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plugins/totp/lib/FixedByteNotation.php
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276
plugins/totp/lib/FixedByteNotation.php
Executable file
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<?php
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/**
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* FixedBitNotation
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*
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* @author Andre DeMarre
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* @package FixedBitNotation
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*/
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/**
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* The FixedBitNotation class is for binary to text conversion. It
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* can handle many encoding schemes, formally defined or not, that
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* use a fixed number of bits to encode each character.
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*
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* @package FixedBitNotation
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*/
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class FixedBitNotation
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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 $_charmap;
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/**
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* Constructor
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*
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* @param integer $bitsPerCharacter Bits to use for each encoded
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* character
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* @param string $chars Base character alphabet
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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
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* output
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* @param string $padCharacter Character to use for padding
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*/
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public function __construct(
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$bitsPerCharacter, $chars = NULL, $rightPadFinalBits = FALSE,
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$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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$chars =
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'0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ-,';
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$charLength = 64;
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}
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// Ensure validity of $bitsPerCharacter
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if ($bitsPerCharacter < 1) {
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// $bitsPerCharacter must be at least 1
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$bitsPerCharacter = 1;
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$radix = 2;
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} elseif ($charLength < 1 << $bitsPerCharacter) {
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// Character length of $chars is too small for $bitsPerCharacter
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// Set $bitsPerCharacter to greatest acceptable value
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$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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$radix >>= 1;
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} elseif ($bitsPerCharacter > 8) {
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// $bitsPerCharacter must not be greater than 8
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$bitsPerCharacter = 8;
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$radix = 256;
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} else {
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$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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}
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/**
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* Encode a string
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*
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* @param string $rawString Binary data to encode
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* @return string
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*/
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public function encode($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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$bitsRead = 0;
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$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 = $this->_padCharacter;
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// Generate encoded output;
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// each loop produces one encoded character
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for ($c = 0; $c < $byteCount * 8 / $bitsPerCharacter; $c++) {
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// Get the bits needed for this encoded character
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if ($bitsRead + $bitsPerCharacter > 8) {
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// Not enough bits remain in this byte for the current
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// character
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// Save the remaining bits before getting the next byte
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$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
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// $bitsPerCharacter and 8, divided by 8
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$lcmMap = array(1 => 1, 2 => 1, 3 => 3, 4 => 1,
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5 => 5, 6 => 3, 7 => 7, 8 => 1);
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$bytesPerGroup = $lcmMap[$bitsPerCharacter];
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$pads = $bytesPerGroup * 8 / $bitsPerCharacter
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- ceil((strlen($rawString) % $bytesPerGroup)
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* 8 / $bitsPerCharacter);
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$encodedString .= str_repeat($padCharacter[0], $pads);
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}
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break;
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}
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// Get next byte
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$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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*
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* @param string $encodedString Data to decode
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* @param boolean $caseSensitive
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* @param boolean $strict Returns NULL if $encodedString contains
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* an undecodable character
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* @return string|NULL
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*/
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public function decode($encodedString, $caseSensitive = TRUE,
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$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 = $this->_padCharacter;
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// Get index of encoded characters
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if ($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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while ($encodedString[$lastNotatedIndex] == $padCharacter[0]) {
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$encodedString = substr($encodedString, 0, $lastNotatedIndex);
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$lastNotatedIndex--;
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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; $c++) {
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if (!isset($charmap[$encodedString[$c]]) && !$caseSensitive) {
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// Encoded character was not found; try other case
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if (isset($charmap[$cUpper
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= strtoupper($encodedString[$c])])) {
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$charmap[$encodedString[$c]] = $charmap[$cUpper];
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} elseif (isset($charmap[$cLower
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= 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 > $bitsPerCharacter) {
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// New bits aren't enough to complete a byte; shift them
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// left into position
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$newBits = $charmap[$encodedString[$c]] << $bitsNeeded
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- $bitsPerCharacter;
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$bitsWritten += $bitsPerCharacter;
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} elseif ($c != $lastNotatedIndex || $rightPadFinalBits) {
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// Zero or more too many bits to complete a byte;
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// shift right
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$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[$c]]
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^ ($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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