c++ - 如何检查 WriteFile 函数是否完成

Question

我想检查 WriteFile 函数是否已完成写入 UART，以便我可以在同一个 ComDev 上调用 ReadFile 而不会导致异常。

似乎WriteFile function可以在写入完成之前返回。

BOOL WriteCommBlock(HANDLE * pComDev, char *pBuffer , int BytesToWrite)
{
while(fComPortInUse){}

fComPortInUse = 1; 

BOOL       bWriteStat   = 0;
DWORD      BytesWritten = 0;
COMSTAT    ComStat      = {0};
OVERLAPPED osWrite      = {0,0,0};

if(WriteFile(*pComDev,pBuffer,BytesToWrite,&BytesWritten,&osWrite) == FALSE)
{
    short Errorcode = GetLastError();
    if( Errorcode != ERROR_IO_PENDING )
        short breakpoint = 5; // Error

    Sleep(1000); // complete write operation TBD

    fComPortInUse = 0; 
    return (FALSE);
}


fComPortInUse = 0; 
return (TRUE);
}

我使用 Sleep(1000) 作为解决方法，但我该如何等待合适的时间？

Answer 1

您可以创建一个事件，将其存储在您的重叠结构中并等待它发出信号。像这样(未经测试):

BOOL WriteCommBlock(HANDLE * pComDev, char *pBuffer , int BytesToWrite)
{
while(fComPortInUse){}

fComPortInUse = 1; 

BOOL       bWriteStat   = 0;
DWORD      BytesWritten = 0;
COMSTAT    ComStat      = {0};
OVERLAPPED osWrite      = {0,0,0};
HANDLE     hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);

if (hEvent != NULL)
{
    osWrite.hEvent = hEvent;
    if(WriteFile(*pComDev,pBuffer,BytesToWrite,&BytesWritten,&osWrite) == FALSE)
    {
        short Errorcode = GetLastError();
        if( Errorcode != ERROR_IO_PENDING )
            short breakpoint = 5; // Error

        WaitForSingleObject(hEvent, INFINITE);

        fComPortInUse = 0; 
        return (FALSE);
    }
    CloseHandle(hEvent);
}


fComPortInUse = 0; 
return (TRUE);
}

请注意，根据您尝试执行的其他操作，简单地调用 WaitForSingleObject() 可能不是最好的主意。 INFINITE 超时也不会。