/*
* description:  "Provides methodes to encode and decode integers with fragments flags."
* date:		"$Date: 2009-05-15 15:41:52 -0700 (Fri, 15 May 2009) $"
* revision:	"$Revision: 78721 $"
* copyright:	"Copyright (c) 1985-2007, Eiffel Software."
* license:	"GPL version 2 see http://www.eiffel.com/licensing/gpl.txt)"
* licensing_options:	"Commercial license is available at http://www.eiffel.com/licensing"
* copying: ""
* source: 	"[
* 			Eiffel Software
* 			5949 Hollister Ave #B, Goleta, CA 93117
* 			Telephone 805-685-1006, Fax 805-685-6869
* 			Website http://www.eiffel.com
* 			Customer support http://support.eiffel.com
* 			]"
*/
using System;
using System.Collections.Generic;
using System.Text;

namespace Xebra
{
    /// <summary>
    /// Provides methodes to encode and decode integers with fragments flags.
    /// </summary>
    class XEncoder
    {
        /// <summary>
        /// Converts an array of byte to integer32
        /// </summary>
        /// <param name="b"></param>
        /// <returns></returns>
        public static int byteArrayToInt(byte[] b)
        {
            return System.BitConverter.ToInt32(b, 0);
        }

        /// <summary>
        /// Converts an int32 to a byte array
        /// </summary>
        /// <param name="i"></param>
        /// <returns></returns>
        public static byte[] intToByteArray(int i)
        {
            return System.BitConverter.GetBytes(i);
        }

        /// <summary>
        /// Encodes an unsigned int to include a flag
        /// </summary>
        /// <param name="i">The unsigned int</param>
        /// <param name="flag">The flag</param>
        /// <returns>The encoded unsigned int</returns>
        public static uint encodeNatural(uint i, uint flag)
        {
            if (i > 0x7FFFFFFF)
            {
                return 0;
            }
            else
            {
                return (uint)((i << 1) + flag);
            }
        }

        /// <summary>
        /// Extracts the unsigned int from an encoded unsigned int
        /// </summary>
        /// <param name="i">The encoded unsigned int</param>
        /// <returns>The decoded unsigned int</returns>
        public static uint decodeNatural(uint i)
        {
            return (i >> 1);
        }

        /// <summary>
        /// Extracts a flag from an unsigned int
        /// </summary>
        /// <param name="i">The encoded unsigned int</param>
        /// <returns>The flag</returns>
        public static bool decodeFlag(uint i)
        {
            return ((i & (uint)1) == 1);
        }              
    }
}