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https://github.com/tokio-rs/tokio.git
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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
73 lines
2.0 KiB
Rust
73 lines
2.0 KiB
Rust
//! A UDP client that just sends everything it gets via `stdio` in a single datagram, and then
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//! waits for a reply.
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//!
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//! For the reasons of simplicity data from `stdio` is read until `EOF` in a blocking manner.
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//!
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//! You can test this out by running an echo server:
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//!
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//! ```
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//! $ cargo run --example echo-udp -- 127.0.0.1:8080
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//! ```
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//!
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//! and running the client in another terminal:
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//!
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//! ```
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//! $ cargo run --example udp-client
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//! ```
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//!
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//! You can optionally provide any custom endpoint address for the client:
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//!
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//! ```
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//! $ cargo run --example udp-client -- 127.0.0.1:8080
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//! ```
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//!
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//! Don't forget to pass `EOF` to the standard input of the client!
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//!
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//! Please mind that since the UDP protocol doesn't have any capabilities to detect a broken
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//! connection the server needs to be run first, otherwise the client will block forever.
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#![warn(rust_2018_idioms)]
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use std::env;
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use std::error::Error;
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use std::io::{stdin, Read};
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use std::net::SocketAddr;
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use tokio::net::UdpSocket;
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fn get_stdin_data() -> Result<Vec<u8>, Box<dyn std::error::Error>> {
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let mut buf = Vec::new();
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stdin().read_to_end(&mut buf)?;
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Ok(buf)
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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 remote_addr: SocketAddr = env::args()
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.nth(1)
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.unwrap_or_else(|| "127.0.0.1:8080".into())
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.parse()?;
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// We use port 0 to let the operating system allocate an available port for us.
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let local_addr: SocketAddr = if remote_addr.is_ipv4() {
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"0.0.0.0:0"
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} else {
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"[::]:0"
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}
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.parse()?;
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let socket = UdpSocket::bind(local_addr).await?;
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const MAX_DATAGRAM_SIZE: usize = 65_507;
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socket.connect(&remote_addr).await?;
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let data = get_stdin_data()?;
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socket.send(&data).await?;
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let mut data = vec![0u8; MAX_DATAGRAM_SIZE];
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let len = socket.recv(&mut data).await?;
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println!(
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"Received {} bytes:\n{}",
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len,
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String::from_utf8_lossy(&data[..len])
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);
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Ok(())
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}
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