gb-emu/src/lib.rs

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

use crate::{
    processor::memory::Memory,
    util::{pause, print_cycles},
};
use connect::{EmulatorMessage, Renderer};
use once_cell::sync::OnceCell;
use processor::{memory::Rom, Cpu};
use std::{
    fs::{self},
    io::{stdout, Write},
    path::PathBuf,
    process::exit,
    str::FromStr,
    sync::mpsc::Receiver,
};
use util::pause_then_step;

pub mod connect;
mod constants;
mod processor;
pub mod util;

pub struct Options {
    pub rom_path: String,
    pub save_path: Option<String>,
    pub no_save: bool,
    pub bootrom_path: Option<String>,
    pub connect_serial: bool,
    pub verbose: bool,
    pub step_by: Option<usize>,
    pub cycle_count: bool,
}

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;

pub fn init(
    receiver: Receiver<EmulatorMessage>,
    options: Options,
    mut window: Box<dyn Renderer>,
    tile_window: Option<Box<dyn Renderer>>,
) {
    VERBOSE.set(options.verbose).unwrap();

    let maybe_save = if options.no_save {
        None
    } else {
        Some(if let Some(path) = options.save_path {
            PathBuf::from_str(&path).unwrap()
        } else {
            PathBuf::from_str(&options.rom_path)
                .unwrap()
                .with_extension("sav")
        })
    };

    let rom: Rom = match fs::read(options.rom_path) {
        Ok(data) => Rom::load(data, maybe_save),
        Err(e) => {
            println!("Error reading ROM: {e}");
            return;
        }
    };

    window.prepare(WIDTH, HEIGHT);
    window.set_title(format!("{} on {}", rom.get_title(), rom.mbc_type()));

    let bootrom_enabled = options.bootrom_path.is_some();
    let bootrom: Option<Vec<u8>> = if let Some(path) = options.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, options.connect_serial, tile_window),
        bootrom_enabled,
    );

    let mut cycle_num = 0;

    verbose_println!("\n\n    Begin execution...\n");
    match options.step_by {
        Some(step_size) => loop {
            process_messages(&receiver, &mut cpu);
            for _ in 0..step_size {
                cycle_num += 1;
                if options.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 {
            process_messages(&receiver, &mut cpu);
            cycle_num += 1;
            if options.cycle_count {
                print_cycles(&cycle_num);
            }
            run_cycle(&mut cpu);
        },
    }
}

fn process_messages(receiver: &Receiver<EmulatorMessage>, cpu: &mut Cpu) {
    while let Ok(msg) = receiver.try_recv() {
        match msg {
            EmulatorMessage::Stop => {
                cpu.memory.flush_rom();
                exit(0);
            }
        }
    }
}

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();
    }
}