private static byte[] GenerateTable(Crc8Type type)
{
byte[] csTable = new byte[256];
for (int i = 0; i < 256; ++i)
{
int curr = i;
for (int j = 0; j < 8; ++j)
{
if ((curr & 0x80) != 0)
{
curr = (curr << 1) ^ (int)type;
}
else
{
curr <<= 1;
}
}
csTable[i] = (byte)curr;
}
return(csTable);
}
public Crc8(Crc8Type type, Endianness endianness)
{
_polynomial = GetPolynomialByType(type);
if (endianness == Endianness.Big)
{
_polynomial = FlipPolynomial(_polynomial);
_endianness = endianness;
}
Reset();
}
/// <summary>
/// Calculate crc
/// </summary>
/// <param name="type">Polinom type</param>
/// <param name="source">source for calculation</param>
/// <param name="length">num of elements</param>
/// <param name="offset">array offset from begining</param>
/// <returns></returns>
public static byte Calculate(Crc8Type type, byte[] source, int length, int offset)
{
if (source == null)
{
throw new ArgumentNullException(nameof(source));
}
if (source.Length < offset + length)
{
throw new ArgumentException($"{nameof(offset)} and {nameof(length)}");
}
byte[] table = GenerateTable(type);
byte c = 0;
for (int i = 0; i < length; i++)
{
c = table[c ^ source[i + offset]];
}
return(c);
}
private byte GetPolynomialByType(Crc8Type type)
{
switch (type)
{
case Crc8Type.AUTOSAR:
return(0xF4);
case Crc8Type.Bluetooth:
return(0xE5);
case Crc8Type.CCITT:
return(0xE0);
case Crc8Type.Dallas:
return(0x8C);
case Crc8Type.DARC:
return(0x9C);
case Crc8Type.DVB:
return(0xAB);
case Crc8Type.GSM_B:
return(0x92);
case Crc8Type.Maxim:
return(0x8C);
case Crc8Type.SAE_J1850:
return(0xB8);
case Crc8Type.WCDMA:
return(0xD9);
default:
throw new ArgumentOutOfRangeException("type", "The type parameter must be a valid Crc8Type.");
}
}
public Crc8(Crc8Type type)
{
_polynomial = GetPolynomialByType(type);
Reset();
}
