gzinflate

anonymous at dekho-ji dot com (2013-05-16 11:34:46)

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.

felix dot klee at inka dot de (2013-02-27 22:38:49)

The code below illustrates usage of the second parameter, in particular to protect against fatal out-of-memory errors. It outputs:

1000000
1000000
error

Tested with PHP 5.3 on 32bit Linux.

<?php

function tryToGzinflate($deflatedData, $maxLen = 0) {
  $data = gzinflate($deflatedData, $maxLen);
  if ($data === false)
    echo 'error<br>';
  else
    echo strlen($data).'<br>';
}

// random data:
$data = '';
for ($i = 0; $i < 1000000; $i++)
  $data .= chr(mt_rand(97, 122)); // a-z

$deflatedData = gzdeflate($data);

ini_set('memory_limit', '5M'); // plenty of memory
tryToGzinflate($deflatedData);
tryToGzinflate($deflatedData, strlen($data));

ini_set('memory_limit', '100'); // little memory
tryToGzinflate($deflatedData, 100);
tryToGzinflate($deflatedData); // causes fatal out-of-memory error
?>

akniep at rayo dot info (2012-12-11 15:11:39)

Take care when using the optional second parameter $length!
In our tests -at least in certain situations- we were unable to determine the actual use of this parameter, plus, it lead to the script either being unable to inflate compressed data or crash due to memory-problems.

Example:
When trying to inflate the compressed data from a website, we were literally unable to find a value (other than 0) for $length in order to make gzinflate work... while without the second parameter (or setting it to 0) gzinflate worked like a charm:

<?php
// -----------------------------------------------------------------------
// Test 1 works without problems. Memory peak usage: Before inflating: 24.787 kB; after: 24.844 kB.
gzinflate( substr($deflated_body, 10) );

// -----------------------------------------------------------------------
// ALL three of the following tests failed with a warning. Memory peak usage: Before inflating: 24.787 kB; after: 298.262 kB.
gzinflate( substr($deflated_body, 10),       200 * strlen($deflated_body) );
gzinflate( substr($deflated_body, 10),     32768 * strlen($deflated_body) );
gzinflate( substr($deflated_body, 10),     11000 );
gzinflate( substr($deflated_body, 10), 280000000 );    // the PHP memory limit was set to 300MB  (memory_limit=300M)
=>
Warning:  gzinflate() [function.gzinflate]: insufficient memory in [...]

// -----------------------------------------------------------------------
// The last test failed with a fatal error. Memory peak usage: Before inflating: 24.787 kB; after: ? (> 300M).
gzinflate( substr($deflated_body, 10), 300000000 );    // the PHP memory limit was set to 300MB  (memory_limit=300M)
=>
Fatal error:  Allowed memory size of 314572800 bytes exhausted (tried to allocate 300000000 bytes) in 
?>

In short: We were unable to determine the actual use of the second parameter in certain situations.
Be careful with using the second parameter $length!

niblett at gmail dot com (2012-06-07 14:08:11)

alternative, with detection for optional filename header
<?php
function gzdecode($data) {

        // check if filename field is set in FLG, is 4th byte
        $hex = bin2hex($data);

        $flg = (int)hexdec(substr($hex, 6, 2));

        // remove headers
        $hex = substr($hex, 20);

        $ret = '';
        if (  ($flg & 0x8) == 8 ){
                print "ello";
                for ( $i = 0; $i < strlen($hex); $i += 2 ){
                        $value = substr($hex, $i, 2);
                        if ( $value == '00' ){
                                $ret = substr($hex, ($i+2));
                                break;
                        }
                }
        }
        return gzinflate(pack('H*', $ret));
}
?>

Steven Lustig (2010-11-05 09:44:20)

You can use this to uncompress a string from Linux command line gzip by stripping the first 10 bytes:

<?php
$inflatedOutput = gzinflate(substr($output, 10, -8));
?>

vitall at ua dot fm (2009-09-09 17:10:19)

The correct function for gzip and chunked data particularly when you get "Content-Encoding: gzip" and "Transfer-Encoding: chunked" headers:

<?php
function decode_gzip($h,$d,$rn="\r\n"){
if (isset($h['Transfer-Encoding'])){
 $lrn = strlen($rn);
 $str = '';
 $ofs=0;
 do{
    $p = strpos($d,$rn,$ofs);
    $len = hexdec(substr($d,$ofs,$p-$ofs));
    $str .= substr($d,$p+$lrn,$len);
     $ofs = $p+$lrn*2+$len;
 }while ($d[$ofs]!=='0');
 $d=$str;
}
if (isset($h['Content-Encoding'])) $d = gzinflate(substr($d,10));
return $d;
}
?>

Enjoy!

John (2008-06-12 22:22:38)

And when retrieving mod_deflate gzip'ed content and using gzinflate() to decode the data, be sure to strip the first 11 chars from the retrieved content.

<?php $dec = gzinflate(substr($enc,11)); ?>

patatraboum at free dot fr (2007-08-24 10:57:03)

Some gz string strip header and return inflated
It actualy processes some first member of the gz
See rfc1952 at http://www.faqs.org/rfcs/rfc1952.html for more details and improvment as gzdecode

<?php
function gzBody($gzData){
    if(substr($gzData,0,3)=="\x1f\x8b\x08"){
        $i=10;
        $flg=ord(substr($gzData,3,1));
        if($flg>0){
            if($flg&4){
                list($xlen)=unpack('v',substr($gzData,$i,2));
                $i=$i+2+$xlen;
            }
            if($flg&8) $i=strpos($gzData,"\0",$i)+1;
            if($flg&16) $i=strpos($gzData,"\0",$i)+1;
            if($flg&2) $i=$i+2;
        }
        return gzinflate(substr($gzData,$i,-8));
    }
    else return false;
}
?>

spikeles_ at hotmail dot com (2006-11-01 20:12:26)

This can be used to inflate streams compressed by the Java class java.util.zip.Deflater but you must strip the first 2 bytes off it. ( much like the above comment )

<?php $result = gzinflate(substr($compressedData, 2)); ?>

boris at gamate dot com (2003-07-08 05:49:19)

When retrieving mod_gzip'ed content and using gzinflate() to decode the data, be sure to strip the first 10 chars from the retrieved content.

<?php $dec = gzinflate(substr($enc,10)); ?>