简介

CountDownLatch称为门阀，用于等待另外线程执行完成

结构

内部使用count_来计数，表示需要等待的线程数，线程执行完后减1，等待线程等待直到计数为0

构造函数

初始化互斥量，条件变量，以及需要等待的线程数

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

wait

等待线程执行完

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

countDown

线程执行完后，调用countDown将计数减1，当减到0时，会唤醒等待线程

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

getCount

获取等待的线程数

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