main.rs

const :u8 ZERO_FLAG_BYTE_POSITION = 7;
const :u8 SUBTRACT_FLAG_BYTE_POSITION = 6;
const :u8 HALF_CARRY_FLAG_BYTE_POSITION = 5;
const :u8 CARRY_FLAG_BYTE_POSITION = 4;


impl std::convert::From<FlagsRegister> for u8  {
    fn from(flag: FlagsRegister) -> u8 {
        (if flag.zero       { 1 } else { 0 }) << ZERO_FLAG_BYTE_POSITION |
        (if flag.subtract   { 1 } else { 0 }) << SUBTRACT_FLAG_BYTE_POSITION |
        (if flag.half_carry { 1 } else { 0 }) << HALF_CARRY_FLAG_BYTE_POSITION |
        (if flag.carry      { 1 } else { 0 }) << CARRY_FLAG_BYTE_POSITION
    }
}

impl std::convert::From<u8> for FlagsRegister {
    fn from(byte: u8) -> Self {
        let zero = ((byte >> ZERO_FLAG_BYTE_POSITION) & 0b1) != 0;
        let subtract = ((byte >> SUBTRACT_FLAG_BYTE_POSITION) & 0b1) != 0;
        let half_carry = ((byte >> HALF_CARRY_FLAG_BYTE_POSITION) & 0b1) != 0;
        let carry = ((byte >> CARRY_FLAG_BYTE_POSITION) & 0b1) != 0;

        FlagsRegister {
            zero,
            subtract,
            half_carry,
            carry
        }
    }
}