Bug #49874 [Com]: ftell() and fseek() inconsistency when using stream filters

Edit report at https://bugs.php.net/bug.php?id=49874&edit=1 ID: 49874 Comment by: php at bohwaz dot net Reported by: jketterl at chipxonio dot de Summary: ftell() and fseek() inconsistency when using stream filters Status: Open Type: Bug Package: Filesystem function related Operating System: linux (ubuntu) PHP Version: 5.5.4 Block user comment: N Private report: N New Comment: Same issue with zlib: <?php $fh = fopen('php://temp', 'w+'); fwrite($fh, '123'); var_dump(ftell($fh)); stream_filter_append($fh, 'zlib.deflate', STREAM_FILTER_WRITE, 9); fwrite($fh, 'abc'); var_dump(ftell($fh)); fseek($fh, 0); var_dump(fread($fh, 1024)); fclose($fh); ?> Will return: int(3) int(3) string(3) "123" See: https://3v4l.org/VAfmR Previous Comments: ------------------------------------------------------------------------ [2017-08-01 12:06:31] paul dot smith at deepseaplc dot com I'm also having this problem with the zlib.deflate filter in PHP 5.6.20. I attempted to append a user filter after zlib.deflate with the intention of totalling the datalen of the buckets. The filter() function is called but stream_bucket_make_writeable($in) returns null. I suspect this is related to the ftell problem. ------------------------------------------------------------------------ [2013-10-24 08:19:46] yohgaki@php.net It seems 5.5 has this problem still string(8) "Line 01 " string(8) "Line 02 " string(8) "Line 01 " string(5) "e 01 " [yohgaki@dev php-5.4]$ php -v PHP 5.5.4 (cli) (built: Sep 19 2013 13:06:40) ------------------------------------------------------------------------ [2009-10-15 06:54:31] jketterl at chipxonio dot de thanks for having a look i tried with and without. the challenge is to get it working without, because that's the worst case my app has to deal with, but the BOM doesn't seem to solve this. $ hexdump test-with-bom.csv 0000000 feff 004c 0069 006e 0065 0020 0030 0031 0000010 000a 004c 0069 006e 0065 0020 0030 0032 0000020 000a 004c 0069 006e 0065 0020 0030 0033 0000030 000a 004c 0069 006e 0065 0020 0030 0034 0000040 000a 0000042 $ php test.php string(8) "Line 01 " string(8) "Line 02 " string(8) "Line 01 " string(5) "e 01 " i also tried opening the file including the BOM without a stream filter, but that just resulted in php reading in two extra chars (the BOM converted in some way i guess) on the beginning of the first line. i thought i'd attach the sample files to this bug, but it seems like i can't. i've uploaded them here instead: http://www.djmacgyver.net/tmp/php-ftell/ ------------------------------------------------------------------------ [2009-10-14 16:40:00] Sjoerd@php.net Thank you for your bug report. Does your test.csv file start with a BOM? You can determine this by viewing the file in a hex editor. If it starts with fffe or feff, it has a BOM (byte order mark). ------------------------------------------------------------------------ [2009-10-14 11:39:39] jketterl at chipxonio dot de Description: ------------ exact php version: PHP 5.2.11-0.dotdeb.1 with Suhosin-Patch 0.9.7 (cli) (built: Sep 20 2009 09:41:43) this bug is also be filter-/stream-related. i just believe it might be easier to fix on the filesystem side, that's why i chose that category. when using a php stream filter to convert input from utf-16 into iso8859 (or most probably from any 2byte-encoded charset into any single-byte-encode charset) the ftell() and fseek() functions start to behave inconsistently. more precisely: fseek() jumps to exact offsets ignoring the 2byte-encoding, whereas ftell() seems to return the number of bytes read *after* the filter has been applied. thus it is not possible to fseek() back to a certain offset that has been stored with ftell() before. the content of the testfile used in the code examples is as follows: Line 01 Line 02 Line 03 Line 04 Reproduce code: --------------- $file = 'test.csv'; $fp = fopen($file, 'r'); stream_filter_append($fp, 'convert.iconv.utf16/iso8859-15'); $line = fgets($fp); var_dump($line); $line = fgets($fp); var_dump($line); fclose($fp); $fp = fopen($file, 'r'); stream_filter_append($fp, 'convert.iconv.utf16/iso8859-15'); $line = fgets($fp); var_dump($line); fseek($fp, ftell($fp)); // this shouldn't move anything - but it does... $line = fgets($fp); var_dump($line); fclose($fp); Expected result: ---------------- string(8) "Line 01 " string(8) "Line 02 " string(8) "Line 01 " string(8) "Line 02 " Actual result: -------------- string(8) "Line 01 " string(8) "Line 02 " string(8) "Line 01 " string(4) " 01 " ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=49874&edit=1