3 more bugs found and fixed:
1. failed to work when the gz contained a filename - FIXED
2. failed to work on 64-bit architecture (checksum) - FIXED
3. failed to work when the gz contained a comment - cannot verify.
Returns some errors (not all!) and filename.
<?php function gzdecode($data,&$filename='',&$error='',$maxlength=null)
{
$len = strlen($data);
if ($len < 18 || strcmp(substr($data,0,2),"\x1f\x8b")) {
$error = "Not in GZIP format.";
return null; }
$method = ord(substr($data,2,1)); $flags = ord(substr($data,3,1)); if ($flags & 31 != $flags) {
$error = "Reserved bits not allowed.";
return null;
}
$mtime = unpack("V", substr($data,4,4));
$mtime = $mtime[1];
$xfl = substr($data,8,1);
$os = substr($data,8,1);
$headerlen = 10;
$extralen = 0;
$extra = "";
if ($flags & 4) {
if ($len - $headerlen - 2 < 8) {
return false; }
$extralen = unpack("v",substr($data,8,2));
$extralen = $extralen[1];
if ($len - $headerlen - 2 - $extralen < 8) {
return false; }
$extra = substr($data,10,$extralen);
$headerlen += 2 + $extralen;
}
$filenamelen = 0;
$filename = "";
if ($flags & 8) {
if ($len - $headerlen - 1 < 8) {
return false; }
$filenamelen = strpos(substr($data,$headerlen),chr(0));
if ($filenamelen === false || $len - $headerlen - $filenamelen - 1 < 8) {
return false; }
$filename = substr($data,$headerlen,$filenamelen);
$headerlen += $filenamelen + 1;
}
$commentlen = 0;
$comment = "";
if ($flags & 16) {
if ($len - $headerlen - 1 < 8) {
return false; }
$commentlen = strpos(substr($data,$headerlen),chr(0));
if ($commentlen === false || $len - $headerlen - $commentlen - 1 < 8) {
return false; }
$comment = substr($data,$headerlen,$commentlen);
$headerlen += $commentlen + 1;
}
$headercrc = "";
if ($flags & 2) {
if ($len - $headerlen - 2 < 8) {
return false; }
$calccrc = crc32(substr($data,0,$headerlen)) & 0xffff;
$headercrc = unpack("v", substr($data,$headerlen,2));
$headercrc = $headercrc[1];
if ($headercrc != $calccrc) {
$error = "Header checksum failed.";
return false; }
$headerlen += 2;
}
$datacrc = unpack("V",substr($data,-8,4));
$datacrc = sprintf('%u',$datacrc[1] & 0xFFFFFFFF);
$isize = unpack("V",substr($data,-4));
$isize = $isize[1];
$bodylen = $len-$headerlen-8;
if ($bodylen < 1) {
return null;
}
$body = substr($data,$headerlen,$bodylen);
$data = "";
if ($bodylen > 0) {
switch ($method) {
case 8:
$data = gzinflate($body,$maxlength);
break;
default:
$error = "Unknown compression method.";
return false;
}
} $crc = sprintf("%u",crc32($data));
$crcOK = $crc == $datacrc;
$lenOK = $isize == strlen($data);
if (!$lenOK || !$crcOK) {
$error = ( $lenOK ? '' : 'Length check FAILED. ') . ( $crcOK ? '' : 'Checksum FAILED.');
return false;
}
return $data;
}
?>