99 lines
2.9 KiB
Rust
99 lines
2.9 KiB
Rust
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use crate::{JsonRpcClient, Middleware, Provider};
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use ethers_core::types::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;
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use std::{
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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 = Value>;
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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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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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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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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 {
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id,
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provider,
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rx,
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ret: PhantomData,
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})
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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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}
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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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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_value(item) {
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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::Pending,
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}
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}
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}
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#[pinned_drop]
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impl<'a, P, R> PinnedDrop 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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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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