mirror of
https://github.com/tokio-rs/tokio.git
synced 2026-08-18 00:00:09 +02:00
Lucio Franco
8efa62013b
This change removes all references to `Stream` from within the `tokio` crate and moves them into a new `tokio-stream` crate. Most types have had their `impl Stream` removed as well in-favor of their inherent methods. Closes #2870
665 lines
19 KiB
Rust
665 lines
19 KiB
Rust
use crate::Stream;
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use std::borrow::Borrow;
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use std::hash::Hash;
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use std::pin::Pin;
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use std::task::{Context, Poll};
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/// Combine many streams into one, indexing each source stream with a unique
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/// key.
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///
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/// `StreamMap` is similar to [`StreamExt::merge`] in that it combines source
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/// streams into a single merged stream that yields values in the order that
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/// they arrive from the source streams. However, `StreamMap` has a lot more
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/// flexibility in usage patterns.
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///
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/// `StreamMap` can:
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///
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/// * Merge an arbitrary number of streams.
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/// * Track which source stream the value was received from.
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/// * Handle inserting and removing streams from the set of managed streams at
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/// any point during iteration.
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///
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/// All source streams held by `StreamMap` are indexed using a key. This key is
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/// included with the value when a source stream yields a value. The key is also
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/// used to remove the stream from the `StreamMap` before the stream has
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/// completed streaming.
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///
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/// # `Unpin`
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///
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/// Because the `StreamMap` API moves streams during runtime, both streams and
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/// keys must be `Unpin`. In order to insert a `!Unpin` stream into a
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/// `StreamMap`, use [`pin!`] to pin the stream to the stack or [`Box::pin`] to
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/// pin the stream in the heap.
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///
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/// # Implementation
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///
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/// `StreamMap` is backed by a `Vec<(K, V)>`. There is no guarantee that this
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/// internal implementation detail will persist in future versions, but it is
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/// important to know the runtime implications. In general, `StreamMap` works
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/// best with a "smallish" number of streams as all entries are scanned on
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/// insert, remove, and polling. In cases where a large number of streams need
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/// to be merged, it may be advisable to use tasks sending values on a shared
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/// [`mpsc`] channel.
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///
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/// [`StreamExt::merge`]: crate::StreamExt::merge
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/// [`mpsc`]: https://docs.rs/tokio/1.0/tokio/sync/mpsc/index.html
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/// [`pin!`]: https://docs.rs/tokio/1.0/tokio/macro.pin.html
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/// [`Box::pin`]: std::boxed::Box::pin
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///
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/// # Examples
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///
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/// Merging two streams, then remove them after receiving the first value
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///
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/// ```
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/// use tokio_stream::{StreamExt, StreamMap, Stream};
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/// use tokio::sync::mpsc;
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/// use std::pin::Pin;
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///
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/// #[tokio::main]
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/// async fn main() {
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/// let (tx1, mut rx1) = mpsc::channel::<usize>(10);
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/// let (tx2, mut rx2) = mpsc::channel::<usize>(10);
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///
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/// // Convert the channels to a `Stream`.
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/// let rx1 = Box::pin(async_stream::stream! {
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/// while let Some(item) = rx1.recv().await {
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/// yield item;
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/// }
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/// }) as Pin<Box<dyn Stream<Item = usize> + Send>>;
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///
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/// let rx2 = Box::pin(async_stream::stream! {
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/// while let Some(item) = rx2.recv().await {
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/// yield item;
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/// }
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/// }) as Pin<Box<dyn Stream<Item = usize> + Send>>;
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///
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/// tokio::spawn(async move {
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/// tx1.send(1).await.unwrap();
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///
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/// // This value will never be received. The send may or may not return
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/// // `Err` depending on if the remote end closed first or not.
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/// let _ = tx1.send(2).await;
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/// });
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///
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/// tokio::spawn(async move {
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/// tx2.send(3).await.unwrap();
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/// let _ = tx2.send(4).await;
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/// });
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///
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/// let mut map = StreamMap::new();
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///
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/// // Insert both streams
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/// map.insert("one", rx1);
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/// map.insert("two", rx2);
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///
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/// // Read twice
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/// for _ in 0..2 {
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/// let (key, val) = map.next().await.unwrap();
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///
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/// if key == "one" {
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/// assert_eq!(val, 1);
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/// } else {
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/// assert_eq!(val, 3);
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/// }
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///
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/// // Remove the stream to prevent reading the next value
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/// map.remove(key);
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/// }
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/// }
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/// ```
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///
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/// This example models a read-only client to a chat system with channels. The
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/// client sends commands to join and leave channels. `StreamMap` is used to
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/// manage active channel subscriptions.
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///
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/// For simplicity, messages are displayed with `println!`, but they could be
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/// sent to the client over a socket.
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///
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/// ```no_run
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/// use tokio_stream::{Stream, StreamExt, StreamMap};
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///
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/// enum Command {
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/// Join(String),
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/// Leave(String),
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/// }
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///
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/// fn commands() -> impl Stream<Item = Command> {
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/// // Streams in user commands by parsing `stdin`.
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/// # tokio_stream::pending()
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/// }
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///
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/// // Join a channel, returns a stream of messages received on the channel.
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/// fn join(channel: &str) -> impl Stream<Item = String> + Unpin {
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/// // left as an exercise to the reader
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/// # tokio_stream::pending()
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/// }
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///
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/// #[tokio::main]
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/// async fn main() {
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/// let mut channels = StreamMap::new();
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///
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/// // Input commands (join / leave channels).
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/// let cmds = commands();
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/// tokio::pin!(cmds);
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///
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/// loop {
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/// tokio::select! {
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/// Some(cmd) = cmds.next() => {
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/// match cmd {
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/// Command::Join(chan) => {
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/// // Join the channel and add it to the `channels`
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/// // stream map
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/// let msgs = join(&chan);
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/// channels.insert(chan, msgs);
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/// }
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/// Command::Leave(chan) => {
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/// channels.remove(&chan);
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/// }
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/// }
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/// }
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/// Some((chan, msg)) = channels.next() => {
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/// // Received a message, display it on stdout with the channel
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/// // it originated from.
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/// println!("{}: {}", chan, msg);
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/// }
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/// // Both the `commands` stream and the `channels` stream are
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/// // complete. There is no more work to do, so leave the loop.
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/// else => break,
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/// }
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/// }
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/// }
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/// ```
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#[derive(Debug)]
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pub struct StreamMap<K, V> {
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/// Streams stored in the map
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entries: Vec<(K, V)>,
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}
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impl<K, V> StreamMap<K, V> {
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/// An iterator visiting all key-value pairs in arbitrary order.
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///
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/// The iterator element type is &'a (K, V).
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///
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/// # Examples
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///
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/// ```
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/// use tokio_stream::{StreamMap, pending};
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///
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/// let mut map = StreamMap::new();
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///
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/// map.insert("a", pending::<i32>());
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/// map.insert("b", pending());
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/// map.insert("c", pending());
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///
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/// for (key, stream) in map.iter() {
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/// println!("({}, {:?})", key, stream);
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/// }
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/// ```
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pub fn iter(&self) -> impl Iterator<Item = &(K, V)> {
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self.entries.iter()
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}
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/// An iterator visiting all key-value pairs mutably in arbitrary order.
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///
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/// The iterator element type is &'a mut (K, V).
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///
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/// # Examples
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///
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/// ```
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/// use tokio_stream::{StreamMap, pending};
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///
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/// let mut map = StreamMap::new();
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///
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/// map.insert("a", pending::<i32>());
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/// map.insert("b", pending());
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/// map.insert("c", pending());
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///
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/// for (key, stream) in map.iter_mut() {
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/// println!("({}, {:?})", key, stream);
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/// }
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/// ```
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pub fn iter_mut(&mut self) -> impl Iterator<Item = &mut (K, V)> {
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self.entries.iter_mut()
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}
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/// Creates an empty `StreamMap`.
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///
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/// The stream map is initially created with a capacity of `0`, so it will
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/// not allocate until it is first inserted into.
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///
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/// # Examples
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///
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/// ```
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/// use tokio_stream::{StreamMap, Pending};
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///
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/// let map: StreamMap<&str, Pending<()>> = StreamMap::new();
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/// ```
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pub fn new() -> StreamMap<K, V> {
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StreamMap { entries: vec![] }
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}
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/// Creates an empty `StreamMap` with the specified capacity.
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///
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/// The stream map will be able to hold at least `capacity` elements without
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/// reallocating. If `capacity` is 0, the stream map will not allocate.
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///
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/// # Examples
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///
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/// ```
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/// use tokio_stream::{StreamMap, Pending};
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///
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/// let map: StreamMap<&str, Pending<()>> = StreamMap::with_capacity(10);
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/// ```
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pub fn with_capacity(capacity: usize) -> StreamMap<K, V> {
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StreamMap {
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entries: Vec::with_capacity(capacity),
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}
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}
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/// Returns an iterator visiting all keys in arbitrary order.
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///
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/// The iterator element type is &'a K.
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///
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/// # Examples
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///
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/// ```
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/// use tokio_stream::{StreamMap, pending};
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///
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/// let mut map = StreamMap::new();
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///
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/// map.insert("a", pending::<i32>());
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/// map.insert("b", pending());
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/// map.insert("c", pending());
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///
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/// for key in map.keys() {
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/// println!("{}", key);
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/// }
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/// ```
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pub fn keys(&self) -> impl Iterator<Item = &K> {
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self.iter().map(|(k, _)| k)
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}
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/// An iterator visiting all values in arbitrary order.
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///
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/// The iterator element type is &'a V.
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///
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/// # Examples
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///
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/// ```
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/// use tokio_stream::{StreamMap, pending};
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///
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/// let mut map = StreamMap::new();
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///
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/// map.insert("a", pending::<i32>());
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/// map.insert("b", pending());
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/// map.insert("c", pending());
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///
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/// for stream in map.values() {
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/// println!("{:?}", stream);
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/// }
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/// ```
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pub fn values(&self) -> impl Iterator<Item = &V> {
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self.iter().map(|(_, v)| v)
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}
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/// An iterator visiting all values mutably in arbitrary order.
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///
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/// The iterator element type is &'a mut V.
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///
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/// # Examples
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///
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/// ```
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/// use tokio_stream::{StreamMap, pending};
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///
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/// let mut map = StreamMap::new();
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///
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/// map.insert("a", pending::<i32>());
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/// map.insert("b", pending());
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/// map.insert("c", pending());
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///
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/// for stream in map.values_mut() {
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/// println!("{:?}", stream);
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/// }
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/// ```
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pub fn values_mut(&mut self) -> impl Iterator<Item = &mut V> {
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self.iter_mut().map(|(_, v)| v)
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}
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/// Returns the number of streams the map can hold without reallocating.
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///
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/// This number is a lower bound; the `StreamMap` might be able to hold
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/// more, but is guaranteed to be able to hold at least this many.
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///
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/// # Examples
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///
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/// ```
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/// use tokio_stream::{StreamMap, Pending};
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///
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/// let map: StreamMap<i32, Pending<()>> = StreamMap::with_capacity(100);
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/// assert!(map.capacity() >= 100);
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/// ```
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pub fn capacity(&self) -> usize {
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self.entries.capacity()
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}
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/// Returns the number of streams in the map.
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///
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/// # Examples
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///
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/// ```
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/// use tokio_stream::{StreamMap, pending};
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///
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/// let mut a = StreamMap::new();
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/// assert_eq!(a.len(), 0);
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/// a.insert(1, pending::<i32>());
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/// assert_eq!(a.len(), 1);
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/// ```
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pub fn len(&self) -> usize {
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self.entries.len()
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}
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/// Returns `true` if the map contains no elements.
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///
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/// # Examples
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///
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/// ```
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/// use std::collections::HashMap;
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///
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/// let mut a = HashMap::new();
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/// assert!(a.is_empty());
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/// a.insert(1, "a");
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/// assert!(!a.is_empty());
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/// ```
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pub fn is_empty(&self) -> bool {
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self.entries.is_empty()
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}
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/// Clears the map, removing all key-stream pairs. Keeps the allocated
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/// memory for reuse.
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///
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/// # Examples
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///
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/// ```
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/// use tokio_stream::{StreamMap, pending};
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///
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/// let mut a = StreamMap::new();
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/// a.insert(1, pending::<i32>());
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/// a.clear();
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/// assert!(a.is_empty());
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/// ```
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pub fn clear(&mut self) {
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self.entries.clear();
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}
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/// Insert a key-stream pair into the map.
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///
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/// If the map did not have this key present, `None` is returned.
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///
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/// If the map did have this key present, the new `stream` replaces the old
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/// one and the old stream is returned.
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///
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/// # Examples
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///
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/// ```
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/// use tokio_stream::{StreamMap, pending};
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///
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/// let mut map = StreamMap::new();
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///
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/// assert!(map.insert(37, pending::<i32>()).is_none());
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/// assert!(!map.is_empty());
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///
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/// map.insert(37, pending());
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/// assert!(map.insert(37, pending()).is_some());
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/// ```
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pub fn insert(&mut self, k: K, stream: V) -> Option<V>
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where
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K: Hash + Eq,
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{
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let ret = self.remove(&k);
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self.entries.push((k, stream));
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ret
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}
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/// Removes a key from the map, returning the stream at the key if the key was previously in the map.
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///
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/// The key may be any borrowed form of the map's key type, but `Hash` and
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/// `Eq` on the borrowed form must match those for the key type.
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///
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/// # Examples
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///
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/// ```
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/// use tokio_stream::{StreamMap, pending};
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///
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/// let mut map = StreamMap::new();
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/// map.insert(1, pending::<i32>());
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/// assert!(map.remove(&1).is_some());
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/// assert!(map.remove(&1).is_none());
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/// ```
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pub fn remove<Q: ?Sized>(&mut self, k: &Q) -> Option<V>
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where
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K: Borrow<Q>,
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Q: Hash + Eq,
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{
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for i in 0..self.entries.len() {
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if self.entries[i].0.borrow() == k {
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return Some(self.entries.swap_remove(i).1);
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}
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}
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None
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}
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/// Returns `true` if the map contains a stream for the specified key.
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///
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/// The key may be any borrowed form of the map's key type, but `Hash` and
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/// `Eq` on the borrowed form must match those for the key type.
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///
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/// # Examples
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///
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/// ```
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/// use tokio_stream::{StreamMap, pending};
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///
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/// let mut map = StreamMap::new();
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/// map.insert(1, pending::<i32>());
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/// assert_eq!(map.contains_key(&1), true);
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/// assert_eq!(map.contains_key(&2), false);
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/// ```
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pub fn contains_key<Q: ?Sized>(&self, k: &Q) -> bool
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where
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K: Borrow<Q>,
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Q: Hash + Eq,
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{
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for i in 0..self.entries.len() {
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if self.entries[i].0.borrow() == k {
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return true;
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}
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}
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false
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}
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}
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impl<K, V> StreamMap<K, V>
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where
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K: Unpin,
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V: Stream + Unpin,
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{
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/// Polls the next value, includes the vec entry index
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fn poll_next_entry(&mut self, cx: &mut Context<'_>) -> Poll<Option<(usize, V::Item)>> {
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use Poll::*;
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let start = self::rand::thread_rng_n(self.entries.len() as u32) as usize;
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let mut idx = start;
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for _ in 0..self.entries.len() {
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let (_, stream) = &mut self.entries[idx];
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match Pin::new(stream).poll_next(cx) {
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Ready(Some(val)) => return Ready(Some((idx, val))),
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Ready(None) => {
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// Remove the entry
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self.entries.swap_remove(idx);
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// Check if this was the last entry, if so the cursor needs
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// to wrap
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if idx == self.entries.len() {
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idx = 0;
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} else if idx < start && start <= self.entries.len() {
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// The stream being swapped into the current index has
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// already been polled, so skip it.
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idx = idx.wrapping_add(1) % self.entries.len();
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}
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}
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Pending => {
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idx = idx.wrapping_add(1) % self.entries.len();
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}
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}
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}
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// If the map is empty, then the stream is complete.
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if self.entries.is_empty() {
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Ready(None)
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} else {
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Pending
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}
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}
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}
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|
impl<K, V> Default for StreamMap<K, V> {
|
|
fn default() -> Self {
|
|
Self::new()
|
|
}
|
|
}
|
|
|
|
impl<K, V> Stream for StreamMap<K, V>
|
|
where
|
|
K: Clone + Unpin,
|
|
V: Stream + Unpin,
|
|
{
|
|
type Item = (K, V::Item);
|
|
|
|
fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
|
|
if let Some((idx, val)) = ready!(self.poll_next_entry(cx)) {
|
|
let key = self.entries[idx].0.clone();
|
|
Poll::Ready(Some((key, val)))
|
|
} else {
|
|
Poll::Ready(None)
|
|
}
|
|
}
|
|
|
|
fn size_hint(&self) -> (usize, Option<usize>) {
|
|
let mut ret = (0, Some(0));
|
|
|
|
for (_, stream) in &self.entries {
|
|
let hint = stream.size_hint();
|
|
|
|
ret.0 += hint.0;
|
|
|
|
match (ret.1, hint.1) {
|
|
(Some(a), Some(b)) => ret.1 = Some(a + b),
|
|
(Some(_), None) => ret.1 = None,
|
|
_ => {}
|
|
}
|
|
}
|
|
|
|
ret
|
|
}
|
|
}
|
|
|
|
mod rand {
|
|
use std::cell::Cell;
|
|
|
|
mod loom {
|
|
#[cfg(not(loom))]
|
|
pub(crate) mod rand {
|
|
use std::collections::hash_map::RandomState;
|
|
use std::hash::{BuildHasher, Hash, Hasher};
|
|
use std::sync::atomic::AtomicU32;
|
|
use std::sync::atomic::Ordering::Relaxed;
|
|
|
|
static COUNTER: AtomicU32 = AtomicU32::new(1);
|
|
|
|
pub(crate) fn seed() -> u64 {
|
|
let rand_state = RandomState::new();
|
|
|
|
let mut hasher = rand_state.build_hasher();
|
|
|
|
// Hash some unique-ish data to generate some new state
|
|
COUNTER.fetch_add(1, Relaxed).hash(&mut hasher);
|
|
|
|
// Get the seed
|
|
hasher.finish()
|
|
}
|
|
}
|
|
|
|
#[cfg(loom)]
|
|
pub(crate) mod rand {
|
|
pub(crate) fn seed() -> u64 {
|
|
1
|
|
}
|
|
}
|
|
}
|
|
|
|
/// Fast random number generate
|
|
///
|
|
/// Implement xorshift64+: 2 32-bit xorshift sequences added together.
|
|
/// Shift triplet [17,7,16] was calculated as indicated in Marsaglia's
|
|
/// Xorshift paper: https://www.jstatsoft.org/article/view/v008i14/xorshift.pdf
|
|
/// This generator passes the SmallCrush suite, part of TestU01 framework:
|
|
/// http://simul.iro.umontreal.ca/testu01/tu01.html
|
|
#[derive(Debug)]
|
|
pub(crate) struct FastRand {
|
|
one: Cell<u32>,
|
|
two: Cell<u32>,
|
|
}
|
|
|
|
impl FastRand {
|
|
/// Initialize a new, thread-local, fast random number generator.
|
|
pub(crate) fn new(seed: u64) -> FastRand {
|
|
let one = (seed >> 32) as u32;
|
|
let mut two = seed as u32;
|
|
|
|
if two == 0 {
|
|
// This value cannot be zero
|
|
two = 1;
|
|
}
|
|
|
|
FastRand {
|
|
one: Cell::new(one),
|
|
two: Cell::new(two),
|
|
}
|
|
}
|
|
|
|
pub(crate) fn fastrand_n(&self, n: u32) -> u32 {
|
|
// This is similar to fastrand() % n, but faster.
|
|
// See https://lemire.me/blog/2016/06/27/a-fast-alternative-to-the-modulo-reduction/
|
|
let mul = (self.fastrand() as u64).wrapping_mul(n as u64);
|
|
(mul >> 32) as u32
|
|
}
|
|
|
|
fn fastrand(&self) -> u32 {
|
|
let mut s1 = self.one.get();
|
|
let s0 = self.two.get();
|
|
|
|
s1 ^= s1 << 17;
|
|
s1 = s1 ^ s0 ^ s1 >> 7 ^ s0 >> 16;
|
|
|
|
self.one.set(s0);
|
|
self.two.set(s1);
|
|
|
|
s0.wrapping_add(s1)
|
|
}
|
|
}
|
|
|
|
// Used by `StreamMap`
|
|
pub(crate) fn thread_rng_n(n: u32) -> u32 {
|
|
thread_local! {
|
|
static THREAD_RNG: FastRand = FastRand::new(loom::rand::seed());
|
|
}
|
|
|
|
THREAD_RNG.with(|rng| rng.fastrand_n(n))
|
|
}
|
|
}
|