101 lines
3.4 KiB
PHP
101 lines
3.4 KiB
PHP
<?php
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// IntegerBaseConverter.php
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// Created: 2024-07-31
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// Updated: 2024-08-04
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namespace Index;
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use InvalidArgumentException;
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/**
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* Provides methods for encoding integers in different bases.
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*/
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class IntegerBaseConverter {
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private int $maxBase;
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/**
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* @param string $characterSet Specifies the provided character set, must be a string consisting out of at least two unique characters.
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* @throws InvalidArgumentException If $characterSet contains less than two characters.
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* @throws InvalidArgumentException If $characterSet contains duplicate characters.
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*/
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public function __construct(
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private string $characterSet
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) {
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$length = strlen($characterSet);
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if($length < 2)
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throw new InvalidArgumentException('$characterSet must contain at least two characters');
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if(XString::countUnique($characterSet) !== $length)
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throw new InvalidArgumentException('$characterSet must contain a set of entirely unique characters');
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$this->maxBase = $length;
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}
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/**
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* Converts a positive base10 integer to another base.
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*
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* @param int $integer The integer to encode.
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* @param int $toBase Target base, 0 for the base of the provided character set.
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* @return string The encoded data, as a string.
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*/
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public function encode(int $integer, int $toBase = 0): string {
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if($integer < 0)
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throw new InvalidArgumentException('$integer contains a negative value, which cannot be represented');
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if($toBase === 0)
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$toBase = $this->maxBase;
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else {
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if($toBase < 2)
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throw new InvalidArgumentException('lowest supported value for $toBase is 2');
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if($toBase > $this->maxBase)
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throw new InvalidArgumentException('specified $toBase value is greater than the amount of characters in the provided character set');
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}
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if($integer === 0)
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return '';
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$output = '';
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for($i = floor(log10($integer) / log10($toBase)); $i >= 0; --$i) {
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$exp = $toBase ** $i;
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$index = (int)floor($integer / $exp);
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$output .= $this->characterSet[$index];
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$integer -= $index * $exp;
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}
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return $output;
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}
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/**
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* Converts another base encoded integer to a base10 integer.
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*
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* @param string $string The encoded integer.
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* @param int $fromBase Source base, 0 for the base of the provided character set.
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* @return int|false Returns the decoded integer or false on failure.
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*/
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public function decode(string $string, int $fromBase = 0): int|false {
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if($fromBase === 0)
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$fromBase = $this->maxBase;
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else {
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if($fromBase < 2)
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throw new InvalidArgumentException('lowest supported value for $fromBase is 2');
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if($fromBase > $this->maxBase)
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throw new InvalidArgumentException('specified $fromBase value is greater than the amount of characters in the provided character set');
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}
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if($string === '')
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return 0;
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$output = 0;
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$length = strlen($string) - 1;
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for($i = 0; $i <= $length; ++$i) {
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$pos = strpos($this->characterSet, $string[$i]);
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if($pos === false)
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return false;
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$output += $pos * ($fromBase ** ($length - $i));
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}
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return (int)$output;
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}
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}
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