<?php

/**

 * SimplePie

 *

 * A PHP-Based RSS and Atom Feed Framework.

 * Takes the hard work out of managing a complete RSS/Atom solution.

 *

 * All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or without modification, are

 * permitted provided that the following conditions are met:

 *

 * 	* Redistributions of source code must retain the above copyright notice, this list of

 * 	  conditions and the following disclaimer.

 *

 * 	* Redistributions in binary form must reproduce the above copyright notice, this list

 * 	  of conditions and the following disclaimer in the documentation and/or other materials

 * 	  provided with the distribution.

 *

 * 	* Neither the name of the SimplePie Team nor the names of its contributors may be used

 * 	  to endorse or promote products derived from this software without specific prior

 * 	  written permission.

 *

 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS

 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY

 * AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS

 * AND CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR

 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR

 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY

 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR

 * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE

 * POSSIBILITY OF SUCH DAMAGE.

 *

 * @package SimplePie

 * @author Ryan Parman

 * @author Ryan McCue

 * @link http://simplepie.org/ SimplePie

 * @license http://www.opensource.org/licenses/bsd-license.php BSD License

 */

/**

 * Decode 'gzip' encoded HTTP data

 *

 * @package SimplePie

 * @subpackage HTTP

 * @link http://www.gzip.org/format.txt

 */

class SimplePie_gzdecode

{

	/**

	 * Compressed data

	 *

	 * @access private

	 * @var string

	 * @see gzdecode::$data

	 */

	var $compressed_data;

	/**

	 * Size of compressed data

	 *

	 * @access private

	 * @var int

	 */

	var $compressed_size;

	/**

	 * Minimum size of a valid gzip string

	 *

	 * @access private

	 * @var int

	 */

	var $min_compressed_size = 18;

	/**

	 * Current position of pointer

	 *

	 * @access private

	 * @var int

	 */

	var $position = 0;

	/**

	 * Flags (FLG)

	 *

	 * @access private

	 * @var int

	 */

	var $flags;

	/**

	 * Uncompressed data

	 *

	 * @access public

	 * @see gzdecode::$compressed_data

	 * @var string

	 */

	var $data;

	/**

	 * Modified time

	 *

	 * @access public

	 * @var int

	 */

	var $MTIME;

	/**

	 * Extra Flags

	 *

	 * @access public

	 * @var int

	 */

	var $XFL;

	/**

	 * Operating System

	 *

	 * @access public

	 * @var int

	 */

	var $OS;

	/**

	 * Subfield ID 1

	 *

	 * @access public

	 * @see gzdecode::$extra_field

	 * @see gzdecode::$SI2

	 * @var string

	 */

	var $SI1;

	/**

	 * Subfield ID 2

	 *

	 * @access public

	 * @see gzdecode::$extra_field

	 * @see gzdecode::$SI1

	 * @var string

	 */

	var $SI2;

	/**

	 * Extra field content

	 *

	 * @access public

	 * @see gzdecode::$SI1

	 * @see gzdecode::$SI2

	 * @var string

	 */

	var $extra_field;

	/**

	 * Original filename

	 *

	 * @access public

	 * @var string

	 */

	var $filename;

	/**

	 * Human readable comment

	 *

	 * @access public

	 * @var string

	 */

	var $comment;

	/**

	 * Don't allow anything to be set

	 *

	 * @param string $name

	 * @param mixed $value

	 */

	public function __set($name, $value)

	{

		trigger_error("Cannot write property $name", E_USER_ERROR);

	}

	/**

	 * Set the compressed string and related properties

	 *

	 * @param string $data

	 */

	public function __construct($data)

	{

		$this->compressed_data = $data;

		$this->compressed_size = strlen($data);

	}

	/**

	 * Decode the GZIP stream

	 *

	 * @return bool Successfulness

	 */

	public function parse()

	{

		if ($this->compressed_size >= $this->min_compressed_size)

		{

			// Check ID1, ID2, and CM

			if (substr($this->compressed_data, 0, 3) !== "\x1F\x8B\x08")

			{

				return false;

			}

			// Get the FLG (FLaGs)

			$this->flags = ord($this->compressed_data[3]);

			// FLG bits above (1 << 4) are reserved

			if ($this->flags > 0x1F)

			{

				return false;

			}

			// Advance the pointer after the above

			$this->position += 4;

			// MTIME

			$mtime = substr($this->compressed_data, $this->position, 4);

			// Reverse the string if we're on a big-endian arch because l is the only signed long and is machine endianness

			if (current(unpack('S', "\x00\x01")) === 1)

			{

				$mtime = strrev($mtime);

			}

			$this->MTIME = current(unpack('l', $mtime));

			$this->position += 4;

			// Get the XFL (eXtra FLags)

			$this->XFL = ord($this->compressed_data[$this->position++]);

			// Get the OS (Operating System)

			$this->OS = ord($this->compressed_data[$this->position++]);

			// Parse the FEXTRA

			if ($this->flags & 4)

			{

				// Read subfield IDs

				$this->SI1 = $this->compressed_data[$this->position++];

				$this->SI2 = $this->compressed_data[$this->position++];

				// SI2 set to zero is reserved for future use

				if ($this->SI2 === "\x00")

				{

					return false;

				}

				// Get the length of the extra field

				$len = current(unpack('v', substr($this->compressed_data, $this->position, 2)));

				$this->position += 2;

				// Check the length of the string is still valid

				$this->min_compressed_size += $len + 4;

				if ($this->compressed_size >= $this->min_compressed_size)

				{

					// Set the extra field to the given data

					$this->extra_field = substr($this->compressed_data, $this->position, $len);

					$this->position += $len;

				}

				else

				{

					return false;

				}

			}

			// Parse the FNAME

			if ($this->flags & 8)

			{

				// Get the length of the filename

				$len = strcspn($this->compressed_data, "\x00", $this->position);

				// Check the length of the string is still valid

				$this->min_compressed_size += $len + 1;

				if ($this->compressed_size >= $this->min_compressed_size)

				{

					// Set the original filename to the given string

					$this->filename = substr($this->compressed_data, $this->position, $len);

					$this->position += $len + 1;

				}

				else

				{

					return false;

				}

			}

			// Parse the FCOMMENT

			if ($this->flags & 16)

			{

				// Get the length of the comment

				$len = strcspn($this->compressed_data, "\x00", $this->position);

				// Check the length of the string is still valid

				$this->min_compressed_size += $len + 1;

				if ($this->compressed_size >= $this->min_compressed_size)

				{

					// Set the original comment to the given string

					$this->comment = substr($this->compressed_data, $this->position, $len);

					$this->position += $len + 1;

				}

				else

				{

					return false;

				}

			}

			// Parse the FHCRC

			if ($this->flags & 2)

			{

				// Check the length of the string is still valid

				$this->min_compressed_size += $len + 2;

				if ($this->compressed_size >= $this->min_compressed_size)

				{

					// Read the CRC

					$crc = current(unpack('v', substr($this->compressed_data, $this->position, 2)));

					// Check the CRC matches

					if ((crc32(substr($this->compressed_data, 0, $this->position)) & 0xFFFF) === $crc)

					{

						$this->position += 2;

					}

					else

					{

						return false;

					}

				}

				else

				{

					return false;

				}

			}

			// Decompress the actual data

			if (($this->data = gzinflate(substr($this->compressed_data, $this->position, -8))) === false)

			{

				return false;

			}

			// Check CRC of data

			$crc = current(unpack('V', substr($this->compressed_data, $this->position, 4)));

			$this->position += 4;

			/*if (extension_loaded('hash') && sprintf('%u', current(unpack('V', hash('crc32b', $this->data)))) !== sprintf('%u', $crc))

			{

				return false;

			}*/

			// Check ISIZE of data

			$isize = current(unpack('V', substr($this->compressed_data, $this->position, 4)));

			$this->position += 4;

			if (sprintf('%u', strlen($this->data) & 0xFFFFFFFF) !== sprintf('%u', $isize))

			{

				return false;

			}

			// Wow, against all odds, we've actually got a valid gzip string

			return true;

		}

	}

}