| /* |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you 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 |
| * |
| * http://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 common |
| |
| import ( |
| "sync" |
| ) |
| |
| // A simple lock-and-condition-variable based semaphore implementation. |
| type Semaphore struct { |
| lock sync.Mutex |
| cond *sync.Cond |
| count int64 |
| } |
| |
| func NewSemaphore(count int64) *Semaphore { |
| sem := &Semaphore{ |
| count: int64(count), |
| } |
| sem.cond = &sync.Cond{ |
| L: &sem.lock, |
| } |
| return sem |
| } |
| |
| func (sem *Semaphore) Post() { |
| sem.lock.Lock() |
| sem.count++ |
| if sem.count > 0 { |
| sem.cond.Broadcast() |
| } |
| sem.lock.Unlock() |
| } |
| |
| func (sem *Semaphore) Posts(amt int64) { |
| sem.lock.Lock() |
| sem.count += amt |
| if sem.count > 0 { |
| sem.cond.Broadcast() |
| } |
| sem.lock.Unlock() |
| } |
| |
| func (sem *Semaphore) Wait() { |
| sem.lock.Lock() |
| for { |
| if sem.count > 0 { |
| sem.count-- |
| sem.lock.Unlock() |
| return |
| } |
| sem.cond.Wait() |
| } |
| } |
| |
| func (sem *Semaphore) Waits(amt int64) { |
| var i int64 |
| for i = 0; i < amt; i++ { |
| sem.Wait() |
| } |
| } |