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// Copyright 2016 The Gogs Authors. All rights reserved.
// Use of this source code is governed by a MIT-style
// license that can be found in the LICENSE file.
package sync
import (
"github.com/Unknwon/com"
)
// UniqueQueue is a queue which guarantees only one instance of same
// identity is in the line. Instances with same identity will be
// discarded if there is already one in the line.
//
// This queue is particularly useful for preventing duplicated task
// of same purpose.
type UniqueQueue struct {
table *StatusTable
queue chan string
}
// NewUniqueQueue initializes and returns a new UniqueQueue object.
func NewUniqueQueue(queueLength int) *UniqueQueue {
if queueLength <= 0 {
queueLength = 100
}
return &UniqueQueue{
table: NewStatusTable(),
queue: make(chan string, queueLength),
}
}
// Queue returns channel of queue for retrieving instances.
func (q *UniqueQueue) Queue() <-chan string {
return q.queue
}
// Exist returns true if there is an instance with given identity
// exists in the queue.
func (q *UniqueQueue) Exist(id interface{}) bool {
return q.table.IsRunning(com.ToStr(id))
}
// AddFunc adds new instance to the queue with a custom runnable function,
// the queue is blocked until the function exits.
func (q *UniqueQueue) AddFunc(id interface{}, fn func()) {
if q.Exist(id) {
return
}
idStr := com.ToStr(id)
q.table.lock.Lock()
q.table.pool[idStr] = struct{}{}
if fn != nil {
fn()
}
q.table.lock.Unlock()
q.queue <- idStr
}
// Add adds new instance to the queue.
func (q *UniqueQueue) Add(id interface{}) {
q.AddFunc(id, nil)
}
// Remove removes instance from the queue.
func (q *UniqueQueue) Remove(id interface{}) {
q.table.Stop(com.ToStr(id))
}
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