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Message-ID: <3F269CB0.7040706@cs.york.ac.uk>
Date: Tue, 29 Jul 2003 17:11:28 +0100
From: chris <caj AT cs DOT york DOT ac DOT uk>
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CC: cygwin AT cygwin DOT com
Subject: Re: Limit to size of pipe
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David Rothenberger wrote:

>chris writes:
> > Hello!
> > 
> > Further to an earlier message I sent, I now attach an example. This 
> > tries to send a message of a fixed sized down a pipe. Under windows I 
> > can't seem to send much more than 25k down in one go, although I can 
> > send more if I chop it up into sections. Under linux however I can send 
> > as large amounts as I like. While it is possible to work around it, I 
> > thought I would mention it in case it was easy to fix, just no-one had 
> > requested it :)
> > 
> > 
> > ------------
> > Example program follows: setting MSGSIZE>25000ish on my computer causes 
> > fail (ie pipeval=-1)
> > ------------
> > #include <unistd.h>
> > #include <stdio.h>
> > #define MSGSIZE 23000
> > char *msg1 = "message";
>
>I modified the program to allocate the message buffer to send on the
>heap and to initialize the entire thing.  The test seems to work for
>any size at that point.
>  
>
<snip program>

Thanks! I notice (by some fiddling) that it seems I have to instansiate 
(at least most of) the buffer before I send it. Is there some rule that 
you should instansiate memory before reading it? of course doing so is 
sensible, but I didn't know nessasary? Out of interest (because I 
couldn't actually find a 'mission plan'), what is the "plan" of Cygwin? 
to create a system wherebye any linux / unix program will compile 
without changes under windows? Or to simply make it much easier to 
convert but not try to support "stupid" activities?

Having said that, I've been convinced I should change the program I'm 
converting from *BSD to not send stupidly large mostly-empty buffers 
anyway :)

Chris


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