/usr/share/php/Horde/Stream/Filter/Crc32.php is in php-horde-stream-filter 2.0.2-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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/**
* Stream filter class to compute the CRC32 value of a string.
*
* Usage:
* <pre>
* $params = new stdClass;
* stream_filter_register('horde_crc32', 'Horde_Stream_Filter_Crc32');
* stream_filter_[app|pre]pend($stream, 'horde_crc32',
* [ STREAM_FILTER_[READ|WRITE|ALL] ],
* [ $params ]);
* while (fread($stream, 8192)) {}
* // CRC32 data in $params->crc32
* </pre>
*
* Copyright 2011-2013 Horde LLC (http://www.horde.org/)
*
* See the enclosed file COPYING for license information (LGPL). If you
* did not receive this file, see http://www.horde.org/licenses/lgpl21.
*
* @author Michael Slusarz <slusarz@horde.org>
* @category Horde
* @license http://www.horde.org/licenses/lgpl21 LGPL 2.1
* @package Stream_Filter
*/
class Horde_Stream_Filter_Crc32 extends php_user_filter
{
/**
* @see stream_filter_register()
*/
public function onCreate()
{
$this->params->crc32 = 0;
return true;
}
/**
* @see stream_filter_register()
*/
public function filter($in, $out, &$consumed, $closing)
{
while ($bucket = stream_bucket_make_writeable($in)) {
$consumed += $bucket->datalen;
$this->params->crc32 = $this->_crc32Combine($this->params->crc32, crc32($bucket->data), $bucket->datalen);
stream_bucket_append($out, $bucket);
}
return PSFS_PASS_ON;
}
/**
*/
protected function _crc32Combine($crc1, $crc2, $len2)
{
$odd = array(0xedb88320);
$row = 1;
for ($n = 1; $n < 32; ++$n) {
$odd[$n] = $row;
$row <<= 1;
}
$this->_gf2MatrixSquare($even, $odd);
$this->_gf2MatrixSquare($odd, $even);
do {
/* Apply zeros operator for this bit of len2. */
$this->_gf2MatrixSquare($even, $odd);
if ($len2 & 1) {
$crc1 = $this->_gf2MatrixTimes($even, $crc1);
}
$len2>>=1;
/* If no more bits set, then done. */
if ($len2 == 0) {
break;
}
/* Another iteration of the loop with odd and even swapped. */
$this->_gf2MatrixSquare($odd, $even);
if ($len2 & 1) {
$crc1 = $this->_gf2MatrixTimes($odd, $crc1);
}
$len2>>= 1;
} while ($len2 != 0);
$crc1 ^= $crc2;
return $crc1;
}
/**
*/
protected function _gf2MatrixSquare(&$square, &$mat)
{
for ($n = 0; $n < 32; ++$n) {
$square[$n] = $this->_gf2MatrixTimes($mat, $mat[$n]);
}
}
/**
*/
protected function _gf2MatrixTimes($mat, $vec)
{
$i = $sum = 0;
while ($vec) {
if ($vec & 1) {
$sum ^= $mat[$i];
}
$vec = ($vec >> 1) & 0x7FFFFFFF;
++$i;
}
return $sum;
}
}
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