base5. MutexLock和MutexLockGuard互斥量类、Condition条件变量类、CountDownLatch倒计时门栓类（计数类）

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MutexLock类图

数据成员：

pthread_mutex_t mutex_：pthread_mutex_t类型的线程互斥量mutex_
pid_t holder_：holder_用于保存锁拥有者的线程tid

成员函数：

MutexLock()：构造函数，初始化mutex_
~MutexLock()：析构函数，销毁mutex_
bool isLockedByThisThread()：判断当前线程是否拥有该锁
void assertLocked()：断言当前线程拥有该锁
void lock()：加锁，并将holder_设置为被加锁线程的tid
void unlock()：解锁，并将holder_设置为0
pthread_mutex_t* getPthreadMutex()：获取mutex_数据成员

MutexLockGuard类图

MutexLockGuard通过RAII方式管理MutexLock资源：构造MutexLockGuard对象时，取得mutex_锁；释放对象时，释放mutex_锁。

数据成员：

MutexLock& mutex_：一个引用类型的MutexLock对象，MutexLock和MutexLockGuard是关联关系

成员函数：
explicit MutexLockGuard(MutexLock& mutex)：构造函数，获取mutex_并加锁
~MutexLockGuard()：析构函数，释放mutex_并解锁

Mutex.h

#ifndef MUDUO_BASE_MUTEX_H
#define MUDUO_BASE_MUTEX_H#include <muduo/base/CurrentThread.h>
#include <boost/noncopyable.hpp>
#include <assert.h>
#include <pthread.h>namespace muduo
{class MutexLock : boost::noncopyable
{public:MutexLock(): holder_(0){int ret = pthread_mutex_init(&mutex_, NULL);assert(ret == 0); (void) ret;}~MutexLock(){assert(holder_ == 0);int ret = pthread_mutex_destroy(&mutex_);assert(ret == 0); (void) ret;}//当前线程是否拥有该锁bool isLockedByThisThread(){return holder_ == CurrentThread::tid();}//断言当前线程拥有该锁void assertLocked(){assert(isLockedByThisThread());}// internal usage//加锁void lock(){pthread_mutex_lock(&mutex_);holder_ = CurrentThread::tid();}//解锁void unlock(){holder_ = 0;pthread_mutex_unlock(&mutex_);}//获取mutex_数据成员pthread_mutex_t* getPthreadMutex() /* non-const */{return &mutex_;}private://pthread_mutex_t类型的线程互斥量mutex_pthread_mutex_t mutex_;//pid_t类型的锁拥有者的线程tidpid_t holder_;
};
//MutexLockGuard更常用，自动对MutexLock对象加锁和解锁
class MutexLockGuard : boost::noncopyable
{public://构造函数中获取锁explicit MutexLockGuard(MutexLock& mutex): mutex_(mutex){mutex_.lock();}//析构函数中释放锁~MutexLockGuard(){mutex_.unlock();}private://一个引用类型的MutexLock对象，两个类是关联关系MutexLock& mutex_;
};}// Prevent misuse like:
// MutexLockGuard(mutex_);
// A tempory object doesn't hold the lock for long!//这个宏是防止MutexLockGuard(mutex_)的用法
#define MutexLockGuard(x) error "Missing guard object name"#endif  // MUDUO_BASE_MUTEX_H

Condition类图

数据成员：

MutexLock& mutex_：一个MutexLock类型的引用对象mutex_
pthread_cond_t pcond_：一个pthread_cond_t类型的条件变量pcond_

成员函数：
explicit Condition(MutexLock& mutex)：构造函数中初始化条件变量pcond_
~Condition()：析构函数中销毁条件变量pcond_
void wait()：等待函数
bool waitForSeconds(int seconds)：等待一定时间，超过这个时间之后就超时
void notify()：调用signal函数，通知一个处于阻塞状态的线程
void notifyAll()：调用broadcast函数，通知所有处于阻塞状态的线程

Condition.h

#ifndef MUDUO_BASE_CONDITION_H
#define MUDUO_BASE_CONDITION_H#include <muduo/base/Mutex.h>#include <boost/noncopyable.hpp>
#include <pthread.h>namespace muduo
{class Condition : boost::noncopyable
{public://构造函数中初始化条件变量explicit Condition(MutexLock& mutex): mutex_(mutex){pthread_cond_init(&pcond_, NULL);}//析构函数中销毁条件变量~Condition(){pthread_cond_destroy(&pcond_);}//等待函数void wait(){pthread_cond_wait(&pcond_, mutex_.getPthreadMutex());}//等待一定时间，超过这个时间之后就超时// returns true if time out, false otherwise.bool waitForSeconds(int seconds);//调用signal函数，通知一个处于阻塞状态的线程void notify(){pthread_cond_signal(&pcond_);}//调用broadcast函数，通知所有处于阻塞状态的线程void notifyAll(){pthread_cond_broadcast(&pcond_);}private://一个MutexLock类型的引用对象MutexLock& mutex_;//一个pthread_cond_t类型的条件变量pthread_cond_t pcond_;
};}
#endif  // MUDUO_BASE_CONDITION_H

Condition.cc

#include <muduo/base/Condition.h>#include <errno.h>// returns true if time out, false otherwise.
bool muduo::Condition::waitForSeconds(int seconds)
{struct timespec abstime;clock_gettime(CLOCK_REALTIME, &abstime);abstime.tv_sec += seconds;return ETIMEDOUT == pthread_cond_timedwait(&pcond_, mutex_.getPthreadMutex(), &abstime);
}

CountDownLatch类图

对条件变量的封装类，既可以用于所有子线程等待主线程发起 “起跑” ，也可以用于主线程等待子线程初始化完毕才开始工作。

数据成员：

mutable MutexLock mutex_：一个MutexLock锁对象，并且这个对象声明为mutable，说明其可在const函数中被修改
Condition condition_：一个Condition条件变量对象condition_
int count_：计数器count_

成员函数：

explicit CountDownLatch(int count)：构造函数，用count初始化count_
void wait()：等待函数，若count_>0，等待
void countDown()：计数器count_减一，计数器count_==0时，唤醒所有线程
int getCount() const：获取计数器count_的值

CountDownLatch.h

//对条件变量的封装类
//既可以用于所有子线程等待主线程发起 “起跑” 
//也可以用于主线程等待子线程初始化完毕才开始工作
#ifndef MUDUO_BASE_COUNTDOWNLATCH_H
#define MUDUO_BASE_COUNTDOWNLATCH_H#include <muduo/base/Condition.h>
#include <muduo/base/Mutex.h>#include <boost/noncopyable.hpp>namespace muduo
{class CountDownLatch : boost::noncopyable
{public://explicit CountDownLatch(int count);//等待函数，count_>0，等待void wait();//计数器count_减一，计数器count_==0时，唤醒所有线程void countDown();//获取计数器count_的值int getCount() const;private://一个MutexLock锁对象，并且这个对象声明为mutable，说明其可在const函数中被修改mutable MutexLock mutex_;//一个Condition条件变量对象Condition condition_;//计数器int count_;
};}
#endif  // MUDUO_BASE_COUNTDOWNLATCH_H

CountDownLatch.cc

#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_;
}

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