include/marnav/nmea/checksum.hpp

   1 #ifndef MARNAV_NMEA_CHECKSUM_HPP
   2 #define MARNAV_NMEA_CHECKSUM_HPP
   3
   4 #include <algorithm>
   5 #include <stdexcept>
   6 #include <string>
   7 #include <cstdint>
   8
   9 namespace marnav::nmea
  10 {
  11 /// Exception for cases where the checksum is wrong.
  12 ///
  13 /// This exception carries the actual as well as the expected
  14 /// checksum and will provide this information in the explanation.
  15 class checksum_error : public std::exception
  16 {
  17 public:
  18         checksum_error() = delete;
  19         explicit checksum_error(uint8_t exp, uint8_t act);
  20         checksum_error(const checksum_error &) = default;
  21         checksum_error(checksum_error &&) = default;
  22
  23         checksum_error & operator=(const checksum_error &) = default;
  24         checksum_error & operator=(checksum_error &&) = default;
  25
  26         const char * what() const noexcept override { return text_; }
  27
  28         uint8_t expected() const noexcept { return expected_; }
  29         uint8_t actual() const noexcept { return actual_; }
  30
  31 private:
  32         uint8_t expected_ = 0u;
  33         uint8_t actual_ = 0u;
  34         char text_[64];
  35 };
  36
  37 /// Computes and returns the checksum of the specified range.
  38 ///
  39 /// @tparam Iterator Iterator type which dereferences to a \c char.
  40 /// @param[in] a The starting point to compute the checksum.
  41 /// @param[in] b The ending point (exclusive) to compute the checksum.
  42 /// @return The computed checksum.
  43 ///
  44 template <class Iterator>
  45 uint8_t checksum(Iterator a, Iterator b) noexcept
  46 {
  47         uint8_t sum = 0x00;
  48         std::for_each(a, b, [&sum](char c) { sum ^= static_cast<uint8_t>(c); });
  49         return sum;
  50 }
  51
  52 std::string checksum_to_string(uint8_t sum);
  53 }
  54
  55 #endif