inst.rs

    cpu.set_half_carry((first ^ second ^ result) & 0x10 == 0x10);
    cpu.set_carry(result & 0x100 == 0x100);

    result_b
}

fn add_carry_set_flags(cpu: &mut Cpu, first: u8, second: u8) -> u8 {
    let first = first as u32;
    let second = second as u32;
    let carry = cpu.get_carry() as u32;

    let result = first.wrapping_add(second).wrapping_add(carry);
    let result_b = result as u8;

    cpu.set_sub(false);
    cpu.set_zero(result_b == 0);
    cpu.set_half_carry((first ^ second ^ result) & 0x10 == 0x10);
    cpu.set_carry(result & 0x100 == 0x100);

    result_b
}

fn sub_set_flags(cpu: &mut Cpu, first: u8, second: u8) -> u8 {
    let first = first as u32;
    let second = second as u32;

    let result = first.wrapping_sub(second);
    let result_b = result as u8;

    cpu.set_sub(true);
    cpu.set_zero(result_b == 0);
    cpu.set_half_carry((first ^ second ^ result) & 0x10 == 0x10);
    cpu.set_carry(result & 0x100 == 0x100);

    result_b
}

fn sub_carry_set_flags(cpu: &mut Cpu, first: u8, second: u8) -> u8 {
    let first = first as u32;
    let second = second as u32;
    let carry = cpu.get_carry() as u32;

    let result = first.wrapping_sub(second).wrapping_sub(carry);
    let result_b = result as u8;

    cpu.set_sub(true);
    cpu.set_zero(result_b == 0);
    cpu.set_half_carry((first ^ second ^ result) & 0x10 == 0x10);
    cpu.set_carry(result & 0x100 == 0x100);

    result_b
}

fn add_u16_u16(cpu: &mut Cpu, first: u16, second: u16) -> u16 {
    let first = first as u32;
    let second = second as u32;
    let result = first.wrapping_add(second);

    cpu.set_sub(false);
    cpu.set_half_carry((first ^ second ^ result) & 0x1000 == 0x1000);
    cpu.set_carry(result & 0x10000 == 0x10000);

    result as u16
}

fn swap(cpu: &mut Cpu, value: u8) -> u8 {
    cpu.set_sub(false);
    cpu.set_zero(value == 0);
    cpu.set_half_carry(false);
    cpu.set_carry(false);

    (value << 4) | (value >> 4)
}

/// Helper function to shift an `u8` to the left and update CPU
/// flags.
fn sla(cpu: &mut Cpu, value: u8) -> u8 {
    let result = value << 1;

    cpu.set_sub(false);
    cpu.set_zero(result == 0);
    cpu.set_half_carry(false);
    cpu.set_carry(value & 0x80 == 0x80);

    result
}

fn sra(cpu: &mut Cpu, value: u8) -> u8 {
    let result = (value >> 1) | (value & 0x80);

    cpu.set_sub(false);
    cpu.set_zero(result == 0);
    cpu.set_half_carry(false);
    cpu.set_carry(value & 0x01 == 0x01);

    result
}

fn srl(cpu: &mut Cpu, value: u8) -> u8 {
    let result = value >> 1;

    cpu.set_sub(false);
    cpu.set_zero(result == 0);
    cpu.set_half_carry(false);
    cpu.set_carry(value & 0x01 == 0x01);

    result
}

/// Helper function for RST instructions, pushes the
/// current PC to the stack and jumps to the provided
/// address.
fn rst(cpu: &mut Cpu, addr: u16) {
    cpu.push_word(cpu.pc);
    cpu.pc = addr;
}