Bug #47171 [Opn->Fbk]: Incorrect tell values when trying to seek beyond file range

Edit report at https://bugs.php.net/bug.php?id=47171&edit=1 ID: 47171 Updated by: cmb@php.net Reported by: d_kelsey at uk dot ibm dot com Summary: Incorrect tell values when trying to seek beyond file range -Status: Open +Status: Feedback Type: Bug Package: Zlib related Operating System: * PHP Version: 5.*, 6CVS (2009-01-21) -Assigned To: +Assigned To: cmb Block user comment: N Private report: N New Comment: Seeking to a negative position should indeed fail (and subsequent telling should return false). However, seeking to a position beyond the end of the file should work like for plain files; in this case the file pointer should be advanced, and that should be reflected when telling. Anyhow, this issue appears to have been fixed in the meantime (possibly it was a zlib issue), or can anybody still reproduce this with any of the actively supported PHP versions[1]? [1] <https://www.php.net/supported-versions.php> Previous Comments: ------------------------------------------------------------------------ [2009-01-21 07:36:09] d_kelsey at uk dot ibm dot com The problem still exists in the latest windows snapshot for php 5.2 ------------------------------------------------------------------------ [2009-01-20 17:25:01] d_kelsey at uk dot ibm dot com The provided test only covers the read scenario, but similar issues result when opening a zlib stream for write as well. ------------------------------------------------------------------------ [2009-01-20 17:24:00] d_kelsey at uk dot ibm dot com Description: ------------ When attempting to seek a zlib stream outside the range of the file eg -50 or 2000 (and the uncompressed length is < 2000) in either read or write mode, after the seek operation a gztell call returns false. In most cases the file pointer doesn't move so I can perform further reads or writes but the tell value returns now an invalid value. If a attempt to seek forward in read mode beyond the end of the uncompressed stream it looks like the file pointer remains at the end of the stream as a subsequent read returns nothing. In all cases I would expect - seek & gzseek to return -1 - the file pointer to remain where it was - the tell to return the same value as before the seek In other words the operation fails and nothing changes. Reproduce code: --------------- <?php $f = dirname(__FILE__)."/004.txt.gz"; $h = gzopen($f, 'r'); echo "move to the 40th byte\n"; echo "seek="; var_dump(gzseek( $h, 40 ) ); echo "tell=".gztell($h)."\n"; echo "try to move beyond the file\n"; echo "seek="; var_dump(gzseek( $h, 1000 ) ); echo "tell="; var_dump(gztell($h)); var_dump(gzread($h, 10)); echo "tell="; var_dump(gztell($h)); echo "\nrewinding and try to move to before the start\n"; gzrewind($h); echo "tell=".gztell($h)."\n"; echo "gzseek="; var_dump(gzseek( $h, -5 ) ); echo "tell="; var_dump(gztell($h)); var_dump(gzread($h, 10)); echo "tell="; var_dump(gztell($h)); gzclose($h); ?> Expected result: ---------------- move to the 40th byte seek=int(0) tell=40 try to move beyond the file seek=int(-1) tell=int(40) string(10) "iny flying" tell=int(50) rewinding and try to move to before the start tell=0 gzseek=int(-1) tell=int(0) string(10) "When you'r" tell=int(10) Actual result: -------------- move to the 40th byte seek=int(0) tell=40 try to move beyond the file seek=int(-1) tell=bool(false) string(0) "" tell=bool(false) rewinding and try to move to before the start tell=0 gzseek=int(-1) tell=bool(false) string(10) "When you'r" tell=int(9) ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=47171&edit=1