msgque.cpp

VC++ 串口通信的dll. MsgQue 和SerialBase中重要的数据结构和通信函数,其可以完全复用. SerialComm是具体的应用, 大家实际应用中要做相应的修改. 代码注释详细,书写规

//File Name: MsgQue.cpp: implementation of the MsgQue and SafeMsgQue structure.
//References: None
//Purpose: To implement a Safe Message Queue and some essential functions about it.

//History
//*Data          *Name      *comments.
//2008-Feb-03    Rock Li    Initialization

//////////////////////////////////////////////////////////////////////

#include "stdafx.h"
#include "MsgQue.h"

//////////////////////////////////////////////////////////////////////
// Construction/Destruction
//////////////////////////////////////////////////////////////////////

//Purpose: To initialize the  the pSafeQue message queue
//Arguments description:
//hProExit --> program exit flag
//pSafeQue      --> the point to safe message queue
//return value: true for success and false for failure

bool SafeMsgQueInit(HANDLE hProExit, pSafeMsgQue pSafeQue)
{
	HANDLE hOpSem = CreateSemaphore( 
									NULL,   // default security attributes
									1,   // initial count
									1,   // maximum count
									NULL);  // unnamed semaphore

	if (hOpSem == NULL) 
	{
		//printf("CreateSemaphore error: %d\n", GetLastError());
		return false; //failure to Create  
	}

	HANDLE hMsgSem = CreateSemaphore( 
										NULL,   // default security attributes
										0,   // initial count
										1,   // maximum count
										NULL);  // unnamed semaphore

	if (hMsgSem == NULL) 
	{
		//printf("CreateSemaphore error: %d\n", GetLastError());
		return false; //failure to Create  
	}

	pSafeQue->pMsg = NULL;

	pSafeQue->hOpSem = hOpSem;
	pSafeQue->hProExitEvn = hProExit;
	pSafeQue->hMsgSem = hMsgSem;

	pSafeQue->pHead = NULL;
	pSafeQue->pTail = NULL;

	return true;
}

//Purpose: To Insert a message into the safe message queue
//Arguments description:
//msg --> the message to be inserted into the safe message queue
//pSafeQue --> the pointer to the safe message queue
//return value: true for success and false for failure  
//Notice: only one node should be in the Pmsg.

bool InsertOneMsg(pMsgQue pMsg, pSafeMsgQue pSafeQue)
{

	if(!LockQue(pSafeQue))   // safe operation; To get the right to use the resurece
	{
		return false;
	}

	if(pSafeQue->pHead == NULL)
	{
		pSafeQue->pHead = pMsg;
		pMsg->next  =NULL;
	}

	if(pSafeQue->pTail == NULL)
	{
		pSafeQue->pTail = pMsg;
		pMsg->next  =NULL;
	}
	else
	{
		pSafeQue->pTail->next = pMsg;
		pMsg->next  =NULL;
	}

// there is one or more messages in the queue
	long previousCount =0;
	ReleaseSemaphore(pSafeQue->hMsgSem,
					1,				//Release Count is 1.
					&previousCount	//Previous Count. no use for this program
					);

	UnlockQue(pSafeQue);// safe operation; To give up the right to use the resurece to let another to use it.	

	return true;
}

//Purpose: To Wait the data in the queue. this function will return until program exits 
//			or there is one or more data in the queue 
//Arguments description:
//pSafeQue --> the pointer to the safe message queue that contains two important semaphores.
//return value: true for success and false for failure  
bool WaitDataInQue(pSafeMsgQue pSafeQue)
{
	HANDLE hArr[2] ={
						pSafeQue->hProExitEvn,   //the flag of the program exit
						pSafeQue->hMsgSem			//semaphore for operation. 
					};

	DWORD dResult = WaitForMultipleObjects(	2,     //we have two semaphores
											hArr,  // the semaphore array
											false, //we do not need to wait all the semaphore
											INFINITE  //wait the semaphore forever until the flag of the semaphore is true;
											);
	if (dResult - WAIT_OBJECT_0 == 0)
	{
		return false; //program exits;
	}
	else if (dResult - WAIT_OBJECT_0 == 1 )
	{
		return true;
	}
	else
	{
		return false;
	}

	return true;
}

//Purpose: To read and remove a message from the safe message queue
//Arguments description:
//msg --> the message to be gotten from the safe message queue
//pSafeQue --> the pointer to the safe message queue
//return value: true for success and false for failure  

bool ReadOneMsg(pMsgQue* pMsg, pSafeMsgQue pSafeQue)
{
	if(!WaitDataInQue(pSafeQue))//safe opreation; To get the right to use the resurece
	{
		return false;
	}

	if(pSafeQue == NULL || pSafeQue->pHead == NULL) //safe check
	{
		return false;
	}

	if(!LockQue(pSafeQue))   // safe opreation; To get the right to use the resurece
	{
		return false;
	}

	*pMsg = pSafeQue->pHead; 

	pMsgQue pTempMsg = pSafeQue->pHead;
	pSafeQue->pHead = pTempMsg->next;  
	pTempMsg->next = NULL;

//	memcpy(pMsg, pSafeQue->pHead, sizeof());


	if(pSafeQue->pHead != NULL)
	{
		long previousCount =0;

		ReleaseSemaphore(pSafeQue->hMsgSem,
						1,				//Release Count is 1.
						&previousCount	//Previous Count. no use for this program
						);
	}
	else
	{
		pSafeQue->pTail = NULL;
	}

	UnlockQue(pSafeQue);// safe operation; To give up the right to use the resurece to let another to use it.

	return true;
}

//Purpose: To get the right to use the resource of the safe message queue
//Arguments description:
//pSafeQue --> the pointer to the safe message queue that contains two important semaphores.
//return value: true for success and false for failure  
bool LockQue(pSafeMsgQue pSafeQue)
{
	HANDLE hArr[2] ={
						pSafeQue->hProExitEvn,   //the flag of the program exit
						pSafeQue->hOpSem			//semaphore for operation. 
					};

	DWORD dResult = WaitForMultipleObjects(	2,     //we have two semaphores
											hArr,  // the semaphore array
											false, //we do not need to wait all the semaphore
											INFINITE  //wait the semaphore forever until the flag of the semaphore is true;
											);
	if (dResult - WAIT_OBJECT_0 == 0)
	{
		return false; //program exits;
	}
	else if (dResult - WAIT_OBJECT_0 == 1 )
	{
		return true;
	}
	else
	{
		return false;
	}

	return true;
}

//Purpose: To give up the right to use the resource of the safe message queue

//Arguments description:
//pSafeQue --> the pointer to the safe message queue that contains two important semaphores.

//return value: true for success and false for failure  

bool UnlockQue(pSafeMsgQue pSafeQue)
{
	// Increment the count of the semaphore.
	if (!ReleaseSemaphore( 
							pSafeQue->hOpSem, // handle to semaphore
							1,           // increase count by one
							NULL) )      // not interested in previous count
	{
		return false;
	}

	return true;
}