foundation/concurrenz/semaphore.go

/*
	Copyright NetFoundry Inc.

	Licensed under the Apache License, Version 2.0 (the "License");
	you may not use this file except in compliance with the License.
	You may obtain a copy of the License at

	https://www.apache.org/licenses/LICENSE-2.0

	Unless required by applicable law or agreed to in writing, software
	distributed under the License is distributed on an "AS IS" BASIS,
	WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	See the License for the specific language governing permissions and
	limitations under the License.
*/

package concurrenz

import "time"

type Semaphore interface {
	Acquire()
	AcquireWithTimeout(t time.Duration) bool
	TryAcquire() bool
	Release() bool
}

func NewSemaphore(size int) Semaphore {
	result := &semaphoreImpl{
		c: make(chan struct{}, size),
	}
	for result.Release() {
	}
	return result
}

type semaphoreImpl struct {
	c chan struct{}
}

func (self *semaphoreImpl) Acquire() {
	<-self.c
}

func (self *semaphoreImpl) AcquireWithTimeout(t time.Duration) bool {
	timer := time.NewTimer(t)
	defer timer.Stop()

	select {
	case <-self.c:
		return true
	case <-timer.C:
		return false
	}
}

func (self *semaphoreImpl) TryAcquire() bool {
	select {
	case <-self.c:
		return true
	default:
		return false
	}
}

func (self *semaphoreImpl) Release() bool {
	select {
	case self.c <- struct{}{}:
		return true
	default:
		return false
	}
}