gb-emu/src/lib.rs

#![feature(
    exclusive_range_pattern,
    let_chains,
    slice_flatten,
    async_closure,
    bigint_helper_methods
)]

use std::{
    fs,
    io::{self, stdout, Write},
};

use gilrs::Gilrs;
use minifb::Window;
use once_cell::sync::OnceCell;
use processor::{memory::Rom, Cpu};

use crate::processor::memory::Memory;

mod constants;
mod processor;
mod util;

#[macro_export]
macro_rules! verbose_println {
    ($($tts:tt)*) => {
            if $crate::is_verbose() {
                    println!($($tts)*);
            }
    };
}

#[macro_export]
macro_rules! verbose_print {
    ($($tts:tt)*) => {
            if $crate::is_verbose() {
                    print!($($tts)*);
            }
    };
}

static mut PAUSE_ENABLED: bool = false;
static mut PAUSE_QUEUED: bool = false;

static VERBOSE: OnceCell<bool> = OnceCell::new();

pub const WIDTH: usize = 160;
pub const HEIGHT: usize = 144;
static FACTOR: OnceCell<usize> = OnceCell::new();

#[allow(clippy::too_many_arguments)]
pub fn init(
    rom_path: String,
    bootrom_path: Option<String>,
    mut window: Window,
    connect_serial: bool,
    tile_window: bool,
    verbose: bool,
    step_by: Option<usize>,
    cycle_count: bool,
    factor: usize,
) {
    VERBOSE.set(verbose).unwrap();
    FACTOR.set(factor).unwrap();
    crate::processor::memory::mmio::gpu::init_statics();

    let rom: Rom = match fs::read(rom_path) {
        Ok(data) => Rom::load(data),
        Err(e) => {
            println!("Error reading ROM: {e}");
            return;
        }
    };
    window.set_title(format!("{} on {}", rom.get_title(), rom.mbc_type()).as_str());

    let bootrom_enabled = bootrom_path.is_some();
    let bootrom: Option<Vec<u8>> = if let Some(path) = bootrom_path {
        match fs::read(path) {
            Ok(data) => Some(data),
            Err(e) => {
                println!("Error reading bootROM: {e}");
                return;
            }
        }
    } else {
        None
    };

    let mut cpu = Cpu::new(
        Memory::init(bootrom, rom, window, connect_serial, tile_window),
        bootrom_enabled,
        Gilrs::new().unwrap(),
    );

    let mut cycle_num = 0;

    verbose_println!("\n\n    Begin execution...\n");
    match step_by {
        Some(step_size) => loop {
            for _ in 0..step_size {
                cycle_num += 1;
                if cycle_count {
                    print_cycles(&cycle_num);
                }
                run_cycle(&mut cpu);
            }
            print!("                       ...{cycle_num} cycles - press enter to continue\r");
            stdout().flush().unwrap();
            pause();
        },
        None => loop {
            cycle_num += 1;
            if cycle_count {
                print_cycles(&cycle_num);
            }
            run_cycle(&mut cpu);
        },
    }
}

fn run_cycle(cpu: &mut Cpu) {
    let will_pause = unsafe { PAUSE_QUEUED };
    let pause_enabled = unsafe { PAUSE_ENABLED };
    cpu.exec_next();
    if !pause_enabled && cpu.reg.pc >= 0x100 {
        unsafe { PAUSE_ENABLED = true };
    }
    if will_pause {
        pause_then_step();
    }
}

fn pause_then_step() {
    unsafe {
        if PAUSE_ENABLED {
            let line = pause();
            PAUSE_QUEUED = !line.contains("continue");
        }
    }
}

#[allow(dead_code)]
fn pause_once() {
    println!("paused...");
    pause();
}

fn pause() -> String {
    let mut line = String::new();
    match io::stdin().read_line(&mut line) {
        Ok(_) => line,
        Err(_) => String::from(""),
    }
}

fn print_cycles(cycles: &i32) {
    if *cycles % 45678 != 0 {
        return;
    }
    let instructions_per_second = 400000;
    print!(
        "cycle {} - approx {} seconds on real hardware\r",
        cycles,
        cycles / instructions_per_second
    );
    stdout().flush().unwrap();
}

fn is_verbose() -> bool {
    match VERBOSE.get() {
        Some(v) => *v,
        None => false,
    }
}