2015-02-16 13:28:33 +00:00
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// Copyright (c) 2012, Suryandaru Triandana <syndtr@gmail.com>
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// All rights reserved.
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//
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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// Package memdb provides in-memory key/value database implementation.
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package memdb
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import (
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"math/rand"
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"sync"
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"github.com/syndtr/goleveldb/leveldb/comparer"
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2015-04-28 09:18:01 +00:00
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"github.com/syndtr/goleveldb/leveldb/errors"
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2015-02-16 13:28:33 +00:00
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"github.com/syndtr/goleveldb/leveldb/iterator"
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"github.com/syndtr/goleveldb/leveldb/util"
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)
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2016-10-20 12:56:34 +00:00
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// Common errors.
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var (
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ErrNotFound = errors.ErrNotFound
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ErrIterReleased = errors.New("leveldb/memdb: iterator released")
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)
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const tMaxHeight = 12
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type dbIter struct {
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util.BasicReleaser
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p *DB
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slice *util.Range
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node int
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forward bool
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key, value []byte
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err error
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}
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func (i *dbIter) fill(checkStart, checkLimit bool) bool {
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if i.node != 0 {
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n := i.p.nodeData[i.node]
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m := n + i.p.nodeData[i.node+nKey]
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i.key = i.p.kvData[n:m]
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if i.slice != nil {
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switch {
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case checkLimit && i.slice.Limit != nil && i.p.cmp.Compare(i.key, i.slice.Limit) >= 0:
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fallthrough
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case checkStart && i.slice.Start != nil && i.p.cmp.Compare(i.key, i.slice.Start) < 0:
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i.node = 0
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goto bail
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}
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}
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i.value = i.p.kvData[m : m+i.p.nodeData[i.node+nVal]]
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return true
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}
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bail:
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i.key = nil
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i.value = nil
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return false
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}
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func (i *dbIter) Valid() bool {
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return i.node != 0
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}
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func (i *dbIter) First() bool {
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if i.Released() {
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i.err = ErrIterReleased
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return false
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}
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2015-02-16 13:28:33 +00:00
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i.forward = true
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i.p.mu.RLock()
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defer i.p.mu.RUnlock()
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if i.slice != nil && i.slice.Start != nil {
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i.node, _ = i.p.findGE(i.slice.Start, false)
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} else {
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i.node = i.p.nodeData[nNext]
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}
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return i.fill(false, true)
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}
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func (i *dbIter) Last() bool {
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if i.Released() {
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i.err = ErrIterReleased
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return false
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}
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i.forward = false
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i.p.mu.RLock()
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defer i.p.mu.RUnlock()
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if i.slice != nil && i.slice.Limit != nil {
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i.node = i.p.findLT(i.slice.Limit)
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} else {
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i.node = i.p.findLast()
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}
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return i.fill(true, false)
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}
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func (i *dbIter) Seek(key []byte) bool {
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if i.Released() {
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i.err = ErrIterReleased
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return false
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}
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2015-04-28 09:18:01 +00:00
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2015-02-16 13:28:33 +00:00
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i.forward = true
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i.p.mu.RLock()
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defer i.p.mu.RUnlock()
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if i.slice != nil && i.slice.Start != nil && i.p.cmp.Compare(key, i.slice.Start) < 0 {
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key = i.slice.Start
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}
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i.node, _ = i.p.findGE(key, false)
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return i.fill(false, true)
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}
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func (i *dbIter) Next() bool {
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if i.Released() {
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i.err = ErrIterReleased
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return false
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}
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2015-04-28 09:18:01 +00:00
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2015-02-16 13:28:33 +00:00
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if i.node == 0 {
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if !i.forward {
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return i.First()
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}
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return false
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}
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i.forward = true
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i.p.mu.RLock()
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defer i.p.mu.RUnlock()
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i.node = i.p.nodeData[i.node+nNext]
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return i.fill(false, true)
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}
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func (i *dbIter) Prev() bool {
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if i.Released() {
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i.err = ErrIterReleased
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return false
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}
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2015-04-28 09:18:01 +00:00
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2015-02-16 13:28:33 +00:00
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if i.node == 0 {
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if i.forward {
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return i.Last()
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}
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return false
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}
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i.forward = false
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i.p.mu.RLock()
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defer i.p.mu.RUnlock()
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i.node = i.p.findLT(i.key)
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return i.fill(true, false)
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}
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func (i *dbIter) Key() []byte {
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return i.key
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}
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func (i *dbIter) Value() []byte {
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return i.value
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}
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func (i *dbIter) Error() error { return i.err }
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func (i *dbIter) Release() {
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if !i.Released() {
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i.p = nil
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i.node = 0
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i.key = nil
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i.value = nil
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i.BasicReleaser.Release()
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}
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}
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const (
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nKV = iota
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nKey
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nVal
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nHeight
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nNext
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)
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// DB is an in-memory key/value database.
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type DB struct {
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cmp comparer.BasicComparer
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rnd *rand.Rand
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mu sync.RWMutex
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kvData []byte
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// Node data:
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// [0] : KV offset
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// [1] : Key length
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// [2] : Value length
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// [3] : Height
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// [3..height] : Next nodes
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nodeData []int
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prevNode [tMaxHeight]int
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maxHeight int
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n int
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kvSize int
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}
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func (p *DB) randHeight() (h int) {
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const branching = 4
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h = 1
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for h < tMaxHeight && p.rnd.Int()%branching == 0 {
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h++
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}
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return
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}
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2016-02-11 14:16:52 +00:00
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// Must hold RW-lock if prev == true, as it use shared prevNode slice.
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func (p *DB) findGE(key []byte, prev bool) (int, bool) {
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node := 0
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h := p.maxHeight - 1
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for {
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next := p.nodeData[node+nNext+h]
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cmp := 1
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if next != 0 {
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o := p.nodeData[next]
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cmp = p.cmp.Compare(p.kvData[o:o+p.nodeData[next+nKey]], key)
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}
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if cmp < 0 {
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// Keep searching in this list
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node = next
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} else {
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if prev {
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p.prevNode[h] = node
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} else if cmp == 0 {
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return next, true
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}
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if h == 0 {
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return next, cmp == 0
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}
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h--
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}
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}
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}
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func (p *DB) findLT(key []byte) int {
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node := 0
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h := p.maxHeight - 1
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for {
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next := p.nodeData[node+nNext+h]
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o := p.nodeData[next]
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if next == 0 || p.cmp.Compare(p.kvData[o:o+p.nodeData[next+nKey]], key) >= 0 {
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if h == 0 {
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break
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}
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h--
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} else {
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node = next
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}
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}
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return node
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}
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func (p *DB) findLast() int {
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node := 0
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h := p.maxHeight - 1
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for {
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next := p.nodeData[node+nNext+h]
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if next == 0 {
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if h == 0 {
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break
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}
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h--
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} else {
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node = next
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}
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}
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return node
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}
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// Put sets the value for the given key. It overwrites any previous value
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// for that key; a DB is not a multi-map.
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//
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// It is safe to modify the contents of the arguments after Put returns.
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func (p *DB) Put(key []byte, value []byte) error {
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p.mu.Lock()
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defer p.mu.Unlock()
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if node, exact := p.findGE(key, true); exact {
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kvOffset := len(p.kvData)
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p.kvData = append(p.kvData, key...)
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p.kvData = append(p.kvData, value...)
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p.nodeData[node] = kvOffset
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m := p.nodeData[node+nVal]
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p.nodeData[node+nVal] = len(value)
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p.kvSize += len(value) - m
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return nil
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}
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h := p.randHeight()
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if h > p.maxHeight {
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for i := p.maxHeight; i < h; i++ {
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p.prevNode[i] = 0
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}
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p.maxHeight = h
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}
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kvOffset := len(p.kvData)
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p.kvData = append(p.kvData, key...)
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p.kvData = append(p.kvData, value...)
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// Node
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node := len(p.nodeData)
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p.nodeData = append(p.nodeData, kvOffset, len(key), len(value), h)
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for i, n := range p.prevNode[:h] {
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2016-02-11 14:16:52 +00:00
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m := n + nNext + i
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2015-02-16 13:28:33 +00:00
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p.nodeData = append(p.nodeData, p.nodeData[m])
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p.nodeData[m] = node
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}
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p.kvSize += len(key) + len(value)
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p.n++
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return nil
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}
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// Delete deletes the value for the given key. It returns ErrNotFound if
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// the DB does not contain the key.
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//
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// It is safe to modify the contents of the arguments after Delete returns.
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func (p *DB) Delete(key []byte) error {
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p.mu.Lock()
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defer p.mu.Unlock()
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node, exact := p.findGE(key, true)
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if !exact {
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return ErrNotFound
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}
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h := p.nodeData[node+nHeight]
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for i, n := range p.prevNode[:h] {
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2018-03-08 12:59:00 +00:00
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m := n + nNext + i
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2015-02-16 13:28:33 +00:00
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p.nodeData[m] = p.nodeData[p.nodeData[m]+nNext+i]
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}
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p.kvSize -= p.nodeData[node+nKey] + p.nodeData[node+nVal]
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p.n--
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return nil
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}
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// Contains returns true if the given key are in the DB.
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//
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// It is safe to modify the contents of the arguments after Contains returns.
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func (p *DB) Contains(key []byte) bool {
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p.mu.RLock()
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_, exact := p.findGE(key, false)
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p.mu.RUnlock()
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return exact
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}
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// Get gets the value for the given key. It returns error.ErrNotFound if the
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// DB does not contain the key.
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//
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// The caller should not modify the contents of the returned slice, but
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// it is safe to modify the contents of the argument after Get returns.
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func (p *DB) Get(key []byte) (value []byte, err error) {
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p.mu.RLock()
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if node, exact := p.findGE(key, false); exact {
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o := p.nodeData[node] + p.nodeData[node+nKey]
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value = p.kvData[o : o+p.nodeData[node+nVal]]
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} else {
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err = ErrNotFound
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}
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p.mu.RUnlock()
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return
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}
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// Find finds key/value pair whose key is greater than or equal to the
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// given key. It returns ErrNotFound if the table doesn't contain
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// such pair.
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//
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// The caller should not modify the contents of the returned slice, but
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// it is safe to modify the contents of the argument after Find returns.
|
|
|
|
func (p *DB) Find(key []byte) (rkey, value []byte, err error) {
|
|
|
|
p.mu.RLock()
|
|
|
|
if node, _ := p.findGE(key, false); node != 0 {
|
|
|
|
n := p.nodeData[node]
|
|
|
|
m := n + p.nodeData[node+nKey]
|
|
|
|
rkey = p.kvData[n:m]
|
|
|
|
value = p.kvData[m : m+p.nodeData[node+nVal]]
|
|
|
|
} else {
|
|
|
|
err = ErrNotFound
|
|
|
|
}
|
|
|
|
p.mu.RUnlock()
|
|
|
|
return
|
|
|
|
}
|
|
|
|
|
|
|
|
// NewIterator returns an iterator of the DB.
|
2016-10-20 12:56:34 +00:00
|
|
|
// The returned iterator is not safe for concurrent use, but it is safe to use
|
2015-02-16 13:28:33 +00:00
|
|
|
// multiple iterators concurrently, with each in a dedicated goroutine.
|
|
|
|
// It is also safe to use an iterator concurrently with modifying its
|
|
|
|
// underlying DB. However, the resultant key/value pairs are not guaranteed
|
|
|
|
// to be a consistent snapshot of the DB at a particular point in time.
|
|
|
|
//
|
|
|
|
// Slice allows slicing the iterator to only contains keys in the given
|
|
|
|
// range. A nil Range.Start is treated as a key before all keys in the
|
|
|
|
// DB. And a nil Range.Limit is treated as a key after all keys in
|
|
|
|
// the DB.
|
|
|
|
//
|
2019-09-26 14:44:00 +00:00
|
|
|
// WARNING: Any slice returned by interator (e.g. slice returned by calling
|
|
|
|
// Iterator.Key() or Iterator.Key() methods), its content should not be modified
|
|
|
|
// unless noted otherwise.
|
|
|
|
//
|
2015-02-16 13:28:33 +00:00
|
|
|
// The iterator must be released after use, by calling Release method.
|
|
|
|
//
|
|
|
|
// Also read Iterator documentation of the leveldb/iterator package.
|
|
|
|
func (p *DB) NewIterator(slice *util.Range) iterator.Iterator {
|
|
|
|
return &dbIter{p: p, slice: slice}
|
|
|
|
}
|
|
|
|
|
|
|
|
// Capacity returns keys/values buffer capacity.
|
|
|
|
func (p *DB) Capacity() int {
|
|
|
|
p.mu.RLock()
|
|
|
|
defer p.mu.RUnlock()
|
|
|
|
return cap(p.kvData)
|
|
|
|
}
|
|
|
|
|
|
|
|
// Size returns sum of keys and values length. Note that deleted
|
2016-10-20 12:56:34 +00:00
|
|
|
// key/value will not be accounted for, but it will still consume
|
2015-02-16 13:28:33 +00:00
|
|
|
// the buffer, since the buffer is append only.
|
|
|
|
func (p *DB) Size() int {
|
|
|
|
p.mu.RLock()
|
|
|
|
defer p.mu.RUnlock()
|
|
|
|
return p.kvSize
|
|
|
|
}
|
|
|
|
|
|
|
|
// Free returns keys/values free buffer before need to grow.
|
|
|
|
func (p *DB) Free() int {
|
|
|
|
p.mu.RLock()
|
|
|
|
defer p.mu.RUnlock()
|
|
|
|
return cap(p.kvData) - len(p.kvData)
|
|
|
|
}
|
|
|
|
|
|
|
|
// Len returns the number of entries in the DB.
|
|
|
|
func (p *DB) Len() int {
|
|
|
|
p.mu.RLock()
|
|
|
|
defer p.mu.RUnlock()
|
|
|
|
return p.n
|
|
|
|
}
|
|
|
|
|
|
|
|
// Reset resets the DB to initial empty state. Allows reuse the buffer.
|
|
|
|
func (p *DB) Reset() {
|
2016-02-11 14:16:52 +00:00
|
|
|
p.mu.Lock()
|
2015-02-16 13:28:33 +00:00
|
|
|
p.rnd = rand.New(rand.NewSource(0xdeadbeef))
|
|
|
|
p.maxHeight = 1
|
|
|
|
p.n = 0
|
|
|
|
p.kvSize = 0
|
|
|
|
p.kvData = p.kvData[:0]
|
2016-02-11 14:16:52 +00:00
|
|
|
p.nodeData = p.nodeData[:nNext+tMaxHeight]
|
2015-02-16 13:28:33 +00:00
|
|
|
p.nodeData[nKV] = 0
|
|
|
|
p.nodeData[nKey] = 0
|
|
|
|
p.nodeData[nVal] = 0
|
|
|
|
p.nodeData[nHeight] = tMaxHeight
|
|
|
|
for n := 0; n < tMaxHeight; n++ {
|
2016-02-11 14:16:52 +00:00
|
|
|
p.nodeData[nNext+n] = 0
|
2015-02-16 13:28:33 +00:00
|
|
|
p.prevNode[n] = 0
|
|
|
|
}
|
2016-02-11 14:16:52 +00:00
|
|
|
p.mu.Unlock()
|
2015-02-16 13:28:33 +00:00
|
|
|
}
|
|
|
|
|
2016-10-20 12:56:34 +00:00
|
|
|
// New creates a new initialized in-memory key/value DB. The capacity
|
2015-02-16 13:28:33 +00:00
|
|
|
// is the initial key/value buffer capacity. The capacity is advisory,
|
|
|
|
// not enforced.
|
2015-04-28 09:18:01 +00:00
|
|
|
//
|
2016-10-20 12:56:34 +00:00
|
|
|
// This DB is append-only, deleting an entry would remove entry node but not
|
|
|
|
// reclaim KV buffer.
|
|
|
|
//
|
|
|
|
// The returned DB instance is safe for concurrent use.
|
2015-02-16 13:28:33 +00:00
|
|
|
func New(cmp comparer.BasicComparer, capacity int) *DB {
|
|
|
|
p := &DB{
|
|
|
|
cmp: cmp,
|
|
|
|
rnd: rand.New(rand.NewSource(0xdeadbeef)),
|
|
|
|
maxHeight: 1,
|
|
|
|
kvData: make([]byte, 0, capacity),
|
|
|
|
nodeData: make([]int, 4+tMaxHeight),
|
|
|
|
}
|
|
|
|
p.nodeData[nHeight] = tMaxHeight
|
|
|
|
return p
|
|
|
|
}
|