src/marnav/seatalk/message_51.cpp

   1 #include "message_51.hpp"
   2
   3 namespace marnav
   4 {
   5 namespace seatalk
   6 {
   7
   8 message_51::message_51()
   9         : message(ID)
  10 {
  11 }
  12
  13 std::unique_ptr<message> message_51::parse(const raw & data)
  14 {
  15         if (data.size() != 5)
  16                 throw std::invalid_argument{"invalid number of bytes in message_51::parse"};
  17         if ((data[1] & 0x0f) != 0x02)
  18                 throw std::invalid_argument{"invalid size specified in message"};
  19
  20         std::unique_ptr<message> result = utils::make_unique<message_51>();
  21         message_51 & msg = static_cast<message_51 &>(*result);
  22
  23         // 51  Z2  XX  YY  YY
  24         // raw  1   2   3   4
  25
  26         const uint32_t degrees = data[2];
  27         uint32_t m = 0;
  28         m += data[3];
  29         m <<= 8;
  30         m += data[4];
  31
  32         const uint32_t minutes = (m & 0x7fff) / 100;
  33         const uint32_t seconds = (((m & 0x7fff) % 100) * 60) / 100;
  34         const geo::longitude::hemisphere hemisphere
  35                 = (m & 0x8000) ? geo::longitude::hemisphere::EAST : geo::longitude::hemisphere::WEST;
  36
  37         msg.lon = geo::longitude{degrees, minutes, seconds, hemisphere};
  38
  39         // deliberately ignored 'Z'
  40
  41         return result;
  42 }
  43
  44 raw message_51::get_data() const
  45 {
  46         uint16_t m = 0;
  47         m += lon.minutes() * 100;
  48         m += (lon.seconds() * 100) / 60;
  49         if (lon.hem() == geo::longitude::hemisphere::EAST)
  50                 m |= 0x8000;
  51
  52         return raw{static_cast<uint8_t>(ID), 0x02, static_cast<uint8_t>(lon.degrees() & 0xff),
  53                 static_cast<uint8_t>((m >> 8) & 0xff), static_cast<uint8_t>((m >> 0) & 0xff)};
  54 }
  55 }
  56 }