commonmutex.cpp

来自「linux下的垃圾收集」· C++ 代码 · 共 67 行

#include "CommonMutex.h"

CCommonMutex::CCommonMutex()
{
	sem_init( &m_Semaphore, 0, 1 );
	m_nCount = 0 ;	 
	m_nPid = 0 ;
}


CCommonMutex::~CCommonMutex()
{ 
	sem_destroy( &m_Semaphore );
}
	
void CCommonMutex::Lock()
{
	//如果是锁的持有者再次调用，则增加访问计数，否则挂起
	if(m_nPid != getpid())
	{
		sem_wait( &m_Semaphore );
		m_nPid = getpid();
	}	
	m_nCount++;
}

bool CCommonMutex::tryLock()
{
	if(m_nPid != getpid())
	{
		if(sem_trywait( &m_Semaphore )==0)
		{
			m_nPid = getpid();
			m_nCount++;
			return TRUE ;
		}	
		else
		{
			return FALSE ;	
		}
	}	
	else
	{
		m_nCount++;
		return TRUE ;
	}
}

void CCommonMutex::Unlock()
{
	if(m_nPid == getpid())
	{
		if(m_nCount == 1)
		{
			//锁的持有者最后一次调用unlock
			m_nPid = 0 ;				
		}	
		if(m_nCount > 0)
		{
			//减少持有者对锁的访问计数
			m_nCount--;
		}			
		if(m_nCount == 0)
			//当访问计数为0时，释放锁
			sem_post( &m_Semaphore );
	}	
}