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a0557840eb
This refactors I/O registration in a few ways: - Cleans up the cached readiness in `PollEvented`. This cache used to be helpful when readiness was a linked list of `*mut Node`s in `Registration`. Previous refactors have turned `Registration` into just an `AtomicUsize` holding the current readiness, so the cache is just extra work and complexity. Gone. - Polling the `Registration` for readiness now gives a `ReadyEvent`, which includes the driver tick. This event must be passed back into `clear_readiness`, so that the readiness is only cleared from `Registration` if the tick hasn't changed. Previously, it was possible to clear the readiness even though another thread had *just* polled the driver and found the socket ready again. - Registration now also contains an `async fn readiness`, which stores wakers in an instrusive linked list. This allows an unbounded number of tasks to register for readiness (previously, only 1 per direction (read and write)). By using the intrusive linked list, there is no concern of leaking the storage of the wakers, since they are stored inside the `async fn` and released when the future is dropped. - Registration retains a `poll_readiness(Direction)` method, to support `AsyncRead` and `AsyncWrite`. They aren't able to use `async fn`s, and so there are 2 reserved slots for those methods. - IO types where it makes sense to have multiple tasks waiting on them now take advantage of this new `async fn readiness`, such as `UdpSocket` and `UnixDatagram`. Additionally, this makes the `io-driver` "feature" internal-only (no longer documented, not part of public API), and adds a second internal-only feature, `io-readiness`, to group together linked list part of registration that is only used by some of the IO types. After a bit of discussion, changing stream-based transports (like `TcpStream`) to have `async fn read(&self)` is punted, since that is likely too easy of a footgun to activate. Refs: #2779, #2728
71 lines
1.8 KiB
Rust
71 lines
1.8 KiB
Rust
//! An UDP echo server that just sends back everything that it receives.
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//!
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//! If you're on Unix you can test this out by in one terminal executing:
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//!
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//! cargo run --example echo-udp
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//!
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//! and in another terminal you can run:
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//!
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//! cargo run --example connect -- --udp 127.0.0.1:8080
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//!
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//! Each line you type in to the `nc` terminal should be echo'd back to you!
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#![warn(rust_2018_idioms)]
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use std::error::Error;
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use std::net::SocketAddr;
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use std::{env, io};
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use tokio::net::UdpSocket;
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struct Server {
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socket: UdpSocket,
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buf: Vec<u8>,
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to_send: Option<(usize, SocketAddr)>,
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}
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impl Server {
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async fn run(self) -> Result<(), io::Error> {
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let Server {
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socket,
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mut buf,
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mut to_send,
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} = self;
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loop {
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// First we check to see if there's a message we need to echo back.
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// If so then we try to send it back to the original source, waiting
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// until it's writable and we're able to do so.
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if let Some((size, peer)) = to_send {
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let amt = socket.send_to(&buf[..size], &peer).await?;
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println!("Echoed {}/{} bytes to {}", amt, size, peer);
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}
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// If we're here then `to_send` is `None`, so we take a look for the
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// next message we're going to echo back.
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to_send = Some(socket.recv_from(&mut buf).await?);
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}
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}
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}
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#[tokio::main]
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async fn main() -> Result<(), Box<dyn Error>> {
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let addr = env::args()
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.nth(1)
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.unwrap_or_else(|| "127.0.0.1:8080".to_string());
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let socket = UdpSocket::bind(&addr).await?;
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println!("Listening on: {}", socket.local_addr()?);
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let server = Server {
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socket,
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buf: vec![0; 1024],
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to_send: None,
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};
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// This starts the server task.
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server.run().await?;
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Ok(())
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}
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