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<?php
namespace Cdb;
/**
* This is a port of D.J. Bernstein's CDB to PHP. It's based on the copy that
* appears in PHP 5.3. Changes are:
* * Error returns replaced with exceptions
* * Exception thrown if sizes or offsets are between 2GB and 4GB
* * Some variables renamed
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
* http://www.gnu.org/copyleft/gpl.html
*
* @file
*/
/**
* Common functions for readers and writers
*/
class Util {
/**
* Take a modulo of a signed integer as if it were an unsigned integer.
* $b must be less than 0x40000000 and greater than 0
*
* @param int $a
* @param int $b
*
* @return int
*/
public static function unsignedMod( $a, $b ) {
if ( $a & 0x80000000 ) {
$m = ( $a & 0x7fffffff ) % $b + 2 * ( 0x40000000 % $b );
return $m % $b;
} else {
return $a % $b;
}
}
/**
* Shift a signed integer right as if it were unsigned
* @param int $a
* @param int $b
* @return int
*/
public static function unsignedShiftRight( $a, $b ) {
if ( $b == 0 ) {
return $a;
}
if ( $a & 0x80000000 ) {
return ( ( $a & 0x7fffffff ) >> $b ) | ( 0x40000000 >> ( $b - 1 ) );
} else {
return $a >> $b;
}
}
/**
* The CDB hash function.
*
* @param string $s
*
* @return int
*/
public static function hash( $s ) {
$h = 5381;
$len = strlen( $s );
for ( $i = 0; $i < $len; $i++ ) {
$h5 = ( $h << 5 ) & 0xffffffff;
// Do a 32-bit sum
// Inlined here for speed
$sum = ( $h & 0x3fffffff ) + ( $h5 & 0x3fffffff );
$h =
(
( $sum & 0x40000000 ? 1 : 0 )
+ ( $h & 0x80000000 ? 2 : 0 )
+ ( $h & 0x40000000 ? 1 : 0 )
+ ( $h5 & 0x80000000 ? 2 : 0 )
+ ( $h5 & 0x40000000 ? 1 : 0 )
) << 30
| ( $sum & 0x3fffffff );
$h ^= ord( $s[$i] );
$h &= 0xffffffff;
}
return $h;
}
}
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