iz80 0.5.0

Z80 and 8080 emulator
Documentation 
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use super::opcode::Opcode;
use super::environment::Environment;
use super::registers::{Reg16, Reg8};

/*
    From "The undocumented Z80 documented" TUZD-4.4:

Officially the Z80 has an 8 bit I/O port address space. When using the I/O ports, the 16 address
lines are used. And in fact, the high 8 bit do actually have some value, so you can use 65536
ports after all. IN r,(C), OUT (C),r, and the Block I/O instructions actually place the entire BC
register on the address bus. Similarly IN A,(n) and OUT (n),A put A × 256 + n on the address
bus.
The INI/INIR/IND/INDR instructions use BC after decrementing B, and the OUTI/OTIR/OUTD/OTDR
instructions before.
*/


pub fn build_out_c_r(r: Reg8) -> Opcode {
    Opcode::new(
        format!("OUT (C), {r}"),
        move |env: &mut Environment| {
            let address = env.state.reg.get16(Reg16::BC);
            let value = env.state.reg.get8(r);
            env.port_out(address, value);
        }
    )
}

pub fn build_out_c_0() -> Opcode {
    Opcode::new(
        "OUT (C), 0".to_string(),
        |env: &mut Environment| {
            let address = env.state.reg.get16(Reg16::BC);
            env.port_out(address, 0);
        }
    )
}

pub fn build_out_n_a() -> Opcode {
    Opcode::new(
        "OUT (n), A".to_string(),
        |env: &mut Environment| {
            let a = env.state.reg.a();
            let address = ((a as u16) << 8) + env.advance_pc() as u16;
            env.port_out(address, a);
        }
    )
}

pub fn build_in_r_c(r: Reg8) -> Opcode {
    Opcode::new(
        format!("IN {r}, (C)"),
        move |env: &mut Environment| {
            let address = env.state.reg.get16(Reg16::BC);
            let value = env.port_in(address);
            env.state.reg.set8(r, value);

            env.state.reg.update_bits_in_flags(value);
        }
    )
}

pub fn build_in_0_c() -> Opcode {
    Opcode::new(
        "IN (C)".to_string(),
        |env: &mut Environment| {
            let address = env.state.reg.get16(Reg16::BC);
            let value = env.port_in(address);

            env.state.reg.update_bits_in_flags(value);
        }
    )
}

pub fn build_in_a_n() -> Opcode {
    Opcode::new(
        "IN A, (n)".to_string(),
        |env: &mut Environment| {
            let a = env.state.reg.a();
            let address = ((a as u16) << 8) + env.advance_pc() as u16;
            let value = env.port_in(address);
            env.state.reg.set_a(value);
        }
    )
}

/*
, and the OUTI/OTIR/OUTD/OTDR
instructions before.
*/

pub fn build_in_block((inc, repeat, postfix) : (bool, bool, &'static str)) -> Opcode {
    Opcode::new(
        format!("IN{postfix}"),
        move |env: &mut Environment| {
            // The INI/INIR/IND/INDR instructions use BC after decrementing B
            let b = env.state.reg.inc_dec8(Reg8::B, false /* decrement */);
            let address = env.state.reg.get16(Reg16::BC);

            let value = env.port_in(address);
            // We won't have IX and IY cases to consider
            env.set_reg(Reg8::_HL, value);
            env.state.reg.inc_dec16(Reg16::HL, inc);

            // TUZD-4.3
            let j = (env.state.reg.get8(Reg8::C) as u16).wrapping_add(if inc { 1 } else { 0xFFFF });
            let k = value as u16 + (j & 0xff);
            env.state.reg.update_block_flags(value, k, b);

            if repeat && b != 0 {
                // Back to redo the instruction
                env.set_branch_taken();
                let pc = env.state.reg.pc().wrapping_sub(2);
                env.state.reg.set_pc(pc);
            }
        }
    )
}

pub fn build_out_block((inc, repeat, postfix) : (bool, bool, &'static str)) -> Opcode {
    let n0 = if repeat {"OT"} else {"OUT"};
    Opcode::new(
        format!("{n0}{postfix}"),
        move |env: &mut Environment| {
            // the OUTI/OTIR/OUTD/OTDR instructions use BC before decrementing B
            let address = env.state.reg.get16(Reg16::BC);
            let b = env.state.reg.inc_dec8(Reg8::B, false /* decrement */);

            // We won't have IX and IY cases to consider
            let value = env.reg8_ext(Reg8::_HL);
            env.port_out(address, value);
            env.state.reg.inc_dec16(Reg16::HL, inc);

            // TUZD-4.3
            let k = value as u16 + env.state.reg.get8(Reg8::L) as u16;
            env.state.reg.update_block_flags(value, k, b);

            if repeat && b != 0 {
                // Back to redo the instruction
                env.set_branch_taken();
                let pc = env.state.reg.pc().wrapping_sub(2);
                env.state.reg.set_pc(pc);
            }
        }
    )
}