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list.go
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list.go
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// Copyright 2015 PingCAP, Inc.
//
// 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,
// See the License for the specific language governing permissions and
// limitations under the License.
package structure
import (
"encoding/binary"
"github.com/pingcap/tidb/kv"
"github.com/pkg/errors"
)
type listMeta struct {
LIndex int64
RIndex int64
}
func (meta listMeta) Value() []byte {
buf := make([]byte, 16)
binary.BigEndian.PutUint64(buf[0:8], uint64(meta.LIndex))
binary.BigEndian.PutUint64(buf[8:16], uint64(meta.RIndex))
return buf
}
func (meta listMeta) IsEmpty() bool {
return meta.LIndex >= meta.RIndex
}
// LPush prepends one or multiple values to a list.
func (t *TxStructure) LPush(key []byte, values ...[]byte) error {
return t.listPush(key, true, values...)
}
// RPush appends one or multiple values to a list.
func (t *TxStructure) RPush(key []byte, values ...[]byte) error {
return t.listPush(key, false, values...)
}
func (t *TxStructure) listPush(key []byte, left bool, values ...[]byte) error {
if t.readWriter == nil {
return errWriteOnSnapshot
}
if len(values) == 0 {
return nil
}
metaKey := t.encodeListMetaKey(key)
meta, err := t.loadListMeta(metaKey)
if err != nil {
return errors.Trace(err)
}
index := int64(0)
for _, v := range values {
if left {
meta.LIndex--
index = meta.LIndex
} else {
index = meta.RIndex
meta.RIndex++
}
dataKey := t.encodeListDataKey(key, index)
if err = t.readWriter.Set(dataKey, v); err != nil {
return errors.Trace(err)
}
}
return t.readWriter.Set(metaKey, meta.Value())
}
// LPop removes and gets the first element in a list.
func (t *TxStructure) LPop(key []byte) ([]byte, error) {
return t.listPop(key, true)
}
// RPop removes and gets the last element in a list.
func (t *TxStructure) RPop(key []byte) ([]byte, error) {
return t.listPop(key, false)
}
func (t *TxStructure) listPop(key []byte, left bool) ([]byte, error) {
if t.readWriter == nil {
return nil, errWriteOnSnapshot
}
metaKey := t.encodeListMetaKey(key)
meta, err := t.loadListMeta(metaKey)
if err != nil || meta.IsEmpty() {
return nil, errors.Trace(err)
}
index := int64(0)
if left {
index = meta.LIndex
meta.LIndex++
} else {
meta.RIndex--
index = meta.RIndex
}
dataKey := t.encodeListDataKey(key, index)
var data []byte
data, err = t.reader.Get(dataKey)
if err != nil {
return nil, errors.Trace(err)
}
if err = t.readWriter.Delete(dataKey); err != nil {
return nil, errors.Trace(err)
}
if !meta.IsEmpty() {
err = t.readWriter.Set(metaKey, meta.Value())
} else {
err = t.readWriter.Delete(metaKey)
}
return data, errors.Trace(err)
}
// LLen gets the length of a list.
func (t *TxStructure) LLen(key []byte) (int64, error) {
metaKey := t.encodeListMetaKey(key)
meta, err := t.loadListMeta(metaKey)
return meta.RIndex - meta.LIndex, errors.Trace(err)
}
// LGetAll gets all elements of this list in order from right to left.
func (t *TxStructure) LGetAll(key []byte) ([][]byte, error) {
metaKey := t.encodeListMetaKey(key)
meta, err := t.loadListMeta(metaKey)
if err != nil || meta.IsEmpty() {
return nil, errors.Trace(err)
}
length := int(meta.RIndex - meta.LIndex)
elements := make([][]byte, 0, length)
for index := meta.RIndex - 1; index >= meta.LIndex; index-- {
e, err := t.reader.Get(t.encodeListDataKey(key, index))
if err != nil {
return nil, errors.Trace(err)
}
elements = append(elements, e)
}
return elements, nil
}
// LIndex gets an element from a list by its index.
func (t *TxStructure) LIndex(key []byte, index int64) ([]byte, error) {
metaKey := t.encodeListMetaKey(key)
meta, err := t.loadListMeta(metaKey)
if err != nil || meta.IsEmpty() {
return nil, errors.Trace(err)
}
index = adjustIndex(index, meta.LIndex, meta.RIndex)
if index >= meta.LIndex && index < meta.RIndex {
return t.reader.Get(t.encodeListDataKey(key, index))
}
return nil, nil
}
// LSet updates an element in the list by its index.
func (t *TxStructure) LSet(key []byte, index int64, value []byte) error {
if t.readWriter == nil {
return errWriteOnSnapshot
}
metaKey := t.encodeListMetaKey(key)
meta, err := t.loadListMeta(metaKey)
if err != nil || meta.IsEmpty() {
return errors.Trace(err)
}
index = adjustIndex(index, meta.LIndex, meta.RIndex)
if index >= meta.LIndex && index < meta.RIndex {
return t.readWriter.Set(t.encodeListDataKey(key, index), value)
}
return errInvalidListIndex.GenWithStack("invalid list index %d", index)
}
// LClear removes the list of the key.
func (t *TxStructure) LClear(key []byte) error {
if t.readWriter == nil {
return errWriteOnSnapshot
}
metaKey := t.encodeListMetaKey(key)
meta, err := t.loadListMeta(metaKey)
if err != nil || meta.IsEmpty() {
return errors.Trace(err)
}
for index := meta.LIndex; index < meta.RIndex; index++ {
dataKey := t.encodeListDataKey(key, index)
if err = t.readWriter.Delete(dataKey); err != nil {
return errors.Trace(err)
}
}
return t.readWriter.Delete(metaKey)
}
func (t *TxStructure) loadListMeta(metaKey []byte) (listMeta, error) {
v, err := t.reader.Get(metaKey)
if kv.ErrNotExist.Equal(err) {
err = nil
} else if err != nil {
return listMeta{}, errors.Trace(err)
}
meta := listMeta{0, 0}
if v == nil {
return meta, nil
}
if len(v) != 16 {
return meta, errInvalidListMetaData
}
meta.LIndex = int64(binary.BigEndian.Uint64(v[0:8]))
meta.RIndex = int64(binary.BigEndian.Uint64(v[8:16]))
return meta, nil
}
func adjustIndex(index int64, min, max int64) int64 {
if index >= 0 {
return index + min
}
return index + max
}