Re: Patch for ReadFile with NULL hEvent

[Scott W Gifford]

I wrote a simple test program and ran it under Windows, to see what
Windows does.  I've attached the program here.  I found that...

Eric Pouech  writes:

[...]
> I'm not sure this is a correct fix:
> - you modify the passed overlapped structure (by filling in the
>
> hEvent), I'm not sure Windows does it this way

...Windows doesn't do it this way, although according to the docs
other members of the overlapped structure are modified by Windows.

Unfortunately, I'm not sure of another straightforward way to
implement this.  Unless somebody can come up with one, I think it's
better to have Wine's behavior deviate slightly from Windows than to
completely fail to support this feature.

[...]
> I'd rather say it's GetOverlappedResult which is to blame. If the
> hEvent is NULL, then we shouldn't return any error (as we do) but
> rather assume all wait operation succeed (if hEven is NULL, ReadFile
> and WriteFile operations are synchronous, so calling
> GetOverlappedResult is a no-op).

This turns out not to be the case.  As long as lpOverlapped is
supplied, a NULL hEvent will work fine and allows overlapped reads.
> But, this should be verified by small tests (and added to wine's test
> suite).

I agree; consider the attached file the first stab at a test program
for this feature.
> PS: some comments on your patch (not so useless regarding what I wrote
> above):
> - CreateEvent can take a NULL parameter (for the name) which would
>
> solve the name construction issue

Ah, I didn't know that.  If we keep calling CreateEvent over and over
again with a NULL parameter, will we eventually run out of some
resource?  If so, it may still be best to construct a name, since
calling CreateEvent with the same name twice will apparently avoid
creating another event.
> - you don't need to but the hEvent as a static variable

Thanks, that's a relic from an earlier version.  If the other aspects
of this patch are OK, I'll fix it in an update.

The attached test program uses overlapped reads with a NULL hEvent in
the OVERLAPPED structure to connect to an IP address and port given on
the command line.  Here's an example from Windows:

C:>overlapped-test 216.12.213.139 25
    Calling ReadFile
    ReadFile returned ERROR_IO_PENDING, as expected
    ov      .hEvent=00000000
    Calling Sleep(2000)
    Calling GetOverlappedResult
    GetOverlappedresult read 85 bytes:
    220 2search2.com ESMTP Sendmail 8.10.2-SOL3/8.10.2; Mon, 17 May 2004  11:58:26 -0400

----ScottG.