added example

exemples/reactor_executor/Cargo.lock

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exemples/reactor_executor/Cargo.toml

+[package]
+name = "reactor_executor"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+mio = { version = "1.0.3", features = ["net", "os-poll"] }

exemples/reactor_executor/src/future.rs

+use crate::runtime::Waker;
+
+// Future trait looks like standard Future except for the missing context
+// pub trait Future {
+//    type Output;
+//    fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output>;
+//}
+// We now also have the `Waker` as an argument of the `Future` trait. We see that in the standard
+// library the Waker is hidden in a Context which we do not need here
+pub trait Future {
+    type Output;
+
+    // TODO:
+    // Add the Waker into poll
+    fn poll(&mut self) -> PollState<Self::Output>;
+}
+
+// Similar to the Poll #[derive(Debug)]
+// pub enum Poll<T> {
+//     Ready(T),
+//     Pending,
+// }
+pub enum PollState<T> {
+    Ready(T),
+    NotReady,
+}
+
+// Exercise adapt the join_all function to accept the Waker structs

exemples/reactor_executor/src/http.rs

+use mio::Interest;
+
+use crate::future::{Future, PollState};
+use crate::runtime::{self, reactor, Waker};
+use std::io::{ErrorKind, Read, Write};
+
+// Simple helper function to write GET requests
+fn get_req(path: &str) -> String {
+    format!(
+        "GET {path} HTTP/1.1\r\n\
+        Host: localhost\r\n\
+        Connection: close\r\n\
+        \r\n"
+    )
+}
+
+pub struct Http;
+
+impl Http {
+    pub fn get(path: &str) -> impl Future<Output = String> {
+        HttpGetFuture::new(path)
+    }
+}
+
+// The id of the `Future` is also a needed information to register it for the `Waker` and `Poll`
+struct HttpGetFuture {
+    // Option since we will not conect upon creation
+    stream: Option<mio::net::TcpStream>,
+    // buffer to read from the TcpStream
+    buffer: Vec<u8>,
+    // The GET request we will construct
+    path: String,
+    // NEW: The id of our Future
+    id: usize,
+}
+
+impl HttpGetFuture {
+    fn new(path: &str) -> Self {
+        unimplemented!();
+        // TODO:
+        // get the id from the next_id of the reactor
+        let id = 1;
+        Self {
+            stream: None,
+            buffer: vec![],
+            path: String::from(path),
+            id,
+        }
+    }
+
+    // Writes the request to a non bocking stream. Here we are using mio t connect to the socket
+    // We just create the stream and do not perform any request here
+    fn write_request(&mut self) {
+        let stream = std::net::TcpStream::connect("localhost:8080").unwrap();
+        stream.set_nonblocking(true).unwrap();
+        let mut stream = mio::net::TcpStream::from_std(stream);
+        stream.write_all(get_req(&self.path).as_bytes()).unwrap();
+        self.stream = Some(stream);
+    }
+}
+
+impl Future for HttpGetFuture {
+    type Output = String;
+
+    // TODO:
+    // Add the waker into poll()
+    fn poll(&mut self) -> PollState<Self::Output> {
+        if self.stream.is_none() {
+            println!("First poll - start operation");
+            self.write_request();
+            //TODO:
+            // From the reactor()
+            // 1. Registering the Tcp stream as a source of events in the poll instance
+            // 2. We also set the `Waker` responsible for handling the `Future` with the self.id
+        }
+        let mut buf = vec![0u8; 4096];
+        // We loop until everything is read and return Ready when done
+        loop {
+            // We listen on the socket and read
+            match self.stream.as_mut().unwrap().read(&mut buf) {
+                // 0 bytes read so we are finished we got the entire GET response
+                Ok(0) => {
+                    let s = String::from_utf8_lossy(&self.buffer);
+                    // TODO:
+                    // The future is over we deregister our interest from this source of events for
+                    // the current id
+                    break PollState::Ready(String::from(s));
+                }
+                // We read n bytes so we continue reading
+                Ok(n) => {
+                    self.buffer.extend(&buf[0..n]);
+                    continue;
+                }
+                // This error indicates that the data is not ready yet or that that there is more
+                // data we did not received yet
+                Err(e) if e.kind() == ErrorKind::WouldBlock => {
+                    println!("Data not ready");
+                    // TODO:
+                    // We need to set the `waker` again since the data is not ready
+                    break PollState::NotReady;
+                }
+                // This error can happen if a signal interrupted the read (which can happen) we
+                // handle this case by reading again
+                Err(e) if e.kind() == ErrorKind::Interrupted => {
+                    continue;
+                }
+                // Nothing we can do. We panic!
+                Err(e) => panic!("{e:?}"),
+            }
+        }
+    }
+}

exemples/reactor_executor/src/main.rs

+mod future;
+mod http;
+mod runtime;
+
+use future::{Future, PollState};
+use http::Http;
+use runtime::Waker;
+
+fn main() {
+    let mut executor = runtime::init();
+    executor.block_on(async_main());
+}
+
+fn async_main() -> impl Future<Output = String> {
+    Coroutine::new()
+}
+
+enum State {
+    Start,
+    Wait1(Box<dyn Future<Output = String>>),
+    Wait2(Box<dyn Future<Output = String>>),
+    Resolved,
+}
+
+struct Coroutine {
+    state: State,
+}
+
+impl Coroutine {
+    fn new() -> Self {
+        Self {
+            state: State::Start,
+        }
+    }
+}
+
+// We need to adapt `poll()` and the subsequent calls of the children `Future` to have an extra
+// argument: the `Waker`.
+impl Future for Coroutine {
+    type Output = String;
+
+    //TODO:
+    //add Waker into poll
+    fn poll(&mut self) -> PollState<Self::Output> {
+        loop {
+            match self.state {
+                State::Start => {
+                    println!("Program starting");
+                    let fut1 = Box::new(Http::get("/600/HelloAsyncAwait"));
+                    self.state = State::Wait1(fut1);
+                }
+
+                //TODO:
+                //add Waker into poll
+                State::Wait1(ref mut future) => match future.poll() {
+                    PollState::Ready(txt) => {
+                        println!("{txt}");
+                        let fut2 = Box::new(Http::get("/400/HelloAsyncAwait"));
+                        self.state = State::Wait2(fut2);
+                    }
+                    PollState::NotReady => break PollState::NotReady,
+                },
+
+                //TODO:
+                //add Waker into poll
+                State::Wait2(ref mut future) => match future.poll() {
+                    PollState::Ready(txt) => {
+                        println!("{txt}");
+                        self.state = State::Resolved;
+                        break PollState::Ready(String::new());
+                    }
+                    PollState::NotReady => break PollState::NotReady,
+                },
+
+                State::Resolved => panic!("Polled a resolved future"),
+            }
+        }
+    }
+}

exemples/reactor_executor/src/runtime.rs

+mod executor;
+mod reactor;
+
+pub use executor::{Executor, Waker};
+pub use reactor::reactor;
+
+pub fn init() -> Executor {
+    reactor::start();
+    Executor::new()
+}

exemples/reactor_executor/src/runtime/executor.rs

+use std::{
+    cell::{Cell, RefCell},
+    collections::HashMap,
+    sync::{Arc, Mutex},
+    thread::{self, Thread},
+};
+
+use crate::future::{Future, PollState};
+
+#[derive(Clone)]
+pub struct Waker {
+    thread: Thread,
+    id: usize,
+    ready_queue: Arc<Mutex<Vec<usize>>>,
+}
+
+impl Waker {
+    pub fn wake(&self) {
+        // TODO:
+        // 1. push id into the ready_queue
+        // 2. unpark the thread
+        unimplemented!()
+    }
+}
+
+type Task = Box<dyn Future<Output = String>>;
+
+thread_local! {
+    static CURRENT_EXECUTOR: ExecutorCore = ExecutorCore::default();
+}
+
+#[derive(Default)]
+struct ExecutorCore {
+    tasks: RefCell<HashMap<usize, Task>>,
+    ready_queue: Arc<Mutex<Vec<usize>>>,
+    next_id: Cell<usize>,
+}
+
+pub fn spawn<F>(future: F)
+where
+    F: Future<Output = String> + 'static,
+{
+    unimplemented!();
+    // TODO:
+    CURRENT_EXECUTOR.with(|e| {
+        // 1. insert (next_id and future)
+        // 2. push id into ready_queue
+        // 3. add one to next_id
+    });
+}
+
+pub struct Executor;
+impl Executor {
+    pub fn new() -> Self {
+        Self {}
+    }
+
+    fn pop_ready(&self) -> Option<usize> {
+        // TODO:
+        // pop from ready queue, CURRENT_EXECUTOR.with
+        // dont forget the lock()
+        unimplemented!()
+    }
+    fn get_future(&self, id: usize) -> Option<Task> {
+        // TODO:
+        // remove &id from tasks thanks to borrow_mut
+        unimplemented!()
+    }
+    fn get_waker(&self, id: usize) -> Waker {
+        // TODO:
+        // create a new waker from: id, thread::current(), and a clone from ready_queue
+        unimplemented!()
+    }
+
+    // Inserts a new task with a given id into the tasks HashMap
+    fn insert_task(&self, id: usize, task: Task) {
+        // TODO:
+        //insert a pair id, task into tasks
+        unimplemented!()
+    }
+
+    // Counts how many tasks are left to be executed
+    fn task_count(&self) -> usize {
+        CURRENT_EXECUTOR.with(|e| e.tasks.borrow().len())
+    }
+
+    pub fn block_on<F>(&mut self, future: F)
+    where
+        F: Future<Output = String> + 'static,
+    {
+        // TODO:
+        // 1. spawn a future
+        loop {
+            // TODO:
+            // 1. while there are something left into ready_queue, pop_ready the id
+            // 2. get the future by id
+            // 3. get a waker by id
+            // 4. poll the future
+            // 5. if NotReady => insert the (id, future)
+            // 6. else continue
+            //
+            let task_count = self.task_count();
+            let name = String::from(thread::current().name().unwrap_or_default());
+
+            // TODO: if not finished park()
+            // otherwise break
+            if task_count > 0 {
+                println!("{name}:  {task_count}, pending tasks. Sleep until notified.");
+            } else {
+                println!("{name}: All tasks finished");
+            }
+        }
+    }
+}

exemples/reactor_executor/src/runtime/reactor.rs

+use std::{
+    collections::HashMap,
+    sync::{atomic::AtomicUsize, Arc, Mutex, OnceLock},
+};
+
+use mio::{net::TcpStream, Events, Interest, Poll, Registry, Token};
+
+use crate::runtime::Waker;
+
+type Wakers = Arc<Mutex<HashMap<usize, Waker>>>;
+
+static REACTOR: OnceLock<Reactor> = OnceLock::new();
+
+pub fn reactor() -> &'static Reactor {
+    REACTOR.get().expect("Called outside a runtime context")
+}
+
+pub struct Reactor {
+    wakers: Wakers,
+    registry: Registry,
+    next_id: AtomicUsize,
+}
+
+impl Reactor {
+    pub fn register(&self, stream: &mut TcpStream, interest: Interest, id: usize) {
+        // TODO:
+        // register on the registry for stream, id, and interest
+        unimplemented!()
+    }
+
+    pub fn set_waker(&self, waker: &Waker, id: usize) {
+        // TODO:
+        // insert a pair id, waker into wakers
+        unimplemented!()
+    }
+
+    pub fn deregister(&self, stream: &mut TcpStream, id: usize) {
+        //TODO:
+        // 1. remove the if from the wakers (don't forget to lock/map)
+        // 2. deregister the stream from the registry
+        unimplemented!()
+    }
+    pub fn next_id(&self) -> usize {
+        self.next_id
+            .fetch_add(1, std::sync::atomic::Ordering::Relaxed)
+    }
+}
+
+fn event_loop(mut poll: Poll, wakers: Wakers) {
+    unimplemented!();
+    let mut events = Events::with_capacity(100);
+    loop {
+        // TODO:
+        // 1. poll event with None timeout
+        // 2. for_each event get the .token()
+        // 3. lock the wakers and the the waker by id
+        // 4. wake() the waker
+    }
+}
+
+pub fn start() {
+    unimplemented!();
+    // TODO:
+    // 1. create a new empty wakers HashMap<usize, Waker>
+    // 2. create a new Poll
+    // 3. create a try_clone poll.registry()
+    // 4. initialize a new next_id to 1
+    // 5. create a new Reactor
+    REACTOR.set(reactor).ok().expect("Rector already running");
+    // 6. move the event loop of poll and wakers into a new system thread:
+}