Bug #52335 [Opn->Csd]: fseek() on memory stream behavior different then file

Edit report at https://bugs.php.net/bug.php?id=52335&edit=1 ID: 52335 Updated by: git@php.net Reported by: jbondc at openmv dot com Summary: fseek() on memory stream behavior different then file -Status: Open +Status: Closed Type: Bug Package: Streams related Operating System: FreeBSD 7.2 PHP Version: 5.2.14RC2 Block user comment: N Private report: N New Comment: Automatic comment on behalf of bukka Revision: https://github.com/php/php-src/commit/ba9650d697b9433061c0396d08d111f433cae43a Log: Fix bug #52335 (fseek() on memory stream behavior different then file) Previous Comments: ------------------------------------------------------------------------ [2023-03-13 04:54:45] belisoful at icloud dot com I am making a TDataWriter class that acts as a wrapper for writing data to a seekable stream. I was trying to figure out why it fseek was failing when moving after the end but then found this bug. I was using memory. It happens on temp as well even though temp is sometimes a file and sometimes not a file (aka cache below a threshold) Writing to memory should add the null bytes as happens with files. I have a stream wrapper, so i can easily check the stream and if fseeking is past the end, then to ftruncate the stream larger, but getting to this point is just adding difficulty where there should be none. In some instances my class would be writing to memory and others it might be writing to a file. Standardizing this behavior is important. It should be documented until it is corrected. ------------------------------------------------------------------------ [2010-11-22 14:55:08] jbondc at openmv dot com Thanks, saw the changes in fseek.xml What about adding streamWrapper::hasFeature(/* int */$featureId) const STREAM_FEAT_FWDSEEK = 1; const STREAM_FEAT_OTHER = 2; //... $stream = new File_Stream('/tmp/foo'); $stream->isSupported(STREAM_FEAT_FWDSEEK); // true fseek($stream, 1024); // NULL bytes added $stream = new Memory_Stream('/tmp/foo'); $stream->isSupported(STREAM_FEAT_FWDSEEK); // false fseek($stream, 1024); // false The goal is to have a consistent api to write to a binary stream. I can give it some more thought, other stream 'features'. ------------------------------------------------------------------------ [2010-11-13 16:10:48] cataphract@php.net I've fixed the doc part, but on a closer inspection the behavior of the memory stream on past-the-end-of-file seeks could be improved. ------------------------------------------------------------------------ [2010-11-13 16:09:54] cataphract@php.net Automatic comment from SVN on behalf of cataphract Revision: http://svn.php.net/viewvc/?view=revision&revision=305317 Log: - Behavior when seeking past the end of file. Partially addresses bug #52335. - Expanded note on how the stream may not support seeking. ------------------------------------------------------------------------ [2010-07-14 13:18:10] jbondc at openmv dot com Description: ------------ May not be a bug but a documentation issue With a file, fseek() to an offset that doesn't exist results in NULL bytes added. Using a memory stream, fseek() just fails. Which one is the expected behavior? Also for streamWrapper::stream_seek() Test script: --------------- $sp = fopen("php://memory", 'w+'); fseek($sp, 1024); // fails why? echo fwrite($sp, "abc"); // 3 fseek($sp, 1024); // echo fread($sp, 3); // NULL.. $sp = fopen("/tmp/foo", 'w+'); fseek($sp, 1024); echo fwrite($sp, "abc"); // 3 fseek($sp, 1024); echo fread($sp, 3); // abc Expected result: ---------------- 3abc3abc Actual result: -------------- 33abc ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=52335&edit=1