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BitUtils.php
42 lines
| 1 | <?php |
| 2 | declare(strict_types = 1); |
| 3 | |
| 4 | namespace BaconQrCode\Common; |
| 5 | |
| 6 | /** |
| 7 | * General bit utilities. |
| 8 | * |
| 9 | * All utility methods are based on 32-bit integers and also work on 64-bit |
| 10 | * systems. |
| 11 | */ |
| 12 | final class BitUtils |
| 13 | { |
| 14 | private function __construct() |
| 15 | { |
| 16 | } |
| 17 | |
| 18 | /** |
| 19 | * Performs an unsigned right shift. |
| 20 | * |
| 21 | * This is the same as the unsigned right shift operator ">>>" in other |
| 22 | * languages. |
| 23 | */ |
| 24 | public static function unsignedRightShift(int $a, int $b) : int |
| 25 | { |
| 26 | return ( |
| 27 | $a >= 0 |
| 28 | ? $a >> $b |
| 29 | : (($a & 0x7fffffff) >> $b) | (0x40000000 >> ($b - 1)) |
| 30 | ); |
| 31 | } |
| 32 | |
| 33 | /** |
| 34 | * Gets the number of trailing zeros. |
| 35 | */ |
| 36 | public static function numberOfTrailingZeros(int $i) : int |
| 37 | { |
| 38 | $lastPos = strrpos(str_pad(decbin($i), 32, '0', STR_PAD_LEFT), '1'); |
| 39 | return $lastPos === false ? 32 : 31 - $lastPos; |
| 40 | } |
| 41 | } |
| 42 |