104 lines
3.1 KiB
C#
104 lines
3.1 KiB
C#
|
using System;
|
||
|
|
using System.Text;
|
||
|
|
using DotNetty.Buffers;
|
||
|
|
|
||
|
|
namespace dotNetty_kcp
|
||
|
|
{
|
||
|
|
/// <summary>
|
||
|
|
/// Computes a CRC32 checksum.
|
||
|
|
/// </summary>
|
||
|
|
/// <remarks>Based on <see cref="http://sanity-free.org/12/crc32_implementation_in_csharp.html"/></remarks>
|
||
|
|
public static class Crc32
|
||
|
|
{
|
||
|
|
readonly static uint[] Table = CreateTable();
|
||
|
|
|
||
|
|
static Crc32()
|
||
|
|
{
|
||
|
|
}
|
||
|
|
|
||
|
|
// /// <summary>
|
||
|
|
// /// Compute the checksum of a UTF8 text.
|
||
|
|
// /// </summary>
|
||
|
|
// /// <param name="text">Text to calculate</param>
|
||
|
|
// /// <returns>Checksum</returns>
|
||
|
|
// public static int ComputeChecksum(string text)
|
||
|
|
// {
|
||
|
|
// return ComputeChecksum(text, Encoding.UTF8);
|
||
|
|
// }
|
||
|
|
//
|
||
|
|
// /// <summary>
|
||
|
|
// /// Compute the checksum of a text using a specific encoding.
|
||
|
|
// /// </summary>
|
||
|
|
// /// <param name="text">Text to calculate</param>
|
||
|
|
// /// <param name="encoding">Text encoding</param>
|
||
|
|
// /// <returns>Checksum</returns>
|
||
|
|
// public static int ComputeChecksum(string text, Encoding encoding)
|
||
|
|
// {
|
||
|
|
// if (string.IsNullOrEmpty(text)) return 0;
|
||
|
|
// byte[] bytes = encoding.GetBytes(text);
|
||
|
|
// return ComputeChecksum(bytes);
|
||
|
|
// }
|
||
|
|
|
||
|
|
/// <summary>
|
||
|
|
/// Compute the checksum of a binary buffer.
|
||
|
|
/// </summary>
|
||
|
|
/// <param name="bytes">Buffer to calculate</param>
|
||
|
|
/// <returns></returns>
|
||
|
|
public static int ComputeChecksum(sbyte[] bytes)
|
||
|
|
{
|
||
|
|
uint crc = 0xffffffff;
|
||
|
|
for (int i = 0; i < bytes.Length; i++)
|
||
|
|
{
|
||
|
|
byte index = (byte) (((crc) & 0xff) ^ bytes[i]);
|
||
|
|
crc = (crc >> 8) ^ Table[index];
|
||
|
|
}
|
||
|
|
|
||
|
|
return unchecked((int) ~crc);
|
||
|
|
}
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
/// <summary>
|
||
|
|
/// Compute the checksum of a binary buffer.
|
||
|
|
/// </summary>
|
||
|
|
/// <param name="bytes">Buffer to calculate</param>
|
||
|
|
/// <returns></returns>
|
||
|
|
public static uint ComputeChecksum(IByteBuffer byteBuffer,int offset,int lenth)
|
||
|
|
{
|
||
|
|
var crc = 0xffffffff;
|
||
|
|
lenth += offset;
|
||
|
|
for (var i = offset; i < lenth; i++)
|
||
|
|
{
|
||
|
|
var index = (byte) (((crc) & 0xff) ^ byteBuffer.GetByte(i));
|
||
|
|
crc = (crc >> 8) ^ Table[index];
|
||
|
|
}
|
||
|
|
return ~crc;
|
||
|
|
}
|
||
|
|
|
||
|
|
static uint[] CreateTable()
|
||
|
|
{
|
||
|
|
const uint poly = 0xedb88320;
|
||
|
|
var table = new uint[256];
|
||
|
|
uint temp = 0;
|
||
|
|
for (uint i = 0; i < table.Length; ++i)
|
||
|
|
{
|
||
|
|
temp = i;
|
||
|
|
for (int j = 8; j > 0; --j)
|
||
|
|
{
|
||
|
|
if ((temp & 1) == 1)
|
||
|
|
{
|
||
|
|
temp = (uint) ((temp >> 1) ^ poly);
|
||
|
|
}
|
||
|
|
else
|
||
|
|
{
|
||
|
|
temp >>= 1;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
table[i] = temp;
|
||
|
|
}
|
||
|
|
|
||
|
|
return table;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|