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/**
 * 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 &quot;AS IS&quot; 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\Net;

/**
 * Class to validate and to work with IPv6 addresses.
 *
 * @package SimplePie
 * @subpackage HTTP
 * @copyright 2003-2005 The PHP Group
 * @license http://www.opensource.org/licenses/bsd-license.php
 * @link http://pear.php.net/package/Net_IPv6
 * @author Alexander Merz &lt;alexander.merz@web.de&gt;
 * @author elfrink at introweb dot nl
 * @author Josh Peck &lt;jmp at joshpeck dot org&gt;
 * @author Sam Sneddon &lt;geoffers@gmail.com&gt;
 */
class IPv6
{
    /**
     * Uncompresses an IPv6 address
     *
     * RFC 4291 allows you to compress concecutive zero pieces in an address to
     * '::'. This method expects a valid IPv6 address and expands the '::' to
     * the required number of zero pieces.
     *
     * Example:  FF01::101   -&gt;  FF01:0:0:0:0:0:0:101
     *           ::1         -&gt;  0:0:0:0:0:0:0:1
     *
     * @author Alexander Merz &lt;alexander.merz@web.de&gt;
     * @author elfrink at introweb dot nl
     * @author Josh Peck &lt;jmp at joshpeck dot org&gt;
     * @copyright 2003-2005 The PHP Group
     * @license http://www.opensource.org/licenses/bsd-license.php
     * @param string $ip An IPv6 address
     * @return string The uncompressed IPv6 address
     */
    public static function uncompress($ip)
    {
        $c1 = -1;
        $c2 = -1;
        if (substr_count($ip, '::') === 1) {
            [$ip1, $ip2] = explode('::', $ip);
            if ($ip1 === '') {
                $c1 = -1;
            } else {
                $c1 = substr_count($ip1, ':');
            }
            if ($ip2 === '') {
                $c2 = -1;
            } else {
                $c2 = substr_count($ip2, ':');
            }
            if (strpos($ip2, '.') !== false) {
                $c2++;
            }
            // ::
            if ($c1 === -1 &amp;&amp; $c2 === -1) {
                $ip = '0:0:0:0:0:0:0:0';
            }
            // ::xxx
            elseif ($c1 === -1) {
                $fill = str_repeat('0:', 7 - $c2);
                $ip = str_replace('::', $fill, $ip);
            }
            // xxx::
            elseif ($c2 === -1) {
                $fill = str_repeat(':0', 7 - $c1);
                $ip = str_replace('::', $fill, $ip);
            }
            // xxx::xxx
            else {
                $fill = ':' . str_repeat('0:', 6 - $c2 - $c1);
                $ip = str_replace('::', $fill, $ip);
            }
        }
        return $ip;
    }

    /**
     * Compresses an IPv6 address
     *
     * RFC 4291 allows you to compress concecutive zero pieces in an address to
     * '::'. This method expects a valid IPv6 address and compresses consecutive
     * zero pieces to '::'.
     *
     * Example:  FF01:0:0:0:0:0:0:101   -&gt;  FF01::101
     *           0:0:0:0:0:0:0:1        -&gt;  ::1
     *
     * @see uncompress()
     * @param string $ip An IPv6 address
     * @return string The compressed IPv6 address
     */
    public static function compress($ip)
    {
        // Prepare the IP to be compressed
        $ip = self::uncompress($ip);
        $ip_parts = self::split_v6_v4($ip);

        // Replace all leading zeros
        $ip_parts[0] = preg_replace('/(^|:)0+([0-9])/', '\1\2', $ip_parts[0]);

        // Find bunches of zeros
        if (preg_match_all('/(?:^|:)(?:0(?::|$))+/', $ip_parts[0], $matches, PREG_OFFSET_CAPTURE)) {
            $max = 0;
            $pos = null;
            foreach ($matches[0] as $match) {
                if (strlen($match[0]) &gt; $max) {
                    $max = strlen($match[0]);
                    $pos = $match[1];
                }
            }

            $ip_parts[0] = substr_replace($ip_parts[0], '::', $pos, $max);
        }

        if ($ip_parts[1] !== '') {
            return implode(':', $ip_parts);
        }

        return $ip_parts[0];
    }

    /**
     * Splits an IPv6 address into the IPv6 and IPv4 representation parts
     *
     * RFC 4291 allows you to represent the last two parts of an IPv6 address
     * using the standard IPv4 representation
     *
     * Example:  0:0:0:0:0:0:13.1.68.3
     *           0:0:0:0:0:FFFF:129.144.52.38
     *
     * @param string $ip An IPv6 address
     * @return array [0] contains the IPv6 represented part, and [1] the IPv4 represented part
     */
    private static function split_v6_v4($ip)
    {
        if (strpos($ip, '.') !== false) {
            $pos = strrpos($ip, ':');
            $ipv6_part = substr($ip, 0, $pos);
            $ipv4_part = substr($ip, $pos + 1);
            return [$ipv6_part, $ipv4_part];
        }

        return [$ip, ''];
    }

    /**
     * Checks an IPv6 address
     *
     * Checks if the given IP is a valid IPv6 address
     *
     * @param string $ip An IPv6 address
     * @return bool true if $ip is a valid IPv6 address
     */
    public static function check_ipv6($ip)
    {
        $ip = self::uncompress($ip);
        [$ipv6, $ipv4] = self::split_v6_v4($ip);
        $ipv6 = explode(':', $ipv6);
        $ipv4 = explode('.', $ipv4);
        if (count($ipv6) === 8 &amp;&amp; count($ipv4) === 1 || count($ipv6) === 6 &amp;&amp; count($ipv4) === 4) {
            foreach ($ipv6 as $ipv6_part) {
                // The section can't be empty
                if ($ipv6_part === '') {
                    return false;
                }

                // Nor can it be over four characters
                if (strlen($ipv6_part) &gt; 4) {
                    return false;
                }

                // Remove leading zeros (this is safe because of the above)
                $ipv6_part = ltrim($ipv6_part, '0');
                if ($ipv6_part === '') {
                    $ipv6_part = '0';
                }

                // Check the value is valid
                $value = hexdec($ipv6_part);
                if (dechex($value) !== strtolower($ipv6_part) || $value &lt; 0 || $value &gt; 0xFFFF) {
                    return false;
                }
            }
            if (count($ipv4) === 4) {
                foreach ($ipv4 as $ipv4_part) {
                    $value = (int) $ipv4_part;
                    if ((string) $value !== $ipv4_part || $value &lt; 0 || $value &gt; 0xFF) {
                        return false;
                    }
                }
            }
            return true;
        }

        return false;
    }

    /**
     * Checks if the given IP is a valid IPv6 address
     *
     * @codeCoverageIgnore
     * @deprecated Use {@see IPv6::check_ipv6()} instead
     * @see check_ipv6
     * @param string $ip An IPv6 address
     * @return bool true if $ip is a valid IPv6 address
     */
    public static function checkIPv6($ip)
    {
        return self::check_ipv6($ip);
    }
}

class_alias('SimplePie\Net\IPv6', 'SimplePie_Net_IPv6');
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