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muduo CountdownLatch

文章目录
  1. 1. CountDownLatch
  2. 2. 代码大赏
  3. 3. 参考资料

CountDownLatch

用途如下：

  1. 主线程发起多个子线程，等这些子线程各自都完成一定的任务之后，主线程才继续执行。通常用于主线程等待多个子线程完成初始化。
  2. 主线程发起多个子线程，子线程都等待主线程，主线程完成其他一些任务之后通知所有子线程开始执行。通常用于多个子线程等待主线程发出起跑命令。

代码大赏

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// Use of this source code is governed by a BSD-style license
// that can be found in the License file.
//
// Author: Shuo Chen (chenshuo at chenshuo dot com)

#ifndef MUDUO_BASE_COUNTDOWNLATCH_H
#define MUDUO_BASE_COUNTDOWNLATCH_H

#include "muduo/base/Condition.h"
#include "muduo/base/Mutex.h"

namespace muduo
{

class CountDownLatch : noncopyable
{
 public:

  explicit CountDownLatch(int count);

  void wait();

  void countDown();

  int getCount() const;

 private:
  mutable MutexLock mutex_;
  Condition condition_ GUARDED_BY(mutex_);
  int count_ GUARDED_BY(mutex_);
};

}  // namespace muduo
#endif  // MUDUO_BASE_COUNTDOWNLATCH_H
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// Use of this source code is governed by a BSD-style license
// that can be found in the License file.
//
// Author: Shuo Chen (chenshuo at chenshuo dot com)

#include "muduo/base/CountDownLatch.h"

using namespace muduo;

CountDownLatch::CountDownLatch(int count)
  : mutex_(),
    condition_(mutex_),
    count_(count)
{
}

void CountDownLatch::wait()
{
  MutexLockGuard lock(mutex_);
  while (count_ > 0)
  {
    condition_.wait();
  }
}

void CountDownLatch::countDown()
{
  MutexLockGuard lock(mutex_);
  --count_;
  if (count_ == 0)
  {
    condition_.notifyAll();
  }
}

int CountDownLatch::getCount() const
{
  MutexLockGuard lock(mutex_);
  return count_;
}

参考资料

  • CountDownLacth
  • Linux 多线程服务端编程–使用 muduo C++ 网络库