128 lines
4.2 KiB
Rust
128 lines
4.2 KiB
Rust
use crate::{JsonRpcClient, Middleware, Provider, TransactionStream};
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use ethers_core::types::{TxHash, U256};
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use futures_util::stream::Stream;
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use pin_project::{pin_project, pinned_drop};
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use serde::de::DeserializeOwned;
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use serde_json::value::RawValue;
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use std::{
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collections::VecDeque,
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marker::PhantomData,
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pin::Pin,
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task::{Context, Poll},
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};
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/// A transport implementation supporting pub sub subscriptions.
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pub trait PubsubClient: JsonRpcClient {
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/// The type of stream this transport returns
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type NotificationStream: futures_core::Stream<Item = Box<RawValue>> + Send + Unpin;
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/// Add a subscription to this transport
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fn subscribe<T: Into<U256>>(&self, id: T) -> Result<Self::NotificationStream, Self::Error>;
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/// Remove a subscription from this transport
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fn unsubscribe<T: Into<U256>>(&self, id: T) -> Result<(), Self::Error>;
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}
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#[must_use = "subscriptions do nothing unless you stream them"]
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#[pin_project(PinnedDrop)]
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/// Streams data from an installed filter via `eth_subscribe`
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pub struct SubscriptionStream<'a, P: PubsubClient, R: DeserializeOwned> {
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/// The subscription's installed id on the ethereum node
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pub id: U256,
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loaded_elements: VecDeque<R>,
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provider: &'a Provider<P>,
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#[pin]
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rx: P::NotificationStream,
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ret: PhantomData<R>,
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}
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impl<'a, P, R> SubscriptionStream<'a, P, R>
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where
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P: PubsubClient,
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R: DeserializeOwned,
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{
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/// Creates a new subscription stream for the provided subscription id.
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///
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/// ### Note
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/// Most providers treat `SubscriptionStream` IDs as global singletons.
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/// Instantiating this directly with a known ID will likely cause any
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/// existing streams with that ID to end. To avoid this, start a new stream
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/// using [`Provider::subscribe`] instead of `SubscriptionStream::new`.
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pub fn new(id: U256, provider: &'a Provider<P>) -> Result<Self, P::Error> {
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// Call the underlying PubsubClient's subscribe
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let rx = provider.as_ref().subscribe(id)?;
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Ok(Self { id, provider, rx, ret: PhantomData, loaded_elements: VecDeque::new() })
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}
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/// Unsubscribes from the subscription.
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pub async fn unsubscribe(&self) -> Result<bool, crate::ProviderError> {
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self.provider.unsubscribe(self.id).await
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}
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pub fn set_loaded_elements(&mut self, loaded_elements: VecDeque<R>) {
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self.loaded_elements = loaded_elements;
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}
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}
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// Each subscription item is a serde_json::Value which must be decoded to the
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// subscription's return type.
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// TODO: Can this be replaced with an `rx.map` in the constructor?
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impl<'a, P, R> Stream for SubscriptionStream<'a, P, R>
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where
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P: PubsubClient,
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R: DeserializeOwned,
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{
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type Item = R;
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fn poll_next(self: Pin<&mut Self>, ctx: &mut Context) -> Poll<Option<Self::Item>> {
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if !self.loaded_elements.is_empty() {
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let next_element = self.get_mut().loaded_elements.pop_front();
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return Poll::Ready(next_element)
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}
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let this = self.project();
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match futures_util::ready!(this.rx.poll_next(ctx)) {
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Some(item) => match serde_json::from_str(item.get()) {
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Ok(res) => Poll::Ready(Some(res)),
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_ => Poll::Pending,
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},
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None => Poll::Ready(None),
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}
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}
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}
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#[pinned_drop]
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impl<P, R> PinnedDrop for SubscriptionStream<'_, P, R>
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where
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P: PubsubClient,
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R: DeserializeOwned,
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{
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fn drop(self: Pin<&mut Self>) {
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// on drop it removes the handler from the websocket so that it stops
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// getting populated. We need to call `unsubscribe` explicitly to cancel
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// the subscription
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let _ = (*self.provider).as_ref().unsubscribe(self.id);
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}
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}
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impl<'a, P> SubscriptionStream<'a, P, TxHash>
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where
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P: PubsubClient,
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{
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/// Returns a stream that yields the `Transaction`s for the transaction hashes this stream
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/// yields.
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///
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/// This internally calls `Provider::get_transaction` with every new transaction.
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/// No more than n futures will be buffered at any point in time, and less than n may also be
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/// buffered depending on the state of each future.
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pub fn transactions_unordered(self, n: usize) -> TransactionStream<'a, P, Self> {
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TransactionStream::new(self.provider, self, n)
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}
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}
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