C++条件变量实现

最新推荐文章于 2025-06-21 21:38:50 发布

yinhua405

最新推荐文章于 2025-06-21 21:38:50 发布

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这个博客展示了在Windows和Unix环境下实现条件变量的类`CondVito`，用于多线程同步。类中包含了信号、广播、等待等操作，并在析构时正确释放资源。在`main`函数中通过`CondVito`实现了两个线程间的同步，一个线程负责递减计数，另一个负责递增计数。

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#ifndef COND_VITO_H
#define COND_VITO_H

#ifdef _WIN32
#include<windows.h>
#else
#include <pthread.h>
#endif

class CondVito
{
public:
   CondVito();
   ~CondVito();
   void signal();
   void broadcast();
   void waitImpl() const;
   //bool timedWaitImpl() const;

private:
#ifdef _WIN32
   mutable CRITICAL_SECTION _mutex;
   mutable CONDITION_VARIABLE _cond;
#else
   mutable pthread_mutex_t _mutex;
   mutable pthread_cond_t _cond;
#endif

};

#endif

#include "CondVito.h"
#include<assert.h>

CondVito::CondVito()
{
#ifdef _WIN32
   InitializeCriticalSection(&_mutex);
   InitializeConditionVariable(&_cond);
#else
   int rc;
   pthread_mutexattr_t attr;
   rc = pthread_mutexattr_init(&attr);
   assert(rc == 0);
   if (rc != 0)
   {
       pthread_mutexattr_destroy(&attr);
   }
#ifndef NDEBUG
#if defined(__linux) && !defined(__USE_UNIX98)
   rc = pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_ERRORCHECK_NP);
#else
   rc = pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_ERRORCHECK);
#endif
   assert(rc == 0);
   if (rc != 0)
   {
       pthread_mutexattr_destroy(&attr);

   }
#endif
#if defined(_POSIX_THREAD_PRIO_INHERIT) && _POSIX_THREAD_PRIO_INHERIT > 0
   if (PrioInherit == protocol)
   {
       rc = pthread_mutexattr_setprotocol(&attr, PTHREAD_PRIO_INHERIT);
       if (rc != 0)
       {
           pthread_mutexattr_destroy(&attr);
       }
}
#endif
   rc = pthread_mutex_init(&_mutex, &attr);
   assert(rc == 0);
   if (rc != 0)
   {
       pthread_mutexattr_destroy(&attr);
   }
   rc = pthread_mutexattr_destroy(&attr);
   assert(rc == 0);
   pthread_condattr_t attr2;
   rc = pthread_condattr_init(&attr2);
   if (rc != 0)
   {

   }

#if !defined(__hppa) && !defined(__APPLE__) && !defined(__FreeBSD__)
   rc = pthread_condattr_setclock(&attr2, CLOCK_MONOTONIC);
   if (rc != 0)
   {

   }
#endif

   rc = pthread_cond_init(&_cond, &attr2);
   if (rc != 0)
   {

   }
   rc = pthread_condattr_destroy(&attr2);
   if (rc != 0)
   {

   }
#endif
}

CondVito::~CondVito()
{
#ifndef _WIN32
#ifndef NDEBUG
   int rc = pthread_cond_destroy(&_cond);
   assert(rc == 0);
#else
   pthread_cond_destroy(&_cond);
#endif
#endif
}

void CondVito::signal()
{
#ifdef _WIN32
   WakeConditionVariable(&_cond);
#else
   int rc = pthread_cond_signal(&_cond);
   if (rc != 0)
   {

   }
#endif
}
void CondVito::broadcast()
{
#ifdef _WIN32
   WakeAllConditionVariable(&_cond);
#else
   int rc = pthread_cond_broadcast(&_cond);
   if (rc != 0)
   {

   }
#endif
}
void CondVito::waitImpl() const
{
#ifdef _WIN32
   EnterCriticalSection(&_mutex);
   BOOL ok = SleepConditionVariableCS(&_cond, &_mutex, INFINITE);
   LeaveCriticalSection(&_mutex);
#else
   int rc = pthread_mutex_lock(&_mutex);
   rc = pthread_cond_wait(&_cond, &_mutex);
   rc = pthread_mutex_unlock(&_mutex);
#endif
}

#include "MutexVito.h"
#include "ThreadVito.h"
#include "CondVito.h"
#include<iostream>
#include<thread>

#ifdef _WIN32
#include<windows.h>
#include<process.h>
#else
#include <pthread.h>
#include <unistd.h>
#endif

int count = 0;
CondVito cond;
void de()
{
   while (true)
   {
       printf("in derement.\n");
       if (count == 0)
       {
           cond.waitImpl();
       }
       count--;
       printf("----decrement:%d.\n", count);
       printf("out decrement.\n");
       sleep(1);
   }
}

void in() {
   while (true)
   {
       printf("in increment.\n");
       count++;
       printf("----increment:%d.\n", count);
       if (count != 0)
           cond.signal();
       printf("out increment.\n");
       sleep(2);
   }
}

void test_cond()
{
std::thread t1(de);
std::thread t2(in);

t1.join();
t2.join();
}

int main()
{
test_cond();
return 0;
}