modules/sync: add UniqueQueue

1 files changed, 70 insertions, 0 deletions

diff --git a/modules/sync/unique_queue.go b/modules/sync/unique_queue.go
new file mode 100644
index 0000000000..3f3c1c8661
--- /dev/null
+++ b/modules/sync/unique_queue.go
@@ -0,0 +1,70 @@
+// 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 indentity
+// 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] = true
+	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))
+}