gzdeflate
Had some trouble finding the correct way to send a Content-Length header with HTTP compression.
The pitch is to use gzencode (not gzdeflaten not gzcompress).
<?php
// disable ZLIB ouput compression
ini_set('zlib.output_compression','Off');
// compress data
$gzipoutput = gzencode($output,6);
// various headers, those with # are mandatory
header('Content-Type: application/x-download');
header('Content-Encoding: gzip'); #
header('Content-Length: '.strlen($gzipoutput)); #
header('Content-Disposition: attachment; filename="myfile.name"');
header('Cache-Control: no-cache, no-store, max-age=0, must-revalidate');
header('Pragma: no-cache');
// output data
echo $gzipoutput;
?>
gzencode
(PHP 4 >= 4.0.4, PHP 5)
gzencode — ساخت رشته فشرده gzip
Description
string gzencode
( string $data
[, int $level = -1
[, int $encoding_mode = FORCE_GZIP
]] )
این تابع نسخه فشرده ورودی data منطبق بر برنامه gzip را باز میگرداند.
برای اطلاعات بیشتر قالب فایل GZIP مستندات زیر را ببینید: » مشخصات قالب فایل GZIPنسخه 4.3 (RFC 1952).
Parameters
- data
-
داده برای کدگذاری.
- level
-
سطح فشردهسازی. میتواند 0 برای عدم فشردهسازی تا 9 برای حداکثر فشردهسازی باشد. اگر داده نشود سطح فشردهسازی پیشفرض همان سطح فشردهسازی پیشفرض کتابخانه zlib است.
- encoding_mode
-
حالت کدگذاری. میتواند FORCE_GZIP (پیشفرض) یا FORCE_DEFLATE باشد.
اگر از FORCE_DEFLATE استفاده کنید رشته کاهش یافته استاندارد zlib (شامل سرایندهای zlib) پس از سرایند فایل gzip دریافت میکنید که بدون crc32 checksum است.
Return Values
رشته کدگذاری شده یا FALSE در صورت خطا.
Changelog
| Version | Description |
|---|---|
| 4.2.0 | پارامتر encoding_mode اضافه شد |
Examples
داده حاصل شامل سرایندهای مناسب و ساختار داده استاندارد فایل .gz file است به عنوان مثال:
Example #1 ساخت فایل gzip
<?php
$data = implode("", file("bigfile.txt"));
$gzdata = gzencode($data, 9);
$fp = fopen("bigfile.txt.gz", "w");
fwrite($fp, $gzdata);
fclose($fp);
?>
See Also
- gzdecode() - کدگشایی رشته فشرده شده gzip
- gzdeflate() - کاهش رشته
- gzinflate() - کاهش دادن string
- gzuncompress() - غیرفشردهسازی رشته فشرده شده
- gzcompress() - فشرده کردن رشته
add a note
User Contributed Notes
gzencode - [11 notes]
geompse at gmail dot com ¶
1 year ago
Sam Dowling ¶
1 year ago
this is a benchmark test of gzencode (.txt file)
----------------------------------------------
original file size = 3.29 MB (3,459,978 bytes)
compress lvl 1 = 1.09 MB (1,144,006 bytes)
compress lvl 2 = 1.06 MB (1,119,518 bytes)
compress lvl 3 = 1.03 MB (1,085,567 bytes)
compress lvl 4 = 953 KB (976,538 bytes)
compress lvl 5 = 909 KB (931,486 bytes)
compress lvl 6 = 910 KB (932,516 bytes)
compress lvl 7 = 910 KB (932,608 bytes)
compress lvl 8 = 910 KB (932,646 bytes)
compress lvl 9 = 910 KB (932,652 bytes)
----------------------------------------------
getmequick at dot com ¶
4 years ago
NOTE:
doing like this and so on
<?php
file_put_contents('output.gz', gzencode( file_get_contents('input.file'),9));
?>
(complete file reading)
may cause memory overflow (Fatal error: Allowed memory size of ..), so it's better to read by parts/bytes.
katzlbtjunk at hotmail dot com ¶
5 years ago
Aaron G. 07-Aug-2004 03:29 posted the excellent function gzdecode() (SEE BELOW)
BUGFIX: Change: if($flags & 1) to ... if($flags & 2)
Unfortunately the function gzencode() does NOT append a CRC! So the previous version worked with output of gzencode but not with output of the gzip program itself.
gazj at nukemodified dot com ¶
5 years ago
here is my clean up of supaplex %at% pcbkits %d0t% c0m
submission above.
function alt_gzdecode($gzdatadecode) {
// seed with microseconds since last "whole" second.
mt_srand((float)microtime()*1000000);
$eh="/tmp/php-" . md5(mt_rand(0,mt_getrandmax())) . ".gz";
if(file_exists($eh)){
$gzf=fopen($eh,"w");
fwrite($gzf,$gzdatadecode);
fclose($gzf);
$gzf = gzopen ($eh, "r");
$gzdatadecode=gzpassthru($gzf);
unlink($eh);
return $gzdatadecode;
}else{
return 'File '.$eh.' was not found.';
}
}
cbrunon at free dot fr ¶
6 years ago
Correct is:
<?php
file_put_contents('output.gz', gzencode( file_get_contents('input.file'),9));
?>
Aaron G. ¶
8 years ago
<?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 & 1) {
// 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 $data;
}
?>
tychay at alumni dot caltech dot edu ¶
11 years ago
The 10 byte string in gzencode is the standard gzip header. The first two bytes (1f 8b) define the return as a gzip file, the third byte (08) means that the body is compressed using the "deflate" algorithm. The rest is padding (00)'s.
Technically, I believe one should check if the third byte is hex 08 and if so strip off the first ten bytes and last four bytes and run inflate on it. The last four bytes are file size and checksum bits.
In practice, you can get away with just stripping the first 10 bytes and running inflate on it.
Hope this helps,
terry
henryk at ploetzli dot ch ¶
11 years ago
Well, I was looking for a gzdecode too and didn't consider the temporary file example above to be very elegant.
However, as is noted in the very first comment: gzencode() only adds a 10 byte header.
I don't quite know what this header is supposed to be used for, but gzinflate() certainly doesn't like it, so I stripped it off:
function my_gzdecode($string) {
$string = substr($string, 10);
return gzinflate($string);
}
That's useful to read HTTP-Connections that were compressed by mod_gzip.
--
Henryk Pltz
Gre aus Berlin
mm.. oops? - amendum (yes, tested hehe.) ¶
11 years ago
function alt_gzdecode($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 $str;
}
< supaplex %at% pcbkits %d0t% c0m > ¶
11 years ago
I was almost discouraged when I didn't find a gzdecode() function! However, fear not, for I'll contribute my work... :)
function alt_gzdecode($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!