CRC.h

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/*
 * CRC.h
 *
 *  Created on: 10.01.2023
 *      Author: Yannick
 */
 
#ifndef SRC_CRC_H_
#define SRC_CRC_H_
#include "main.h"
#include "array"
 
 
template<typename T>
T reverseBits(T value)
{
    static_assert(sizeof(T) == 1 || sizeof(T) == 2 || sizeof(T) == 4, "Type must be 1,2 or 4 bytes long");
    value = ((value & 0xAAAAAAAA) >> 1) | ((value & 0x55555555) << 1);
    value = ((value & 0xCCCCCCCC) >> 2) | ((value & 0x33333333) << 2);
 
    if(sizeof(T)>1)
        value = ((value & 0xF0F0F0F0) >> 4) | ((value & 0x0F0F0F0F) << 4);
 
    if(sizeof(T)>3)
        value = ((value & 0xFF00FF00) >> 8) | ((value & 0x00FF00FF) << 8);
 
    value = (value >> (4*sizeof(T))) | (value << (4*sizeof(T)));
 
    return value; // & (1 << (sizeof(T)*8)) - 1
}
 
template<typename T,size_t LEN>
void makeCrcTable(std::array<T,LEN> &table, const T crcpoly,const uint8_t bits,const bool refin = false,const bool refout = false)
{
    T mask = 1 << (bits-1);
    for (uint16_t byte = 0; byte < LEN; ++byte)
    {
        uint8_t shiftin = std::max<int16_t>(bits-8,0);
        T crc = (refin ? reverseBits<T>(byte) >> shiftin : byte);
        for (uint8_t bit = 0; bit < bits; ++bit)
        {
            if (crc & mask)
            {
                crc = (crc << 1) ^ crcpoly;
            }
            else
            {
                crc <<= 1;
            }
        }
        table[byte] =  (refout ? reverseBits<T>(crc) : crc);
    }
}
 
 
uint8_t calculateCrc8(std::array<uint8_t,256> &crctable,uint8_t* buf,uint16_t len,uint8_t crc=0);
uint16_t calculateCrc16_8(std::array<uint16_t,256> &crctable,uint8_t* buf,uint16_t len,uint16_t crc=0);
uint16_t calculateCrc16_8_rev(std::array<uint16_t,256> &crctable,uint8_t* buf,uint16_t len,uint16_t crc=0);
 
#endif /* SRC_CRC_H_ */