具有Reset功能的多线程同步队列 - 4

王朝vc·作者佚名  2006-01-08
窄屏简体版  字體: |||超大  

BOOL CTreadSafeMsgQueue::PostMsg(const MsgItem Msg, int WaitTime)

{

if (!m_bInitedOK) return FALSE;

// 防止在reset期间导致Semaphore计数不正确

while (m_bStop)

{

TRACE("Thread %d Sleep\n", GetCurrentThreadId());

Sleep(SLEEP_TIME);

}

// 进入同步操作状态

m_WritingThreadNum++;

if (WaitForSingleObject(m_S_Producer, WaitTime) == WAIT_OBJECT_0)

{

if (WaitForSingleObject(m_E_Queue, WaitTime) == WAIT_OBJECT_0)

{

// OK now, post message then

m_Queue[m_HeaderToWrite++] = Msg;

if (m_HeaderToWrite >= MAX_QUE_SIZE) m_HeaderToWrite = 0;

TRACE("Post message *** %d\n", Msg.MsgID);

ReleaseSemaphore(m_S_Consumer, 1, NULL);

SetEvent(m_E_Queue);

m_WritingThreadNum--;

return TRUE;

}

else // wait event time out

{

// not post message so release producer

ReleaseSemaphore(m_S_Producer, 1, NULL);

SetEvent(m_E_Queue);

m_WritingThreadNum--;

return FALSE;

}

}

else // wait semaphore time out

{

m_WritingThreadNum--;

return FALSE;

}

}

BOOL CTreadSafeMsgQueue::Reset()

{

if (!m_bInitedOK) return FALSE;

// 防止重入Reset

while (m_bStop) Sleep(SLEEP_TIME);

// 防止新的线程进入读写操作状态

m_bStop = TRUE;

TRACE("--------------Begin to Reset-------------\n");

// 等待至少一类线程(读线程或写线程)退出同步状态

while ( (m_WritingThreadNum != 0) && (m_ReadingThreadNum != 0)) Sleep(SLEEP_TIME);

// 此时,可能(最坏可能)还有一类线程处于同步状态,并被阻塞。

// 它们必定都被阻塞于信号量(Semaphore)状态, 注意此时Event事件处于信号态!!

// 如果被阻塞的是写线程,它们将被释放,并写入数据,但它们写入的数据将被抛弃。

// 释放写线程将改写m_S_Consumer,所以必须先释放写线程;

// ReleaseSemaphore(m_S_Producer)令m_S_Producer=MAX_QUE_SIZE;

while (m_WritingThreadNum > 0)

{

// 必须Sleep以出让CPU控制权

ReleaseSemaphore(m_S_Producer, 1, NULL);

Sleep(5);

}

// 继续阻塞读线程,令m_S_Consumer=0;

while (WaitForSingleObject(m_S_Consumer, 10) == WAIT_OBJECT_0);

// 由于写操作会改变m_HeaderToWrite,必须在写操作之后对其重置

m_HeaderToWrite = m_TailToRead = 0;

// 注意

TRACE("--------------Finished Reseting-------------\n");

m_bStop = FALSE;

return TRUE;

}

 
 
 
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