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Date: Fri, 16 Jan 2009 13:42:09 +0100
From: Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
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Subject: Re: how to get mmap page size?
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On Jan 16 12:24, Jay Foad wrote:
> I have an application that wants to use mmap() to read a file, but
> only if it can guarantee that this will leave one or more zero bytes
> after the end of the contents of the file in memory:
> 
>   if ((filesize & (pagesize - 1) != 0)
>     use_mmap();
>   else
>     use_read();
> 
> How do I get the appropriate page size on cygwin?
> 
> If I call getpagesize() it returns 64k, the "allocation granularity".

That's what you want.  mmap always allocates in 64K chunks.

> Internally cygwin has a getsystempagesize() (introduced here:
> http://cygwin.com/ml/cygwin-cvs/2005-q4/msg00099.html) that returns
> the appropriate page size, 4k, but that doesn't seem to be exposed to
> applications.

And it's not required.  The system pagesize is really only used
internally.  Applications should rely on getpagesize().


Corinna

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Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Project Co-Leader          cygwin AT cygwin DOT com
Red Hat

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