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| 1 | <?php |
| 2 | declare( strict_types = 1 ); |
| 3 | |
| 4 | namespace Wikimedia\Alea; |
| 5 | |
| 6 | /** |
| 7 | * Alea non-cryptographic pseudo-random number generator. |
| 8 | * |
| 9 | * Compatible with https://www.npmjs.com/package/alea |
| 10 | * |
| 11 | * From http://baagoe.com/en/RandomMusings/javascript/ |
| 12 | * |
| 13 | * Archived at: |
| 14 | * * https://web.archive.org/web/20120619002808/http://baagoe.org/en/wiki/Better_random_numbers_for_javascript |
| 15 | * * https://web.archive.org/web/20120502223108/http://baagoe.com/en/RandomMusings/javascript/ |
| 16 | */ |
| 17 | class Alea { |
| 18 | |
| 19 | private $s0; |
| 20 | private $s1; |
| 21 | private $s2; |
| 22 | private $c; |
| 23 | private $args; |
| 24 | |
| 25 | /** |
| 26 | * Create a new pseudo-random number generator. |
| 27 | * @param mixed ...$args Seeds for the PRNG. Can be anything which can be |
| 28 | * converted to a string with 'strval'. |
| 29 | */ |
| 30 | public function __construct( ...$args ) { |
| 31 | // Johannes Baagøe <baagoe@baagoe.com>, 2010 |
| 32 | $s0 = 0; |
| 33 | $s1 = 0; |
| 34 | $s2 = 0; |
| 35 | $c = 1; |
| 36 | |
| 37 | if ( count( $args ) == 0 ) { |
| 38 | $args = [ gettimeofday( true ) ]; |
| 39 | } |
| 40 | $mash = new Mash(); |
| 41 | $s0 = $mash->mash( ' ' ); |
| 42 | $s1 = $mash->mash( ' ' ); |
| 43 | $s2 = $mash->mash( ' ' ); |
| 44 | |
| 45 | foreach ( $args as $a ) { |
| 46 | $s0 -= $mash->mash( $a ); |
| 47 | if ( $s0 < 0 ) { |
| 48 | $s0 += 1; |
| 49 | } |
| 50 | $s1 -= $mash->mash( $a ); |
| 51 | if ( $s1 < 0 ) { |
| 52 | $s1 += 1; |
| 53 | } |
| 54 | $s2 -= $mash->mash( $a ); |
| 55 | if ( $s2 < 0 ) { |
| 56 | $s2 += 1; |
| 57 | } |
| 58 | } |
| 59 | |
| 60 | $this->s0 = $s0; |
| 61 | $this->s1 = $s1; |
| 62 | $this->s2 = $s2; |
| 63 | $this->c = $c; |
| 64 | $this->args = $args; |
| 65 | } |
| 66 | |
| 67 | /** |
| 68 | * Get a float with 32 bits of randomness. |
| 69 | * @return float |
| 70 | */ |
| 71 | public function random(): float { |
| 72 | $t = 2091639 * $this->s0 + $this->c * 2.3283064365386963e-10; // 2^-32 |
| 73 | $this->s0 = $this->s1; |
| 74 | $this->s1 = $this->s2; |
| 75 | $this->c = (int)$t; |
| 76 | $this->s2 = $t - ( $this->c ); |
| 77 | return $this->s2; |
| 78 | } |
| 79 | |
| 80 | /** |
| 81 | * Get a random 32-bit unsigned integer. |
| 82 | * @return int |
| 83 | */ |
| 84 | public function uint32(): int { |
| 85 | return intval( $this->random() * 0x100000000 ); // 2^32 |
| 86 | } |
| 87 | |
| 88 | /** |
| 89 | * Get a float with the full 53 bits of randomness. |
| 90 | * @return float |
| 91 | */ |
| 92 | public function fract53(): float { |
| 93 | return $this->random() + |
| 94 | // Using `| 0` to get a truncating conversion to int32 is |
| 95 | // unconventional, but perfectly legit. |
| 96 | // @phan-suppress-next-line PhanTypeInvalidBitwiseBinaryOperator,PhanTypeInvalidLeftOperandOfBitwiseOp |
| 97 | ( $this->random() * 0x200000 | 0 ) * 1.1102230246251565e-16; // 2^-53 |
| 98 | } |
| 99 | |
| 100 | public static function version(): string { |
| 101 | return 'Alea 1.0'; |
| 102 | } |
| 103 | |
| 104 | public function args(): array { |
| 105 | return $this->args; |
| 106 | } |
| 107 | |
| 108 | // coverslide's additions to sync state between two generators |
| 109 | |
| 110 | /** |
| 111 | * @return array The exported state of this PRNG. |
| 112 | */ |
| 113 | public function exportState(): array { |
| 114 | return [ $this->s0, $this->s1, $this->s2, $this->c ]; |
| 115 | } |
| 116 | |
| 117 | /** |
| 118 | * @param array $i The exported state of some other Alea PRNG. |
| 119 | */ |
| 120 | public function importState( array $i ): void { |
| 121 | $this->s0 = $i[ 0 ]; |
| 122 | $this->s1 = $i[ 1 ]; |
| 123 | $this->s2 = $i[ 2 ]; |
| 124 | $this->c = $i[ 3 ]; |
| 125 | } |
| 126 | |
| 127 | /** |
| 128 | * Create a new generator synced with some exported state. |
| 129 | * |
| 130 | * @param array $i The exported state of some other Alea PRNG. |
| 131 | * @return Alea a new Alea PRNG. |
| 132 | */ |
| 133 | public static function createWithState( array $i ): Alea { |
| 134 | $random = new Alea(); |
| 135 | $random->importState( $i ); |
| 136 | return $random; |
| 137 | } |
| 138 | } |