forked from Shiloh/githaven
56 lines
1.3 KiB
Go
56 lines
1.3 KiB
Go
|
// Copyright 2012, Google Inc. All rights reserved.
|
||
|
|
// Use of this source code is governed by a BSD-style
|
||
|
|
// license that can be found in the LICENSE file.
|
||
|
|
|
||
|
|
package sync2
|
||
|
|
|
||
|
|
// What's in a name? Channels have all you need to emulate a counting
|
||
|
|
// semaphore with a boatload of extra functionality. However, in some
|
||
|
|
// cases, you just want a familiar API.
|
||
|
|
|
||
|
|
import (
|
||
|
|
"time"
|
||
|
|
)
|
||
|
|
|
||
|
|
// Semaphore is a counting semaphore with the option to
|
||
|
|
// specify a timeout.
|
||
|
|
type Semaphore struct {
|
||
|
|
slots chan struct{}
|
||
|
|
timeout time.Duration
|
||
|
|
}
|
||
|
|
|
||
|
|
// NewSemaphore creates a Semaphore. The count parameter must be a positive
|
||
|
|
// number. A timeout of zero means that there is no timeout.
|
||
|
|
func NewSemaphore(count int, timeout time.Duration) *Semaphore {
|
||
|
|
sem := &Semaphore{
|
||
|
|
slots: make(chan struct{}, count),
|
||
|
|
timeout: timeout,
|
||
|
|
}
|
||
|
|
for i := 0; i < count; i++ {
|
||
|
|
sem.slots <- struct{}{}
|
||
|
|
}
|
||
|
|
return sem
|
||
|
|
}
|
||
|
|
|
||
|
|
// Acquire returns true on successful acquisition, and
|
||
|
|
// false on a timeout.
|
||
|
|
func (sem *Semaphore) Acquire() bool {
|
||
|
|
if sem.timeout == 0 {
|
||
|
|
<-sem.slots
|
||
|
|
return true
|
||
|
|
}
|
||
|
|
select {
|
||
|
|
case <-sem.slots:
|
||
|
|
return true
|
||
|
|
case <-time.After(sem.timeout):
|
||
|
|
return false
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
// Release releases the acquired semaphore. You must
|
||
|
|
// not release more than the number of semaphores you've
|
||
|
|
// acquired.
|
||
|
|
func (sem *Semaphore) Release() {
|
||
|
|
sem.slots <- struct{}{}
|
||
|
|
}
|