Re: serial reader ui-thread solution?
On Jan 7, 5:32 pm, mfc <mfcp...@googlemail.com> wrote:
Hi,
is it also possible to use an ui-thread for the serial reader-method?
I`ve two threads which "can" receive the receive message from the
serial reader-thread; but only one of these two threads will receive
the message from the serial-reader-thread. The user is able to switch
between these two threads.
Using a normal workerthread (for the serial reader thread), I always
have to close the thread (serial-reader) and re-create it, if the user
switch between the two threads receiving the message fromt he serial
reader.
Using a ui thread I can post message to the serial reader thread, that
the user wants that threadA will receive the pkts or threadB.
while(running)
{ /* read loop */
BYTE buffer[MAX_RXD_BUFFER_SIZE];
BOOL ok = ::ReadFile(parms->hCom, buffer, MAX_RXD_BUFFER_SIZE - 1,
&bytesRead, &ovl);
if(!ok)
{ /* error */
DWORD err = ::GetLastError();
if(err != ERROR_IO_PENDING)
{ /* read error */
shutdown = err;
::PostThreadMessage(parms->artnetTh, UWM_READER_SHUTTING_DOWN,
(WPARAM)parms->channelID, (LPARAM)err);
running = FALSE;
continue;
} /* read error */
// otherwise, it is ERROR_IO_PENDING
DWORD result = ::WaitForMultipleObjects(2, waiters, FALSE, INFINITE);
switch(result)
{ /* wait */
case WAIT_OBJECT_0: // shutdown
::CancelIo(parms->hCom);
shutdown = ERROR_SUCCESS; // clean shutdown
running = FALSE;
continue;
case WAIT_OBJECT_0 + 1: // I/O complete
ok = ::GetOverlappedResult(parms->hCom, &ovl, &bytesRead, TRUE);
if(!ok)
{ /* GetOverlappedResult failed */
DWORD err = ::GetLastError();
::PostThreadMessage(parms->artnetTh, UWM_READER_SHUTTING_DOWN,
(WPARAM)parms->channelID, (LPARAM)err);
running = FALSE;
continue;} /* GetOverlappedResult failed */
break;
default:
{ /* trouble */
shutdown = ::GetLastError();
running = FALSE;
} /* trouble */
} /* wait */
}
//write this received data msg to threadA or threadB (determining of
threadID)
::PostThreadMessage(threadID, UWM_READER_SENDING_DATA,(WPARAM)pData,
0);
if the thread waits in the (DWORD result = ::WaitForMultipleObjects(2,
waiters, FALSE, INFINITE)) the whole thread is blocked so that I can
not send any postmessages to this thread - or better the thread didn`t
process these messages.
How is it possible to write this function in an ui-thread, so that the
ui thread is always able to get / process any postmessages?
I am not sure what you are doing, but... Are you talking about one and
only thread here? If so, and if your thread is NOT your main UI
thread, you might do it using MsgWaitForMultipleObjects. Replace
WaitForMultipleObjects with MsgWaitForMultipleObjects.
MsgWaitForMultipleObjects returns when there are messages to process
with WAIT_OBJECT_0 + 2 (well, 2 in your case), so your thread can both
wait for IO completion and process messages if they arrive.
If you are in your main thread, I think you should not be meddling
with the message queue (or at least, I don't remember seeing a design
where doing this didn't result in one or another mess), so Scott's
advice stands.
Any kind of static methods is not the solution because I can`t change
the "threadID" of the PostThreadMessage to write this message to
threadA or threadB; because I`ve no access to any class members of the
ui thread within a static method.
Static function or not, if you know what's the thread you're in, can
use AfxGetThread, then cast to the type of the thread. Or...?
Goran.