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<ol class="chapter"><li class="affix"><a href="introduction.html">Introduction</a></li><li><a href="1_background_information.html"><strong aria-hidden="true">1.</strong> Some background information</a></li><li><a href="2_trait_objects.html"><strong aria-hidden="true">2.</strong> Trait objects and fat pointers</a></li><li><a href="3_generators_pin.html"><strong aria-hidden="true">3.</strong> Generators</a></li><li><a href="4_pin.html"><strong aria-hidden="true">4.</strong> Pin</a></li><li><a href="6_future_example.html"><strong aria-hidden="true">5.</strong> Futures - our main example</a></li><li><a href="8_finished_example.html" class="active"><strong aria-hidden="true">6.</strong> Finished example (editable)</a></li><li class="affix"><a href="conclusion.html">Conclusion and exercises</a></li></ol>
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<h1><a class="header" href="#our-finished-code" id="our-finished-code">Our finished code</a></h1>
<p>Here is the whole example. You can edit it right here in your browser and
run it yourself. Have fun!</p>
<pre><pre class="playpen"><code class="language-rust editable edition2018">use std::{
future::Future, pin::Pin, sync::{mpsc::{channel, Sender}, Arc, Mutex},
task::{Context, Poll, RawWaker, RawWakerVTable, Waker},
thread::{self, JoinHandle}, time::{Duration, Instant}
};
fn main() {
let start = Instant::now();
let reactor = Reactor::new();
let reactor = Arc::new(Mutex::new(reactor));
let future1 = Task::new(reactor.clone(), 1, 1);
let future2 = Task::new(reactor.clone(), 2, 2);
let fut1 = async {
let val = future1.await;
let dur = (Instant::now() - start).as_secs_f32();
println!(&quot;Future got {} at time: {:.2}.&quot;, val, dur);
};
let fut2 = async {
let val = future2.await;
let dur = (Instant::now() - start).as_secs_f32();
println!(&quot;Future got {} at time: {:.2}.&quot;, val, dur);
};
let mainfut = async {
let handle1 = spawn(fut1);
let handle2 = spawn(fut2);
handle1.await;
handle2.await;
};
block_on(mainfut);
reactor.lock().map(|mut r| r.close()).unwrap();
}
// ============================= EXECUTOR ====================================
fn block_on&lt;F: Future&gt;(mut future: F) -&gt; F::Output {
let mywaker = Arc::new(MyWaker{ thread: thread::current() });
let waker = waker_into_waker(Arc::into_raw(mywaker));
let mut cx = Context::from_waker(&amp;waker);
let val = loop {
let pinned = unsafe { Pin::new_unchecked(&amp;mut future) };
match Future::poll(pinned, &amp;mut cx) {
Poll::Ready(val) =&gt; break val,
Poll::Pending =&gt; thread::park(),
};
};
val
}
fn spawn&lt;F: Future&gt;(future: F) -&gt; Pin&lt;Box&lt;F&gt;&gt; {
let mywaker = Arc::new(MyWaker{ thread: thread::current() });
let waker = waker_into_waker(Arc::into_raw(mywaker));
let mut cx = Context::from_waker(&amp;waker);
let mut boxed = Box::pin(future);
let _ = Future::poll(boxed.as_mut(), &amp;mut cx);
boxed
}
// ====================== FUTURE IMPLEMENTATION ==============================
#[derive(Clone)]
struct MyWaker {
thread: thread::Thread,
}
#[derive(Clone)]
pub struct Task {
id: usize,
reactor: Arc&lt;Mutex&lt;Reactor&gt;&gt;,
data: u64,
is_registered: bool,
}
fn mywaker_wake(s: &amp;MyWaker) {
let waker_ptr: *const MyWaker = s;
let waker_arc = unsafe {Arc::from_raw(waker_ptr)};
waker_arc.thread.unpark();
}
fn mywaker_clone(s: &amp;MyWaker) -&gt; RawWaker {
let arc = unsafe { Arc::from_raw(s).clone() };
std::mem::forget(arc.clone()); // increase ref count
RawWaker::new(Arc::into_raw(arc) as *const (), &amp;VTABLE)
}
const VTABLE: RawWakerVTable = unsafe {
RawWakerVTable::new(
|s| mywaker_clone(&amp;*(s as *const MyWaker)), // clone
|s| mywaker_wake(&amp;*(s as *const MyWaker)), // wake
|s| mywaker_wake(*(s as *const &amp;MyWaker)), // wake by ref
|s| drop(Arc::from_raw(s as *const MyWaker)), // decrease refcount
)
};
fn waker_into_waker(s: *const MyWaker) -&gt; Waker {
let raw_waker = RawWaker::new(s as *const (), &amp;VTABLE);
unsafe { Waker::from_raw(raw_waker) }
}
impl Task {
fn new(reactor: Arc&lt;Mutex&lt;Reactor&gt;&gt;, data: u64, id: usize) -&gt; Self {
Task {
id,
reactor,
data,
is_registered: false,
}
}
}
impl Future for Task {
type Output = usize;
fn poll(mut self: Pin&lt;&amp;mut Self&gt;, cx: &amp;mut Context&lt;'_&gt;) -&gt; Poll&lt;Self::Output&gt; {
let mut r = self.reactor.lock().unwrap();
if r.is_ready(self.id) {
Poll::Ready(self.id)
} else if self.is_registered {
Poll::Pending
} else {
r.register(self.data, cx.waker().clone(), self.id);
drop(r);
self.is_registered = true;
Poll::Pending
}
}
}
// =============================== REACTOR ===================================
struct Reactor {
dispatcher: Sender&lt;Event&gt;,
handle: Option&lt;JoinHandle&lt;()&gt;&gt;,
readylist: Arc&lt;Mutex&lt;Vec&lt;usize&gt;&gt;&gt;,
}
#[derive(Debug)]
enum Event {
Close,
Timeout(Waker, u64, usize),
}
impl Reactor {
fn new() -&gt; Self {
let (tx, rx) = channel::&lt;Event&gt;();
let readylist = Arc::new(Mutex::new(vec![]));
let rl_clone = readylist.clone();
let mut handles = vec![];
let handle = thread::spawn(move || {
// This simulates some I/O resource
for event in rx {
println!(&quot;REACTOR: {:?}&quot;, event);
let rl_clone = rl_clone.clone();
match event {
Event::Close =&gt; break,
Event::Timeout(waker, duration, id) =&gt; {
let event_handle = thread::spawn(move || {
thread::sleep(Duration::from_secs(duration));
rl_clone.lock().map(|mut rl| rl.push(id)).unwrap();
waker.wake();
});
handles.push(event_handle);
}
}
}
for handle in handles {
handle.join().unwrap();
}
});
Reactor {
readylist,
dispatcher: tx,
handle: Some(handle),
}
}
fn register(&amp;mut self, duration: u64, waker: Waker, data: usize) {
self.dispatcher
.send(Event::Timeout(waker, duration, data))
.unwrap();
}
fn close(&amp;mut self) {
self.dispatcher.send(Event::Close).unwrap();
}
fn is_ready(&amp;self, id_to_check: usize) -&gt; bool {
self.readylist
.lock()
.map(|rl| rl.iter().any(|id| *id == id_to_check))
.unwrap()
}
}
impl Drop for Reactor {
fn drop(&amp;mut self) {
self.handle.take().map(|h| h.join().unwrap()).unwrap();
}
}
</code></pre></pre>
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