119 lines
3.6 KiB
C#
119 lines
3.6 KiB
C#
/*
|
|
This file is part of PacketDotNet.
|
|
|
|
PacketDotNet is free software: you can redistribute it and/or modify
|
|
it under the terms of the GNU Lesser General Public License as published by
|
|
the Free Software Foundation, either version 3 of the License, or
|
|
(at your option) any later version.
|
|
|
|
PacketDotNet 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 Lesser General Public License for more details.
|
|
|
|
You should have received a copy of the GNU Lesser General Public License
|
|
along with PacketDotNet. If not, see <http://www.gnu.org/licenses/>.
|
|
*/
|
|
/*
|
|
* Copyright 2005 Tamir Gal <tamir@tamirgal.com>
|
|
* Copyright 2008-2009 Chris Morgan <chmorgan@gmail.com>
|
|
* Copyright 2008-2009 Phillip Lemon <lucidcomms@gmail.com>
|
|
*/
|
|
|
|
using System;
|
|
using System.IO;
|
|
|
|
namespace PacketDotNet.Utils
|
|
{
|
|
/// <summary>
|
|
/// Computes the one's sum on a byte array.
|
|
/// Based TCP/IP Illustrated Vol. 2(1995) by Gary R. Wright and W. Richard
|
|
/// Stevens. Page 236. And on http://www.cs.utk.edu/~cs594np/unp/checksum.html
|
|
/// </summary>
|
|
|
|
/*
|
|
* taken from TCP/IP Illustrated Vol. 2(1995) by Gary R. Wright and W.
|
|
* Richard Stevens. Page 236
|
|
*/
|
|
public sealed class ChecksumUtils
|
|
{
|
|
private ChecksumUtils() { }
|
|
|
|
/// <summary>
|
|
/// Computes the one's complement sum on a byte array
|
|
/// </summary>
|
|
public static int OnesComplementSum(byte[] bytes)
|
|
{
|
|
//just complement the one's sum
|
|
return OnesComplementSum(bytes, 0, bytes.Length);
|
|
}
|
|
|
|
/// <summary>
|
|
/// Computes the one's complement sum on a byte array
|
|
/// </summary>
|
|
public static int OnesComplementSum(byte[] bytes, int start, int len)
|
|
{
|
|
//just complement the one's sum
|
|
return (~OnesSum(bytes, start, len)) & 0xFFFF;
|
|
}
|
|
|
|
/// <summary>
|
|
/// Compute a ones sum of a byte array
|
|
/// </summary>
|
|
/// <param name="bytes">
|
|
/// A <see cref="System.Byte"/>
|
|
/// </param>
|
|
/// <returns>
|
|
/// A <see cref="System.Int32"/>
|
|
/// </returns>
|
|
public static int OnesSum(byte[] bytes)
|
|
{
|
|
return OnesSum(bytes, 0, bytes.Length);
|
|
}
|
|
|
|
/// <summary>
|
|
/// 16 bit sum of all values
|
|
/// http://en.wikipedia.org/wiki/Signed_number_representations#Ones.27_complement
|
|
/// </summary>
|
|
/// <param name="bytes">
|
|
/// A <see cref="System.Byte"/>
|
|
/// </param>
|
|
/// <param name="start">
|
|
/// A <see cref="System.Int32"/>
|
|
/// </param>
|
|
/// <param name="len">
|
|
/// A <see cref="System.Int32"/>
|
|
/// </param>
|
|
/// <returns>
|
|
/// A <see cref="System.Int32"/>
|
|
/// </returns>
|
|
public static int OnesSum(byte[] bytes, int start, int len)
|
|
{
|
|
MemoryStream memStream = new MemoryStream(bytes, start, len);
|
|
BinaryReader br = new BinaryReader(memStream);
|
|
Int32 sum = 0;
|
|
|
|
UInt16 val;
|
|
|
|
while (memStream.Position < memStream.Length -1)
|
|
{
|
|
val = (UInt16)System.Net.IPAddress.NetworkToHostOrder(br.ReadInt16());
|
|
sum += val;
|
|
}
|
|
|
|
// if we have a remaining byte we should add it
|
|
if (memStream.Position < len)
|
|
{
|
|
sum += br.ReadByte();
|
|
}
|
|
|
|
// fold the sum into 16 bits
|
|
while((sum >> 16) != 0)
|
|
{
|
|
sum = (sum & 0xffff) + (sum >> 16);
|
|
}
|
|
|
|
return sum;
|
|
}
|
|
}
|
|
} |