sdrangel/modemm17/CRC16.h

73 wiersze
1.4 KiB
C++

// Copyright 2020 Mobilinkd LLC.
#pragma once
#include <cstdint>
#include <array>
#include <cstddef>
namespace modemm17
{
template <uint16_t Poly = 0x5935, uint16_t Init = 0xFFFF>
struct CRC16
{
static constexpr uint16_t MASK = 0xFFFF;
static constexpr uint16_t LSB = 0x0001;
static constexpr uint16_t MSB = 0x8000;
uint16_t reg_ = Init;
void reset()
{
reg_ = Init;
for (size_t i = 0; i != 16; ++i)
{
auto bit = reg_ & LSB;
if (bit) reg_ ^= Poly;
reg_ >>= 1;
if (bit) reg_ |= MSB;
}
reg_ &= MASK;
}
void operator()(uint8_t byte)
{
reg_ = crc(byte, reg_);
}
uint16_t crc(uint8_t byte, uint16_t reg)
{
for (size_t i = 0; i != 8; ++i)
{
auto msb = reg & MSB;
reg = ((reg << 1) & MASK) | ((byte >> (7 - i)) & LSB);
if (msb) reg ^= Poly;
}
return reg & MASK;
}
uint16_t get()
{
auto reg = reg_;
for (size_t i = 0; i != 16; ++i)
{
auto msb = reg & MSB;
reg = ((reg << 1) & MASK);
if (msb) reg ^= Poly;
}
return reg;
}
std::array<uint8_t, 2> get_bytes()
{
auto crc = get();
std::array<uint8_t, 2> result{uint8_t((crc >> 8) & 0xFF), uint8_t(crc & 0xFF)};
return result;
}
};
} // modemm17