# crc32 - Thread: https://externals.io/message/18675 - Original archive: https://news-web.php.net/php.internals/18675 - Started by Wojtek Meler on 2005-09-05T11:08:40+00:00 - Messages: 7 - Reply by email to internals@lists.php.net - More for agents: search with https://externals.io/search.md?q={query} · JSON API at https://externals.io/api · documentation at https://externals.io/llms.txt --- ## #18675 — Wojtek Meler — 2005-09-05T11:08:40+00:00 URL: https://externals.io/message/18675#18675 I've patched original crc32 PHP function to allow incremental crc32 counting. It touches only a few lines of original code. New crc32 function signature is int crc32(string str [,int prev_sum]) With this patch you can generate crc32 checksum for even large files without reading it contents to single variable. Fe. instead of doing | $file_string = file_get_contents($file); $crc = crc32($file_string); | you can do $crc=0; $f =fopen($file,'r'); while ( $data=fread($f,1024)) $crc = crc32($data,$crc); fclose($f); Icremental processing has less memory requirements. I'd like also change base64_* functions to allow incremental processing. Any chances apply such changes ? Regards, Wojtek --- ## #18676 — Wojtek Meler — 2005-09-05T11:37:55+00:00 URL: https://externals.io/message/18675#18676 · In reply to: #18675 Oops !!! I've left old license header. Here is smaller clean version that apply to CVS HEAD. --- ## #18678 — Ron Korving — 2005-09-05T14:02:21+00:00 URL: https://externals.io/message/18675#18678 · In reply to: #18675 Wouldn't it be more practical to implement these as stream filters? Ron "Wojtek Meler" schreef in bericht news:431C2738.2040602@wp.pl... > I've patched original crc32 PHP function to allow incremental crc32 > counting. > It touches only a few lines of original code. > New crc32 function signature is > > int crc32(string str [,int prev_sum]) > > With this patch you can generate crc32 checksum for even large files > without reading it contents to single variable. > Fe. instead of doing > > | $file_string = file_get_contents($file); > $crc = crc32($file_string); > | > you can do > > $crc=0; > $f =fopen($file,'r'); > while ( $data=fread($f,1024)) $crc = crc32($data,$crc); > fclose($f); > > Icremental processing has less memory requirements. > I'd like also change base64_* functions to allow incremental processing. > > Any chances apply such changes ? > > Regards, > Wojtek > ---------------------------------------------------------------------------- ---- > Index: crc32.c > =================================================================== > RCS file: /repository/php-src/ext/standard/crc32.c,v > retrieving revision 1.16 > diff -u -r1.16 crc32.c > --- crc32.c 3 Aug 2005 14:07:57 -0000 1.16 > +++ crc32.c 5 Sep 2005 11:02:00 -0000 > @@ -1,13 +1,13 @@ > /* > +----------------------------------------------------------------------+ > - | PHP Version 5 | > + | PHP Version 4 | > +----------------------------------------------------------------------+ > - | Copyright (c) 1997-2005 The PHP Group | > + | Copyright (c) 1997-2003 The PHP Group | > +----------------------------------------------------------------------+ > - | This source file is subject to version 3.0 of the PHP license, | > + | This source file is subject to version 2.02 of the PHP license, | > | that is bundled with this package in the file LICENSE, and is | > - | available through the world-wide-web at the following url: | > - | http://www.php.net/license/3_0.txt. | > + | available at through the world-wide-web at | > + | http://www.php.net/license/2_02.txt. | > | If you did not receive a copy of the PHP license and are unable to | > | obtain it through the world-wide-web, please send a note to | > | license@php.net so we can mail you a copy immediately. | > @@ -22,20 +22,19 @@ > #include "basic_functions.h" > #include "crc32.h" > > -/* {{{ proto string crc32(string str) > +/* {{{ proto int crc32(string str[,int prev_crc]) > Calculate the crc32 polynomial of a string */ > PHP_NAMED_FUNCTION(php_if_crc32) > { > - unsigned int crc = ~0; > + unsigned int crc = 0; > char *p; > - int len, nr; > + int len; > > - if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "s", &p, &nr) == FAILURE) { > + if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "s|l", &p, &len, &crc) == FAILURE) { > return; > } > - > - len = 0 ; > - for (len += nr; nr--; ++p) { > + crc = ~crc; > + for (; len--; ++p) { > CRC32(crc, *p); > } > RETVAL_LONG(~crc); --- ## #18687 — Wojtek Meler — 2005-09-06T06:46:21+00:00 URL: https://externals.io/message/18675#18687 · In reply to: #18678 Ron Korving wrote: > Wouldn't it be more practical to implement these as stream filters? Sure - I was not aware PHP5 streams - I'm still using PHP4 string.base64 is good choice. But I'm not sure if crc fit to streams. You can always implement fast userland filter with such function ;) . Wojtek --- ## #18689 — Ron Korving — 2005-09-06T11:48:42+00:00 URL: https://externals.io/message/18675#18689 · In reply to: #18687 With a crc function the way you propose it, such a filter could be effectively made in userspace, but you could of course also implement such a filter in the core of php which could do the same trick. Maybe both would be nice. Ron "Wojtek Meler" schreef in bericht news:431D3B3D.3050607@wp.pl... > Ron Korving wrote: > > […] > > Sure - I was not aware PHP5 streams - I'm still using PHP4 > string.base64 is good choice. But I'm not sure if crc fit to streams. > You can always implement fast userland filter with such function ;) . > > > Wojtek --- ## #18692 — Sara Golemon — 2005-09-06T13:57:38+00:00 URL: https://externals.io/message/18675#18692 · In reply to: #18689 I'd suggest a set of filters as an add-on to the mhash extension: mhash.crc32 mhash.md5 mhash.sha1 mhash.sha256 etc.... -Sara ----- Original Message ----- From: ""Ron Korving"" Newsgroups: php.internals To: Sent: Tuesday, September 06, 2005 4:48 AM Subject: Re: crc32 > With a crc function the way you propose it, such a filter could be > effectively made in userspace, but you could of course also implement such > a > filter in the core of php which could do the same trick. Maybe both would > be > nice. > > Ron > > > "Wojtek Meler" schreef in bericht > news:431D3B3D.3050607@wp.pl... > > […] --- ## #18897 — Marcus Boerger — 2005-09-14T14:02:22+00:00 URL: https://externals.io/message/18675#18897 · In reply to: #18692 Hello Sara, nice and helpfull idea best regards marcus Tuesday, September 6, 2005, 3:57:38 PM, you wrote: > I'd suggest a set of filters as an add-on to the mhash extension: > mhash.crc32 > mhash.md5 > mhash.sha1 > mhash.sha256 > etc.... > -Sara > ----- Original Message ----- > From: ""Ron Korving"" > Newsgroups: php.internals > To: > Sent: Tuesday, September 06, 2005 4:48 AM > Subject: Re: crc32 > > […]