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Re: svn commit: r40378 - in trunk/subversion: include libsvn_subr tests/libsvn_subr

From: Daniel Rall <dlr_at_finemaltcoding.com>
Date: Mon, 9 Nov 2009 08:51:59 -0800

On Mon, Nov 9, 2009 at 8:04 AM, Hyrum K. Wright
<hyrum_wright_at_mail.utexas.edu> wrote:
>
> On Nov 5, 2009, at 6:53 PM, Daniel Rall wrote:
>
>> On Thu, Nov 5, 2009 at 12:33 AM, Bert Huijben <rhuijben_at_sharpsvn.net>
>> wrote:
>>>>
>>>> -----Original Message-----
>>>> From: Hyrum K. Wright [mailto:hyrum_at_hyrumwright.org]
>>>> Sent: donderdag 5 november 2009 5:00
>>>> To: svn_at_subversion.tigris.org
>>>> Subject: svn commit: r40378 - in trunk/subversion: include libsvn_subr
>>>> tests/libsvn_subr
>>>>
>>>> Author: hwright
>>>> Date: Wed Nov  4 20:00:08 2009
>>>> New Revision: 40378
>>>>
>>>> Log:
>>>> Add a duplication facility to our stream toolbox.  Along the lines of
>>>> the tee(1), the new svn_stream_tee() function returns a stream which,
>>>> when
>>>> written to, writes to both of the underlying streams.  This allows
>>>> writing
>>>> two files simultaneously, or writing a file while also pushing content
>>>> across the network.
>>>>
>>>> This isn't used directly by this commit, but I envision a couple of
>>>> uses down
>>>> the road.  In any case, it's a potentially useful tool, and a nice
>>>> exercise while stuck in an aluminum tube.
>>>>
>>>> * subversion/libsvn_subr/stream.c
>>>>  (baton_tee, write_handler_tee, svn_stream_tee): New.
>>>
>>> I think it would be useful to add a close handler, to allow closing the
>>> inner streams via the outer stream.
>>>
>>> In libsvn_wc/adm_crawler.c there is a variant of this stream code. It
>>> writes all bytes that are read from another stream. (Search for
>>> copying_stream). It would be nice if we could combine these into one generic
>>> feature. (But currently I don't see how)
>>
>> How about allowing for a sentinel value (e.g. NULL) for one of the
>> output streams, turning the tee into pipe?
>
> I believe that's what the docs say, and what the current implementation
> already does:
>
>
>  if (out1 == NULL)
>    return out2;
>
>  if (out2 == NULL)
>    return out1;
>
>
> Lemme know if I'm missing something.

Meta-comment; didn't examine the implementation on this one.

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Received on 2009-11-09 17:52:14 CET

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