<?php 
/**
 * This file is part of workerman.
 *
 * Licensed under The MIT License
 * For full copyright and license information, please see the MIT-LICENSE.txt
 * Redistributions of files must retain the above copyright notice.
 *
 * @author walkor<walkor@workerman.net>
 * @copyright walkor<walkor@workerman.net>
 * @link http://www.workerman.net/
 * @license http://www.opensource.org/licenses/mit-license.php MIT License
 */
namespace Workerman\Protocols;
use \Workerman\Connection\TcpConnection;

/**
 * Frame Protocol.
 */
class Frame
{
    /**
     * Check the integrity of the package.
     * @param string $buffer
     */
    public static function input($buffer ,TcpConnection $connection)
    {
        if(strlen($buffer)<4)
        {
            return 0;
        }
        $unpack_data = unpack('Ntotal_length', $buffer);
        return $unpack_data['total_length'];
    }
    
    /**
     * Encode.
     * @param string $buffer
     * @return string
     */
    public static function decode($buffer)
    {
        return substr($buffer, 4);
    }
    
    /**
     * Decode.
     * @param string $buffer
     * @return string
     */
    public static function encode($buffer)
    {
        $total_length = 4 + strlen($buffer);
        return pack('N',$total_length) . $buffer;
    }
}