Bug in Win32file WaitCommEvent ???

[Bengt Richter]

On Sat, 23 Nov 2002 05:51:47 GMT, Mark Hammond <mhammond at skippinet.com.au> wrote:
>Grant Edwards wrote:
>> In article <3dde5012$0$4491$a1866201 at newsreader.visi.com>, Grant Edwards wrote:
>> 
>>>>I don't have win32all, but don't you need to have the
>>>>OVERLAPPED struct persist as well? Isn't the event slot there
>>>>also used asynchronously?
>>>
>>>Yes, the OVERLAPPED struct has to be persistent.  I've thought
>>>about using that as storage for the comm event mask value, but
>>>then we've got to add some sort of accessor function to
>>>retreive it later.  The advantantage of using a 4-byte buffer
>>>is that the semantics stay more similar to both the Win32
>>>usage, and the way that data buffers work for overlapped
>>>read/write operations:
>>>
>>>
>>>   rc,mask = WaitCommEvent(handle,overlapped)
>>>   rc = WaitForSingleObject(overlapped.hevent)
>>>   whatHappened = int(mask)
>> 
>> 
>> I should have mentioned that in the non-overlapped case, the
>> returned mask value would be an integer (same as it is now).
>> That way the only change is to the overlapped usage.
>
>Actually, I don't mind the idea of attaching it to the overlapped 
>object.  We already have the concept of attaching an object to an 
>overlapped structure, so adding support for a generic "flags" 32 bit 
>value wouldn't hurt, and 2 bytes per Python-allocated overlapped 
>structure wont kill anyone.
>
>Might be overkill if this is the only case we come across, but it 
>doesn't change any semantics.  ie, the code would look like:
>
>    rc,mask = WaitCommEvent(handle,overlapped)
>    rc = WaitForSingleObject(overlapped.hevent)
>    whatHappened = overlapped.flags
>
>
>Also much easier for me to code ;)  Would only work for overlapped 
>objects created via Python, but I think that is reasonable.  If a non 
>Python overlapped structure is used, we pass the address of a static 
>variable to ensure no one ever crashes.
>
>Sound reasonable?
>
Under what conditions would a non-Python overlapped structure be used?
Would a static restrict some kind of thread usage unacceptably?

Regards,
Bengt Richter