Program Listing for File checksum.hpp

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//
// Created by Pietro Saccardi on 22/12/2020.
//

#ifndef PN532_BITS_ALGO_HPP
#define PN532_BITS_ALGO_HPP

#include <array>
#include <cstdint>
#include <numeric>
#include <pn532/bits.hpp>

namespace pn532 {

    [[nodiscard]] inline std::uint8_t compute_checksum(std::uint8_t byte);

    template <class ByteIterator>
    [[nodiscard]] std::uint8_t compute_checksum(ByteIterator begin, ByteIterator end);

    template <class ByteIterator>
    [[nodiscard]] std::uint8_t compute_checksum(std::uint8_t sum_init, ByteIterator begin, ByteIterator end);

    template <class ByteIterator>
    [[nodiscard]] bool checksum(ByteIterator begin, ByteIterator end);

#ifndef DOXYGEN_SHOULD_SKIP_THIS
    namespace bits {

        [[nodiscard]] inline std::array<std::uint8_t, 2> length_and_checksum_short(std::uint8_t length);

        [[nodiscard]] inline std::array<std::uint8_t, 3> length_and_checksum_long(std::uint16_t length);

        [[nodiscard]] inline std::pair<std::uint8_t, bool> check_length_checksum(std::array<std::uint8_t, 2> const &data);

        [[nodiscard]] inline std::pair<std::uint16_t, bool> check_length_checksum(std::array<std::uint8_t, 3> const &data);

        [[nodiscard]] inline std::uint8_t host_to_pn532_command(command_code cmd);

        [[nodiscard]] inline command_code pn532_to_host_command(std::uint8_t cmd);
    }// namespace bits
#endif
}// namespace pn532

namespace pn532 {

    std::uint8_t compute_checksum(std::uint8_t byte) {
        return ~byte + 1;
    }

    template <class ByteIterator>
    std::uint8_t compute_checksum(ByteIterator begin, ByteIterator end) {
        return compute_checksum(0, begin, end);
    }

    template <class ByteIterator>
    std::uint8_t compute_checksum(std::uint8_t sum_init, ByteIterator begin, ByteIterator end) {
        return compute_checksum(std::accumulate(begin, end, sum_init));
    }

    template <class ByteIterator>
    bool checksum(ByteIterator begin, ByteIterator end) {
        return (std::accumulate(begin, end, 0) & 0xff) == 0;
    }

    namespace bits {
        std::array<std::uint8_t, 2> length_and_checksum_short(std::uint8_t length) {
            return {length, compute_checksum(length)};
        }

        std::array<std::uint8_t, 3> length_and_checksum_long(std::uint16_t length) {
            const std::array<std::uint8_t, 2> bits = {std::uint8_t(length >> 8), std::uint8_t(length & 0xff)};
            return {bits[0], bits[1], compute_checksum(std::begin(bits), std::end(bits))};
        }

        std::pair<std::uint8_t, bool> check_length_checksum(std::array<std::uint8_t, 2> const &data) {
            return {data[0], checksum(std::begin(data), std::end(data))};
        }

        std::pair<std::uint16_t, bool> check_length_checksum(std::array<std::uint8_t, 3> const &data) {
            return {(std::uint16_t(data[0]) << 8) | data[1],
                    checksum(std::begin(data), std::end(data))};
        }

        std::uint8_t host_to_pn532_command(command_code cmd) {
            return static_cast<std::uint8_t>(cmd);
        }

        command_code pn532_to_host_command(std::uint8_t cmd) {
            return static_cast<command_code>(cmd - 1);
        }
    }// namespace bits
}// namespace pn532

#endif//PN532_BITS_ALGO_HPP