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Re: svn commit: r1701633 - /subversion/trunk/subversion/libsvn_subr/stream.c

From: Ivan Zhakov <ivan_at_visualsvn.com>
Date: Tue, 8 Sep 2015 12:21:19 +0300

On 7 September 2015 at 18:06, <kotkov_at_apache.org> wrote:
> Author: kotkov
> Date: Mon Sep 7 15:06:57 2015
> New Revision: 1701633
>
> URL: http://svn.apache.org/r1701633
> Log:
> Fix svn_stream_for_stdin() and related functions for STDOUT and STDERR
> that were returning streams with mark() and seek() capabilities.
>
> STDIN, STDOUT and STDERR don't provide general support for positioning
> requests. This behavior is implementation-specific and depends on what's
> passed as the corresponding handle. For example, on Linux, apr_file_seek()
> that calls lseek() internally fails with ESPIPE [1] when the descriptor is
> associated with a terminal device. As we cannot safely advertise mark()
> and seek() support for these streams, don't do that.
>
> [1] http://pubs.opengroup.org/onlinepubs/9699919799/functions/lseek.html
>
> * subversion/libsvn_subr/stream.c
> (svn_stream_for_stdin, svn_stream_for_stdout, svn_stream_for_stderr):
> Don't install mark and seek handlers.
>
It may be worth to introduce local helper like
'make_stream_from_apr_file(svn_boolean_t supports_seek)' and use it in
svn_stream_from_apr_file2() and svn_stream_for_stdin() instead of
clearing mark/seek handlers after calling svn_stream_from_apr_file2().

Another problem that currently svn_stream_t for stdin/stderr/stdout
pretends to support native svn_stream_skip(), while I'm not sure that
all platforms support seek for stdin.

-- 
Ivan Zhakov
Received on 2015-09-08 11:21:56 CEST

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