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Date: Fri, 16 Jan 2009 12:24:16 +0000
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Subject: how to get mmap page size?
From: Jay Foad <jay DOT foad AT gmail DOT com>
To: cygwin AT cygwin DOT com
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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".
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.

I know that this has been discussed before, e.g. here:

http://www.cygwin.com/ml/cygwin/2002-01/msg00747.html

but I haven't found an answer to this particular question.

Thanks,
Jay.

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