<?php

/**

 * SimplePie

 *

 * A PHP-Based RSS and Atom Feed Framework.

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

 *

 * Copyright (c) 2004-2022, Ryan Parman, Sam Sneddon, Ryan McCue, and contributors

 * 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

 * @copyright 2004-2016 Ryan Parman, Sam Sneddon, Ryan McCue

 * @author Ryan Parman

 * @author Sam Sneddon

 * @author Ryan McCue

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

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

 */

namespace SimplePie;

/**

 * Decode 'gzip' encoded HTTP data

 *

 * @package SimplePie

 * @subpackage HTTP

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

 */

class Gzdecode

{

    /**

     * Compressed data

     *

     * @access private

     * @var string

     * @see gzdecode::$data

     */

    public $compressed_data;

    /**

     * Size of compressed data

     *

     * @access private

     * @var int

     */

    public $compressed_size;

    /**

     * Minimum size of a valid gzip string

     *

     * @access private

     * @var int

     */

    public $min_compressed_size = 18;

    /**

     * Current position of pointer

     *

     * @access private

     * @var int

     */

    public $position = 0;

    /**

     * Flags (FLG)

     *

     * @access private

     * @var int

     */

    public $flags;

    /**

     * Uncompressed data

     *

     * @access public

     * @see gzdecode::$compressed_data

     * @var string

     */

    public $data;

    /**

     * Modified time

     *

     * @access public

     * @var int

     */

    public $MTIME;

    /**

     * Extra Flags

     *

     * @access public

     * @var int

     */

    public $XFL;

    /**

     * Operating System

     *

     * @access public

     * @var int

     */

    public $OS;

    /**

     * Subfield ID 1

     *

     * @access public

     * @see gzdecode::$extra_field

     * @see gzdecode::$SI2

     * @var string

     */

    public $SI1;

    /**

     * Subfield ID 2

     *

     * @access public

     * @see gzdecode::$extra_field

     * @see gzdecode::$SI1

     * @var string

     */

    public $SI2;

    /**

     * Extra field content

     *

     * @access public

     * @see gzdecode::$SI1

     * @see gzdecode::$SI2

     * @var string

     */

    public $extra_field;

    /**

     * Original filename

     *

     * @access public

     * @var string

     */

    public $filename;

    /**

     * Human readable comment

     *

     * @access public

     * @var string

     */

    public $comment;

    /**

     * Don't allow anything to be set

     *

     * @param string $name

     * @param mixed $value

     */

    public function __set($name, $value)

    {

        throw new Exception("Cannot write property $name");

    }

    /**

     * 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) {

            $len = 0;

            // 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;

            }

            $this->position = $this->compressed_size - 8;

            // 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;

        }

        return false;

    }

}

class_alias('SimplePie\Gzdecode', 'SimplePie_gzdecode');