using System;
public enum Crc16Mode : ushort { Standard = 0xA001, CcittKermit = 0x8408 }
public class Crc16 {
static ushort[] table = new ushort[256];
public ushort ComputeChecksum( params byte[] bytes ) {
ushort crc = 0;
for(int i = 0; i < bytes.Length; ++i) {
byte index = (byte)(crc ^ bytes[i]);
crc = (ushort)((crc >> 8) ^ table[index]);
}
return crc;
}
public byte[] ComputeChecksumBytes( params byte[] bytes ) {
ushort crc = ComputeChecksum( bytes );
return BitConverter.GetBytes( crc );
}
public Crc16( Crc16Mode mode ) {
ushort polynomial = (ushort)mode;
ushort value;
ushort temp;
for(ushort i = 0; i < table.Length; ++i) {
value = 0;
temp = i;
for(byte j = 0; j < 8; ++j) {
if(((value ^ temp) & 0x0001) != 0) {
value = (ushort)((value >> 1) ^ polynomial);
}else {
value >>= 1;
}
temp >>= 1;
}
table[i] = value;
}
}
}