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<?php

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namespace WordfenceLS\Crypto;

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/**

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* Binary-to-text PHP Utilities

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* @package binary-to-text-php

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* @link https://github.com/ademarre/binary-to-text-php

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* @author Andre DeMarre

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* @license http://opensource.org/licenses/MIT MIT

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/**

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* Class for binary-to-text encoding with a base of 2^n

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* The Base2n class is for binary-to-text conversion. It employs a

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* generalization of the algorithms used by many encoding schemes that

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* use a fixed number of bits to encode each character. In other words,

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* the base is a power of 2.

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* Earlier versions of this class were named

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* FixedBitNotation and FixedBitEncoding.

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* @package binary-to-text-php

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class Model_Base2n

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{

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protected $_chars;

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protected $_bitsPerCharacter;

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protected $_radix;

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protected $_rightPadFinalBits;

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protected $_padFinalGroup;

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protected $_padCharacter;

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protected $_caseSensitive;

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protected $_charmap;

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/**

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* Constructor

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* @param integer $bitsPerCharacter Bits to use for each encoded character

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* @param string $chars Base character alphabet

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* @param boolean $caseSensitive To decode in a case-sensitive manner

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* @param boolean $rightPadFinalBits How to encode last character

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* @param boolean $padFinalGroup Add padding to end of encoded output

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* @param string $padCharacter Character to use for padding

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* @throws InvalidArgumentException for incompatible parameters

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public function __construct(

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$bitsPerCharacter,

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$chars = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ-_',

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$caseSensitive = TRUE, $rightPadFinalBits = FALSE,

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$padFinalGroup = FALSE, $padCharacter = '=')

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{

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// Ensure validity of $chars

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if (!is_string($chars) || ($charLength = strlen($chars)) < 2) {

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throw new \InvalidArgumentException('$chars must be a string of at least two characters');

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}

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// Ensure validity of $padCharacter

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if ($padFinalGroup) {

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if (!is_string($padCharacter) || !isset($padCharacter[0])) {

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throw new \InvalidArgumentException('$padCharacter must be a string of one character');

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}

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if ($caseSensitive) {

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$padCharFound = strpos($chars, $padCharacter[0]);

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} else {

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$padCharFound = stripos($chars, $padCharacter[0]);

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}

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if ($padCharFound !== FALSE) {

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throw new \InvalidArgumentException('$padCharacter can not be a member of $chars');

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}

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}

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// Ensure validity of $bitsPerCharacter

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if (!is_int($bitsPerCharacter)) {

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throw new \InvalidArgumentException('$bitsPerCharacter must be an integer');

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}

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if ($bitsPerCharacter < 1) {

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// $bitsPerCharacter must be at least 1

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throw new \InvalidArgumentException('$bitsPerCharacter can not be less than 1');

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} elseif ($charLength < 1 << $bitsPerCharacter) {

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// Character length of $chars is too small for $bitsPerCharacter

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// Find greatest acceptable value of $bitsPerCharacter

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$bitsPerCharacter = 1;

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$radix = 2;

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while ($charLength >= ($radix <<= 1) && $bitsPerCharacter < 8) {

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$bitsPerCharacter++;

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}

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$radix >>= 1;

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throw new \InvalidArgumentException(

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'$bitsPerCharacter can not be more than ' . $bitsPerCharacter

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. ' given $chars length of ' . $charLength

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. ' (max radix ' . $radix . ')');

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} elseif ($bitsPerCharacter > 8) {

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// $bitsPerCharacter must not be greater than 8

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throw new \InvalidArgumentException('$bitsPerCharacter can not be greater than 8');

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} else {

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$radix = 1 << $bitsPerCharacter;

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}

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$this->_chars = $chars;

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$this->_bitsPerCharacter = $bitsPerCharacter;

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$this->_radix = $radix;

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$this->_rightPadFinalBits = $rightPadFinalBits;

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$this->_padFinalGroup = $padFinalGroup;

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$this->_padCharacter = $padCharacter[0];

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$this->_caseSensitive = $caseSensitive;

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}

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/**

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* Encode a string

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* @param string $rawString Binary data to encode

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* @return string

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public function encode($rawString)

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{

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// Unpack string into an array of bytes

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$bytes = unpack('C*', $rawString);

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$byteCount = count($bytes);

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$encodedString = '';

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$byte = array_shift($bytes);

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$bitsRead = 0;

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$oldBits = 0;

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$chars = $this->_chars;

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$bitsPerCharacter = $this->_bitsPerCharacter;

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$rightPadFinalBits = $this->_rightPadFinalBits;

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$padFinalGroup = $this->_padFinalGroup;

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$padCharacter = $this->_padCharacter;

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$charsPerByte = 8 / $bitsPerCharacter;

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$encodedLength = $byteCount * $charsPerByte;

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// Generate encoded output; each loop produces one encoded character

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for ($c = 0; $c < $encodedLength; $c++) {

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// Get the bits needed for this encoded character

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if ($bitsRead + $bitsPerCharacter > 8) {

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// Not enough bits remain in this byte for the current character

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// Save the remaining bits before getting the next byte

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$oldBitCount = 8 - $bitsRead;

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$oldBits = $byte ^ ($byte >> $oldBitCount << $oldBitCount);

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$newBitCount = $bitsPerCharacter - $oldBitCount;

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if (!$bytes) {

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// Last bits; match final character and exit loop

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if ($rightPadFinalBits) $oldBits <<= $newBitCount;

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$encodedString .= $chars[$oldBits];

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if ($padFinalGroup) {

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// Array of the lowest common multiples of $bitsPerCharacter and 8, divided by 8

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$lcmMap = array(1 => 1, 2 => 1, 3 => 3, 4 => 1, 5 => 5, 6 => 3, 7 => 7, 8 => 1);

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$bytesPerGroup = $lcmMap[$bitsPerCharacter];

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$pads = $bytesPerGroup * $charsPerByte - ceil((strlen($rawString) % $bytesPerGroup) * $charsPerByte);

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$encodedString .= str_repeat($padCharacter, $pads);

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}

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break;

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}

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// Get next byte

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$byte = array_shift($bytes);

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$bitsRead = 0;

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} else {

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$oldBitCount = 0;

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$newBitCount = $bitsPerCharacter;

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}

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// Read only the needed bits from this byte

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$bits = $byte >> 8 - ($bitsRead + ($newBitCount));

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$bits ^= $bits >> $newBitCount << $newBitCount;

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$bitsRead += $newBitCount;

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if ($oldBitCount) {

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// Bits come from seperate bytes, add $oldBits to $bits

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$bits = ($oldBits << $newBitCount) | $bits;

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}

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$encodedString .= $chars[$bits];

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}

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return $encodedString;

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}

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/**

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* Decode a string

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* @param string $encodedString Data to decode

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* @param boolean $strict Returns NULL if $encodedString contains an undecodable character

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* @return string

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public function decode($encodedString, $strict = FALSE)

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{

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if (!$encodedString || !is_string($encodedString)) {

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// Empty string, nothing to decode

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return '';

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}

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$chars = $this->_chars;

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$bitsPerCharacter = $this->_bitsPerCharacter;

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$radix = $this->_radix;

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$rightPadFinalBits = $this->_rightPadFinalBits;

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$padFinalGroup = $this->_padFinalGroup;

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$padCharacter = $this->_padCharacter;

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$caseSensitive = $this->_caseSensitive;

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// Get index of encoded characters

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if ($this->_charmap) {

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$charmap = $this->_charmap;

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} else {

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$charmap = array();

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for ($i = 0; $i < $radix; $i++) {

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$charmap[$chars[$i]] = $i;

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}

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$this->_charmap = $charmap;

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}

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// The last encoded character is $encodedString[$lastNotatedIndex]

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$lastNotatedIndex = strlen($encodedString) - 1;

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// Remove trailing padding characters

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if ($padFinalGroup) {

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while ($encodedString[$lastNotatedIndex] === $padCharacter) {

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$encodedString = substr($encodedString, 0, $lastNotatedIndex);

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$lastNotatedIndex--;

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}

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}

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$rawString = '';

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$byte = 0;

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$bitsWritten = 0;

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// Convert each encoded character to a series of unencoded bits

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for ($c = 0; $c <= $lastNotatedIndex; $c++) {

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if (!$caseSensitive && !isset($charmap[$encodedString[$c]])) {

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// Encoded character was not found; try other case

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if (isset($charmap[$cUpper = strtoupper($encodedString[$c])])) {

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$charmap[$encodedString[$c]] = $charmap[$cUpper];

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} elseif (isset($charmap[$cLower = strtolower($encodedString[$c])])) {

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$charmap[$encodedString[$c]] = $charmap[$cLower];

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}

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}

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if (isset($charmap[$encodedString[$c]])) {

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$bitsNeeded = 8 - $bitsWritten;

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$unusedBitCount = $bitsPerCharacter - $bitsNeeded;

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// Get the new bits ready

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if ($bitsNeeded > $bitsPerCharacter) {

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// New bits aren't enough to complete a byte; shift them left into position

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$newBits = $charmap[$encodedString[$c]] << $bitsNeeded - $bitsPerCharacter;

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$bitsWritten += $bitsPerCharacter;

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} elseif ($c !== $lastNotatedIndex || $rightPadFinalBits) {

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// Zero or more too many bits to complete a byte; shift right

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$newBits = $charmap[$encodedString[$c]] >> $unusedBitCount;

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$bitsWritten = 8; //$bitsWritten += $bitsNeeded;

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} else {

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// Final bits don't need to be shifted

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$newBits = $charmap[$encodedString[$c]];

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$bitsWritten = 8;

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}

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$byte |= $newBits;

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if ($bitsWritten === 8 || $c === $lastNotatedIndex) {

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// Byte is ready to be written

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$rawString .= pack('C', $byte);

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if ($c !== $lastNotatedIndex) {

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// Start the next byte

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$bitsWritten = $unusedBitCount;

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$byte = ($charmap[$encodedString[$c]] ^ ($newBits << $unusedBitCount)) << 8 - $bitsWritten;

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}

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}

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} elseif ($strict) {

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// Unable to decode character; abort

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return NULL;

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}

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}

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return $rawString;

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}

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}

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