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From:	Ivan Kozik <ivan AT ludios DOT org>
Date:	Tue, 19 Dec 2017 18:45:07 +0000
Message-ID:	<CAKyntiLdwdaPewnyhNKC=yZJJ2Hc_BOrd9-j2HGmjLmiox3z1Q@mail.gmail.com>
Subject:	Re: Wrong file position after writing 65537 bytes to block device
To:	cygwin AT cygwin DOT com
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On Tue, Dec 19, 2017 at 6:19 PM, Corinna Vinschen
<corinna-cygwin AT cygwin DOT com> wrote:
> On Dec 19 16:35, Ivan Kozik wrote:
>> From what I observe on Linux, it supports writing at any offset to the
>> block device because it does a read-modify-write behind the scenes,
>> with accompanying nasty overhead (e.g. writes going at 64MB/s instead
>> of an "expected" 180MB/s).
>
> That's what Cygwin was trying to emulate as well.  Debugging pointed out
> that it only works for reading, not for writing, because the latter
> neglected to fix up buffer pointers.  Those are used in lseek to report
> the Linux-like byte-exact file position.
>
> I pushed a patch and uploaded new developer snapshots to
> https://cygwin.com/snapshts/
>
> Please give them a test.

Hi Corinna,

It is writing correctly now, thank you for the fix!

Ivan

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