gztell
Note that gzuncompress() may not decompress some compressed strings and return a Data Error.
The problem could be that the outside compressed string has a CRC32 checksum at the end of the file instead of Adler-32, like PHP expects.
Workaround:
<?php
function gzuncompress_crc32($data) {
$f = tempnam('/tmp', 'gz_fix');
file_put_contents($f, "\x1f\x8b\x08\x00\x00\x00\x00\x00" . $data);
return file_get_contents('compress.zlib://' . $f);
}
?>
gzuncompress
(PHP 4 >= 4.0.1, PHP 5)
gzuncompress — Dekomprimiert einen komprimierten String
Beschreibung
string gzuncompress
( string $data
[, int $length
] )
Diese Funktion dekomprimiert einen komprimierten String.
Parameter-Liste
- data
-
Mit gzcompress() komprimierte Daten
- length
-
Die maximale Länge der dekodierten Daten.
Rückgabewerte
Die ursprünglichen nicht komprimierten Daten oder FALSE bei Fehlern.
Die Funktion gibt einen Fehler zurück wenn die unkomprimierten Daten mehr als 32768 mal so lang sind wie die komprimierte Eingabe oder länger als mit dem optionalen Parameter length angegeben.
Beispiele
Beispiel #1 gzuncompress() Beispiel
<?php
$compressed = gzcompress('Compress me', 9);
$uncompressed = gzuncompress($compressed);
echo $uncompressed;
?>
add a note
User Contributed Notesgzuncompress
heavyccasey at gmail dot com
07-Nov-2007 08:30
07-Nov-2007 08:30
gabriel at bumpt dot n-et
17-Sep-2007 03:08
17-Sep-2007 03:08
To uncompress in PHP a string that has been compressed using MySQL's COMPRESS() function, you need to discard the first four bytes of the binary data:
<?php
/*
* Example:
*
* insert into mytable (myfield, ...) values (COMPRESS('foobar'), ...)
*
* then:
*/
$compressed = //...select myfield from mytable where...
/*
* then:
*/
$uncompressed = gzuncompress(substr($compressed, 4));
?>
Of course, you can use MySQL's UNCOMPRESS() function.
I was just providing an alternate method.
emanuele at fondani dot it
25-Nov-2006 03:21
25-Nov-2006 03:21
Note that the manual states that the input parameter must be a string compressed with gzcompress(), so it is not guaranteed that it will compress ANY zlib compressed string.
I realized this while decompressing some compressed string in a pdf file. The gzuncompress() function produces a data error, but the string can be successfully decompressed with other zlib decompressors.
More info here:
http://bugs.php.net/?id=39616
chappy at citromail dot hu
13-Apr-2006 07:47
13-Apr-2006 07:47
Reading an ID3v2.3+ tag it is versy useful, because these tag's frames might be compressed. Zlib compressed frame layout (ID3v2.3):
Descriptior Size
-------------------
Frameheader:
Frame id: 4 bytes
Frame size (full frame size - frameheader size): 4 bytes
Frame flags: 2 bytes
The 2nd byte's 7th bit must be 1 (e.g.: %1xy00000)
Frame content decrompessed size: 4 bytes
--------------------
Framecontent:
Compressed string described in 'frame size'
<?php
$frame="[read from a mp3 file]";
$frame_id=substr($frame,0,4);
/*....*/
$cs=substr($frame,10,4);
$checksize=$cs[3]*16777216+$cs[2]*65536+$cs[1]*256+$cs[0];
$content=substr($frame,14,$contentsize);
$content=gzuncompress($content);
if(strlen($content)!=$checksize){
echo 'Error whil uncrompessing frame data<br>';
}
echo $content;
?>