Gameboy DAA instruction

general_instructions.h

// DAA
// opcode: 0x27
// cycles: 4
// flags: Z H C
void CPU::daa(){

    if (!getFlag(FlagBitmaskN)) {  // after an addition, adjust if (half-)carry occurred or if result is out of bounds
        if (getFlag(FlagBitmaskC) || regs.A > 0x99) { regs.A += 0x60; setFlag(FlagBitmaskC,true); }
        if (getFlag(FlagBitmaskHalfCarry) || (regs.A & 0x0f) > 0x09) { regs.A += 0x6; }
    } else {  // after a subtraction, only adjust if (half-)carry occurred
        if (getFlag(FlagBitmaskC)) { regs.A -= 0x60; }
        if (getFlag(FlagBitmaskHalfCarry)) { regs.A -= 0x6; }
    }

    setFlag(FlagBitmaskZero, (regs.A == 0) ); // the usual z flag
    setFlag(FlagBitmaskHalfCarry,false); // h flag is always cleared