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Carl Fredrik Samson d0a018bfd1 introduction draft
2020-01-25 22:11:11 +01:00

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<h1><a class="header" href="#naive-example" id="naive-example">Naive example</a></h1>
<pre><pre class="playpen"><code class="language-rust">use std::sync::atomic::{AtomicUsize, Ordering};
use std::sync::mpsc::{channel, Sender};
use std::sync::{Arc, Mutex};
use std::thread::{self, JoinHandle};
use std::time::{Duration, Instant};
fn main() {
let readylist = Arc::new(Mutex::new(vec![]));
let mut reactor = Reactor::new();
let mywaker = MyWaker::new(1, thread::current(), readylist.clone());
reactor.register(2, mywaker);
let mywaker = MyWaker::new(2, thread::current(), readylist.clone());
reactor.register(2, mywaker);
executor_run(reactor, readylist);
}
// ====== EXECUTOR ======
fn executor_run(mut reactor: Reactor, rl: Arc&lt;Mutex&lt;Vec&lt;usize&gt;&gt;&gt;) {
let start = Instant::now();
loop {
let mut rl_locked = rl.lock().unwrap();
while let Some(event) = rl_locked.pop() {
let dur = (Instant::now() - start).as_secs_f32();
println!(&quot;Event {} just happened at time: {:.2}.&quot;, event, dur);
reactor.outstanding.fetch_sub(1, Ordering::Relaxed);
}
drop(rl_locked);
if reactor.outstanding.load(Ordering::Relaxed) == 0 {
reactor.close();
break;
}
thread::park();
}
}
// ====== &quot;FUTURE&quot; IMPL ======
#[derive(Debug)]
struct MyWaker {
id: usize,
thread: thread::Thread,
readylist: Arc&lt;Mutex&lt;Vec&lt;usize&gt;&gt;&gt;,
}
impl MyWaker {
fn new(id: usize, thread: thread::Thread, readylist: Arc&lt;Mutex&lt;Vec&lt;usize&gt;&gt;&gt;) -&gt; Self {
MyWaker {
id,
thread,
readylist,
}
}
fn wake(&amp;self) {
self.readylist.lock().map(|mut rl| rl.push(self.id)).unwrap();
self.thread.unpark();
}
}
#[derive(Debug, Clone)]
pub struct Task {
id: usize,
pending: bool,
}
// ===== REACTOR =====
struct Reactor {
dispatcher: Sender&lt;Event&gt;,
handle: Option&lt;JoinHandle&lt;()&gt;&gt;,
outstanding: AtomicUsize,
}
#[derive(Debug)]
enum Event {
Close,
Simple(MyWaker, u64),
}
impl Reactor {
fn new() -&gt; Self {
let (tx, rx) = channel::&lt;Event&gt;();
let mut handles = vec![];
let handle = thread::spawn(move || {
// This simulates some I/O resource
for event in rx {
match event {
Event::Close =&gt; break,
Event::Simple(mywaker, duration) =&gt; {
let event_handle = thread::spawn(move || {
thread::sleep(Duration::from_secs(duration));
mywaker.wake();
});
handles.push(event_handle);
}
}
}
for handle in handles {
handle.join().unwrap();
}
});
Reactor {
dispatcher: tx,
handle: Some(handle),
outstanding: AtomicUsize::new(0),
}
}
fn register(&amp;mut self, duration: u64, mywaker: MyWaker) {
self.dispatcher
.send(Event::Simple(mywaker, duration))
.unwrap();
self.outstanding.fetch_add(1, Ordering::Relaxed);
}
fn close(&amp;mut self) {
self.dispatcher.send(Event::Close).unwrap();
}
}
impl Drop for Reactor {
fn drop(&amp;mut self) {
self.handle.take().map(|h| h.join().unwrap()).unwrap();
}
}
</code></pre></pre>
<pre><pre class="playpen"><code class="language-rust">use std::sync::atomic::{AtomicUsize, Ordering};
use std::sync::mpsc::{channel, Sender};
use std::sync::{Arc, Mutex};
use std::thread::{self, JoinHandle};
use std::time::{Duration, Instant};
fn main() {
let readylist = Arc::new(Mutex::new(vec![]));
let mut reactor = Reactor::new();
let mywaker = MyWaker::new(1, thread::current(), readylist.clone());
reactor.register(2, mywaker);
let mywaker = MyWaker::new(2, thread::current(), readylist.clone());
reactor.register(2, mywaker);
executor_run(reactor, readylist);
}
<span class="boring">// ====== EXECUTOR ======
</span><span class="boring">fn executor_run(mut reactor: Reactor, rl: Arc&lt;Mutex&lt;Vec&lt;usize&gt;&gt;&gt;) {
</span><span class="boring"> let start = Instant::now();
</span><span class="boring"> loop {
</span><span class="boring"> let mut rl_locked = rl.lock().unwrap();
</span><span class="boring"> while let Some(event) = rl_locked.pop() {
</span><span class="boring"> let dur = (Instant::now() - start).as_secs_f32();
</span><span class="boring"> println!(&quot;Event {} just happened at time: {:.2}.&quot;, event, dur);
</span><span class="boring"> reactor.outstanding.fetch_sub(1, Ordering::Relaxed);
</span><span class="boring"> }
</span><span class="boring"> drop(rl_locked);
</span><span class="boring">
</span><span class="boring"> if reactor.outstanding.load(Ordering::Relaxed) == 0 {
</span><span class="boring"> reactor.close();
</span><span class="boring"> break;
</span><span class="boring"> }
</span><span class="boring">
</span><span class="boring"> thread::park();
</span><span class="boring"> }
</span><span class="boring">}
</span><span class="boring">
</span><span class="boring">// ====== &quot;FUTURE&quot; IMPL ======
</span><span class="boring">#[derive(Debug)]
</span><span class="boring">struct MyWaker {
</span><span class="boring"> id: usize,
</span><span class="boring"> thread: thread::Thread,
</span><span class="boring"> readylist: Arc&lt;Mutex&lt;Vec&lt;usize&gt;&gt;&gt;,
</span><span class="boring">}
</span><span class="boring">
</span><span class="boring">impl MyWaker {
</span><span class="boring"> fn new(id: usize, thread: thread::Thread, readylist: Arc&lt;Mutex&lt;Vec&lt;usize&gt;&gt;&gt;) -&gt; Self {
</span><span class="boring"> MyWaker {
</span><span class="boring"> id,
</span><span class="boring"> thread,
</span><span class="boring"> readylist,
</span><span class="boring"> }
</span><span class="boring"> }
</span><span class="boring">
</span><span class="boring"> fn wake(&amp;self) {
</span><span class="boring"> self.readylist.lock().map(|mut rl| rl.push(self.id)).unwrap();
</span><span class="boring"> self.thread.unpark();
</span><span class="boring"> }
</span><span class="boring">}
</span><span class="boring">
</span><span class="boring">
</span><span class="boring">#[derive(Debug, Clone)]
</span><span class="boring">pub struct Task {
</span><span class="boring"> id: usize,
</span><span class="boring"> pending: bool,
</span><span class="boring">}
</span><span class="boring">
</span><span class="boring">// ===== REACTOR =====
</span><span class="boring">struct Reactor {
</span><span class="boring"> dispatcher: Sender&lt;Event&gt;,
</span><span class="boring"> handle: Option&lt;JoinHandle&lt;()&gt;&gt;,
</span><span class="boring"> outstanding: AtomicUsize,
</span><span class="boring">}
</span><span class="boring">#[derive(Debug)]
</span><span class="boring">enum Event {
</span><span class="boring"> Close,
</span><span class="boring"> Simple(MyWaker, u64),
</span><span class="boring">}
</span><span class="boring">
</span><span class="boring">impl Reactor {
</span><span class="boring"> fn new() -&gt; Self {
</span><span class="boring"> let (tx, rx) = channel::&lt;Event&gt;();
</span><span class="boring"> let mut handles = vec![];
</span><span class="boring"> let handle = thread::spawn(move || {
</span><span class="boring"> // This simulates some I/O resource
</span><span class="boring"> for event in rx {
</span><span class="boring"> match event {
</span><span class="boring"> Event::Close =&gt; break,
</span><span class="boring"> Event::Simple(mywaker, duration) =&gt; {
</span><span class="boring"> let event_handle = thread::spawn(move || {
</span><span class="boring"> thread::sleep(Duration::from_secs(duration));
</span><span class="boring"> mywaker.wake();
</span><span class="boring"> });
</span><span class="boring"> handles.push(event_handle);
</span><span class="boring"> }
</span><span class="boring"> }
</span><span class="boring"> }
</span><span class="boring">
</span><span class="boring"> for handle in handles {
</span><span class="boring"> handle.join().unwrap();
</span><span class="boring"> }
</span><span class="boring"> });
</span><span class="boring">
</span><span class="boring"> Reactor {
</span><span class="boring"> dispatcher: tx,
</span><span class="boring"> handle: Some(handle),
</span><span class="boring"> outstanding: AtomicUsize::new(0),
</span><span class="boring"> }
</span><span class="boring"> }
</span><span class="boring">
</span><span class="boring"> fn register(&amp;mut self, duration: u64, mywaker: MyWaker) {
</span><span class="boring"> self.dispatcher
</span><span class="boring"> .send(Event::Simple(mywaker, duration))
</span><span class="boring"> .unwrap();
</span><span class="boring"> self.outstanding.fetch_add(1, Ordering::Relaxed);
</span><span class="boring"> }
</span><span class="boring">
</span><span class="boring"> fn close(&amp;mut self) {
</span><span class="boring"> self.dispatcher.send(Event::Close).unwrap();
</span><span class="boring"> }
</span><span class="boring">}
</span><span class="boring">
</span><span class="boring">impl Drop for Reactor {
</span><span class="boring"> fn drop(&amp;mut self) {
</span><span class="boring"> self.handle.take().map(|h| h.join().unwrap()).unwrap();
</span><span class="boring"> }
</span><span class="boring">}
</span></code></pre></pre>
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