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Date: Sat, 3 Feb 2001 19:19:15 +0100
From: Corinna Vinschen <cygwin AT cygwin DOT com>
To: cygwin AT cygwin DOT com
Subject: Re: lseek()/read() to physical drive returning wrong data.
Message-ID: <20010203191915.Z19867@cygbert.vinschen.de>
Mail-Followup-To: cygwin AT cygwin DOT com
References: <3A7C4445 DOT B5F8FAB0 AT compaq DOT com>
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In-Reply-To: <3A7C4445.B5F8FAB0@compaq.com>; from Robin.Miller@compaq.com on Sat, Feb 03, 2001 at 12:47:49PM -0500

On Sat, Feb 03, 2001 at 12:47:49PM -0500, Robin T. Miller wrote:
> Hi All,
> 	I have a Unix test program named 'dt' which runs with Cygwin.
> This program tests a variety of devices as well as file systems.  The
> tests which use lseek() to raw mounted disks, are failing with data
> compare errors.  It appears either lseek() is positioning incorrectly
> or read() is returning the wrong data after lseek'ing.
> 
> 	This random I/O sequence seems to work correctly to a regular
> file, so maybe the raw device buffering is messing up?  I'm not sure.

Lseek on raw devices isn't yet fully implemented. The underlying
*cough* operating system *cough* isn't able to do a bytewise access
to the raw device but only in steps of 512 bytes. A full lseek
implementation would need to do it's own buffering to simulate
bytewise buffering. This is still missing.

> 	The only other program restrictions is 32-bit file offsets.
> 
> 	BTW: Are there any plans to release 64-bit file support?

Not in the near future.


Nobody would complain about contributions, though...

Corinna

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Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Developer                                mailto:cygwin AT cygwin DOT com
Red Hat, Inc.

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