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// TODO: replace "//" with "///" and fix TcpListener with Evented
// Associates readiness notifications with [`Evented`] handles.
//
// `Token` is a wrapper around `usize` and is used as an argument to
// [`Poll::register`] and [`Poll::reregister`].
//
// See [`Poll`] for more documentation on polling.
//
// # Example
//
// Using `Token` to track which socket generated the notification. In this
// example, `HashMap` is used, but usually something like [`slab`] is better.
//
// ```
// # use std::error::Error;
// # fn try_main() -> Result<(), Box<dyn Error>> {
// use urca::{Events, Ready, Poll, PollOpt, Token};
// use urca::net::TcpListener;
//
// use std::thread;
// use std::io::{self, Read};
// use std::collections::HashMap;
//
// // After this number of sockets is accepted, the server will shutdown.
// const MAX_SOCKETS: usize = 32;
//
// // Pick a token that will not be used by any other socket and use that one
// // for the listener.
// const LISTENER: Token = Token(1024);
//
// // Used to store the sockets.
// let mut sockets = HashMap::new();
//
// // This is used to generate a unique token for a socket
// let mut next_socket_index = 0;
//
// // The `Poll` instance
// let poll = Poll::new()?;
//
// // Tcp listener
// let listener = TcpListener::bind(&"127.0.0.1:0".parse()?)?;
//
// // Register the listener
// poll.register(&listener,
// LISTENER,
// Ready::readable(),
// PollOpt::edge())?;
//
// // Spawn a thread that will connect a bunch of sockets then close them
// let addr = listener.local_addr()?;
// thread::spawn(move || {
// use std::net::TcpStream;
//
// // +1 here is to connect an extra socket to signal the socket to close
// for _ in 0..(MAX_SOCKETS+1) {
// // Connect then drop the socket
// let _ = TcpStream::connect(&addr).unwrap();
// }
// });
//
// // Event storage
// let mut events = Events::with_capacity(1024);
//
// // Read buffer, this will never actually get filled
// let mut buf = [0; 256];
//
// // The main event loop
// loop {
// // Wait for events
// poll.poll(&mut events, None)?;
//
// for event in &events {
// match event.token() {
// LISTENER => {
// // Perform operations in a loop until `WouldBlock` is
// // encountered.
// loop {
// match listener.accept() {
// Ok((socket, _)) => {
// // Shutdown the server
// if next_socket_index == MAX_SOCKETS {
// return Ok(());
// }
//
// // Get the token for the socket
// let token = Token(next_socket_index);
// next_socket_index += 1;
//
// // Register the new socket w/ poll
// poll.register(&socket,
// token,
// Ready::readable(),
// PollOpt::edge())?;
//
// // Store the socket
// sockets.insert(token, socket);
// }
// Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
// // Socket is not ready anymore, stop accepting
// break;
// }
// e => panic!("err={:?}", e), // Unexpected error
// }
// }
// }
// token => {
// // Always operate in a loop
// loop {
// match sockets.get_mut(&token).unwrap().read(&mut buf) {
// Ok(0) => {
// // Socket is closed, remove it from the map
// sockets.remove(&token);
// break;
// }
// // Data is not actually sent in this example
// Ok(_) => unreachable!(),
// Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
// // Socket is not ready anymore, stop reading
// break;
// }
// e => panic!("err={:?}", e), // Unexpected error
// }
// }
// }
// }
// }
// }
// # Ok(())
// # }
// #
// # fn main() {
// # try_main().unwrap();
// # }
// ```
//
/// [`Evented`]: event/trait.Evented.html
/// [`Poll`]: struct.Poll.html
/// [`Poll::register`]: struct.Poll.html#method.register
/// [`Poll::reregister`]: struct.Poll.html#method.reregister
/// [`slab`]: https://crates.io/crates/slab
;