Zlib 函数
在线手册：中文 英文
PHP手册

gzdecode

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

gzdecode — Decodes a gzip compressed string

说明

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

This function returns a decoded version of the input data.

参数

data

The data to decode, encoded by gzencode().

length

The maximum length of data to decode.

返回值

The decoded string, or FALSE if an error occurred.

参见

Zlib 函数
在线手册：中文 英文
PHP手册
PHP手册 - N: Decodes a gzip compressed string

用户评论:

tomas at slax dot org (05-Nov-2011 12:25)

I don't have any deep knowledge in compression algorithms and formats, so I have no idea if this works the same on all platforms. But by several experiments on my Linux box I found how to get gzdecoded data without temporary files. Here it is:

<?php
function gzdecode($data)
{
   return gzinflate(substr($data,10,-8));
}
?>

That's it. Simply strip header and footer bytes and you get raw deflated data for inflation.

6869hlopcik at inbox dot lv (28-Sep-2011 11:30)

Windows compitable with auto delete temp file.

<?php
function softcoded_gzdecode($data){
    $g=tempnam('./','gz');
    file_put_contents($g,$data);
    ob_start();
    readgzfile($g);
    $d=ob_get_clean();
    unlink($g);
    return $d;
}
?>

webmaster at askapache dot com (02-Jul-2008 10:32)

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 (02-May-2008 03:15)

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-Apr-2008 09:51)

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-Aug-2007 09:43)

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.