U16 Can_FD_Analyzer::ComputeCrc15(std::vector<BitState> &bits, U32 num_bits)
{

//X15 + X14 + X10 + X8 + X7 + X4 + X3 + X0.
U16 crc_result = 0;
for (U32 i = 0; i < num_bits; i++) {

BitState next_bit = bits[i];

//Exclusive or
if ((crc_result & 0x4000) != 0) {

next_bit = Invert(next_bit); //if the msb of crc_result is zero, then next_bit is not inverted; otherwise, it is.
}
crc_result <<= 1;

if (next_bit == mSettings->Recessive()) {
//normally bit high.
crc_result ^= 0x4599;
}
}

return crc_result & 0x7FFF;
}

//算法2
U16 Can_FD_Analyzer::MakeCRC15(std::vector<BitState> &bits, U32 num_bits)
{

//X15 + X14 + X10 + X8 + X7 + X4 + X3 + X0.
U16 CRC[15] = {
0 };
for (U32 i = 0; i < num_bits; i++) {

U32 DoInvert = (bits[i] == mSettings->Recessive()) ^ CRC[14]; //XOR required?
CRC[14] = (CRC[13] ^ DoInvert); //14
CRC[13] = CRC[12];
CRC[12] = CRC[11];
CRC[11] = CRC[10];
CRC[10] = (CRC[9] ^ DoInvert); //10
CRC[9] = CRC[8];
CRC[8] = (CRC[7] ^ DoInvert); //8
CRC[7] = (CRC[6] ^ DoInvert); //7
CRC[6] = CRC[5];
CRC[5] = CRC[4];
CRC[4] = (CRC[3] ^ DoInvert); //4
CRC[3] = (CRC[2] ^ DoInvert); //3
CRC[2] = CRC[1];
CRC[1] = CRC[0];
CRC[0] = DoInvert;
}

U16 result = 0; // CRC Result
for (U32 i = 0; i < 15; i++) {

result = result | (CRC[i] << i);
}
return (U16)result;
}