mirror of
https://codeberg.org/forgejo/forgejo
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306 lines
6.9 KiB
Go
Vendored
306 lines
6.9 KiB
Go
Vendored
// Copyright 2019 Lunny Xiao. All rights reserved.
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// Use of this source code is governed by a MIT-style
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// license that can be found in the LICENSE file.
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package levelqueue
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import (
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"bytes"
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"encoding/binary"
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"sync"
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"github.com/syndtr/goleveldb/leveldb"
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"github.com/syndtr/goleveldb/leveldb/errors"
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)
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const (
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lowKeyStr = "low"
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highKeyStr = "high"
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)
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// Queue defines a queue struct
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type Queue struct {
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db *leveldb.DB
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highLock sync.Mutex
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lowLock sync.Mutex
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low int64
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high int64
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lowKey []byte
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highKey []byte
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prefix []byte
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closeUnderlyingDB bool
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}
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// Open opens a queue from the db path or creates a
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// queue if it doesn't exist.
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// The keys will not be prefixed by default
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func Open(dataDir string) (*Queue, error) {
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db, err := leveldb.OpenFile(dataDir, nil)
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if err != nil {
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if !errors.IsCorrupted(err) {
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return nil, err
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}
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db, err = leveldb.RecoverFile(dataDir, nil)
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if err != nil {
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return nil, err
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}
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}
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return NewQueue(db, []byte{}, true)
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}
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// NewQueue creates a queue from a db. The keys will be prefixed with prefix
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// and at close the db will be closed as per closeUnderlyingDB
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func NewQueue(db *leveldb.DB, prefix []byte, closeUnderlyingDB bool) (*Queue, error) {
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var err error
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var queue = &Queue{
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db: db,
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closeUnderlyingDB: closeUnderlyingDB,
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}
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queue.prefix = make([]byte, len(prefix))
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copy(queue.prefix, prefix)
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queue.lowKey = withPrefix(prefix, []byte(lowKeyStr))
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queue.highKey = withPrefix(prefix, []byte(highKeyStr))
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queue.low, err = queue.readID(queue.lowKey)
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if err == leveldb.ErrNotFound {
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queue.low = 1
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err = db.Put(queue.lowKey, id2bytes(1), nil)
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}
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if err != nil {
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return nil, err
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}
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queue.high, err = queue.readID(queue.highKey)
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if err == leveldb.ErrNotFound {
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err = db.Put(queue.highKey, id2bytes(0), nil)
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}
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if err != nil {
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return nil, err
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}
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return queue, nil
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}
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func (queue *Queue) readID(key []byte) (int64, error) {
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bs, err := queue.db.Get(key, nil)
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if err != nil {
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return 0, err
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}
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return bytes2id(bs)
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}
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func (queue *Queue) highincrement() (int64, error) {
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id := queue.high + 1
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queue.high = id
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err := queue.db.Put(queue.highKey, id2bytes(queue.high), nil)
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if err != nil {
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queue.high = queue.high - 1
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return 0, err
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}
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return id, nil
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}
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func (queue *Queue) highdecrement() (int64, error) {
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queue.high = queue.high - 1
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err := queue.db.Put(queue.highKey, id2bytes(queue.high), nil)
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if err != nil {
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queue.high = queue.high + 1
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return 0, err
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}
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return queue.high, nil
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}
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func (queue *Queue) lowincrement() (int64, error) {
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queue.low = queue.low + 1
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err := queue.db.Put(queue.lowKey, id2bytes(queue.low), nil)
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if err != nil {
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queue.low = queue.low - 1
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return 0, err
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}
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return queue.low, nil
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}
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func (queue *Queue) lowdecrement() (int64, error) {
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queue.low = queue.low - 1
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err := queue.db.Put(queue.lowKey, id2bytes(queue.low), nil)
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if err != nil {
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queue.low = queue.low + 1
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return 0, err
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}
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return queue.low, nil
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}
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// Len returns the length of the queue
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func (queue *Queue) Len() int64 {
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queue.lowLock.Lock()
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queue.highLock.Lock()
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l := queue.high - queue.low + 1
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queue.highLock.Unlock()
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queue.lowLock.Unlock()
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return l
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}
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func id2bytes(id int64) []byte {
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var buf = make([]byte, 8)
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binary.PutVarint(buf, id)
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return buf
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}
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func bytes2id(b []byte) (int64, error) {
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return binary.ReadVarint(bytes.NewReader(b))
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}
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func withPrefix(prefix []byte, value []byte) []byte {
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if len(prefix) == 0 {
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return value
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}
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prefixed := make([]byte, len(prefix)+1+len(value))
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copy(prefixed[0:len(prefix)], prefix)
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prefixed[len(prefix)] = '-'
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copy(prefixed[len(prefix)+1:], value)
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return prefixed
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}
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// RPush pushes a data from right of queue
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func (queue *Queue) RPush(data []byte) error {
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queue.highLock.Lock()
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id, err := queue.highincrement()
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if err != nil {
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queue.highLock.Unlock()
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return err
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}
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err = queue.db.Put(withPrefix(queue.prefix, id2bytes(id)), data, nil)
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queue.highLock.Unlock()
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return err
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}
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// LPush pushes a data from left of queue
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func (queue *Queue) LPush(data []byte) error {
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queue.lowLock.Lock()
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id, err := queue.lowdecrement()
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if err != nil {
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queue.lowLock.Unlock()
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return err
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}
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err = queue.db.Put(withPrefix(queue.prefix, id2bytes(id)), data, nil)
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queue.lowLock.Unlock()
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return err
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}
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// RPop pop a data from right of queue
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func (queue *Queue) RPop() ([]byte, error) {
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queue.highLock.Lock()
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defer queue.highLock.Unlock()
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currentID := queue.high
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res, err := queue.db.Get(withPrefix(queue.prefix, id2bytes(currentID)), nil)
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if err != nil {
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if err == leveldb.ErrNotFound {
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return nil, ErrNotFound
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}
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return nil, err
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}
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_, err = queue.highdecrement()
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if err != nil {
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return nil, err
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}
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err = queue.db.Delete(withPrefix(queue.prefix, id2bytes(currentID)), nil)
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if err != nil {
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return nil, err
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}
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return res, nil
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}
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// RHandle receives a user callback function to handle the right element of the queue, if function return nil, then delete the element, otherwise keep the element.
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func (queue *Queue) RHandle(h func([]byte) error) error {
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queue.highLock.Lock()
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defer queue.highLock.Unlock()
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currentID := queue.high
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res, err := queue.db.Get(withPrefix(queue.prefix, id2bytes(currentID)), nil)
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if err != nil {
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if err == leveldb.ErrNotFound {
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return ErrNotFound
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}
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return err
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}
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if err = h(res); err != nil {
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return err
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}
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_, err = queue.highdecrement()
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if err != nil {
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return err
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}
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return queue.db.Delete(withPrefix(queue.prefix, id2bytes(currentID)), nil)
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}
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// LPop pop a data from left of queue
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func (queue *Queue) LPop() ([]byte, error) {
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queue.lowLock.Lock()
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defer queue.lowLock.Unlock()
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currentID := queue.low
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res, err := queue.db.Get(withPrefix(queue.prefix, id2bytes(currentID)), nil)
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if err != nil {
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if err == leveldb.ErrNotFound {
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return nil, ErrNotFound
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}
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return nil, err
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}
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_, err = queue.lowincrement()
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if err != nil {
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return nil, err
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}
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err = queue.db.Delete(withPrefix(queue.prefix, id2bytes(currentID)), nil)
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if err != nil {
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return nil, err
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}
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return res, nil
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}
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// LHandle receives a user callback function to handle the left element of the queue, if function return nil, then delete the element, otherwise keep the element.
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func (queue *Queue) LHandle(h func([]byte) error) error {
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queue.lowLock.Lock()
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defer queue.lowLock.Unlock()
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currentID := queue.low
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res, err := queue.db.Get(withPrefix(queue.prefix, id2bytes(currentID)), nil)
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if err != nil {
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if err == leveldb.ErrNotFound {
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return ErrNotFound
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}
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return err
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}
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if err = h(res); err != nil {
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return err
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}
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_, err = queue.lowincrement()
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if err != nil {
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return err
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}
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return queue.db.Delete(withPrefix(queue.prefix, id2bytes(currentID)), nil)
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}
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// Close closes the queue (and the underlying db is set to closeUnderlyingDB)
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func (queue *Queue) Close() error {
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if !queue.closeUnderlyingDB {
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queue.db = nil
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return nil
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}
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err := queue.db.Close()
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queue.db = nil
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return err
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}
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