mirror of
https://codeberg.org/forgejo/forgejo.git
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215 lines
4.2 KiB
Go
215 lines
4.2 KiB
Go
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// 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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)
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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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}
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// Open opens a queue object or create it if not exist
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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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return nil, err
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}
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var queue = &Queue{
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db: db,
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}
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queue.low, err = queue.readID(lowKey)
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if err == leveldb.ErrNotFound {
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queue.low = 1
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err = db.Put(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(highKey)
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if err == leveldb.ErrNotFound {
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err = db.Put(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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var (
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lowKey = []byte("low")
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highKey = []byte("high")
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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(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(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(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(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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// 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(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.highLock.Lock()
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id, err := queue.lowdecrement()
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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(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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// 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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currentID := queue.high
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res, err := queue.db.Get(id2bytes(currentID), nil)
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if err != nil {
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queue.highLock.Unlock()
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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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queue.highLock.Unlock()
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return nil, err
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}
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err = queue.db.Delete(id2bytes(currentID), nil)
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queue.highLock.Unlock()
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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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// 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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currentID := queue.low
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res, err := queue.db.Get(id2bytes(currentID), nil)
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if err != nil {
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queue.lowLock.Unlock()
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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(id2bytes(currentID), nil)
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queue.lowLock.Unlock()
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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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// Close closes the queue
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func (queue *Queue) Close() error {
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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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