Beginnings of rust emulation

.gitignore

@@ -2,3 +2,4 @@
 /shrooms-vb.exe
 .vscode
 output
+/target

Cargo.toml

@@ -0,0 +1,20 @@
+[package]
+name = "shrooms-vb-native"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+anyhow = "1"
+clap = { version = "4", features = ["derive"] }
+imgui = "0.12"
+imgui-wgpu = { git = "https://github.com/Yatekii/imgui-wgpu-rs", rev = "2edd348" }
+imgui-winit-support = "0.13"
+pollster = "0.4"
+wgpu = "22.1"
+winit = "0.30"
+
+[build-dependencies]
+cc = "1"
+
+[profile.release]
+lto = "thin"

build.rs

@@ -0,0 +1,12 @@
+use std::path::Path;
+
+fn main() {
+    println!("cargo::rerun-if-changed=shrooms-vb-core");
+    cc::Build::new()
+        .include(Path::new("shrooms-vb-core/core"))
+        .opt_level(2)
+        .flag_if_supported("-flto")
+        .flag_if_supported("-fno-strict-aliasing")
+        .file(Path::new("shrooms-vb-core/core/vb.c"))
+        .compile("vb");
+}

src/anaglyph.wgsl

@@ -0,0 +1,49 @@
+// Vertex shader
+
+struct VertexOutput {
+    @builtin(position) clip_position: vec4<f32>,
+    @location(0) tex_coords: vec2<f32>,
+};
+
+@vertex
+fn vs_main(
+    @builtin(vertex_index) in_vertex_index: u32,
+) -> VertexOutput {
+    var out: VertexOutput;
+    var x: f32;
+    var y: f32;
+    switch in_vertex_index {
+        case 0u, 3u: {
+            x = -1.0;
+            y = 1.0;
+        }
+        case 1u: {
+            x = -1.0;
+            y = -1.0;
+        }
+        case 2u, 4u: {
+            x = 1.0;
+            y = -1.0;
+        }
+        default: {
+            x = 1.0;
+            y = 1.0;
+        }
+    }
+    out.clip_position = vec4<f32>(x, y, 0.0, 1.0);
+    out.tex_coords = vec2<f32>((x + 1.0) / 2.0, (1.0 - y) / 2.0);
+    return out;
+}
+
+// Fragment shader
+@group(0) @binding(0)
+var u_textures: binding_array<texture_2d<f32>>;
+@group(0) @binding(1)
+var u_sampler: sampler;
+
+
+@fragment
+fn fs_main(in: VertexOutput) -> @location(0) vec4<f32> {
+    return textureSample(u_textures[0], u_sampler, in.tex_coords);
+    // return vec4<f32>(0.3, 0.2, 0.1, 1.0);
+}

src/app.rs

@@ -0,0 +1,450 @@
+use imgui::*;
+use imgui_wgpu::{Renderer, RendererConfig};
+use imgui_winit_support::WinitPlatform;
+use pollster::block_on;
+use std::{num::NonZero, sync::Arc, time::Instant};
+use winit::{
+    application::ApplicationHandler,
+    dpi::LogicalSize,
+    event::{ElementState, Event, WindowEvent},
+    event_loop::ActiveEventLoop,
+    keyboard::Key,
+    platform::windows::{CornerPreference, WindowAttributesExtWindows},
+    window::Window,
+};
+
+use crate::{
+    emulator::{EmulatorClient, EmulatorCommand},
+    renderer::GameRenderer,
+};
+
+struct ImguiState {
+    context: imgui::Context,
+    platform: WinitPlatform,
+    renderer: Renderer,
+    clear_color: wgpu::Color,
+    last_frame: Instant,
+    last_cursor: Option<MouseCursor>,
+}
+
+struct AppWindow {
+    device: wgpu::Device,
+    queue: Arc<wgpu::Queue>,
+    window: Arc<Window>,
+    surface_desc: wgpu::SurfaceConfiguration,
+    surface: wgpu::Surface<'static>,
+    hidpi_factor: f64,
+    pipeline: wgpu::RenderPipeline,
+    bind_group: wgpu::BindGroup,
+    imgui: Option<ImguiState>,
+}
+
+impl AppWindow {
+    fn setup_gpu(event_loop: &ActiveEventLoop, client: &EmulatorClient) -> Self {
+        let instance = wgpu::Instance::new(wgpu::InstanceDescriptor {
+            backends: wgpu::Backends::PRIMARY,
+            ..Default::default()
+        });
+
+        let window = {
+            let size = LogicalSize::new(384, 244);
+
+            let attributes = Window::default_attributes()
+                .with_inner_size(size)
+                .with_title("Shrooms VB")
+                .with_corner_preference(CornerPreference::DoNotRound);
+            Arc::new(event_loop.create_window(attributes).unwrap())
+        };
+
+        let size = window.inner_size();
+        let hidpi_factor = window.scale_factor();
+        let surface = instance.create_surface(window.clone()).unwrap();
+
+        let adapter = block_on(instance.request_adapter(&wgpu::RequestAdapterOptions {
+            power_preference: wgpu::PowerPreference::HighPerformance,
+            compatible_surface: Some(&surface),
+            force_fallback_adapter: false,
+        }))
+        .unwrap();
+
+        let (device, queue) = block_on(adapter.request_device(
+            &wgpu::DeviceDescriptor {
+                required_features: wgpu::Features::TEXTURE_BINDING_ARRAY,
+                ..wgpu::DeviceDescriptor::default()
+            },
+            None,
+        ))
+        .unwrap();
+        let queue = Arc::new(queue);
+        let eyes = [
+            Arc::new(GameRenderer::create_texture(&device, "left eye")),
+            Arc::new(GameRenderer::create_texture(&device, "right eye")),
+        ];
+        client.send_command(EmulatorCommand::SetRenderer(GameRenderer {
+            queue: queue.clone(),
+            eyes: eyes.clone(),
+        }));
+        let eyes = [
+            eyes[0].create_view(&wgpu::TextureViewDescriptor::default()),
+            eyes[1].create_view(&wgpu::TextureViewDescriptor::default()),
+        ];
+        let sampler = device.create_sampler(&wgpu::SamplerDescriptor::default());
+        let texture_bind_group_layout =
+            device.create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor {
+                label: Some("texture bind group layout"),
+                entries: &[
+                    wgpu::BindGroupLayoutEntry {
+                        binding: 0,
+                        visibility: wgpu::ShaderStages::FRAGMENT,
+                        ty: wgpu::BindingType::Texture {
+                            sample_type: wgpu::TextureSampleType::Float { filterable: true },
+                            view_dimension: wgpu::TextureViewDimension::D2,
+                            multisampled: false,
+                        },
+                        count: NonZero::new(2),
+                    },
+                    wgpu::BindGroupLayoutEntry {
+                        binding: 1,
+                        visibility: wgpu::ShaderStages::FRAGMENT,
+                        ty: wgpu::BindingType::Sampler(wgpu::SamplerBindingType::Filtering),
+                        count: None,
+                    },
+                ],
+            });
+        let bind_group = device.create_bind_group(&wgpu::BindGroupDescriptor {
+            label: Some("bind group"),
+            layout: &texture_bind_group_layout,
+            entries: &[
+                wgpu::BindGroupEntry {
+                    binding: 0,
+                    resource: wgpu::BindingResource::TextureViewArray(&[&eyes[0], &eyes[1]]),
+                },
+                wgpu::BindGroupEntry {
+                    binding: 1,
+                    resource: wgpu::BindingResource::Sampler(&sampler),
+                },
+            ],
+        });
+
+        // Set up swap chain
+        let surface_desc = wgpu::SurfaceConfiguration {
+            usage: wgpu::TextureUsages::RENDER_ATTACHMENT,
+            format: wgpu::TextureFormat::Bgra8UnormSrgb,
+            width: size.width,
+            height: size.height,
+            present_mode: wgpu::PresentMode::Fifo,
+            desired_maximum_frame_latency: 2,
+            alpha_mode: wgpu::CompositeAlphaMode::Auto,
+            view_formats: vec![wgpu::TextureFormat::Bgra8Unorm],
+        };
+
+        surface.configure(&device, &surface_desc);
+
+        let shader = device.create_shader_module(wgpu::include_wgsl!("anaglyph.wgsl"));
+        let render_pipeline_layout =
+            device.create_pipeline_layout(&wgpu::PipelineLayoutDescriptor {
+                label: Some("render pipeline layout"),
+                bind_group_layouts: &[&texture_bind_group_layout],
+                push_constant_ranges: &[],
+            });
+        let render_pipeline = device.create_render_pipeline(&wgpu::RenderPipelineDescriptor {
+            label: Some("render pipeline"),
+            layout: Some(&render_pipeline_layout),
+            vertex: wgpu::VertexState {
+                module: &shader,
+                entry_point: "vs_main",
+                buffers: &[],
+                compilation_options: wgpu::PipelineCompilationOptions::default(),
+            },
+            fragment: Some(wgpu::FragmentState {
+                module: &shader,
+                entry_point: "fs_main",
+                targets: &[Some(wgpu::ColorTargetState {
+                    format: wgpu::TextureFormat::Bgra8UnormSrgb,
+                    blend: Some(wgpu::BlendState::REPLACE),
+                    write_mask: wgpu::ColorWrites::ALL,
+                })],
+                compilation_options: wgpu::PipelineCompilationOptions::default(),
+            }),
+            primitive: wgpu::PrimitiveState {
+                topology: wgpu::PrimitiveTopology::TriangleList,
+                strip_index_format: None,
+                front_face: wgpu::FrontFace::Ccw,
+                cull_mode: Some(wgpu::Face::Back),
+                polygon_mode: wgpu::PolygonMode::Fill,
+                unclipped_depth: false,
+                conservative: false,
+            },
+            depth_stencil: None,
+            multisample: wgpu::MultisampleState {
+                count: 1,
+                mask: !0,
+                alpha_to_coverage_enabled: false,
+            },
+            multiview: None,
+            cache: None,
+        });
+
+        let imgui = None;
+        Self {
+            device,
+            queue,
+            window,
+            surface_desc,
+            surface,
+            hidpi_factor,
+            pipeline: render_pipeline,
+            bind_group,
+            imgui,
+        }
+    }
+
+    fn setup_imgui(&mut self) {
+        let mut context = imgui::Context::create();
+        let mut platform = imgui_winit_support::WinitPlatform::new(&mut context);
+        platform.attach_window(
+            context.io_mut(),
+            &self.window,
+            imgui_winit_support::HiDpiMode::Default,
+        );
+        context.set_ini_filename(None);
+
+        let font_size = (13.0 * self.hidpi_factor) as f32;
+        context.io_mut().font_global_scale = (1.0 / self.hidpi_factor) as f32;
+
+        context.fonts().add_font(&[FontSource::DefaultFontData {
+            config: Some(imgui::FontConfig {
+                oversample_h: 1,
+                pixel_snap_h: true,
+                size_pixels: font_size,
+                ..Default::default()
+            }),
+        }]);
+
+        //
+        // Set up dear imgui wgpu renderer
+        //
+        let clear_color = wgpu::Color::BLACK;
+
+        let renderer_config = RendererConfig {
+            texture_format: self.surface_desc.format,
+            ..Default::default()
+        };
+
+        let renderer = Renderer::new(&mut context, &self.device, &self.queue, renderer_config);
+
+        let last_frame = Instant::now();
+        let last_cursor = None;
+
+        self.imgui = Some(ImguiState {
+            context,
+            platform,
+            renderer,
+            clear_color,
+            last_frame,
+            last_cursor,
+        })
+    }
+
+    fn new(event_loop: &ActiveEventLoop, client: &EmulatorClient) -> Self {
+        let mut window = Self::setup_gpu(event_loop, client);
+        window.setup_imgui();
+        window
+    }
+}
+
+pub struct App {
+    window: Option<AppWindow>,
+    client: EmulatorClient,
+}
+
+impl App {
+    pub fn new(client: EmulatorClient) -> Self {
+        Self {
+            window: None,
+            client,
+        }
+    }
+}
+
+impl ApplicationHandler for App {
+    fn resumed(&mut self, event_loop: &ActiveEventLoop) {
+        self.window = Some(AppWindow::new(event_loop, &self.client));
+    }
+
+    fn window_event(
+        &mut self,
+        event_loop: &ActiveEventLoop,
+        window_id: winit::window::WindowId,
+        event: WindowEvent,
+    ) {
+        let window = self.window.as_mut().unwrap();
+        let imgui = window.imgui.as_mut().unwrap();
+
+        match &event {
+            WindowEvent::Resized(size) => {
+                window.surface_desc = wgpu::SurfaceConfiguration {
+                    usage: wgpu::TextureUsages::RENDER_ATTACHMENT,
+                    format: wgpu::TextureFormat::Bgra8UnormSrgb,
+                    width: size.width,
+                    height: size.height,
+                    present_mode: wgpu::PresentMode::Fifo,
+                    desired_maximum_frame_latency: 2,
+                    alpha_mode: wgpu::CompositeAlphaMode::Auto,
+                    view_formats: vec![wgpu::TextureFormat::Bgra8Unorm],
+                };
+
+                window
+                    .surface
+                    .configure(&window.device, &window.surface_desc);
+            }
+            WindowEvent::CloseRequested => event_loop.exit(),
+            WindowEvent::KeyboardInput { event, .. } => {
+                if let Key::Character("s") = event.logical_key.as_ref() {
+                    match event.state {
+                        ElementState::Pressed => {
+                            self.client.send_command(EmulatorCommand::PressStart)
+                        }
+                        ElementState::Released => {
+                            self.client.send_command(EmulatorCommand::ReleaseStart)
+                        }
+                    }
+                }
+            }
+            WindowEvent::RedrawRequested => {
+                let now = Instant::now();
+                imgui
+                    .context
+                    .io_mut()
+                    .update_delta_time(now - imgui.last_frame);
+                imgui.last_frame = now;
+
+                let frame = match window.surface.get_current_texture() {
+                    Ok(frame) => frame,
+                    Err(e) => {
+                        eprintln!("dropped frame: {e:?}");
+                        return;
+                    }
+                };
+                imgui
+                    .platform
+                    .prepare_frame(imgui.context.io_mut(), &window.window)
+                    .expect("Failed to prepare frame");
+                let ui = imgui.context.frame();
+                let mut height = 0.0;
+                ui.main_menu_bar(|| {
+                    height = ui.window_size()[1];
+                    ui.menu("ROM", || {
+                        if ui.menu_item("Open ROM") {
+                            println!("clicked");
+                        }
+                        if ui.menu_item("Quit") {
+                            event_loop.exit();
+                        }
+                    });
+                    ui.menu("Emulation", || {
+                        if ui.menu_item("Pause") {
+                            println!("clicked");
+                        }
+                        if ui.menu_item("Reset") {
+                            println!("clicked");
+                        }
+                    });
+                });
+
+                let mut encoder: wgpu::CommandEncoder = window
+                    .device
+                    .create_command_encoder(&wgpu::CommandEncoderDescriptor { label: None });
+
+                if imgui.last_cursor != ui.mouse_cursor() {
+                    imgui.last_cursor = ui.mouse_cursor();
+                    imgui.platform.prepare_render(ui, &window.window);
+                }
+
+                let view = frame
+                    .texture
+                    .create_view(&wgpu::TextureViewDescriptor::default());
+                let mut rpass = encoder.begin_render_pass(&wgpu::RenderPassDescriptor {
+                    label: None,
+                    color_attachments: &[Some(wgpu::RenderPassColorAttachment {
+                        view: &view,
+                        resolve_target: None,
+                        ops: wgpu::Operations {
+                            load: wgpu::LoadOp::Clear(imgui.clear_color),
+                            store: wgpu::StoreOp::Store,
+                        },
+                    })],
+                    depth_stencil_attachment: None,
+                    timestamp_writes: None,
+                    occlusion_query_set: None,
+                });
+
+                rpass.set_pipeline(&window.pipeline);
+                let hidpi = window.hidpi_factor as f32;
+                rpass.set_viewport(0.0, height * hidpi, 384.0 * hidpi, 224.0 * hidpi, 0.0, 1.0);
+                rpass.set_bind_group(0, &window.bind_group, &[]);
+                rpass.draw(0..6, 0..1);
+
+                rpass.set_viewport(0.0, 0.0, 384.0 * hidpi, 224.0 * hidpi, 0.0, 1.0);
+                imgui
+                    .renderer
+                    .render(
+                        imgui.context.render(),
+                        &window.queue,
+                        &window.device,
+                        &mut rpass,
+                    )
+                    .expect("Rendering failed");
+
+                drop(rpass);
+
+                window.queue.submit(Some(encoder.finish()));
+
+                frame.present();
+            }
+            _ => (),
+        }
+
+        imgui.platform.handle_event::<()>(
+            imgui.context.io_mut(),
+            &window.window,
+            &Event::WindowEvent { window_id, event },
+        );
+    }
+
+    fn user_event(&mut self, _event_loop: &ActiveEventLoop, event: ()) {
+        let window = self.window.as_mut().unwrap();
+        let imgui = window.imgui.as_mut().unwrap();
+        imgui.platform.handle_event::<()>(
+            imgui.context.io_mut(),
+            &window.window,
+            &Event::UserEvent(event),
+        );
+    }
+
+    fn device_event(
+        &mut self,
+        _event_loop: &ActiveEventLoop,
+        device_id: winit::event::DeviceId,
+        event: winit::event::DeviceEvent,
+    ) {
+        let window = self.window.as_mut().unwrap();
+        let imgui = window.imgui.as_mut().unwrap();
+        imgui.platform.handle_event::<()>(
+            imgui.context.io_mut(),
+            &window.window,
+            &Event::DeviceEvent { device_id, event },
+        );
+    }
+
+    fn about_to_wait(&mut self, _event_loop: &ActiveEventLoop) {
+        let window = self.window.as_mut().unwrap();
+        let imgui = window.imgui.as_mut().unwrap();
+        window.window.request_redraw();
+        imgui.platform.handle_event::<()>(
+            imgui.context.io_mut(),
+            &window.window,
+            &Event::AboutToWait,
+        );
+    }
+}

src/emulator.rs

@@ -0,0 +1,93 @@
+use std::{
+    fs,
+    path::Path,
+    sync::mpsc::{self, TryRecvError},
+};
+
+use anyhow::Result;
+
+use crate::{renderer::GameRenderer, shrooms_vb_core::CoreVB};
+
+pub struct Emulator {
+    sim: CoreVB,
+    commands: mpsc::Receiver<EmulatorCommand>,
+    renderer: Option<GameRenderer>,
+}
+
+impl Emulator {
+    pub fn new() -> (Self, EmulatorClient) {
+        let (sink, source) = mpsc::channel();
+        let emu = Emulator {
+            sim: CoreVB::new(),
+            commands: source,
+            renderer: None,
+        };
+        let queue = EmulatorClient { queue: sink };
+        (emu, queue)
+    }
+
+    pub fn load_rom(&mut self, path: &Path) -> Result<()> {
+        let bytes = fs::read(path)?;
+        self.sim.load_rom(bytes)?;
+        Ok(())
+    }
+
+    pub fn run(&mut self) {
+        let mut eye_contents = [vec![0u8; 384 * 224], vec![0u8; 384 * 224]];
+        loop {
+            self.sim.emulate_frame();
+            if let Some(renderer) = &mut self.renderer {
+                if self.sim.read_pixels(&mut eye_contents) {
+                    renderer.render(&eye_contents);
+                }
+            }
+            loop {
+                match self.commands.try_recv() {
+                    Ok(command) => self.handle_command(command),
+                    Err(TryRecvError::Empty) => {
+                        break;
+                    }
+                    Err(TryRecvError::Disconnected) => {
+                        return;
+                    }
+                }
+            }
+        }
+    }
+
+    fn handle_command(&mut self, command: EmulatorCommand) {
+        match command {
+            EmulatorCommand::SetRenderer(renderer) => {
+                self.renderer = Some(renderer);
+            }
+            EmulatorCommand::PressStart => {
+                self.sim.set_keys(0x1003);
+            }
+            EmulatorCommand::ReleaseStart => {
+                self.sim.set_keys(0x0003);
+            }
+        }
+    }
+}
+
+#[derive(Debug)]
+pub enum EmulatorCommand {
+    SetRenderer(GameRenderer),
+    PressStart,
+    ReleaseStart,
+}
+
+pub struct EmulatorClient {
+    queue: mpsc::Sender<EmulatorCommand>,
+}
+
+impl EmulatorClient {
+    pub fn send_command(&self, command: EmulatorCommand) {
+        if let Err(err) = self.queue.send(command) {
+            eprintln!(
+                "could not send command {:?} as emulator is shut down",
+                err.0
+            );
+        }
+    }
+}

src/main.rs

@@ -0,0 +1,32 @@
+use std::{path::PathBuf, thread};
+
+use anyhow::Result;
+use app::App;
+use clap::Parser;
+use emulator::Emulator;
+use winit::event_loop::{ControlFlow, EventLoop};
+
+mod app;
+mod emulator;
+mod renderer;
+mod shrooms_vb_core;
+
+#[derive(Parser)]
+struct Args {
+    rom: PathBuf,
+}
+
+fn main() -> Result<()> {
+    let args = Args::parse();
+
+    let (mut emulator, client) = Emulator::new();
+    emulator.load_rom(&args.rom)?;
+    thread::spawn(move || {
+        emulator.run();
+    });
+
+    let event_loop = EventLoop::new().unwrap();
+    event_loop.set_control_flow(ControlFlow::Poll);
+    event_loop.run_app(&mut App::new(client))?;
+    Ok(())
+}

src/renderer.rs

@@ -0,0 +1,58 @@
+use std::sync::Arc;
+
+use wgpu::{
+    Extent3d, ImageCopyTexture, ImageDataLayout, Origin3d, Queue, Texture, TextureDescriptor,
+    TextureFormat, TextureUsages,
+};
+
+#[derive(Debug)]
+pub struct GameRenderer {
+    pub queue: Arc<Queue>,
+    pub eyes: [Arc<Texture>; 2],
+}
+
+impl GameRenderer {
+    pub fn render(&self, buffers: &[Vec<u8>; 2]) {
+        for (texture, buffer) in self.eyes.iter().zip(buffers) {
+            self.update_texture(texture, buffer);
+        }
+    }
+    fn update_texture(&self, texture: &Texture, buffer: &[u8]) {
+        let texture = ImageCopyTexture {
+            texture,
+            mip_level: 0,
+            origin: Origin3d::ZERO,
+            aspect: wgpu::TextureAspect::All,
+        };
+        let size = Extent3d {
+            width: 384,
+            height: 224,
+            depth_or_array_layers: 1,
+        };
+        let data_layout = ImageDataLayout {
+            offset: 0,
+            bytes_per_row: Some(384),
+            rows_per_image: Some(224),
+        };
+        self.queue.write_texture(texture, buffer, data_layout, size);
+    }
+    pub fn create_texture(device: &wgpu::Device, name: &str) -> Texture {
+        let desc = TextureDescriptor {
+            label: Some(name),
+            size: Extent3d {
+                width: 384,
+                height: 224,
+                depth_or_array_layers: 1,
+            },
+            mip_level_count: 1,
+            sample_count: 1,
+            dimension: wgpu::TextureDimension::D2,
+            format: TextureFormat::R8Unorm,
+            usage: TextureUsages::COPY_SRC
+                | TextureUsages::COPY_DST
+                | TextureUsages::TEXTURE_BINDING,
+            view_formats: &[TextureFormat::R8Unorm],
+        };
+        device.create_texture(&desc)
+    }
+}

src/shrooms_vb_core.rs

@@ -0,0 +1,159 @@
+use std::{ffi::c_void, ptr};
+
+use anyhow::{anyhow, Result};
+
+#[repr(C)]
+struct VB {
+    _data: [u8; 0],
+}
+
+#[allow(non_camel_case_types)]
+type c_int = i32;
+type OnFrame = extern "C" fn(sim: *mut VB) -> c_int;
+
+#[link(name = "vb")]
+extern "C" {
+    #[link_name = "vbEmulate"]
+    fn vb_emulate(sim: *mut VB, cycles: *mut u32) -> c_int;
+    #[link_name = "vbGetCartROM"]
+    fn vb_get_cart_rom(sim: *mut VB, size: *mut u32) -> *mut c_void;
+    #[link_name = "vbGetPixels"]
+    fn vb_get_pixels(
+        sim: *mut VB,
+        left: *mut c_void,
+        left_stride_x: c_int,
+        left_stride_y: c_int,
+        right: *mut c_void,
+        right_stride_x: c_int,
+        right_stride_y: c_int,
+    );
+    #[link_name = "vbGetUserData"]
+    fn vb_get_user_data(sim: *mut VB) -> *mut c_void;
+    #[link_name = "vbInit"]
+    fn vb_init(sim: *mut VB) -> *mut VB;
+    #[link_name = "vbReset"]
+    fn vb_reset(sim: *mut VB);
+    #[link_name = "vbSetCartROM"]
+    fn vb_set_cart_rom(sim: *mut VB, rom: *mut c_void, size: u32) -> c_int;
+    #[link_name = "vbSetKeys"]
+    fn vb_set_keys(sim: *mut VB, keys: u16) -> u16;
+    #[link_name = "vbSetFrameCallback"]
+    fn vb_set_frame_callback(sim: *mut VB, on_frame: OnFrame);
+    #[link_name = "vbSetUserData"]
+    fn vb_set_user_data(sim: *mut VB, tag: *mut c_void);
+    #[link_name = "vbSizeOf"]
+    fn vb_size_of() -> usize;
+}
+
+extern "C" fn on_frame(sim: *mut VB) -> i32 {
+    // SAFETY: the *mut VB owns its userdata.
+    // There is no way for the userdata to be null or otherwise invalid.
+    let data: &mut VBState = unsafe { &mut *vb_get_user_data(sim).cast() };
+    data.frame_seen = true;
+    1
+}
+
+struct VBState {
+    frame_seen: bool,
+}
+
+pub struct CoreVB {
+    sim: *mut VB,
+}
+
+// SAFETY: the memory pointed to by sim is valid
+unsafe impl Send for CoreVB {}
+
+impl CoreVB {
+    pub fn new() -> Self {
+        // init the VB instance itself
+        let size = unsafe { vb_size_of() };
+        // allocate a vec of u64 so that this memory is 8-byte aligned
+        let memory = vec![0u64; size.div_ceil(4)];
+        let sim: *mut VB = Box::into_raw(memory.into_boxed_slice()).cast();
+        unsafe { vb_init(sim) };
+        unsafe { vb_reset(sim) };
+
+        // set up userdata
+        let state = VBState { frame_seen: false };
+        unsafe { vb_set_user_data(sim, Box::into_raw(Box::new(state)).cast()) };
+        unsafe { vb_set_frame_callback(sim, on_frame) };
+
+        CoreVB { sim }
+    }
+
+    pub fn load_rom(&mut self, rom: Vec<u8>) -> Result<()> {
+        self.unload_rom();
+
+        let size = rom.len() as u32;
+        let rom = Box::into_raw(rom.into_boxed_slice()).cast();
+        let status = unsafe { vb_set_cart_rom(self.sim, rom, size) };
+        if status == 0 {
+            Ok(())
+        } else {
+            let _: Vec<u8> =
+                unsafe { Vec::from_raw_parts(rom.cast(), size as usize, size as usize) };
+            Err(anyhow!("Invalid ROM size of {} bytes", size))
+        }
+    }
+
+    fn unload_rom(&mut self) -> Option<Vec<u8>> {
+        let mut size = 0;
+        let rom = unsafe { vb_get_cart_rom(self.sim, &mut size) };
+        if rom.is_null() {
+            return None;
+        }
+        unsafe { vb_set_cart_rom(self.sim, ptr::null_mut(), 0) };
+        let vec = unsafe { Vec::from_raw_parts(rom.cast(), size as usize, size as usize) };
+        Some(vec)
+    }
+
+    pub fn emulate_frame(&mut self) {
+        let mut cycles = 20_000_000;
+        unsafe { vb_emulate(self.sim, &mut cycles) };
+    }
+
+    pub fn read_pixels(&mut self, buffers: &mut [Vec<u8>; 2]) -> bool {
+        // SAFETY: the *mut VB owns its userdata.
+        // There is no way for the userdata to be null or otherwise invalid.
+        let data: &mut VBState = unsafe { &mut *vb_get_user_data(self.sim).cast() };
+        if !data.frame_seen {
+            return false;
+        }
+        data.frame_seen = false;
+
+        assert_eq!(buffers[0].len(), 384 * 224);
+        assert_eq!(buffers[1].len(), 384 * 224);
+        unsafe {
+            vb_get_pixels(
+                self.sim,
+                buffers[0].as_mut_ptr().cast(),
+                1,
+                384,
+                buffers[1].as_mut_ptr().cast(),
+                1,
+                384,
+            );
+        };
+        true
+    }
+
+    pub fn set_keys(&mut self, keys: u16) {
+        unsafe { vb_set_keys(self.sim, keys) };
+    }
+}
+
+impl Drop for CoreVB {
+    fn drop(&mut self) {
+        // SAFETY: the *mut VB owns its userdata.
+        // There is no way for the userdata to be null or otherwise invalid.
+        let ptr: *mut VBState = unsafe { vb_get_user_data(self.sim).cast() };
+        // SAFETY: we made this pointer ourselves, we can for sure free it
+        unsafe { drop(Box::from_raw(ptr)) };
+
+        let len = unsafe { vb_size_of() }.div_ceil(4);
+        // SAFETY: the sim's memory originally came from a Vec<u64>
+        let bytes: Vec<u64> = unsafe { Vec::from_raw_parts(self.sim.cast(), len, len) };
+        drop(bytes);
+    }
+}