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gzencode (PHP 4 >= 4.0.4, PHP 5) gzencode -- Create a gzip compressed string Descriptionstring gzencode ( string data [, int level [, int encoding_mode]] )
This function returns a compressed version of the input
data compatible with the output of the
gzip program.
For more information on the GZIP file format, see the document:
GZIP file format specification
version 4.3 (RFC 1952).
Parameters
- data
The data to encode.
- level
The level of compression. Can be given as 0 for no compression up to 9
for maximum compression. If not given, the default compression level will
be the default compression level of the zlib library.
- encoding_mode
The encoding mode. Can be FORCE_GZIP (the default)
or FORCE_DEFLATE.
If you use FORCE_DEFLATE, you get a standard zlib
deflated string (inclusive zlib headers) after the gzip file header but
without the trailing crc32 checksum.
Return Values
The encoded string, or FALSE if an error occurred.
Examples
The resulting data contains the appropriate headers and data
structure to make a standard .gz file, e.g.:
Example 1. Creating a gzip file |
<?php
$data = implode("", file("bigfile.txt"));
$gzdata = gzencode($data, 9);
$fp = fopen("bigfile.txt.gz", "w");
fwrite($fp, $gzdata);
fclose($fp);
?>
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User Contributed Notes
gzencode
StoneCypher ( http://sc.tri-bit.com/ )
25-Feb-2005 02:19
The example in the notes would be more obvious written as:
<?php
file_put_contents( 'output.gz', gzencode( file_get_contents('input.file', 9) ) );
?>
Aaron G.
06-Aug-2004 08:29
<?php
function gzdecode($data) {
$len = strlen($data);
if ($len < 18 || strcmp(substr($data,0,2),"\x1f\x8b")) {
return null; }
$method = ord(substr($data,2,1)); $flags = ord(substr($data,3,1)); if ($flags & 31 != $flags) {
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,8+$extralen),chr(0));
if ($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,8+$extralen+$filenamelen),chr(0));
if ($commentlen === false || $len - $headerlen - $commentlen - 1 < 8) {
return false; }
$comment = substr($data,$headerlen,$commentlen);
$headerlen += $commentlen + 1;
}
$headercrc = "";
if ($flags & 1) {
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) {
return false; }
$headerlen += 2;
}
$datacrc = unpack("V",substr($data,-8,4));
$datacrc = $datacrc[1];
$isize = unpack("V",substr($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);
break;
default:
return false;
}
} else {
}
if ($isize != strlen($data) || crc32($data) != $datacrc) {
return false;
}
return $data;
}
?>
sjab-x at bergenbosgroep dot nl
26-Dec-2002 08:06
If you want a binary proof function use fread instead of implode.
function create_gzip_file($src_file, $dest_file) {
$fd = fopen ($src_file, "r");
$data = fread ($fd, filesize ($src_file));
fclose ($fd);
$gz_data = gzencode($data);
$fp = fopen($dest_file, "w+");
fwrite($fp, $gz_data);
fclose($fp);
}
This works fine for me :)
tychay at alumni dot caltech dot edu
03-Apr-2002 04:53
The 10 byte string in gzencode is the standard gzip header. The first two bytes (1f 8b) define the return as a gzip file, the third byte (08) means that the body is compressed using the "deflate" algorithm. The rest is padding (00)'s.
Technically, I believe one should check if the third byte is hex 08 and if so strip off the first ten bytes and last four bytes and run inflate on it. The last four bytes are file size and checksum bits.
In practice, you can get away with just stripping the first 10 bytes and running inflate on it.
Hope this helps,
terry
henryk at ploetzli dot ch
14-Feb-2002 08:28
Well, I was looking for a gzdecode too and didn't consider the temporary file example above to be very elegant.
However, as is noted in the very first comment: gzencode() only adds a 10 byte header.
I don't quite know what this header is supposed to be used for, but gzinflate() certainly doesn't like it, so I stripped it off:
function my_gzdecode($string) {
$string = substr($string, 10);
return gzinflate($string);
}
That's useful to read HTTP-Connections that were compressed by mod_gzip.
--
Henryk Plötz
Grüße aus Berlin
g dot benoit at free dot fr
12-Feb-2002 07:21
function create_gzip_file($src_file, $dest_file)
{
$data = implode("", file($src_file));
$gz_data = gzencode($data);
$fp = fopen($dest_file, "w+");
fwrite($fp, $gz_data);
fclose($fp);
}
create_gzip_file("text.txt", "test.txt.gz");
mm.. oops? - amendum (yes, tested hehe.)
09-Sep-2001 02:14
function alt_gzdecode($str) {
// seed with microseconds since last "whole" second
mt_srand((float)microtime()*1000000);
$eh="/tmp/php-" . md5(mt_rand(0,mt_getrandmax())) . ".gz";
$fd=fopen($eh,"w");
fwrite($fd,$str);
fclose($fd);
unset($str);
$fd = gzopen ($eh, "r");
while (1==1) {
$s=gzread($fd,10240);
if ("$s" == "") {
break;
}
$str=$str . $s;
}
unlink($eh);
return $str;
}
< supaplex %at% pcbkits %d0t% c0m >
09-Sep-2001 01:48
I was almost discouraged when I didn't find a gzdecode() function! However, fear not, for I'll contribute my work... :)
function alt_gzdecode($str) {
// seed with microseconds since last "whole" second.
mt_srand((float)microtime()*1000000);
$eh="/tmp/php-" . md5(mt_rand(0,mt_getrandmax())) . ".gz";
$fd=fopen($eh,"w");
fwrite($fd,$str);
fclose($fd);
$fd = gzopen ($eh, "r");
$str=gzpassthru($fd);
unlink($eh);
return $str;
}
It's only ugly point is that it does not check to see if the file already exists. You may also have to adjust reference names like $str and $fd if they stomp on your code. (Sorry, but this is all you get atm! ;} ) If your conserned about a race condition, cry for a internal gzdecode() function that actualy functions...
I spent about 3 hours straight debugging this problem. I know the input data was valid, becuase I validated it with MD5() to compare to the md5's I had made of the input data before hand. I'm not sure whats up with gzuncompress or gzinflate, but this works in its place . . .
Enjoy!
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gzdeflate