/*****************************************************************************
 * Utility.cs: Utility 0.1
 *****************************************************************************
 * Copyright (C) 2005 Jon Lech Johansen <jon@nanocrew.net>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111, USA.
 *****************************************************************************/

using System;
using System.IO;
using System.Security.Cryptography;

public class Utility
{
    public static void LeReverse( byte [] arr, int index, int length )
    {
        if( BitConverter.IsLittleEndian )
        {
            Array.Reverse( arr, index, length );
        }
    }

    public static void LeReverse( byte [] arr )
    {
        LeReverse( arr, 0, arr.Length );
    }

    public static int IndexOf( byte [] buf, uint val )
    {
        for( int i = 0; i < (buf.Length - 3); i += 4 )
        {
            if( BitConverter.ToUInt32( buf, i ) == val )
                return i;
        }

        return -1;
    }

    public static void RijndaelDecrypt( byte [] Buf, int Offset, int Count,
                                        byte [] Key, byte [] IV )
    {
        Rijndael alg = Rijndael.Create();
        alg.Mode = CipherMode.CBC;
        alg.Padding = PaddingMode.None;

        MemoryStream ms = new MemoryStream();

        ICryptoTransform ct = alg.CreateDecryptor( Key, IV );
        CryptoStream cs = new CryptoStream( ms, ct, CryptoStreamMode.Write );
        cs.Write( Buf, Offset, (Count / 16) * 16 );
        cs.Close();

        ms.ToArray().CopyTo( Buf, Offset );
    }
}