use crate::{JsonRpcClient, Middleware, Provider, TransactionStream}; use ethers_core::types::{TxHash, U256}; use futures_util::stream::Stream; use pin_project::{pin_project, pinned_drop}; use serde::de::DeserializeOwned; use serde_json::Value; use std::{ marker::PhantomData, pin::Pin, task::{Context, Poll}, }; /// A transport implementation supporting pub sub subscriptions. pub trait PubsubClient: JsonRpcClient { /// The type of stream this transport returns type NotificationStream: futures_core::Stream + Send + Unpin; /// Add a subscription to this transport fn subscribe>(&self, id: T) -> Result; /// Remove a subscription from this transport fn unsubscribe>(&self, id: T) -> Result<(), Self::Error>; } #[must_use = "subscriptions do nothing unless you stream them"] #[pin_project(PinnedDrop)] /// Streams data from an installed filter via `eth_subscribe` pub struct SubscriptionStream<'a, P: PubsubClient, R: DeserializeOwned> { /// The subscription's installed id on the ethereum node pub id: U256, provider: &'a Provider

, #[pin] rx: P::NotificationStream, ret: PhantomData, } impl<'a, P, R> SubscriptionStream<'a, P, R> where P: PubsubClient, R: DeserializeOwned, { /// Creates a new subscription stream for the provided subscription id. /// /// ### Note /// Most providers treat `SubscriptionStream` IDs as global singletons. /// Instantiating this directly with a known ID will likely cause any /// existing streams with that ID to end. To avoid this, start a new stream /// using [`Provider::subscribe`] instead of `SubscriptionStream::new`. pub fn new(id: U256, provider: &'a Provider

) -> Result { // Call the underlying PubsubClient's subscribe let rx = provider.as_ref().subscribe(id)?; Ok(Self { id, provider, rx, ret: PhantomData }) } /// Unsubscribes from the subscription. pub async fn unsubscribe(&self) -> Result { self.provider.unsubscribe(self.id).await } } // Each subscription item is a serde_json::Value which must be decoded to the // subscription's return type. // TODO: Can this be replaced with an `rx.map` in the constructor? impl<'a, P, R> Stream for SubscriptionStream<'a, P, R> where P: PubsubClient, R: DeserializeOwned, { type Item = R; fn poll_next(self: Pin<&mut Self>, ctx: &mut Context) -> Poll> { let this = self.project(); match futures_util::ready!(this.rx.poll_next(ctx)) { Some(item) => match serde_json::from_value(item) { Ok(res) => Poll::Ready(Some(res)), _ => Poll::Pending, }, None => Poll::Ready(None), } } } #[pinned_drop] impl PinnedDrop for SubscriptionStream<'_, P, R> where P: PubsubClient, R: DeserializeOwned, { fn drop(self: Pin<&mut Self>) { // on drop it removes the handler from the websocket so that it stops // getting populated. We need to call `unsubscribe` explicitly to cancel // the subscription let _ = (*self.provider).as_ref().unsubscribe(self.id); } } impl<'a, P> SubscriptionStream<'a, P, TxHash> where P: PubsubClient, { /// Returns a stream that yields the `Transaction`s for the transaction hashes this stream /// yields. /// /// This internally calls `Provider::get_transaction` with every new transaction. /// No more than n futures will be buffered at any point in time, and less than n may also be /// buffered depending on the state of each future. pub fn transactions_unordered(self, n: usize) -> TransactionStream<'a, P, Self> { TransactionStream::new(self.provider, self, n) } }