(PHP 5 >= 5.4.0, PHP 7)
gzdecode — Decodes a gzip compressed string
$data
[, int $length
] )
This function returns a decoded version of the input
data.
The decoded string, or FALSE if an error occurred.
This can help to decompress the data from tar archive in certain cases, hope this helps somebody
<?php
$tarName = 'example.ini';
try {
/** For files with tar.gz extensions **/
$phar = new \PharData($path, 0, $tarName);
} catch ($e) {
/** Decode the file first **/
$decodedFile = file_put_contents($path, gzdecode(file_get_contents($path)));
/** create PharData object second **/
$phar = new \PharData($path, 0, $tarName);
}
?>
In my case to decode correctly a GZIPOutputStream POST from Android I used
gzinflate( substr($post,10,-8) );
and not
gzinflate( substr($HTTP_RAW_POST_DATA,10,-8) ) . PHP_EOL . PHP_EOL
I use the following code:
function &gzdecodedata(&$data) {
ob_start();
readgzfile('data://application/gzip;base64,' . base64_encode($data));
$d = ob_get_clean();
return $d;
}
if (!function_exists('gzdecode')) {
function gzdecode($data)
{
return gzinflate(substr($data,10,-8));
}
}
To decode / uncompress the received HTTP POST data in PHP code, request data coming from Java / Android application via HTTP POST GZIP / DEFLATE compressed format
1) Data sent from Java Android app to PHP using DeflaterOutputStream java class and received in PHP as shown below
echo gzinflate( substr($HTTP_RAW_POST_DATA,2,-4) ) . PHP_EOL . PHP_EOL;
2) Data sent from Java Android app to PHP using GZIPOutputStream java class and received in PHP code as shown below
echo gzinflate( substr($HTTP_RAW_POST_DATA,10,-8) ) . PHP_EOL . PHP_EOL;
From Java Android side (API level 10+), data being sent in DEFLATE compressed format
String body = "Lorem ipsum shizzle ma nizle";
URL url = new URL("http://www.url.com/postthisdata.php");
URLConnection conn = url.openConnection();
conn.setDoOutput(true);
conn.setRequestProperty("Content-encoding", "deflate");
conn.setRequestProperty("Content-type", "application/octet-stream");
DeflaterOutputStream dos = new DeflaterOutputStream(
conn.getOutputStream());
dos.write(body.getBytes());
dos.flush();
dos.close();
BufferedReader in = new BufferedReader(new InputStreamReader(
conn.getInputStream()));
String decodedString = "";
while ((decodedString = in.readLine()) != null) {
Log.e("dump",decodedString);
}
in.close();
On PHP side (v 5.3.1), code for decompressing this DEFLATE data will be
echo substr($HTTP_RAW_POST_DATA,2,-4);
From Java Android side (API level 10+), data being sent in GZIP compressed format
String body1 = "Lorem ipsum shizzle ma nizle";
URL url1 = new URL("http://www.url.com/postthisdata.php");
URLConnection conn1 = url1.openConnection();
conn1.setDoOutput(true);
conn1.setRequestProperty("Content-encoding", "gzip");
conn1.setRequestProperty("Content-type", "application/octet-stream");
GZIPOutputStream dos1 = new GZIPOutputStream(conn1.getOutputStream());
dos1.write(body1.getBytes());
dos1.flush();
dos1.close();
BufferedReader in1 = new BufferedReader(new InputStreamReader(
conn1.getInputStream()));
String decodedString1 = "";
while ((decodedString1 = in1.readLine()) != null) {
Log.e("dump",decodedString1);
}
in1.close();
On PHP side (v 5.3.1), code for decompressing this GZIP data will be
echo substr($HTTP_RAW_POST_DATA,10,-8);
Useful PHP code for printing out compressed data using all available formats.
$data = "Lorem ipsum shizzle ma nizle";
echo "\n\n\n";
for($i=-1;$i<=9;$i++)
echo chunk_split(strtoupper(bin2hex(gzcompress($data,$i))),2," ") . PHP_EOL . PHP_EOL;
echo "\n\n\n";
for($i=-1;$i<=9;$i++)
echo chunk_split(strtoupper(bin2hex(gzdeflate($data,$i))),2," ") . PHP_EOL . PHP_EOL;
echo "\n\n\n";
for($i=-1;$i<=9;$i++)
echo chunk_split(strtoupper(bin2hex(gzencode($data,$i,FORCE_GZIP))),2," ") . PHP_EOL . PHP_EOL;
echo "\n\n\n";
for($i=-1;$i<=9;$i++)
echo chunk_split(strtoupper(bin2hex(gzencode($data,$i,FORCE_DEFLATE))),2," ") . PHP_EOL . PHP_EOL;
echo "\n\n\n";
Hope this helps. Please ThumbsUp if this saved you a lot of effort and time.
I don't have any deep knowledge in compression algorithms and formats, so I have no idea if this works the same on all platforms. But by several experiments on my Linux box I found how to get gzdecoded data without temporary files. Here it is:
<?php
function gzdecode($data)
{
return gzinflate(substr($data,10,-8));
}
?>
That's it. Simply strip header and footer bytes and you get raw deflated data for inflation.
I have used this simple function to gzdecode gzipped files downloaded from the web.
<?php
function gzdecode($data){
$g=tempnam('/tmp','ff');
@file_put_contents($g,$data);
ob_start();
readgzfile($g);
$d=ob_get_clean();
return $d;
}
?>
3 more bugs found and fixed:
1. failed to work when the gz contained a filename - FIXED
2. failed to work on 64-bit architecture (checksum) - FIXED
3. failed to work when the gz contained a comment - cannot verify.
Returns some errors (not all!) and filename.
<?php function gzdecode($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; // Not GZIP format (See RFC 1952)
}
$method = ord(substr($data,2,1)); // Compression method
$flags = ord(substr($data,3,1)); // Flags
if ($flags & 31 != $flags) {
$error = "Reserved bits not allowed.";
return null;
}
// NOTE: $mtime may be negative (PHP integer limitations)
$mtime = unpack("V", substr($data,4,4));
$mtime = $mtime[1];
$xfl = substr($data,8,1);
$os = substr($data,8,1);
$headerlen = 10;
$extralen = 0;
$extra = "";
if ($flags & 4) {
// 2-byte length prefixed EXTRA data in header
if ($len - $headerlen - 2 < 8) {
return false; // invalid
}
$extralen = unpack("v",substr($data,8,2));
$extralen = $extralen[1];
if ($len - $headerlen - 2 - $extralen < 8) {
return false; // invalid
}
$extra = substr($data,10,$extralen);
$headerlen += 2 + $extralen;
}
$filenamelen = 0;
$filename = "";
if ($flags & 8) {
// C-style string
if ($len - $headerlen - 1 < 8) {
return false; // invalid
}
$filenamelen = strpos(substr($data,$headerlen),chr(0));
if ($filenamelen === false || $len - $headerlen - $filenamelen - 1 < 8) {
return false; // invalid
}
$filename = substr($data,$headerlen,$filenamelen);
$headerlen += $filenamelen + 1;
}
$commentlen = 0;
$comment = "";
if ($flags & 16) {
// C-style string COMMENT data in header
if ($len - $headerlen - 1 < 8) {
return false; // invalid
}
$commentlen = strpos(substr($data,$headerlen),chr(0));
if ($commentlen === false || $len - $headerlen - $commentlen - 1 < 8) {
return false; // Invalid header format
}
$comment = substr($data,$headerlen,$commentlen);
$headerlen += $commentlen + 1;
}
$headercrc = "";
if ($flags & 2) {
// 2-bytes (lowest order) of CRC32 on header present
if ($len - $headerlen - 2 < 8) {
return false; // invalid
}
$calccrc = crc32(substr($data,0,$headerlen)) & 0xffff;
$headercrc = unpack("v", substr($data,$headerlen,2));
$headercrc = $headercrc[1];
if ($headercrc != $calccrc) {
$error = "Header checksum failed.";
return false; // Bad header CRC
}
$headerlen += 2;
}
// GZIP FOOTER
$datacrc = unpack("V",substr($data,-8,4));
$datacrc = sprintf('%u',$datacrc[1] & 0xFFFFFFFF);
$isize = unpack("V",substr($data,-4));
$isize = $isize[1];
// decompression:
$bodylen = $len-$headerlen-8;
if ($bodylen < 1) {
// IMPLEMENTATION BUG!
return null;
}
$body = substr($data,$headerlen,$bodylen);
$data = "";
if ($bodylen > 0) {
switch ($method) {
case 8:
// Currently the only supported compression method:
$data = gzinflate($body,$maxlength);
break;
default:
$error = "Unknown compression method.";
return false;
}
} // zero-byte body content is allowed
// Verifiy CRC32
$crc = sprintf("%u",crc32($data));
$crcOK = $crc == $datacrc;
$lenOK = $isize == strlen($data);
if (!$lenOK || !$crcOK) {
$error = ( $lenOK ? '' : 'Length check FAILED. ') . ( $crcOK ? '' : 'Checksum FAILED.');
return false;
}
return $data;
}
?>
Aaron G. 07-Aug-2004 03:29 posted the function gzdecode()
to gzencode comments. I FIXED the BUG: if($flags & 1) to the correct if($flags & 2)
Unfortunately the function gzencode() does NOT append a CRC so I did not notice until I tried to upload a file compressed with gzip itself.
<?php
function gzdecode($data) {
$len = strlen($data);
if ($len < 18 || strcmp(substr($data,0,2),"\x1f\x8b")) {
return null; // Not GZIP format (See RFC 1952)
}
$method = ord(substr($data,2,1)); // Compression method
$flags = ord(substr($data,3,1)); // Flags
if ($flags & 31 != $flags) {
// Reserved bits are set -- NOT ALLOWED by RFC 1952
return null;
}
// NOTE: $mtime may be negative (PHP integer limitations)
$mtime = unpack("V", substr($data,4,4));
$mtime = $mtime[1];
$xfl = substr($data,8,1);
$os = substr($data,8,1);
$headerlen = 10;
$extralen = 0;
$extra = "";
if ($flags & 4) {
// 2-byte length prefixed EXTRA data in header
if ($len - $headerlen - 2 < 8) {
return false; // Invalid format
}
$extralen = unpack("v",substr($data,8,2));
$extralen = $extralen[1];
if ($len - $headerlen - 2 - $extralen < 8) {
return false; // Invalid format
}
$extra = substr($data,10,$extralen);
$headerlen += 2 + $extralen;
}
$filenamelen = 0;
$filename = "";
if ($flags & 8) {
// C-style string file NAME data in header
if ($len - $headerlen - 1 < 8) {
return false; // Invalid format
}
$filenamelen = strpos(substr($data,8+$extralen),chr(0));
if ($filenamelen === false || $len - $headerlen - $filenamelen - 1 < 8) {
return false; // Invalid format
}
$filename = substr($data,$headerlen,$filenamelen);
$headerlen += $filenamelen + 1;
}
$commentlen = 0;
$comment = "";
if ($flags & 16) {
// C-style string COMMENT data in header
if ($len - $headerlen - 1 < 8) {
return false; // Invalid format
}
$commentlen = strpos(substr($data,8+$extralen+$filenamelen),chr(0));
if ($commentlen === false || $len - $headerlen - $commentlen - 1 < 8) {
return false; // Invalid header format
}
$comment = substr($data,$headerlen,$commentlen);
$headerlen += $commentlen + 1;
}
$headercrc = "";
if ($flags & 2) {
// 2-bytes (lowest order) of CRC32 on header present
if ($len - $headerlen - 2 < 8) {
return false; // Invalid format
}
$calccrc = crc32(substr($data,0,$headerlen)) & 0xffff;
$headercrc = unpack("v", substr($data,$headerlen,2));
$headercrc = $headercrc[1];
if ($headercrc != $calccrc) {
return false; // Bad header CRC
}
$headerlen += 2;
}
// GZIP FOOTER - These be negative due to PHP's limitations
$datacrc = unpack("V",substr($data,-8,4));
$datacrc = $datacrc[1];
$isize = unpack("V",substr($data,-4));
$isize = $isize[1];
// Perform the decompression:
$bodylen = $len-$headerlen-8;
if ($bodylen < 1) {
// This should never happen - IMPLEMENTATION BUG!
return null;
}
$body = substr($data,$headerlen,$bodylen);
$data = "";
if ($bodylen > 0) {
switch ($method) {
case 8:
// Currently the only supported compression method:
$data = gzinflate($body);
break;
default:
// Unknown compression method
return false;
}
} else {
// I'm not sure if zero-byte body content is allowed.
// Allow it for now... Do nothing...
}
// Verifiy decompressed size and CRC32:
// NOTE: This may fail with large data sizes depending on how
// PHP's integer limitations affect strlen() since $isize
// may be negative for large sizes.
if ($isize != strlen($data) || crc32($data) != $datacrc) {
// Bad format! Length or CRC doesn't match!
return false;
}
return $data;
}
?>