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67 lines
2.2 KiB
C++
67 lines
2.2 KiB
C++
#ifndef __CRC_HPP
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#define __CRC_HPP
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#include <limits.h>
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// Default CRC-8 Polynomial: x^8 + x^5 + x^4 + x^2 + x + 1
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// Can protect a 4 byte payload against toggling of up to 5 bits
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// source: https://users.ece.cmu.edu/~koopman/crc/index.html
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constexpr uint8_t CRC8_DEFAULT = 0x37;
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// Default CRC-16 Polynomial: 0x9eb2 x^16 + x^13 + x^12 + x^11 + x^10 + x^8 + x^6 + x^5 + x^2 + 1
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// Can protect a 135 byte payload against toggling of up to 5 bits
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// source: https://users.ece.cmu.edu/~koopman/crc/index.html
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// Also known as CRC-16-DNP
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constexpr uint16_t CRC16_DEFAULT = 0x3d65;
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// Calculates an arbitrary CRC for one byte.
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// Adapted from https://barrgroup.com/Embedded-Systems/How-To/CRC-Calculation-C-Code
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template<typename T, unsigned POLYNOMIAL>
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static T calc_crc(T remainder, uint8_t value) {
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constexpr T BIT_WIDTH = (CHAR_BIT * sizeof(T));
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constexpr T TOPBIT = ((T)1 << (BIT_WIDTH - 1));
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// Bring the next byte into the remainder.
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remainder ^= (value << (BIT_WIDTH - 8));
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// Perform modulo-2 division, a bit at a time.
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for (uint8_t bit = 8; bit; --bit) {
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if (remainder & TOPBIT) {
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remainder = (remainder << 1) ^ POLYNOMIAL;
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} else {
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remainder = (remainder << 1);
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}
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}
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return remainder;
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}
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template<typename T, unsigned POLYNOMIAL>
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static T calc_crc(T remainder, const uint8_t* buffer, size_t length) {
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while (length--)
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remainder = calc_crc<T, POLYNOMIAL>(remainder, *(buffer++));
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return remainder;
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}
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template<unsigned POLYNOMIAL = CRC8_DEFAULT>
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static uint8_t calc_crc8(uint8_t remainder, uint8_t value) {
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return calc_crc<uint8_t, POLYNOMIAL>(remainder, value);
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}
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template<unsigned POLYNOMIAL = CRC16_DEFAULT>
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static uint16_t calc_crc16(uint16_t remainder, uint8_t value) {
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return calc_crc<uint16_t, POLYNOMIAL>(remainder, value);
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}
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template<unsigned POLYNOMIAL = CRC8_DEFAULT>
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static uint8_t calc_crc8(uint8_t remainder, const uint8_t* buffer, size_t length) {
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return calc_crc<uint8_t, POLYNOMIAL>(remainder, buffer, length);
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}
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template<unsigned POLYNOMIAL = CRC16_DEFAULT>
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static uint16_t calc_crc16(uint16_t remainder, const uint8_t* buffer, size_t length) {
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return calc_crc<uint16_t, POLYNOMIAL>(remainder, buffer, length);
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}
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#endif /* __CRC_HPP */
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