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gzdecode

(No version information available, might only be in SVN)

gzdecodeDecodes a gzip compressed string

Beschreibung

string gzdecode ( string $data [, int $length ] )

This function returns a decoded version of the input data.

Parameter-Liste

data

The data to decode, encoded by gzencode().

length

The maximum length of data to decode.

Rückgabewerte

The decoded string, or FALSE if an error occurred.

Siehe auch


4 BenutzerBeiträge:
- Beiträge aktualisieren...
webmaster at askapache dot com
2.07.2008 11:32
I have used this simple function to gzdecode gzipped files downloaded from the web.

<?php

function gzdecode($data){
 
$g=tempnam('/tmp','ff');
  @
file_put_contents($g,$data);
 
ob_start();
 
readgzfile($g);
 
$d=ob_get_clean();
  return
$d;
}

?>
katzlbtjunk at hotmail dot com
2.05.2008 16:15
3 more bugs found and fixed:
1. failed to work when the gz contained a filename - FIXED
2. failed to work on 64-bit architecture (checksum) - FIXED
3. failed to work when the gz contained a comment - cannot verify.
Returns some errors (not all!) and filename.
<?php function gzdecode($data,&$filename='',&$error='',$maxlength=null)
{
   
$len = strlen($data);
    if (
$len < 18 || strcmp(substr($data,0,2),"\x1f\x8b")) {
       
$error = "Not in GZIP format.";
        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) {
       
$error = "Reserved bits not allowed.";
        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
       
}
       
$extralen = unpack("v",substr($data,8,2));
       
$extralen = $extralen[1];
        if (
$len - $headerlen - 2 - $extralen < 8) {
            return
false// invalid
       
}
       
$extra = substr($data,10,$extralen);
       
$headerlen += 2 + $extralen;
    }
   
$filenamelen = 0;
   
$filename = "";
    if (
$flags & 8) {
       
// C-style string
       
if ($len - $headerlen - 1 < 8) {
            return
false; // invalid
       
}
       
$filenamelen = strpos(substr($data,$headerlen),chr(0));
        if (
$filenamelen === false || $len - $headerlen - $filenamelen - 1 < 8) {
            return
false; // invalid
       
}
       
$filename = substr($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
       
}
       
$commentlen = strpos(substr($data,$headerlen),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 & 2) {
       
// 2-bytes (lowest order) of CRC32 on header present
       
if ($len - $headerlen - 2 < 8) {
            return
false;    // invalid
       
}
       
$calccrc = crc32(substr($data,0,$headerlen)) & 0xffff;
       
$headercrc = unpack("v", substr($data,$headerlen,2));
       
$headercrc = $headercrc[1];
        if (
$headercrc != $calccrc) {
           
$error = "Header checksum failed.";
            return
false;    // Bad header CRC
       
}
       
$headerlen += 2;
    }
   
// GZIP FOOTER
   
$datacrc = unpack("V",substr($data,-8,4));
   
$datacrc = sprintf('%u',$datacrc[1] & 0xFFFFFFFF);
   
$isize = unpack("V",substr($data,-4));
   
$isize = $isize[1];
   
// decompression:
   
$bodylen = $len-$headerlen-8;
    if (
$bodylen < 1) {
       
// 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,$maxlength);
            break;
        default:
           
$error = "Unknown compression method.";
            return
false;
        }
    } 
// zero-byte body content is allowed
    // Verifiy CRC32
   
$crc   = sprintf("%u",crc32($data));
   
$crcOK = $crc == $datacrc;
   
$lenOK = $isize == strlen($data);
    if (!
$lenOK || !$crcOK) {
       
$error = ( $lenOK ? '' : 'Length check FAILED. ') . ( $crcOK ? '' : 'Checksum FAILED.');
        return
false;
    }
    return
$data;
}
?>
katzlbtjunk at hotmail dot com
30.04.2008 10:51
Aaron G. 07-Aug-2004 03:29 posted the function gzdecode()
to gzencode comments. I FIXED the BUG: if($flags & 1) to the correct if($flags & 2)

Unfortunately the function gzencode() does NOT append a CRC so I did not notice until I tried to upload a file compressed with gzip itself.

<?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 & 2) {
   
// 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;
}

?>
TheSeoDude
29.08.2007 10:43
This function is not found in any of the PHP distribution I use and used so had to figure out a replacement in order to extract and process my server's raw logs automagically.

Check it here http://www.tellinya.com/art2/83/gzdecode . Just a function to extract gzencoded data and hope it helps any1.



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