gzopen

(PHP 4, PHP 5)

gzopenOpen gz-file

Description

resource gzopen ( string $filename , string $mode [, int $use_include_path = 0 ] )

Opens a gzip (.gz) file for reading or writing.

gzopen() can be used to read a file which is not in gzip format; in this case gzread() will directly read from the file without decompression.

Parameters

filename

The file name.

mode

As in fopen() (rb or wb) but can also include a compression level (wb9) or a strategy: f for filtered data as in wb6f, h for Huffman only compression as in wb1h. (See the description of deflateInit2 in zlib.h for more information about the strategy parameter.)

use_include_path

You can set this optional parameter to 1, if you want to search for the file in the include_path too.

Return Values

Returns a file pointer to the file opened, after that, everything you read from this file descriptor will be transparently decompressed and what you write gets compressed.

If the open fails, the function returns FALSE.

Examples

Example #1 gzopen() Example

<?php
$fp 
gzopen("/tmp/file.gz""r");
?>

See Also

Коментарии

"On the fly" gunzipping actually DOES seem to work - it just appears that only LOCAL streams/files (including php://stdin) can be accessed for some reason.  I THINK (but have not yet tested) that you could similarly gzopen "php://stdout" and pass a stream of gzipped data to the browser (when run from a web page) or console (when run standalone) through there.

I HAVE tested scripts from the command line like:

wget -q -O- ftp://some.host.net/pub/some_gzip_file.gz | php gunzip_stuff.php

where gunzip_stuff.php would be a script that gzopened "php://stdin" and did gzgets from that stream, and it seems to work fine, but that obviously doesn't help someone wanting to grab gzipped streams from remote sites from a web-based script.

Being able to read gzip streams from ftp and http is near the top of my personal wishlist at the moment...
2002-01-02 21:22:08
http://php5.kiev.ua/manual/ru/function.gzopen.html
RE dubious's comment: "Being able to read gzip streams from ftp and http is near the top of my personal wishlist at the moment..."

One way to read a gzip stream over http is to daisychain stream wrappers, e.g.:

<?
$fp 
fopen("compress.zlib://http://some.website.org/example.gz""r");
?>
2004-10-21 15:04:18
http://php5.kiev.ua/manual/ru/function.gzopen.html
Be aware that when opening a remote file on a http server the gzopen will return by default false after 120 seconds waiting to any answer.
2005-01-29 12:36:31
http://php5.kiev.ua/manual/ru/function.gzopen.html
dtorop932 at hotmail dot com's comments, according to my tests, is incorrect. That code wishes to download the entire file before parsing, which is inconvinient. The wget method works though.
2005-06-01 08:28:23
http://php5.kiev.ua/manual/ru/function.gzopen.html
WARNING gzopen and gzread have a major disadvantage. They makes NO checksum and NO length verification of the gzipped data and discard this valuable information. This should be documented here.
2008-04-23 15:15:00
http://php5.kiev.ua/manual/ru/function.gzopen.html
Автор:
This worked unstable for me under high load (50+ files per second):

<?php
    $gz 
gzopen $file'w9' );
   
gzwrite $gz$content );
   
gzclose $gz );
?>

The following works fine:

<?php
    $f 
fopen $file'w' );
   
fwrite $fgzcompress $content) );
   
fclose $f );
?>
2008-09-05 23:06:04
http://php5.kiev.ua/manual/ru/function.gzopen.html
gzopen("php://output","wb") doesn't work on a web server, nor does fopen("compress.zlib://php://output","wb").

Here is a snippet to gzip a file and output it on the fly, without using a temporary file, without reading the file into memory, and without reading the file more than once:

<?php
$fin 
fopen($file"rb");
if (
$fin !== FALSE) {
   
$fout fopen("php://output""wb");
    if (
$fout !== FALSE) {
   
// write gzip header
   
fwrite($fout"\x1F\x8B\x08\x08".pack("V"filemtime($file))."\0\xFF"10);
   
// write the original file name
   
$oname str_replace("\0"""basename($file));
   
fwrite($fout$oname."\0"1+strlen($oname));
   
// add the deflate filter using default compression level
   
$fltr stream_filter_append($fout"zlib.deflate"STREAM_FILTER_WRITE, -1);
   
// set up the CRC32 hashing context
   
$hctx hash_init("crc32b");
   
// turn off the time limit
   
if (!ini_get("safe_mode")) set_time_limit(0);
   
$con TRUE;
   
$fsize 0;
    while ((
$con !== FALSE) && !feof($fin)) {
       
// deflate works best with buffers >32K
       
$con fread($fin64 1024);
        if (
$con !== FALSE) {
       
hash_update($hctx$con);
       
$clen strlen($con);
       
$fsize += $clen;
       
fwrite($fout$con$clen);
        }
    }
   
// remove the deflate filter
   
stream_filter_remove($fltr);
   
// write the CRC32 value
    // hash_final is a string, not an integer
   
$crc hash_final($hctxTRUE);
   
// need to reverse the hash_final string so it's little endian
   
fwrite($fout$crc[3].$crc[2].$crc[1].$crc[0], 4);
   
// write the original uncompressed file size
   
fwrite($foutpack("V"$fsize), 4);
   
fclose($fout);
    }
   
fclose($fin);
}
?>
2011-09-06 17:02:19
http://php5.kiev.ua/manual/ru/function.gzopen.html
An OO-version of David Gero's excellent GZ File format note also on this page:

<?php

// David Gero's example: read a file and output GZ
$gz_to_out = new GZTempFile(basename($file), "php://output");
$fin fopen($file"rb");
while(
$data fread($fin64 1024)) {
   
$gz_to_out->fwrite();
}
close($fin);
$gz_to_out->flushBuffer();

// Example of building your GZ file content on the fly (temp filehandle)
$gz_custom = new GZTempFile();
foreach ( ... ) {
   
//  Some work
   
$str = ...

   
$gz_custom->fwrite($str);
}
//  Store it in a database
$m = new MongoClient();
$gridfs $m->selectDB('test')->getGridFS();
$id $gridfs->storeFile($gz_custom->getReadFilehandle(), array('contentType' => 'application/x-gzip'));

class 
GZTempFile {
    private 
$__fh null;
    public 
$uncompressed_bytes 0;
    public 
$filesize null;
    private 
$gz_filter null;
    private 
$file_hash null;
    private 
$final_read_fh false;
    private 
$__buffer '';
    private 
$__buffer_len 0;

    public function 
__construct($filename 'data'$fh null) {
       
$this->__fh is_null($fh) ? fopen('php://temp','w+') : $fh;
       
fwrite($this->__fh"\x1F\x8B\x08\x08".pack("V"time())."\0\xFF"10); // GZ file header
       
fwrite($this->__fhstr_replace("\0"""basename($filename)) ."\0");  // GZ filename = data, needed???
       
$this->gz_filter stream_filter_append($this->__fh"zlib.deflate"STREAM_FILTER_WRITE, -1);
       
$this->uncompressed_bytes 0;
       
$this->file_hash hash_init("crc32b");
    }

    public function 
fwrite($str,$length null) {
        if ( 
$this->final_read_fh ) { throw new Exception("GZTempFile has already been finalized and closed.  No more writing"); }
       
hash_update($this->file_hash$str);
       
$this->uncompressed_bytes += strlen($str);
       
$this->__buffer_len += strlen($str);
       
$this->__buffer .= $str;
        if ( 
$this->__buffer_len >= 64 1024 ) { $this->flushBuffer(); }
    }
    public function 
flushBuffer() {
        if ( 
$this->__buffer_len == ) { return false; }
       
$return fwrite($this->__fh$this->__buffer);
       
$this->__buffer_len 0;
       
$this->__buffer '';
        return 
$return;
    }

    public function 
getReadFilehandle() {       
        if ( ! 
$this->final_read_fh ) {
           
$this->flushBuffer();
           
stream_filter_remove($this->gz_filter);
           
$crc hash_final($this->file_hashTRUE);            // hash_final is a string, not an integer
           
fwrite($this->__fh$crc[3].$crc[2].$crc[1].$crc[0]); // need to reverse the hash_final string so it's little endian
           
fwrite($this->__fhpack("V"$this->uncompressed_bytes), 4);

           
$this->filesize ftell($this->__fh);
           
rewind($this->__fh);
           
$this->final_read_fh $this->__fh;
        }
        return 
$this->final_read_fh;
    }
}
2015-09-11 05:17:14
http://php5.kiev.ua/manual/ru/function.gzopen.html
There is an active feature request for an xzopen function. The xz program uses the LZMA algorithm for much higher compression ratios than gzip.

Until such time that xzopen might be available, here is my best design for safely reading .xz files which originate remotely and are not trusted.

Below is a CSV log viewer - there is a lot going on here, so I will explain it below:

<?

$PRG_NAME 
basename($_SERVER['PHP_SELF'], '.php');
$PRG_LEN strlen($PRG_NAME);

if(
substr($z $_GET['CSV'], 0$PRG_LEN) == $PRG_NAME)
{
 
header('content-type:application/csv;charset=UTF-8');
 
header('Content-Disposition:attachment;filename="' .
   
$_GET['CSV'] . '.csv"');

 if(
'.xz' == substr($z, -3))
 {
       
$tmpfname tempnam("/tmp""php-log-viewer");
       
$fpx fopen($tmpfname'w');
       
fprintf($fpx"/var/app/log/%s\0"$z);
       
fclose($fpx);

       
$fp popen("xz -cd --files0=" $tmpfname'r');
 }
 else   
$fp fopen('/var/app/log/' $z'r');

 while(
$line fgets($fp))
  echo 
'"' preg_replace('/[~]/''","'rtrim($line)) . "\"\n";

 
fclose($fp); if(is_file($tmpfname)) unlink($tmpfname); exit;
}

?>

The logs are tilde-delimited files (~) in the /var/app/log directory which the code above converts to CSV and injects into Excel. They are regularly compressed by cron, but the latest logs will be uncompressed text files. A separate section of my code (not included here) presents them via opendir()/readdir()/stat().

The file prefix that the viewer will allow the user to see is determined by the name of the script - if I name it FTP-LOG.php, then any file beginning with /var/app/log/FTP-LOG can be read. I am enabling the viewer for different prefixes by making hard links to the script.

Since the log might not (yet) be compressed, I check the extension - if .xz is detected, then the gymnastics begin.

It is not safe to pass form content from remote users to a UNIX shell, and I am trying to avoid this. Fortunately, xz has the --files and --files0 options, and I create a temporary filename, record the file of interest in it, then open an xz process for reading (otherwise, a simple fopen() will suffice). Recording a \0 allows safer processing of files with embedded newlines (which is allowed by POSIX), and is immediately familiar to fans of "find -print0" and "xargs -0".

Unfortunately, neither bzip2 nor lzip have have a --files[0] option. It is quite useful in this case, and appears to improve security.
2019-03-07 20:58:07
http://php5.kiev.ua/manual/ru/function.gzopen.html

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