ScrambleMapping.php

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<?php
 
namespace MediaWiki\User\TempUser;
 
use LogicException;
use OutOfBoundsException;
use RuntimeException;
 
class ScrambleMapping implements SerialMapping {
    private const GENERATORS = [
        [ 56, 97 ],
        [ 511, 887 ],
        [ 5203, 9013 ],
        [ 51947, 90001 ],
        [ 519612, 900001 ],
        [ 5196144, 8999993 ],
        [ 51961523, 89999999 ],
        [ 519615218, 899999963 ],
        [ 5196152444, 9000000043 ],
    ];
 
    private $offset;
 
    private $hasGmp;
    private $hasBcm;
 
    public function __construct( $config ) {
        $this->offset = $config['offset'] ?? 0;
        $this->hasGmp = extension_loaded( 'gmp' );
        $this->hasBcm = extension_loaded( 'bcmath' );
        if ( !$this->hasGmp && !$this->hasBcm ) {
            throw new RuntimeException( __CLASS__ . ' requires the bcmath or gmp extension' );
        }
    }
 
    public function getSerialIdForIndex( int $index ): string {
        if ( $index <= 0 ) {
            return (string)$index;
        }
        $offset = $this->offset;
        if ( $index - $offset < 0 ) {
            throw new OutOfBoundsException( __METHOD__ . ": The configured offset $offset is too large." );
        }
        foreach ( self::GENERATORS as [ $g, $p ] ) {
            if ( $index - $offset < $p ) {
                return (string)( $offset + $this->powmod( $g, $index - $offset, $p ) );
            }
            $offset += $p - 1;
        }
        throw new RuntimeException( __METHOD__ . ": The index $index is too large" );
    }
 
    private function powmod( $num, $exponent, $modulus ) {
        if ( $this->hasGmp ) {
            return \gmp_intval( \gmp_powm( $num, $exponent, $modulus ) );
        } elseif ( $this->hasBcm ) {
            return (int)\bcpowmod( (string)$num, (string)$exponent, (string)$modulus );
        } else {
            throw new LogicException( __CLASS__ . ' requires the bcmath or gmp extension' );
        }
    }
}