gb-emu/src/processor/instructions/instructions.rs

use crate::processor::{get_bit, Direction, Flags, Reg8, SplitRegister, CPU};

impl CPU {
    pub(crate) fn add(&mut self, first: u8, second: u8) -> u8 {
        self.add_u8s(first, second)
    }

    pub(crate) fn adc(&mut self, first: u8, second: u8) -> u8 {
        let val = second + self.get_flag(Flags::Carry);
        self.add_u8s(first, val)
    }

    pub(crate) fn sub(&mut self, first: u8, second: u8) -> u8 {
        self.sub_u8s(first, second)
    }

    pub(crate) fn sbc(&mut self, first: u8, second: u8) -> u8 {
        let val = second + self.get_flag(Flags::Carry);
        self.sub_u8s(first, val)
    }

    pub(crate) fn inc(&mut self, reg: Reg8) {
        let result = self.reg.get_8(reg).wrapping_add(0x1);
        self.clear_flag(Flags::NSubtract);
        self.set_or_clear_flag(Flags::Zero, result == 0x0);
        self.set_or_clear_flag(
            Flags::HalfCarry,
            (((self.reg.get_8(reg) & 0xF).wrapping_add(0x1 & 0xF)) & 0x10) == 0x10,
        );
        self.reg.set_8(reg, result);
    }

    pub(crate) fn dec(&mut self, reg: Reg8) {
        let result = self.reg.get_8(reg).wrapping_sub(0x1);
        self.set_flag(Flags::NSubtract);
        self.set_or_clear_flag(Flags::Zero, result == 0x0);
        self.set_or_clear_flag(
            Flags::HalfCarry,
            (((self.reg.get_8(reg) & 0xF).wrapping_sub(0x1 & 0xF)) & 0x10) == 0x10,
        );
        self.reg.set_8(reg, result);
    }

    pub(crate) fn inc_pair(&mut self, val: u16) -> u16 {
        val.wrapping_add(0x1)
    }

    pub(crate) fn dec_pair(&mut self, val: u16) -> u16 {
        val.wrapping_sub(0x1)
    }

    pub(crate) fn rlc(&mut self, byte: u8) -> u8 {
        self.rotate_with_carry(byte, Direction::Left)
    }

    pub(crate) fn rrc(&mut self, byte: u8) -> u8 {
        self.rotate_with_carry(byte, Direction::Right)
    }

    pub(crate) fn rl(&mut self, byte: u8) -> u8 {
        self.rotate(byte, Direction::Left)
    }

    pub(crate) fn rr(&mut self, byte: u8) -> u8 {
        self.rotate(byte, Direction::Right)
    }

    pub(crate) fn sla(&mut self, byte: u8) -> u8 {
        self.shift(byte, Direction::Left)
    }

    pub(crate) fn sra(&mut self, byte: u8) -> u8 {
        let b = get_bit(byte, 7);
        let val = self.shift(byte, Direction::Right);
        if b {
            val + 0b10000000
        } else {
            val
        }
    }

    pub(crate) fn srl(&mut self, byte: u8) -> u8 {
        self.shift(byte, Direction::Right)
    }

    pub(crate) fn rst(&mut self, address: u8) {
        self.push(self.reg.pc);
        self.reg.pc.set_high(0x0);
        self.reg.pc.set_low(address);
    }

    pub(crate) fn jr(&mut self, jump: i8) {
        self.reg.pc = self.reg.pc.wrapping_add_signed(jump.into());
    }
}