Lzw algorithm implementation php-lzw optimized version-PHP source code

Lzw algorithm implementation php-lzw optimized version

[PHP] code

  $bits_max) {                $bits_max = 1 << ++$bits;            }            while ($rest_length > 7) {                $rest_length -= 8;                $return .= chr($rest >> $rest_length);                $rest &= (1 << $rest_length) - 1;            }            $dict[$y] = $dict_size++;            $word = $x;        }    }    $rest = ($rest << $bits) + $dict[$word];    $rest_length += $bits;    $dict_count++;    if ($dict_count > $bits_max) {        $bits_max = 1 << ++$bits;    }    while ($rest_length > 0) {        if($rest_length>7){            $rest_length -= 8;            $return .= chr($rest >> $rest_length);            $rest &= (1 << $rest_length) - 1;        }else{            $return .= chr($rest << (8 - $rest_length));            $rest_length = 0;        }    }    return $return;}/** LZW decompression * @param string compressed binary data * @return string original data */function lzw_decompress($binary) {    // convert binary string to codes    $rest = 0;    $rest_length = 0;    $out_count = 257;    $bits = 9;    $bits_max = 512;        // decompression    $dict = range("\0", "\xFF");    $w = $binary[0];    $return = $w;        for ($i = 1, $j = strlen($binary); $i < $j; $i++) {        $rest = ($rest << 8) + ord($binary[$i]);        $rest_length += 8;        if ($rest_length >= $bits) {            $rest_length -= $bits;                        // decompression            $e = $dict[$rest >> $rest_length];            if (!isset($e)) {                $e = $w . $w[0];            }            $return .= $e;            $dict[] = $w . $e[0];            $w = $e;            //--decompression                        $rest &= (1 << $rest_length) - 1;            if (++$out_count > $bits_max) {                $bits_max = 1 << ++$bits;            }        }    }        return $return;}?>