Crate oc_wasm_opencomputers

Expand description

This crate provides high-level APIs for accessing components provided by OpenComputers in a vanilla Minecraft environment (e.g. redstone blocks, GPUs, screens, etc.).

As a general rule, APIs in this crate accept an Invoker and a Buffer scratch buffer, the latter being used for encoding parameters and decoding return values. This buffer can be reused between API calls to reduce heap allocations. In some cases the return value of an API may borrow from the scratch buffer.

Important

You must depend on oc-wasm-futures with the proper-waker feature in your own application if your chosen executor requires the proper-waker feature.

Example

extern crate alloc;
use alloc::boxed::Box;
use alloc::string::String;
use alloc::vec::Vec;
use cassette::Cassette;
use oc_wasm_futures::sleep;
use oc_wasm_opencomputers::prelude::*;
use oc_wasm_opencomputers::{gpu, screen};
use oc_wasm_opencomputers::common::{Dimension, Point};
use oc_wasm_safe::{component, computer};
use once_cell::unsync::OnceCell;
use core::future::Future;
use core::panic::PanicInfo;
use core::pin::Pin;
use wee_alloc::WeeAlloc;

#[global_allocator]
static ALLOC: WeeAlloc<'_> = WeeAlloc::INIT;

fn panic_hook(info: &PanicInfo<'_>) {
	if let Some(s) = info.payload().downcast_ref::<&str>() {
		computer::error(s);
	} else if let Some(s) = info.payload().downcast_ref::<String>() {
		computer::error(s);
	} else {
		computer::error("panic occurred");
	}
}

async fn main_impl() -> Result<(), oc_wasm_opencomputers::error::Error> {
	// Grab the one-and-only resources.
	let mut invoker = component::Invoker::take().unwrap();
	let mut lister = component::Lister::take().unwrap();

	// Find the GPU.
	let mut listing = lister.start(Some("gpu"));
	let gpu = *listing.next().expect("no GPU").address();
	let gpu = gpu::Gpu::new(gpu);

	// Find the screen.
	listing = lister.start(Some("screen"));
	let screen = *listing.next().expect("no screen").address();
	let screen = screen::Screen::new(screen);

	// Allocate a scratch buffer to use for method calls.
	let mut buffer = Vec::<u8>::new();

	// Lock the GPU so method calls can be made on it. For gpu_locked’s lifetime, methods can only
	// be called on the GPU, not on anything else. To make method calls on another component, drop
	// this value and recreate it later.
	let mut gpu_locked = gpu.lock(&mut invoker, &mut buffer);

	// Bind the GPU to the screen.
	gpu_locked.bind(*screen.address(), true).await?;

	// Clear the screen.
	gpu_locked.set_foreground(gpu::Colour::Rgb(gpu::Rgb(0x00_FF_FF_FF))).await?;
	gpu_locked.set_background(gpu::Colour::Rgb(gpu::Rgb(0))).await?;
	gpu_locked.fill(Point{x: 1, y: 1}, Dimension{width: 160, height: 80}, ' ').await?;

	// Say hello.
	gpu_locked.set(Point{x: 1, y: 1}, "Hello World!", gpu::TextDirection::Horizontal).await?;

	// Stop running forever.
	loop {
		sleep::for_uptime(core::time::Duration::from_secs(3600)).await;
	}
}

async fn main() {
	match main_impl().await {
		Ok(()) => (),
		Err(e) => computer::error(e.as_str()),
	}
}

#[no_mangle]
pub extern "C" fn run(_: i32) -> i32 {
	static mut PANIC_HOOK_SET: bool = false;
	static mut EXECUTOR: OnceCell<Cassette<Pin<Box<dyn Future<Output = ()>>>>> = OnceCell::new();

	// SAFETY: run() is not reentrant and never touches the PANIC_HOOK_SET variable anywhere else
	// in its body, so run() will never create a second mutable reference. PANIC_HOOK_SET is local
	// to run(), so nobody else can create a second mutable reference on the same thread. OC-Wasm
	// is single-threaded, so no other threads can call run() at the same time.
	let panic_hook_set = unsafe { &mut PANIC_HOOK_SET };
	if !*panic_hook_set {
		std::panic::set_hook(Box::new(panic_hook));
		*panic_hook_set = true;
	}

	// SAFETY: run() is not reentrant and never touches the EXECUTOR variable anywhere else in its
	// body, so run() will never create a second mutable reference. EXECUTOR is local to run(), so
	// nobody else can create a second mutable reference on the same thread. OC-Wasm is
	// single-threaded, so no other threads can call run() at the same time.
	let executor = unsafe { &mut EXECUTOR };
	executor.get_or_init(|| Cassette::new(Box::pin(main())));
	let executor = executor.get_mut().unwrap_or_else(
		// SAFETY: We just called get_or_init(), so it must be populated.
		|| unsafe { core::hint::unreachable_unchecked() },
	);

	sleep::check_for_wakeups();
	if executor.poll_on().is_some() {
		computer::error("main task terminated");
	}
	sleep::shortest_requested()
}