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use crate::{enter, ThreadPool};
use futures_core::future::{Future, FutureObj, LocalFutureObj};
use futures_core::stream::{Stream};
use futures_core::task::{
self, Poll, LocalWaker, Wake,
Spawn, LocalSpawn, SpawnError,
};
use futures_util::stream::FuturesUnordered;
use futures_util::stream::StreamExt;
use lazy_static::lazy_static;
use pin_utils::pin_mut;
use std::cell::{RefCell};
use std::marker::Unpin;
use std::ops::{Deref, DerefMut};
use std::prelude::v1::*;
use std::rc::{Rc, Weak};
use std::sync::Arc;
use std::thread::{self, Thread};
#[derive(Debug)]
pub struct LocalPool {
pool: FuturesUnordered<LocalFutureObj<'static, ()>>,
incoming: Rc<Incoming>,
}
#[derive(Clone, Debug)]
pub struct LocalSpawner {
incoming: Weak<Incoming>,
}
type Incoming = RefCell<Vec<LocalFutureObj<'static, ()>>>;
pub(crate) struct ThreadNotify {
thread: Thread
}
thread_local! {
static CURRENT_THREAD_NOTIFY: Arc<ThreadNotify> = Arc::new(ThreadNotify {
thread: thread::current(),
});
}
impl Wake for ThreadNotify {
fn wake(arc_self: &Arc<Self>) {
arc_self.thread.unpark();
}
}
fn run_executor<T, F: FnMut(&LocalWaker) -> Poll<T>>(mut f: F) -> T {
let _enter = enter()
.expect("cannot execute `LocalPool` executor from within \
another executor");
CURRENT_THREAD_NOTIFY.with(|thread_notify| {
let local_waker =
task::local_waker_from_nonlocal(thread_notify.clone());
loop {
if let Poll::Ready(t) = f(&local_waker) {
return t;
}
thread::park();
}
})
}
impl LocalPool {
pub fn new() -> LocalPool {
LocalPool {
pool: FuturesUnordered::new(),
incoming: Default::default(),
}
}
pub fn spawner(&self) -> LocalSpawner {
LocalSpawner {
incoming: Rc::downgrade(&self.incoming)
}
}
pub fn run(&mut self) {
run_executor(|local_waker| self.poll_pool(local_waker))
}
pub fn run_until<F: Future>(&mut self, future: F) -> F::Output {
pin_mut!(future);
run_executor(|local_waker| {
{
let result = future.as_mut().poll(local_waker);
if let Poll::Ready(output) = result {
return Poll::Ready(output);
}
}
self.poll_pool(local_waker);
Poll::Pending
})
}
fn poll_pool(&mut self, local_waker: &LocalWaker) -> Poll<()> {
loop {
{
let mut incoming = self.incoming.borrow_mut();
for task in incoming.drain(..) {
self.pool.push(task)
}
}
let ret = self.pool.poll_next_unpin(local_waker);
if !self.incoming.borrow().is_empty() {
continue;
}
match ret {
Poll::Pending => return Poll::Pending,
Poll::Ready(None) => return Poll::Ready(()),
_ => {}
}
}
}
}
impl Default for LocalPool {
fn default() -> Self {
Self::new()
}
}
lazy_static! {
static ref GLOBAL_POOL: ThreadPool = ThreadPool::builder()
.name_prefix("block_on-")
.create()
.expect("Unable to create global thread-pool");
}
pub fn block_on<F: Future>(f: F) -> F::Output {
let mut pool = LocalPool::new();
pool.run_until(f)
}
pub fn block_on_stream<S: Stream + Unpin>(stream: S) -> BlockingStream<S> {
BlockingStream { stream }
}
#[derive(Debug)]
pub struct BlockingStream<S: Stream + Unpin> { stream: S }
impl<S: Stream + Unpin> Deref for BlockingStream<S> {
type Target = S;
fn deref(&self) -> &Self::Target {
&self.stream
}
}
impl<S: Stream + Unpin> DerefMut for BlockingStream<S> {
fn deref_mut(&mut self) -> &mut Self::Target {
&mut self.stream
}
}
impl<S: Stream + Unpin> BlockingStream<S> {
pub fn into_inner(self) -> S {
self.stream
}
}
impl<S: Stream + Unpin> Iterator for BlockingStream<S> {
type Item = S::Item;
fn next(&mut self) -> Option<Self::Item> {
LocalPool::new().run_until(self.stream.next())
}
}
impl Spawn for LocalSpawner {
fn spawn_obj(
&mut self,
future: FutureObj<'static, ()>,
) -> Result<(), SpawnError> {
if let Some(incoming) = self.incoming.upgrade() {
incoming.borrow_mut().push(future.into());
Ok(())
} else {
Err(SpawnError::shutdown())
}
}
fn status(&self) -> Result<(), SpawnError> {
if self.incoming.upgrade().is_some() {
Ok(())
} else {
Err(SpawnError::shutdown())
}
}
}
impl LocalSpawn for LocalSpawner {
fn spawn_local_obj(
&mut self,
future: LocalFutureObj<'static, ()>,
) -> Result<(), SpawnError> {
if let Some(incoming) = self.incoming.upgrade() {
incoming.borrow_mut().push(future);
Ok(())
} else {
Err(SpawnError::shutdown())
}
}
fn status_local(&self) -> Result<(), SpawnError> {
if self.incoming.upgrade().is_some() {
Ok(())
} else {
Err(SpawnError::shutdown())
}
}
}