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Date: Thu, 28 Jun 2012 20:33:02 +0200
From: Thomas Wolff <towo AT towo DOT net>
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To: cygwin AT cygwin DOT com
Subject: Re: /dev/clipboard corrupted
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Am 28.06.2012 10:20, schrieb Corinna Vinschen:
> On Jun 28 00:16, Thomas Wolff wrote:
>> If the clipboard contains large data, the contents retrieved from
>> /dev/clipboard gets corrupted.
>> I compared the following in a few cases:
>> * cat /dev/clipboard or cp /dev/clipboard (which are equal)
>> * mouse-paste into mintty, read with cat
>> * read /dev/clipboard within application
>>
>> and I found all three results to be different, the correct one
>> sometimes being cat /dev/clipboard but not always.
>> In today's case, the differences occured at byte 10240 and 65536
>> respectively, thus 10K-1 bytes or 64K-1 bytes being equal.
> I can't reprocude this.  There's also nothing in the /dev/clipboard
> code which would rely on a 10K buffer or so.  64K, yes.  But still,
> I tried with wordpad, vi, mintty, cat, and cp with a text file of
> about 90K.  No problems.  Do you have any reproducible testcase?
Not really reproducible (maybe later) but some more observations.
I made a small test program to read /dev/clipboard directly with 
different buffer sizes.
I verified that this happens at borders of read() invocations.
It is more likely to happen if there are non-ASCII characters just at 
this border, however, in one case it occurred after 2 blocks read where 
the non-ASCII was between blocks 1 and 2. Also, in one case, a CRLF 
newline at a border was just skipped (with non-ASCII somewhere before, 
probably). Typically, I see 2 bytes skipped, sometimes 1 but sometimes 
also ~100. Quite weird.
I looked at the fhandler_clipboard read() code and somehow suspect the 
wcstomb although the observations are not strictly conclusive.
(It's the non-cygwin-specific branch, after filling the clipboard from 
Windows, e.g. Firefox.)
------
Thomas

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