
r := self.Iterator.Key()
if v, ok := r.([]byte); ok {
return v
}
return nil
}
func (self *MemstoreIterator) Value() []byte {
r := self.Iterator.Value()
if v, ok := r.([]byte); ok {
return v
}
return nil
}
func (self *MemstoreIterator) Next() {
self.Iterator.Next()
}
func (self *MemstoreIterator) Prev() {
panic("prev is not supported yet")
}
func (self *MemstoreIterator) Valid() bool {
return self.Iterator.Valid()
}
func (self *MemstoreIterator) Error() error {
return nil
}
func (self *MemstoreIterator) Close() error {
self.Iterator = nil
return nil
}
func NewMemstore() *Memstore {
return &Memstore{
Storage: skiplist.NewSkipList(&skiplist.BytesComparator{}),
Mutex: &sync.RWMutex{},
}
}
type Memstore struct {
Storage *skiplist.SkipList
Mutex *sync.RWMutex
}
func (self *Memstore) Name() string {
return "memstore"
}
func (self *Memstore) Path() string {
return "inmemory"
}
func (self *Memstore) Put(key, value []byte) error {
self.Mutex.Lock()
defer func() {
self.Mutex.Unlock()
}()
self.Storage.Delete(key)
self.Storage.Insert(key, value)
return nil
}
func (self *Memstore) Get(key []byte) ([]byte, error) {
self.Mutex.RLock()
defer func() {
self.Mutex.RUnlock()
}()
itr := self.Iterator()
itr.Seek(key)
if itr.Valid() {
return itr.Value(), nil
}
return nil, errors.New("not found")
}
func (self *Memstore) Del(first, last []byte) error {
self.Mutex.RLock()
itr := self.Iterator()
var targets [][]byte
for itr.Seek(first); itr.Valid(); itr.Next() {
key := itr.Key()
// The result will be 0 if a==b, -1 if a < b, and +1 if a > b.
if bytes.Compare(key, last) > 0 {
break
}
targets = append(targets, key)
}
self.Mutex.RUnlock()
// MEMO: this is more safely.
self.Mutex.Lock()
for i := range targets {
self.Storage.Delete(targets[i])
}
self.Mutex.Unlock()
return nil
}
func (self *Memstore) Iterator() Iterator {
return &MemstoreIterator{
Iterator: self.Storage.Iterator(),
}
}
func (self *Memstore) Close() error {
self.Storage = nil
return nil
}