作者:铱雯_213 | 来源:互联网 | 2018-03-23 08:27
[PHP]代码
$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;
}
?>