gzinflate

(PHP 4 >= 4.0.4, PHP 5, PHP 7, PHP 8)

gzinflate — Descomprime una cadena comprimida

Descripción

gzinflate(string $data, int $max_length = 0): string|false

Esta función descomprime una cadena comprimida.

Parámetros

data: Los datos comprimidos con gzdeflate().
max_length: La longitud máxima de los datos descodificados.

Valores devueltos

Los datos originales descomprimidos o false en caso de error.

La función retornará un error si los datos descomprimidos son más de 32768 veces la longitud de la data de entrada o, a menos que max_length sea 0, mayores que el parámetro opcional max_length.

Ejemplos

Ejemplo #1 Ejemplo de gzinflate()

<?php
$compressed   = gzdeflate('Compress me', 9);
$uncompressed = gzinflate($compressed);
echo $uncompressed;
?>

Ver también

gzdeflate() - Comprime una cadena
gzcompress() - Comprime una cadena
gzuncompress() - Descomprime una cadena comprimida
gzencode() - Crea una cadena comprimida con gzip

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User Contributed Notes 10 notes

down

anonymous at dekho-ji dot com ¶

11 years ago

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.

down

felix dot klee at inka dot de ¶

11 years ago

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

?>

down

vitall at ua dot fm ¶

15 years ago

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!

down

Steven Lustig ¶

14 years ago

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));

?>

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boris at gamate dot com ¶

21 years ago

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)); ?>

down

patatraboum at free dot fr ¶

17 years ago

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;

}

?>

down

spikeles_ at hotmail dot com ¶

18 years ago

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)); ?>

down

niblett at gmail dot com ¶

12 years ago

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));
}
?>

down

akniep at rayo dot info ¶

11 years ago

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!

down

-4

John ¶

16 years ago

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)); ?>

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