PJON_CRC8.h

 
#pragma once
 
/* Compute CRC8 with a table-less implementation:
   Copyright Giovanni Blu Mitolo [email protected] 2018
 
   CRC8 C2, source Baicheva98 (implicit + 1 notation)
   0x97 = (x + 1)(x^7 + x^6 + x^5 + x^2 + 1)^2
   Chosen because it has the largest possible length (119 bit) at which
   HD=4 can be achieved with 8-bit CRC. */
 
struct PJON_crc8 {
 
    static inline uint8_t roll(uint8_t input_byte, uint8_t crc)
    {
        for(uint8_t i = 8; i; i--, input_byte >>= 1) {
            uint8_t result = (crc ^ input_byte) & 0x01;
            crc >>= 1;
            if(result) {
                crc ^= 0x97;
            }
        }
        return crc;
    };
 
 
    static inline uint8_t compute(const uint8_t *input_byte, uint16_t length)
    {
        uint8_t crc = 0;
        for(uint16_t b = 0; b < length; b++) {
            crc = roll(input_byte[b], crc);
        }
        return crc;
    };
 
};