FusionPBX
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<?php
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/**
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* Binary-to-text PHP Utilities
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*
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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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* @copyright 2009-2013 Andre DeMarre
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* @license http://opensource.org/licenses/MIT MIT
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*/
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/**
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* Class for binary-to-text encoding with a base of 2^n
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*
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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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*
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* Earlier versions of this class were named
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* FixedBitNotation and FixedBitEncoding.
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*
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* @package binary-to-text-php
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*/
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class 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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*
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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 $padCharacter Character to use for padding
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*
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* @throws InvalidArgumentException for incompatible parameters
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*/
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public function __construct(
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$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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*
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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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$bitsRead = 0;
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$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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*
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* @param string $encodedString Data to decode
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* @param boolean $strict Returns NULL if $encodedString contains an undecodable character
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* @return string
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*/
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public function decode($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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?>
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