Bug #76268 [Ana]: stream_get_contents fail to seek on streams modified by curl_exec
Edit report at https://bugs.php.net/bug.php?id=76268&edit=1
ID: 76268
Updated by: cmb@php.net
Reported by: divinity76 at gmail dot com
Summary: stream_get_contents fail to seek on streams modified
by curl_exec
Status: Analyzed
Type: Bug
Package: cURL related
Operating System: linux, debian 10 x64 k4.15.11-1
PHP Version: 7.1.16
Block user comment: N
Private report: N
New Comment:
> stream->position is still zero when curl returns.
Yes, but at least after the stream has been flushed[1], the
file-position indicator has been moved, but the PHP stream doesn't
notice. It appears that the stream layer does not have an API to
synchronize the position with the file-position indicator;
otherwise this bug could easily be fixed.
[1] <https://github.com/php/php-src/blob/php-7.3.18/ext/curl/interface.c#L3186>
Previous Comments:
------------------------------------------------------------------------
[2019-03-26 16:29:50] mike@php.net
Related To: Bug #72092
------------------------------------------------------------------------
[2019-03-26 16:27:11] mike@php.net
Related To: Bug #70693
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[2019-03-26 16:25:00] mike@php.net
stream->position is still zero when curl returns.
For all other streams this might be fixable by upgrading ext/curl to streams instead of stdio, looks
like streams came a few years later.
------------------------------------------------------------------------
[2019-03-26 15:54:24] divinity76 at gmail dot com
for the record, i have several times written code like
$stderrh=tmpfile();
curl_setopt($ch,CURLOPT_STDERR,$stderrh);
curl_exec($ch);
rewind($stderrh); // https://bugs.php.net/bug.php?id=76268
$stderr=stream_get_contents($stderrh);
fclose($stderrh);
because of this bug. real examples: https://stackoverflow.com/questions/53128631/curl-php-cannot-display-amazon
and https://stackoverflow.com/questions/50051940/very-long-loadtime-php-curl
and https://github.com/divinity76/autoit_php/blob/master/src/autoit.class.php#L97
and http://qaru.site/questions/15745219/set-a-global-php-curl-upload-download-speed-limit
------------------------------------------------------------------------
[2018-04-25 14:35:04] divinity76 at gmail dot com
Description:
------------
stream_get_contents fail to seek on streams exclusively modified by curl_exec, the optional third
parameter of stream_get_contents is "Seek to the specified offset", and is effectively
ignored when the stream has only been modified by curl_exec.
my best guess is that libcurl calls fwrite directly, and doesn't update php's own
stream->position, and stream_get_contents in turn doesn't call fseek if it's not
necessary (presumably to save up on syscalls), and determines if it's necessary by checking
stream->positioun instead of ftell (presumably to save up on syscalls), then it calls fread()
until EOF, which is where libcurl left it, and thus returns an empty string.
Test script:
---------------
<?php
$ch = curl_init ( "http://gstatic.com/generate_204" );
$h = tmpfile ();
curl_setopt_array ( $ch, array (
CURLOPT_VERBOSE => 1,
CURLOPT_STDERR => $h
) );
curl_exec ( $ch );
$verbose1 = stream_get_contents ( $h, - 1, 0 ); // empty string
fseek ( $h, 0, SEEK_SET ); // a manual fseek fixes it
$verbose2 = stream_get_contents ( $h, - 1, 0 ); // the actual CURLOPT_VERBOSE log
var_dump ( $verbose1 === $verbose2 );
Expected result:
----------------
bool(true)
Actual result:
--------------
bool(false)
------------------------------------------------------------------------
--
Edit this bug report at https://bugs.php.net/bug.php?id=76268&edit=1
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