On Sun, Aug 28, 2011 at 23:54, Christian Kaps <christian.k...@mohiva.com> wrote: > Hi Gustavo, > > thanks for your detailed explanation. > > Nevertheless it might be useful to document these inconsistent(from the > userland point of view) behavior. Please see my comments inline. > > Am 28.08.2011 17:22, schrieb Gustavo Lopes: >> On Sun, 28 Aug 2011 14:29:28 +0100, Christian Kaps >> <christian.k...@mohiva.com> wrote: >> >>> I have some problems with the stream API. The methods stream_tell and >>> stream_seek works not as expected in some cases. >>> >>> Before reading the next lines, please look at the short >>> gist(https://gist.github.com/1176641). >>> >>> First example: >>> >>> $fp = fopen('mfx://test1', 'w'); >>> fwrite($fp, '12345678'); >>> fseek($fp, -1, SEEK_CUR); >>> fclose($fp); >>> // stream_seek: $offset = 7 >>> >>> If you call fseek with the arguments (-1, SEEK_CUR) then the $offset >>> parameter in the method stream_seek is 7. It seems that the internal API >>> takes the written bytes returned by fwrite and then it subtracts the >>> argument (-1) from it before passing it to stream_seek. For the >>> constants SEEK_SET and SEEK_END, the passed value is the same as defined >>> for the fseek call. >> >> SEEK_CUR seeks are internally converted to SEEK_SET seeks. It's been >> this way since at least 2002: >> >> http://svn.php.net/viewvc/php/php-src/trunk/main/streams.c?annotate=96547&pathrev=96547#l582 >> >> >> The first thing you should know is that PHP keeps track internally of >> the position of the stream. That's why PHP knows how to convert SEEK_CUR >> -1 to SEEK_SET 7. >> >> The seek type conversion is an arguable decision, but changing this has >> some risks. Consider that some some streams might not respond to >> SEEK_CUR seeks or that they do so defectively. The only advantages I see >> is that it could mitigate the problems of an inaccurate internal >> position (though this happens mostly with internal code that casts the >> stream into e.g. a FILE* and then manipulates the pointer); it would >> also save stream implementations that only support SEEK_CUR from having >> to reconvert the SEEK_SET to SEEK_CUR. >> > > This behavior should be documented. The possible values for the "whence" > parameter of the "stream_seek" method should only be SEEK_SET and > SEEK_END. And there should be a hint that the SEEK_CUR seeks are > internally converted to SEEK_SET seeks.
Indeed, it should be documented. Please file a doc bug report for it (and the others) :) -Hannes -- PHP Internals - PHP Runtime Development Mailing List To unsubscribe, visit: http://www.php.net/unsub.php
