Help!!!!! : : about multithreading implementation a weighing system code (pure white)-CodePudding

I am a freshman small white recently in self-study using MFC API function to write a serial port communication, and mainly is the realization of an electronic weighing system, I did out in synchronous operation way (because it's easy), but the use of asynchronous do not to come out, the main reason is: to use multithreading knowledge, but after check the information on the Internet or don't understand the concept,,
The problem is mainly how to write a thread function?? Thread function should be given where the CPP?? Read and write the following code is my serial code (haven't join the thread)
But there have been a problem: the fourth parameter writefile function returns the actual number of bytes to write. But I always returns 0 is how to return a responsibility,,

 BOOL write () 
{
X55 char buffer [6]={0, 0 x11, 0 x00 to 0 x00 to 0 x11}; 
The COMSTAT COMSTAT; 
DWORD dwRetwrite=0; 
DWORD dwErrorFlags; 
OVERLAPPED m_osWrite; 
BOOL bWriteStat; 
Memset (& amp; M_osWrite, 0, sizeof (m_osWrite)); 
The ClearCommError (hcom, & amp; DwErrorFlags, & amp; The ComStat); 
PurgeComm (hcom, PURGE_TXABORT | PURGE_RXABORT | PURGE_TXCLEAR | PURGE_RXCLEAR); 
BWriteStat=WriteFile (hcom, buffer, 5, & amp; DwRetwrite, & amp; M_osWrite); 
if(! BWriteStat) 
{
If (GetLastError ()==ERROR_IO_PENDING) 
WaitForSingleObject (m_osWrite hEvent, INFINITE); 
The else 
Return FALSE; 
} 
Return TRUE; 
} 
BOOL read () 
{
Char inBuffer [6]={0}; 

DWORD dwRetread=0; 

OVERLAPPED m_osRead; 
Memset (& amp; M_osRead, 0, sizeof (OVERLAPPED)); 
M_osRead. HEvent=CreateEvent (NULL, TRUE, FALSE, NULL); 
BOOL bReadStatus; 
BReadStatus=ReadFile (hcom, inBuffer, 5, & amp; DwRetread, & amp; M_osRead); 
if(! BReadStatus) 
{
If (GetLastError ()==ERROR_IO_PENDING) 
{
WaitForSingleObject (m_osRead hEvent, INFINITE); 
} 
Return FALSE; 
} 
Return TRUE; 
}

CodePudding user response:

Another is a createevent function in the read function, this is what's the point?

CodePudding user response:

The GetOverlappedResult access to hang the results

 
BWriteStat=WriteFile (hcom, buffer, 5, & amp; DwRetwrite, & amp; M_osWrite); 
if(! BWriteStat & amp; & GetLastError ()==ERROR_IO_PENDING) 
{
BWriteStat=the GetOverlappedResult (hcom, & amp; M_osWrite, & amp; DwRetwrite, TRUE) 
}

CodePudding user response:

Quote: refer to the second floor zgl7903 response:

The GetOverlappedResult access to hang the results
[code]=c
BWriteStat=WriteFile (hcom, buffer, 5, & amp; DwRetwrite, & amp; M_osWrite);
if(! BWriteStat & amp; & GetLastError ()==ERROR_IO_PENDING)
{
BWriteStat=the GetOverlappedResult (hcom, & amp; M_osWrite, & amp; DwRetwrite, TRUE)
}
WaiForSingleObject not also is not very good, can you tell me, what is the difference between these two functions,
And the main thread, I should create several threads, function is used to do?
CodePudding user response:
WaiForSingleObject only waiting for the event, the GetOverlappedResult also returns the number writing values

Asynchronous mode of OVERLAPPED hEvent to create

Serial Communications in Win32
 
BOOL WriteABuffer (char * lpBuf, dwords dwToWrite) 
{
OVERLAPPED osWrite={0}; 
DWORD dwWritten; 
DWORD dwRes; 
BOOL forward; 

//Create this write operation 's OVERLAPPED structure' s hEvent. 
OsWrite. HEvent=CreateEvent (NULL, TRUE, FALSE, NULL); 
If (osWrite hEvent==NULL) 
//the error creating overlapped event handle 
Return FALSE; 

//Issue write. 
if (! WriteFile (hComm lpBuf, dwToWrite, & amp; DwWritten, & amp; OsWrite)) {
If (GetLastError ()!={ERROR_IO_PENDING) 
//WriteFile failed, but isn 't of Report the error and abort. 
The fRes=FALSE; 
} 
The else 
//Write is pending. 
DwRes=WaitForSingleObject (osWrite hEvent, INFINITE). 
The switch (dwRes) 
{
//OVERLAPPED structure 's event has had signaled. 
Case WAIT_OBJECT_0: 
if (! The GetOverlappedResult (hComm, & amp; OsWrite, & amp; DwWritten, FALSE)) 
The fRes=FALSE; 
The else 
//Write operation completed successfully. 
The fRes=TRUE; 
break; 

Default: 
//An error has occurred in WaitForSingleObject. 
//This usually are a problem with the 
//OVERLAPPED structure 's event handle. 
The fRes=FALSE; 
break; 
} 
} 
} 
The else 
//WriteFile completed immediately. 
The fRes=TRUE; 

The CloseHandle (osWrite. HEvent); 
Return the fRes. 
} 
CodePudding user response:
reference 4 floor zgl7903 response:
WaiForSingleObject only waiting for the event, the GetOverlappedResult also returns the number writing values

Asynchronous mode of OVERLAPPED hEvent to create

Serial Communications in Win32

BOOL WriteABuffer (char * lpBuf, dwords dwToWrite)
{
OVERLAPPED osWrite={0};
DWORD dwWritten;
DWORD dwRes;
BOOL forward;

//Create this write operation 's OVERLAPPED structure' s hEvent.
OsWrite. HEvent=CreateEvent (NULL, TRUE, FALSE, NULL);
If (osWrite hEvent==NULL)
//the error creating overlapped event handle
Return FALSE;

//Issue write.
if (! WriteFile (hComm lpBuf, dwToWrite, & amp; DwWritten, & amp; OsWrite)) {
If (GetLastError ()!={ERROR_IO_PENDING)
//WriteFile failed, but isn 't of Report the error and abort.
The fRes=FALSE;
}
The else
//Write is pending.
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