Decoding an old (2014?) SPaT

decodeSpat.h

#include <exception>
#include <array>
#include <stdint.h>

#define BUFFER_SIZE 10240

struct ControllerState
{

    uint16_t PedCallActive = 0;

    uint16_t Green = 0;
    uint16_t Yellow = 0;
    uint16_t Red = 0xFFFF;
    uint16_t Flash = 0;

    uint16_t OvlpGreen = 0;
    uint16_t OvlpYellow = 0;
    uint16_t OvlpRed = 0;
    uint16_t OvlpFlash = 0;

    uint16_t Walk = 0;
    uint16_t PedClear = 0;
    uint16_t DontWalk = 0xFFFF;
};

ControllerState DecodeSpat(array<char, BUFFER_SIZE>& buffer, size_t bytes)
{
    ControllerState result;

    unsigned char* ubuffer = reinterpret_cast<unsigned char*>(buffer.data());

    if ((uint8_t)buffer[0] != 0xcd)
        throw std::runtime_error("Incompatible SPaT");

#define READ_TWO_BYTES_AT_LOCATION(X) (uint16_t)((ubuffer[X] << 8) | ubuffer[X + 1]);

    result.Red = READ_TWO_BYTES_AT_LOCATION(210);
    result.Yellow = READ_TWO_BYTES_AT_LOCATION(212);
    result.Green = READ_TWO_BYTES_AT_LOCATION(214);

    result.DontWalk = READ_TWO_BYTES_AT_LOCATION(216);
    result.PedClear = READ_TWO_BYTES_AT_LOCATION(218);
    result.Walk = READ_TWO_BYTES_AT_LOCATION(220);

    result.OvlpRed = READ_TWO_BYTES_AT_LOCATION(222);
    result.OvlpYellow = READ_TWO_BYTES_AT_LOCATION(224);
    result.OvlpGreen = READ_TWO_BYTES_AT_LOCATION(226);

    result.Flash = READ_TWO_BYTES_AT_LOCATION(228);
    result.OvlpFlash = READ_TWO_BYTES_AT_LOCATION(230);
    result.PedCallActive = READ_TWO_BYTES_AT_LOCATION(241);

    return result;
}