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#![feature(coerce_unsized)]
#![feature(unsize)]
#![feature(once_cell)]
#![deny(missing_docs)]
pub mod state;
mod alloc;
mod noop_waker;
mod unchecked_any;
mod universal_type_id;
pub use universal_type_id::UniversalTypeId;
use std::{
collections::VecDeque,
future::Future,
mem,
pin::Pin,
sync::Mutex,
task::{self, Poll},
};
use alloc::{Chunker, CBox, CArc, CWeak};
use noop_waker::noop_context;
pub struct Executor {
spawn_context: SpawnContext,
tasks: VecDeque<Pin<CBox<dyn Future<Output=()>>>>,
tasks_temp: Vec<Pin<CBox<dyn Future<Output=()>>>>,
exclusive_tasks: Vec<Pin<CBox<dyn Future<Output=()>>>>,
}
pub struct JoinHandle<T: Send>(CArc<Mutex<Option<T>>>);
pub(crate) struct SpawnContext {
alloc: Chunker,
spawned: Vec<Pin<CBox<dyn Future<Output=()>>>>,
}
pub fn yield_now() -> impl Future<Output=()> {
yield_ticks(1)
}
pub fn yield_ticks(count: usize) -> impl Future<Output=()> {
return Roll(count);
struct Roll(usize);
impl Future for Roll {
type Output = ();
fn poll(mut self: Pin<&mut Self>, _: &mut task::Context) -> Poll<()> {
if self.0 == 0 {
Poll::Ready(())
} else {
self.0 -= 1;
Poll::Pending
}
}
}
}
impl Executor {
pub fn new() -> Self {
Self {
spawn_context: SpawnContext {
alloc: Chunker::new(),
spawned: Vec::new(),
},
tasks: VecDeque::new(),
tasks_temp: Vec::new(),
exclusive_tasks: Vec::new(),
}
}
pub fn insert<F>(&mut self, future: F)
where
F: Future<Output=()> + Send + Sync + 'static
{
self.spawn_context.spawn(future);
}
pub fn tick<'a, T>(&mut self, state: &mut T)
where
T: 'a + UniversalTypeId + Sync
{
use state::{AccessMode, AwaitCondition};
self.tasks_temp.extend(self.spawn_context.spawned.drain(..));
self.tasks_temp.extend(self.tasks.drain(..));
unsafe {
state::set_broadcast(&mut self.spawn_context, state);
state::set_access_mode(AccessMode::Shared);
}
for mut task in self.tasks_temp.drain(..) {
let poll_result = task.as_mut().poll(&mut noop_context());
let await_condition = unsafe { state::read_await_condition() };
match (poll_result, await_condition) {
(Poll::Pending, AwaitCondition::NextTick) => self.tasks.push_front(task),
(Poll::Pending, AwaitCondition::Exclusive) => self.exclusive_tasks.push(task),
(Poll::Ready(_), _) => mem::drop(task),
}
}
unsafe {
state::set_access_mode(AccessMode::Exclusive);
}
for mut task in self.exclusive_tasks.drain(..) {
match task.as_mut().poll(&mut noop_context()) {
Poll::Pending => self.tasks.push_front(task),
Poll::Ready(_) => mem::drop(task),
}
}
unsafe {
state::reset_broadcast();
}
self.spawn_context.alloc.quiescent_cleanup();
}
}
impl SpawnContext {
pub(crate) fn spawn<F>(&mut self, future: F)
where
F: Future<Output=()> + Send + Sync + 'static
{
let boxed_future = self.alloc.alloc_box(future) as CBox<dyn Future<Output=()>>;
let task = CBox::pin(boxed_future);
self.spawned.push(task);
}
pub(crate) fn spawn_ret<F, T>(&mut self, future: F) -> JoinHandle<T>
where
F: Future<Output=T> + Send + Sync + 'static,
T: Send + 'static
{
let arc = self.alloc.alloc_arc(Mutex::new(None));
let weak = arc.make_weak();
let handle = JoinHandle(arc);
self.spawn(wrap_return(future, weak));
return handle;
async fn wrap_return<F, T>(fut: F, return_place: CWeak<Mutex<Option<T>>>)
where
F: Future<Output=T>,
T: Send
{
let value = fut.await;
if let Some(arc) = return_place.upgrade() {
*arc.lock().unwrap() = Some(value);
}
}
}
}
impl<T: Send + 'static> Future for JoinHandle<T> {
type Output = T;
fn poll(self: Pin<&mut Self>, _: &mut task::Context) -> Poll<Self::Output> {
let value = self.0.lock().unwrap().take();
match value {
Some(value) => Poll::Ready(value),
None => Poll::Pending,
}
}
}