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semaphore.go
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/
semaphore.go
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// Copyright 2014-2015 Amazon.com, Inc. or its affiliates. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License"). You may
// not use this file except in compliance with the License. A copy of the
// License is located at
//
// http://aws.amazon.com/apache2.0/
//
// or in the "license" file accompanying this file. This file 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 utils
// Implements a simple counting sempahore on top of channels
type empty struct{}
type Semaphore interface {
Post()
Wait()
}
// Implements semaphore
type ChanSemaphore struct {
semaphore chan empty
Count int // Public for introspection; should not be written to
}
func NewSemaphore(count int) Semaphore {
sem := make(chan empty, count)
// Init to all resources available
for i := 0; i < count; i++ {
sem <- empty{}
}
return &ChanSemaphore{
semaphore: sem,
Count: count,
}
}
func (s *ChanSemaphore) Post() {
s.semaphore <- empty{}
}
func (s *ChanSemaphore) Wait() {
<-s.semaphore
}