aboutsummaryrefslogblamecommitdiffstats
path: root/vendor/brick/math/src/BigInteger.php
blob: f213fbedb2ec99a38523b503956c1d16b68a4bda (plain) (tree)
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085



























                                                                                     

                  
       
                   


























































































































































































                                                                                                                       

                                                               






































                                                                                                                        

                                                                      











































                                                                                                                        



                                               

















                                             



                                               

















                                             



                                               


























































































































































































































































































































































































































































































































































































































































































































































                                                                                                                          



                                       





























                                                                                
































                                                                                                                  














                                                                                                    
                                                           















                                                                                                                
<?php

declare(strict_types=1);

namespace Brick\Math;

use Brick\Math\Exception\DivisionByZeroException;
use Brick\Math\Exception\IntegerOverflowException;
use Brick\Math\Exception\MathException;
use Brick\Math\Exception\NegativeNumberException;
use Brick\Math\Exception\NumberFormatException;
use Brick\Math\Internal\Calculator;

/**
 * An arbitrary-size integer.
 *
 * All methods accepting a number as a parameter accept either a BigInteger instance,
 * an integer, or a string representing an arbitrary size integer.
 *
 * @psalm-immutable
 */
final class BigInteger extends BigNumber
{
    /**
     * The value, as a string of digits with optional leading minus sign.
     *
     * No leading zeros must be present.
     * No leading minus sign must be present if the number is zero.
     *
     * @var string
     */
    private $value;

    /**
     * Protected constructor. Use a factory method to obtain an instance.
     *
     * @param string $value A string of digits, with optional leading minus sign.
     */
    protected function __construct(string $value)
    {
        $this->value = $value;
    }

    /**
     * Creates a BigInteger of the given value.
     *
     * @param BigNumber|int|float|string $value
     *
     * @return BigInteger
     *
     * @throws MathException If the value cannot be converted to a BigInteger.
     *
     * @psalm-pure
     */
    public static function of($value) : BigNumber
    {
        return parent::of($value)->toBigInteger();
    }

    /**
     * Creates a number from a string in a given base.
     *
     * The string can optionally be prefixed with the `+` or `-` sign.
     *
     * Bases greater than 36 are not supported by this method, as there is no clear consensus on which of the lowercase
     * or uppercase characters should come first. Instead, this method accepts any base up to 36, and does not
     * differentiate lowercase and uppercase characters, which are considered equal.
     *
     * For bases greater than 36, and/or custom alphabets, use the fromArbitraryBase() method.
     *
     * @param string $number The number to convert, in the given base.
     * @param int    $base   The base of the number, between 2 and 36.
     *
     * @return BigInteger
     *
     * @throws NumberFormatException     If the number is empty, or contains invalid chars for the given base.
     * @throws \InvalidArgumentException If the base is out of range.
     *
     * @psalm-pure
     */
    public static function fromBase(string $number, int $base) : BigInteger
    {
        if ($number === '') {
            throw new NumberFormatException('The number cannot be empty.');
        }

        if ($base < 2 || $base > 36) {
            throw new \InvalidArgumentException(\sprintf('Base %d is not in range 2 to 36.', $base));
        }

        if ($number[0] === '-') {
            $sign = '-';
            $number = \substr($number, 1);
        } elseif ($number[0] === '+') {
            $sign = '';
            $number = \substr($number, 1);
        } else {
            $sign = '';
        }

        if ($number === '') {
            throw new NumberFormatException('The number cannot be empty.');
        }

        $number = \ltrim($number, '0');

        if ($number === '') {
            // The result will be the same in any base, avoid further calculation.
            return BigInteger::zero();
        }

        if ($number === '1') {
            // The result will be the same in any base, avoid further calculation.
            return new BigInteger($sign . '1');
        }

        $pattern = '/[^' . \substr(Calculator::ALPHABET, 0, $base) . ']/';

        if (\preg_match($pattern, \strtolower($number), $matches) === 1) {
            throw new NumberFormatException(\sprintf('"%s" is not a valid character in base %d.', $matches[0], $base));
        }

        if ($base === 10) {
            // The number is usable as is, avoid further calculation.
            return new BigInteger($sign . $number);
        }

        $result = Calculator::get()->fromBase($number, $base);

        return new BigInteger($sign . $result);
    }

    /**
     * Parses a string containing an integer in an arbitrary base, using a custom alphabet.
     *
     * Because this method accepts an alphabet with any character, including dash, it does not handle negative numbers.
     *
     * @param string $number   The number to parse.
     * @param string $alphabet The alphabet, for example '01' for base 2, or '01234567' for base 8.
     *
     * @return BigInteger
     *
     * @throws NumberFormatException     If the given number is empty or contains invalid chars for the given alphabet.
     * @throws \InvalidArgumentException If the alphabet does not contain at least 2 chars.
     *
     * @psalm-pure
     */
    public static function fromArbitraryBase(string $number, string $alphabet) : BigInteger
    {
        if ($number === '') {
            throw new NumberFormatException('The number cannot be empty.');
        }

        $base = \strlen($alphabet);

        if ($base < 2) {
            throw new \InvalidArgumentException('The alphabet must contain at least 2 chars.');
        }

        $pattern = '/[^' . \preg_quote($alphabet, '/') . ']/';

        if (\preg_match($pattern, $number, $matches) === 1) {
            throw NumberFormatException::charNotInAlphabet($matches[0]);
        }

        $number = Calculator::get()->fromArbitraryBase($number, $alphabet, $base);

        return new BigInteger($number);
    }

    /**
     * Translates a string of bytes containing the binary representation of a BigInteger into a BigInteger.
     *
     * The input string is assumed to be in big-endian byte-order: the most significant byte is in the zeroth element.
     *
     * If `$signed` is true, the input is assumed to be in two's-complement representation, and the leading bit is
     * interpreted as a sign bit. If `$signed` is false, the input is interpreted as an unsigned number, and the
     * resulting BigInteger will always be positive or zero.
     *
     * This method can be used to retrieve a number exported by `toBytes()`, as long as the `$signed` flags match.
     *
     * @param string $value  The byte string.
     * @param bool   $signed Whether to interpret as a signed number in two's-complement representation with a leading
     *                       sign bit.
     *
     * @return BigInteger
     *
     * @throws NumberFormatException If the string is empty.
     */
    public static function fromBytes(string $value, bool $signed = true) : BigInteger
    {
        if ($value === '') {
            throw new NumberFormatException('The byte string must not be empty.');
        }

        $twosComplement = false;

        if ($signed) {
            $x = \ord($value[0]);

            if (($twosComplement = ($x >= 0x80))) {
                $value = ~$value;
            }
        }

        $number = self::fromBase(\bin2hex($value), 16);

        if ($twosComplement) {
            return $number->plus(1)->negated();
        }

        return $number;
    }

    /**
     * Generates a pseudo-random number in the range 0 to 2^numBits - 1.
     *
     * Using the default random bytes generator, this method is suitable for cryptographic use.
     *
     * @psalm-param callable(int): string $randomBytesGenerator
     *
     * @param int           $numBits              The number of bits.
     * @param callable|null $randomBytesGenerator A function that accepts a number of bytes as an integer, and returns a
     *                                            string of random bytes of the given length. Defaults to the
     *                                            `random_bytes()` function.
     *
     * @return BigInteger
     *
     * @throws \InvalidArgumentException If $numBits is negative.
     */
    public static function randomBits(int $numBits, ?callable $randomBytesGenerator = null) : BigInteger
    {
        if ($numBits < 0) {
            throw new \InvalidArgumentException('The number of bits cannot be negative.');
        }

        if ($numBits === 0) {
            return BigInteger::zero();
        }

        if ($randomBytesGenerator === null) {
            $randomBytesGenerator = 'random_bytes';
        }

        $byteLength = \intdiv($numBits - 1, 8) + 1;

        $extraBits = ($byteLength * 8 - $numBits);
        $bitmask   = \chr(0xFF >> $extraBits);

        $randomBytes    = $randomBytesGenerator($byteLength);
        $randomBytes[0] = $randomBytes[0] & $bitmask;

        return self::fromBytes($randomBytes, false);
    }

    /**
     * Generates a pseudo-random number between `$min` and `$max`.
     *
     * Using the default random bytes generator, this method is suitable for cryptographic use.
     *
     * @psalm-param (callable(int): string)|null $randomBytesGenerator
     *
     * @param BigNumber|int|float|string $min                  The lower bound. Must be convertible to a BigInteger.
     * @param BigNumber|int|float|string $max                  The upper bound. Must be convertible to a BigInteger.
     * @param callable|null              $randomBytesGenerator A function that accepts a number of bytes as an integer,
     *                                                         and returns a string of random bytes of the given length.
     *                                                         Defaults to the `random_bytes()` function.
     *
     * @return BigInteger
     *
     * @throws MathException If one of the parameters cannot be converted to a BigInteger,
     *                       or `$min` is greater than `$max`.
     */
    public static function randomRange($min, $max, ?callable $randomBytesGenerator = null) : BigInteger
    {
        $min = BigInteger::of($min);
        $max = BigInteger::of($max);

        if ($min->isGreaterThan($max)) {
            throw new MathException('$min cannot be greater than $max.');
        }

        if ($min->isEqualTo($max)) {
            return $min;
        }

        $diff      = $max->minus($min);
        $bitLength = $diff->getBitLength();

        // try until the number is in range (50% to 100% chance of success)
        do {
            $randomNumber = self::randomBits($bitLength, $randomBytesGenerator);
        } while ($randomNumber->isGreaterThan($diff));

        return $randomNumber->plus($min);
    }

    /**
     * Returns a BigInteger representing zero.
     *
     * @return BigInteger
     *
     * @psalm-pure
     */
    public static function zero() : BigInteger
    {
        /**
         * @psalm-suppress ImpureStaticVariable
         * @var BigInteger|null $zero
         */
        static $zero;

        if ($zero === null) {
            $zero = new BigInteger('0');
        }

        return $zero;
    }

    /**
     * Returns a BigInteger representing one.
     *
     * @return BigInteger
     *
     * @psalm-pure
     */
    public static function one() : BigInteger
    {
        /**
         * @psalm-suppress ImpureStaticVariable
         * @var BigInteger|null $one
         */
        static $one;

        if ($one === null) {
            $one = new BigInteger('1');
        }

        return $one;
    }

    /**
     * Returns a BigInteger representing ten.
     *
     * @return BigInteger
     *
     * @psalm-pure
     */
    public static function ten() : BigInteger
    {
        /**
         * @psalm-suppress ImpureStaticVariable
         * @var BigInteger|null $ten
         */
        static $ten;

        if ($ten === null) {
            $ten = new BigInteger('10');
        }

        return $ten;
    }

    /**
     * Returns the sum of this number and the given one.
     *
     * @param BigNumber|int|float|string $that The number to add. Must be convertible to a BigInteger.
     *
     * @return BigInteger The result.
     *
     * @throws MathException If the number is not valid, or is not convertible to a BigInteger.
     */
    public function plus($that) : BigInteger
    {
        $that = BigInteger::of($that);

        if ($that->value === '0') {
            return $this;
        }

        if ($this->value === '0') {
            return $that;
        }

        $value = Calculator::get()->add($this->value, $that->value);

        return new BigInteger($value);
    }

    /**
     * Returns the difference of this number and the given one.
     *
     * @param BigNumber|int|float|string $that The number to subtract. Must be convertible to a BigInteger.
     *
     * @return BigInteger The result.
     *
     * @throws MathException If the number is not valid, or is not convertible to a BigInteger.
     */
    public function minus($that) : BigInteger
    {
        $that = BigInteger::of($that);

        if ($that->value === '0') {
            return $this;
        }

        $value = Calculator::get()->sub($this->value, $that->value);

        return new BigInteger($value);
    }

    /**
     * Returns the product of this number and the given one.
     *
     * @param BigNumber|int|float|string $that The multiplier. Must be convertible to a BigInteger.
     *
     * @return BigInteger The result.
     *
     * @throws MathException If the multiplier is not a valid number, or is not convertible to a BigInteger.
     */
    public function multipliedBy($that) : BigInteger
    {
        $that = BigInteger::of($that);

        if ($that->value === '1') {
            return $this;
        }

        if ($this->value === '1') {
            return $that;
        }

        $value = Calculator::get()->mul($this->value, $that->value);

        return new BigInteger($value);
    }

    /**
     * Returns the result of the division of this number by the given one.
     *
     * @param BigNumber|int|float|string $that         The divisor. Must be convertible to a BigInteger.
     * @param int                        $roundingMode An optional rounding mode.
     *
     * @return BigInteger The result.
     *
     * @throws MathException If the divisor is not a valid number, is not convertible to a BigInteger, is zero,
     *                       or RoundingMode::UNNECESSARY is used and the remainder is not zero.
     */
    public function dividedBy($that, int $roundingMode = RoundingMode::UNNECESSARY) : BigInteger
    {
        $that = BigInteger::of($that);

        if ($that->value === '1') {
            return $this;
        }

        if ($that->value === '0') {
            throw DivisionByZeroException::divisionByZero();
        }

        $result = Calculator::get()->divRound($this->value, $that->value, $roundingMode);

        return new BigInteger($result);
    }

    /**
     * Returns this number exponentiated to the given value.
     *
     * @param int $exponent The exponent.
     *
     * @return BigInteger The result.
     *
     * @throws \InvalidArgumentException If the exponent is not in the range 0 to 1,000,000.
     */
    public function power(int $exponent) : BigInteger
    {
        if ($exponent === 0) {
            return BigInteger::one();
        }

        if ($exponent === 1) {
            return $this;
        }

        if ($exponent < 0 || $exponent > Calculator::MAX_POWER) {
            throw new \InvalidArgumentException(\sprintf(
                'The exponent %d is not in the range 0 to %d.',
                $exponent,
                Calculator::MAX_POWER
            ));
        }

        return new BigInteger(Calculator::get()->pow($this->value, $exponent));
    }

    /**
     * Returns the quotient of the division of this number by the given one.
     *
     * @param BigNumber|int|float|string $that The divisor. Must be convertible to a BigInteger.
     *
     * @return BigInteger
     *
     * @throws DivisionByZeroException If the divisor is zero.
     */
    public function quotient($that) : BigInteger
    {
        $that = BigInteger::of($that);

        if ($that->value === '1') {
            return $this;
        }

        if ($that->value === '0') {
            throw DivisionByZeroException::divisionByZero();
        }

        $quotient = Calculator::get()->divQ($this->value, $that->value);

        return new BigInteger($quotient);
    }

    /**
     * Returns the remainder of the division of this number by the given one.
     *
     * The remainder, when non-zero, has the same sign as the dividend.
     *
     * @param BigNumber|int|float|string $that The divisor. Must be convertible to a BigInteger.
     *
     * @return BigInteger
     *
     * @throws DivisionByZeroException If the divisor is zero.
     */
    public function remainder($that) : BigInteger
    {
        $that = BigInteger::of($that);

        if ($that->value === '1') {
            return BigInteger::zero();
        }

        if ($that->value === '0') {
            throw DivisionByZeroException::divisionByZero();
        }

        $remainder = Calculator::get()->divR($this->value, $that->value);

        return new BigInteger($remainder);
    }

    /**
     * Returns the quotient and remainder of the division of this number by the given one.
     *
     * @param BigNumber|int|float|string $that The divisor. Must be convertible to a BigInteger.
     *
     * @return BigInteger[] An array containing the quotient and the remainder.
     *
     * @throws DivisionByZeroException If the divisor is zero.
     */
    public function quotientAndRemainder($that) : array
    {
        $that = BigInteger::of($that);

        if ($that->value === '0') {
            throw DivisionByZeroException::divisionByZero();
        }

        [$quotient, $remainder] = Calculator::get()->divQR($this->value, $that->value);

        return [
            new BigInteger($quotient),
            new BigInteger($remainder)
        ];
    }

    /**
     * Returns the modulo of this number and the given one.
     *
     * The modulo operation yields the same result as the remainder operation when both operands are of the same sign,
     * and may differ when signs are different.
     *
     * The result of the modulo operation, when non-zero, has the same sign as the divisor.
     *
     * @param BigNumber|int|float|string $that The divisor. Must be convertible to a BigInteger.
     *
     * @return BigInteger
     *
     * @throws DivisionByZeroException If the divisor is zero.
     */
    public function mod($that) : BigInteger
    {
        $that = BigInteger::of($that);

        if ($that->value === '0') {
            throw DivisionByZeroException::modulusMustNotBeZero();
        }

        $value = Calculator::get()->mod($this->value, $that->value);

        return new BigInteger($value);
    }

    /**
     * Returns the modular multiplicative inverse of this BigInteger modulo $m.
     *
     * @param BigInteger $m
     *
     * @return BigInteger
     *
     * @throws DivisionByZeroException If $m is zero.
     * @throws NegativeNumberException If $m is negative.
     * @throws MathException           If this BigInteger has no multiplicative inverse mod m (that is, this BigInteger
     *                                 is not relatively prime to m).
     */
    public function modInverse(BigInteger $m) : BigInteger
    {
        if ($m->value === '0') {
            throw DivisionByZeroException::modulusMustNotBeZero();
        }

        if ($m->isNegative()) {
            throw new NegativeNumberException('Modulus must not be negative.');
        }

        if ($m->value === '1') {
            return BigInteger::zero();
        }

        $value = Calculator::get()->modInverse($this->value, $m->value);

        if ($value === null) {
            throw new MathException('Unable to compute the modInverse for the given modulus.');
        }

        return new BigInteger($value);
    }

    /**
     * Returns this number raised into power with modulo.
     *
     * This operation only works on positive numbers.
     *
     * @param BigNumber|int|float|string $exp The exponent. Must be positive or zero.
     * @param BigNumber|int|float|string $mod The modulus. Must be strictly positive.
     *
     * @return BigInteger
     *
     * @throws NegativeNumberException If any of the operands is negative.
     * @throws DivisionByZeroException If the modulus is zero.
     */
    public function modPow($exp, $mod) : BigInteger
    {
        $exp = BigInteger::of($exp);
        $mod = BigInteger::of($mod);

        if ($this->isNegative() || $exp->isNegative() || $mod->isNegative()) {
            throw new NegativeNumberException('The operands cannot be negative.');
        }

        if ($mod->isZero()) {
            throw DivisionByZeroException::modulusMustNotBeZero();
        }

        $result = Calculator::get()->modPow($this->value, $exp->value, $mod->value);

        return new BigInteger($result);
    }

    /**
     * Returns the greatest common divisor of this number and the given one.
     *
     * The GCD is always positive, unless both operands are zero, in which case it is zero.
     *
     * @param BigNumber|int|float|string $that The operand. Must be convertible to an integer number.
     *
     * @return BigInteger
     */
    public function gcd($that) : BigInteger
    {
        $that = BigInteger::of($that);

        if ($that->value === '0' && $this->value[0] !== '-') {
            return $this;
        }

        if ($this->value === '0' && $that->value[0] !== '-') {
            return $that;
        }

        $value = Calculator::get()->gcd($this->value, $that->value);

        return new BigInteger($value);
    }

    /**
     * Returns the integer square root number of this number, rounded down.
     *
     * The result is the largest x such that x² ≤ n.
     *
     * @return BigInteger
     *
     * @throws NegativeNumberException If this number is negative.
     */
    public function sqrt() : BigInteger
    {
        if ($this->value[0] === '-') {
            throw new NegativeNumberException('Cannot calculate the square root of a negative number.');
        }

        $value = Calculator::get()->sqrt($this->value);

        return new BigInteger($value);
    }

    /**
     * Returns the absolute value of this number.
     *
     * @return BigInteger
     */
    public function abs() : BigInteger
    {
        return $this->isNegative() ? $this->negated() : $this;
    }

    /**
     * Returns the inverse of this number.
     *
     * @return BigInteger
     */
    public function negated() : BigInteger
    {
        return new BigInteger(Calculator::get()->neg($this->value));
    }

    /**
     * Returns the integer bitwise-and combined with another integer.
     *
     * This method returns a negative BigInteger if and only if both operands are negative.
     *
     * @param BigNumber|int|float|string $that The operand. Must be convertible to an integer number.
     *
     * @return BigInteger
     */
    public function and($that) : BigInteger
    {
        $that = BigInteger::of($that);

        return new BigInteger(Calculator::get()->and($this->value, $that->value));
    }

    /**
     * Returns the integer bitwise-or combined with another integer.
     *
     * This method returns a negative BigInteger if and only if either of the operands is negative.
     *
     * @param BigNumber|int|float|string $that The operand. Must be convertible to an integer number.
     *
     * @return BigInteger
     */
    public function or($that) : BigInteger
    {
        $that = BigInteger::of($that);

        return new BigInteger(Calculator::get()->or($this->value, $that->value));
    }

    /**
     * Returns the integer bitwise-xor combined with another integer.
     *
     * This method returns a negative BigInteger if and only if exactly one of the operands is negative.
     *
     * @param BigNumber|int|float|string $that The operand. Must be convertible to an integer number.
     *
     * @return BigInteger
     */
    public function xor($that) : BigInteger
    {
        $that = BigInteger::of($that);

        return new BigInteger(Calculator::get()->xor($this->value, $that->value));
    }

    /**
     * Returns the bitwise-not of this BigInteger.
     *
     * @return BigInteger
     */
    public function not() : BigInteger
    {
        return $this->negated()->minus(1);
    }

    /**
     * Returns the integer left shifted by a given number of bits.
     *
     * @param int $distance The distance to shift.
     *
     * @return BigInteger
     */
    public function shiftedLeft(int $distance) : BigInteger
    {
        if ($distance === 0) {
            return $this;
        }

        if ($distance < 0) {
            return $this->shiftedRight(- $distance);
        }

        return $this->multipliedBy(BigInteger::of(2)->power($distance));
    }

    /**
     * Returns the integer right shifted by a given number of bits.
     *
     * @param int $distance The distance to shift.
     *
     * @return BigInteger
     */
    public function shiftedRight(int $distance) : BigInteger
    {
        if ($distance === 0) {
            return $this;
        }

        if ($distance < 0) {
            return $this->shiftedLeft(- $distance);
        }

        $operand = BigInteger::of(2)->power($distance);

        if ($this->isPositiveOrZero()) {
            return $this->quotient($operand);
        }

        return $this->dividedBy($operand, RoundingMode::UP);
    }

    /**
     * Returns the number of bits in the minimal two's-complement representation of this BigInteger, excluding a sign bit.
     *
     * For positive BigIntegers, this is equivalent to the number of bits in the ordinary binary representation.
     * Computes (ceil(log2(this < 0 ? -this : this+1))).
     *
     * @return int
     */
    public function getBitLength() : int
    {
        if ($this->value === '0') {
            return 0;
        }

        if ($this->isNegative()) {
            return $this->abs()->minus(1)->getBitLength();
        }

        return \strlen($this->toBase(2));
    }

    /**
     * Returns the index of the rightmost (lowest-order) one bit in this BigInteger.
     *
     * Returns -1 if this BigInteger contains no one bits.
     *
     * @return int
     */
    public function getLowestSetBit() : int
    {
        $n = $this;
        $bitLength = $this->getBitLength();

        for ($i = 0; $i <= $bitLength; $i++) {
            if ($n->isOdd()) {
                return $i;
            }

            $n = $n->shiftedRight(1);
        }

        return -1;
    }

    /**
     * Returns whether this number is even.
     *
     * @return bool
     */
    public function isEven() : bool
    {
        return \in_array($this->value[-1], ['0', '2', '4', '6', '8'], true);
    }

    /**
     * Returns whether this number is odd.
     *
     * @return bool
     */
    public function isOdd() : bool
    {
        return \in_array($this->value[-1], ['1', '3', '5', '7', '9'], true);
    }

    /**
     * Returns true if and only if the designated bit is set.
     *
     * Computes ((this & (1<<n)) != 0).
     *
     * @param int $n The bit to test, 0-based.
     *
     * @return bool
     *
     * @throws \InvalidArgumentException If the bit to test is negative.
     */
    public function testBit(int $n) : bool
    {
        if ($n < 0) {
            throw new \InvalidArgumentException('The bit to test cannot be negative.');
        }

        return $this->shiftedRight($n)->isOdd();
    }

    /**
     * {@inheritdoc}
     */
    public function compareTo($that) : int
    {
        $that = BigNumber::of($that);

        if ($that instanceof BigInteger) {
            return Calculator::get()->cmp($this->value, $that->value);
        }

        return - $that->compareTo($this);
    }

    /**
     * {@inheritdoc}
     */
    public function getSign() : int
    {
        return ($this->value === '0') ? 0 : (($this->value[0] === '-') ? -1 : 1);
    }

    /**
     * {@inheritdoc}
     */
    public function toBigInteger() : BigInteger
    {
        return $this;
    }

    /**
     * {@inheritdoc}
     */
    public function toBigDecimal() : BigDecimal
    {
        return BigDecimal::create($this->value);
    }

    /**
     * {@inheritdoc}
     */
    public function toBigRational() : BigRational
    {
        return BigRational::create($this, BigInteger::one(), false);
    }

    /**
     * {@inheritdoc}
     */
    public function toScale(int $scale, int $roundingMode = RoundingMode::UNNECESSARY) : BigDecimal
    {
        return $this->toBigDecimal()->toScale($scale, $roundingMode);
    }

    /**
     * {@inheritdoc}
     */
    public function toInt() : int
    {
        $intValue = (int) $this->value;

        if ($this->value !== (string) $intValue) {
            throw IntegerOverflowException::toIntOverflow($this);
        }

        return $intValue;
    }

    /**
     * {@inheritdoc}
     */
    public function toFloat() : float
    {
        return (float) $this->value;
    }

    /**
     * Returns a string representation of this number in the given base.
     *
     * The output will always be lowercase for bases greater than 10.
     *
     * @param int $base
     *
     * @return string
     *
     * @throws \InvalidArgumentException If the base is out of range.
     */
    public function toBase(int $base) : string
    {
        if ($base === 10) {
            return $this->value;
        }

        if ($base < 2 || $base > 36) {
            throw new \InvalidArgumentException(\sprintf('Base %d is out of range [2, 36]', $base));
        }

        return Calculator::get()->toBase($this->value, $base);
    }

    /**
     * Returns a string representation of this number in an arbitrary base with a custom alphabet.
     *
     * Because this method accepts an alphabet with any character, including dash, it does not handle negative numbers;
     * a NegativeNumberException will be thrown when attempting to call this method on a negative number.
     *
     * @param string $alphabet The alphabet, for example '01' for base 2, or '01234567' for base 8.
     *
     * @return string
     *
     * @throws NegativeNumberException   If this number is negative.
     * @throws \InvalidArgumentException If the given alphabet does not contain at least 2 chars.
     */
    public function toArbitraryBase(string $alphabet) : string
    {
        $base = \strlen($alphabet);

        if ($base < 2) {
            throw new \InvalidArgumentException('The alphabet must contain at least 2 chars.');
        }

        if ($this->value[0] === '-') {
            throw new NegativeNumberException(__FUNCTION__ . '() does not support negative numbers.');
        }

        return Calculator::get()->toArbitraryBase($this->value, $alphabet, $base);
    }

    /**
     * Returns a string of bytes containing the binary representation of this BigInteger.
     *
     * The string is in big-endian byte-order: the most significant byte is in the zeroth element.
     *
     * If `$signed` is true, the output will be in two's-complement representation, and a sign bit will be prepended to
     * the output. If `$signed` is false, no sign bit will be prepended, and this method will throw an exception if the
     * number is negative.
     *
     * The string will contain the minimum number of bytes required to represent this BigInteger, including a sign bit
     * if `$signed` is true.
     *
     * This representation is compatible with the `fromBytes()` factory method, as long as the `$signed` flags match.
     *
     * @param bool $signed Whether to output a signed number in two's-complement representation with a leading sign bit.
     *
     * @return string
     *
     * @throws NegativeNumberException If $signed is false, and the number is negative.
     */
    public function toBytes(bool $signed = true) : string
    {
        if (! $signed && $this->isNegative()) {
            throw new NegativeNumberException('Cannot convert a negative number to a byte string when $signed is false.');
        }

        $hex = $this->abs()->toBase(16);

        if (\strlen($hex) % 2 !== 0) {
            $hex = '0' . $hex;
        }

        $baseHexLength = \strlen($hex);

        if ($signed) {
            if ($this->isNegative()) {
                $bin = \hex2bin($hex);
                assert($bin !== false);

                $hex = \bin2hex(~$bin);
                $hex = self::fromBase($hex, 16)->plus(1)->toBase(16);

                $hexLength = \strlen($hex);

                if ($hexLength < $baseHexLength) {
                    $hex = \str_repeat('0', $baseHexLength - $hexLength) . $hex;
                }

                if ($hex[0] < '8') {
                    $hex = 'FF' . $hex;
                }
            } else {
                if ($hex[0] >= '8') {
                    $hex = '00' . $hex;
                }
            }
        }

        return \hex2bin($hex);
    }

    /**
     * {@inheritdoc}
     */
    public function __toString() : string
    {
        return $this->value;
    }

    /**
     * This method is required for serializing the object and SHOULD NOT be accessed directly.
     *
     * @internal
     *
     * @return array{value: string}
     */
    public function __serialize(): array
    {
        return ['value' => $this->value];
    }

    /**
     * This method is only here to allow unserializing the object and cannot be accessed directly.
     *
     * @internal
     * @psalm-suppress RedundantPropertyInitializationCheck
     *
     * @param array{value: string} $data
     *
     * @return void
     *
     * @throws \LogicException
     */
    public function __unserialize(array $data): void
    {
        if (isset($this->value)) {
            throw new \LogicException('__unserialize() is an internal function, it must not be called directly.');
        }

        $this->value = $data['value'];
    }

    /**
     * This method is required by interface Serializable and SHOULD NOT be accessed directly.
     *
     * @internal
     *
     * @return string
     */
    public function serialize() : string
    {
        return $this->value;
    }

    /**
     * This method is only here to implement interface Serializable and cannot be accessed directly.
     *
     * @internal
     * @psalm-suppress RedundantPropertyInitializationCheck
     *
     * @param string $value
     *
     * @return void
     *
     * @throws \LogicException
     */
    public function unserialize($value) : void
    {
        if (isset($this->value)) {
            throw new \LogicException('unserialize() is an internal function, it must not be called directly.');
        }

        $this->value = $value;
    }
}