🚀 go-pugleaf

Michel,

Thank you for your reply.



You wrote:

> You read one byte at a time. Why don't you read all bytes available in the 
> queue?
I understand your point here, and I could change my code to read all of the 
bytes at once, but that is not what is causing the delay.  The delay is 
caused by the call to GetOverlappedResult().  If I do a read of 4 bytes, the 
function is called 4 times.  The first time through, I see the delay at the 
GetOverlappedResult call, but for the next 3 bytes, the ReadFile() is 
successful, so GetOverlappedResult does not get called, and the delay does 
not occur.



> if(!ReadFile(hCom,buffer,numbyte,&BytesRead,&OvlRead))
> {
>    if(GetLastError() == ERROR_IO_PENDING)
>    {
>      if(WaitForSingleObject(OvlRead.hEvent,5000))
>      {
>         BytesRead = 0;
>      }
>      else
>      {
>         GetOverlappedResult(hCom,&OvlRead,&BytesRead,false);
>         OvlRead.Offset += BytesRead;
>      }
>    }
>    else BytesRead = 0;
> }



I tried this approach as well.  Just like before, when I'm connected 
directly with a serial cable the communications are fast.  However, when I 
use my modem, I still see a delay of about 125ms.  However, this time it is 
in the WaitForSingleObject() function.



To me it looks like the delay occurrs when the modem signals to the 
operating system that a byte has arrived.  I'm just not sure if there is a 
way to speed it up.



Phil


"Michel Leunen" <nospam@noreply.be> wrote in message 
news:46004649$1@newsgroups.borland.com...
> Phil wrote:
>
>> if (!ReadFile(hcomm, xbyte, 1, &ibytes, &overlapped))
>
> You read one byte at a time. Why don't you read all bytes available in the 
> queue?
>
>> while ((!ibytes) &&
>>             (clock() < (int)timeout) &&
>>             ((ierr == ERROR_IO_PENDING) ||
>>             (ierr == ERROR_IO_INCOMPLETE)))
>
> You don't need to put this in a while loop and why don't you use
> WaitForSingleObject() with the overlapped struct event to get your 
> timeout?
>
> I personnaly do something like this:
>
> if(!ReadFile(hCom,buffer,numbyte,&BytesRead,&OvlRead))
> {
>    if(GetLastError() == ERROR_IO_PENDING)
>    {
>      if(WaitForSingleObject(OvlRead.hEvent,5000))
>      {
>         BytesRead = 0;
>      }
>      else
>      {
>         GetOverlappedResult(hCom,&OvlRead,&BytesRead,false);
>         OvlRead.Offset += BytesRead;
>      }
>    }
>    else BytesRead = 0;
> }
>
> HTH
> Michel
> -- 
> ----------------------------------------
> Michel Leunen
> mailto: see my homepage.
> C++Builder, BCC5.5.1 Web site:
> http://www.leunen.com/
> ----------------------------------------