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| 1 | <?php |
| 2 | /** |
| 3 | * This program is free software; you can redistribute it and/or modify |
| 4 | * it under the terms of the GNU General Public License as published by |
| 5 | * the Free Software Foundation; either version 2 of the License, or |
| 6 | * (at your option) any later version. |
| 7 | * |
| 8 | * This program is distributed in the hope that it will be useful, |
| 9 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 10 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 11 | * GNU General Public License for more details. |
| 12 | * |
| 13 | * You should have received a copy of the GNU General Public License along |
| 14 | * with this program; if not, write to the Free Software Foundation, Inc., |
| 15 | * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. |
| 16 | * http://www.gnu.org/copyleft/gpl.html |
| 17 | */ |
| 18 | |
| 19 | namespace Cdb; |
| 20 | |
| 21 | /** |
| 22 | * Common functions for readers and writers |
| 23 | * |
| 24 | * This is a port of D.J. Bernstein's CDB to PHP. It's based on the copy that |
| 25 | * appears in PHP 5.3. |
| 26 | */ |
| 27 | class Util { |
| 28 | /** |
| 29 | * Take a modulo of a signed integer as if it were an unsigned integer. |
| 30 | * $b must be less than 0x40000000 and greater than 0 |
| 31 | * |
| 32 | * @param int $a |
| 33 | * @param int $b |
| 34 | * @return int |
| 35 | */ |
| 36 | public static function unsignedMod( $a, $b ): int { |
| 37 | if ( $a & 0x80000000 ) { |
| 38 | $m = ( $a & 0x7fffffff ) % $b + 2 * ( 0x40000000 % $b ); |
| 39 | |
| 40 | return $m % $b; |
| 41 | } else { |
| 42 | return $a % $b; |
| 43 | } |
| 44 | } |
| 45 | |
| 46 | /** |
| 47 | * Shift a signed integer right as if it were unsigned |
| 48 | * |
| 49 | * @param int $a |
| 50 | * @param int $b |
| 51 | * @return int |
| 52 | */ |
| 53 | public static function unsignedShiftRight( $a, $b ): int { |
| 54 | if ( $b == 0 ) { |
| 55 | return $a; |
| 56 | } |
| 57 | if ( $a & 0x80000000 ) { |
| 58 | return ( ( $a & 0x7fffffff ) >> $b ) | ( 0x40000000 >> ( $b - 1 ) ); |
| 59 | } else { |
| 60 | return $a >> $b; |
| 61 | } |
| 62 | } |
| 63 | |
| 64 | /** |
| 65 | * The CDB hash function. |
| 66 | * |
| 67 | * @param string $s |
| 68 | * @return int |
| 69 | */ |
| 70 | public static function hash( $s ): int { |
| 71 | $h = 5381; |
| 72 | $len = strlen( $s ); |
| 73 | for ( $i = 0; $i < $len; $i++ ) { |
| 74 | $h5 = ( $h << 5 ) & 0xffffffff; |
| 75 | // Do a 32-bit sum |
| 76 | // Inlined here for speed |
| 77 | $sum = ( $h & 0x3fffffff ) + ( $h5 & 0x3fffffff ); |
| 78 | $h = ( |
| 79 | ( $sum & 0x40000000 ? 1 : 0 ) |
| 80 | + ( $h & 0x80000000 ? 2 : 0 ) |
| 81 | + ( $h & 0x40000000 ? 1 : 0 ) |
| 82 | + ( $h5 & 0x80000000 ? 2 : 0 ) |
| 83 | + ( $h5 & 0x40000000 ? 1 : 0 ) |
| 84 | ) << 30 | ( $sum & 0x3fffffff ); |
| 85 | $h ^= ord( $s[$i] ); |
| 86 | $h &= 0xffffffff; |
| 87 | } |
| 88 | |
| 89 | return $h; |
| 90 | } |
| 91 | } |