Drop futures dependency from lightning-block-sync

lightning-background-processor/Cargo.toml

@@ -14,7 +14,7 @@ all-features = true
 rustdoc-args = ["--cfg", "docsrs"]
 
 [features]
-futures = [ "futures-util" ]
+futures = [ ]
 std = ["lightning/std", "lightning-rapid-gossip-sync/std"]
 
 default = ["std"]
@@ -23,7 +23,6 @@ default = ["std"]
 bitcoin = { version = "0.29.0", default-features = false }
 lightning = { version = "0.0.114", path = "../lightning", default-features = false }
 lightning-rapid-gossip-sync = { version = "0.0.114", path = "../lightning-rapid-gossip-sync", default-features = false }
-futures-util = { version = "0.3", default-features = false, features = ["async-await-macro"], optional = true }
 
 [dev-dependencies]
 lightning = { version = "0.0.114", path = "../lightning", features = ["_test_utils"] }

lightning-background-processor/src/lib.rs

@@ -7,7 +7,7 @@
 #![deny(private_intra_doc_links)]
 
 #![deny(missing_docs)]
-#![deny(unsafe_code)]
+#![cfg_attr(not(feature = "futures"), deny(unsafe_code))]
 
 #![cfg_attr(docsrs, feature(doc_auto_cfg))]
 
@@ -52,8 +52,6 @@ use std::thread::{self, JoinHandle};
 #[cfg(feature = "std")]
 use std::time::Instant;
 
-#[cfg(feature = "futures")]
-use futures_util::{select_biased, future::FutureExt, task};
 #[cfg(not(feature = "std"))]
 use alloc::vec::Vec;
 
@@ -384,6 +382,50 @@ macro_rules! define_run_body {
 	} }
 }
 
+#[cfg(feature = "futures")]
+pub(crate) mod futures_util {
+	use core::future::Future;
+	use core::task::{Poll, Waker, RawWaker, RawWakerVTable};
+	use core::pin::Pin;
+	use core::marker::Unpin;
+	pub(crate) struct Selector<A: Future<Output=()> + Unpin, B: Future<Output=bool> + Unpin> {
+		pub a: A,
+		pub b: B,
+	}
+	pub(crate) enum SelectorOutput {
+		A, B(bool),
+	}
+
+	impl<A: Future<Output=()> + Unpin, B: Future<Output=bool> + Unpin> Future for Selector<A, B> {
+		type Output = SelectorOutput;
+		fn poll(mut self: Pin<&mut Self>, ctx: &mut core::task::Context<'_>) -> Poll<SelectorOutput> {
+			match Pin::new(&mut self.a).poll(ctx) {
+				Poll::Ready(()) => { return Poll::Ready(SelectorOutput::A); },
+				Poll::Pending => {},
+			}
+			match Pin::new(&mut self.b).poll(ctx) {
+				Poll::Ready(res) => { return Poll::Ready(SelectorOutput::B(res)); },
+				Poll::Pending => {},
+			}
+			Poll::Pending
+		}
+	}
+
+	// If we want to poll a future without an async context to figure out if it has completed or
+	// not without awaiting, we need a Waker, which needs a vtable...we fill it with dummy values
+	// but sadly there's a good bit of boilerplate here.
+	fn dummy_waker_clone(_: *const ()) -> RawWaker { RawWaker::new(core::ptr::null(), &DUMMY_WAKER_VTABLE) }
+	fn dummy_waker_action(_: *const ()) { }
+
+	const DUMMY_WAKER_VTABLE: RawWakerVTable = RawWakerVTable::new(
+		dummy_waker_clone, dummy_waker_action, dummy_waker_action, dummy_waker_action);
+	pub(crate) fn dummy_waker() -> Waker { unsafe { Waker::from_raw(RawWaker::new(core::ptr::null(), &DUMMY_WAKER_VTABLE)) } }
+}
+#[cfg(feature = "futures")]
+use futures_util::{Selector, SelectorOutput, dummy_waker};
+#[cfg(feature = "futures")]
+use core::task;
+
 /// Processes background events in a future.
 ///
 /// `sleeper` should return a future which completes in the given amount of time and returns a
@@ -470,16 +512,20 @@ where
 		chain_monitor, chain_monitor.process_pending_events_async(async_event_handler).await,
 		channel_manager, channel_manager.process_pending_events_async(async_event_handler).await,
 		gossip_sync, peer_manager, logger, scorer, should_break, {
-			select_biased! {
-				_ = channel_manager.get_persistable_update_future().fuse() => true,
-				exit = sleeper(Duration::from_millis(100)).fuse() => {
+			let fut = Selector {
+				a: channel_manager.get_persistable_update_future(),
+				b: sleeper(Duration::from_millis(100)),
+			};
+			match fut.await {
+				SelectorOutput::A => true,
+				SelectorOutput::B(exit) => {
 					should_break = exit;
 					false
 				}
 			}
 		}, |t| sleeper(Duration::from_secs(t)),
 		|fut: &mut SleepFuture, _| {
-			let mut waker = task::noop_waker();
+			let mut waker = dummy_waker();
 			let mut ctx = task::Context::from_waker(&mut waker);
 			core::pin::Pin::new(fut).poll(&mut ctx).is_ready()
 		})

lightning-block-sync/Cargo.toml

@@ -20,7 +20,6 @@ rpc-client = [ "serde_json", "chunked_transfer" ]
 [dependencies]
 bitcoin = "0.29.0"
 lightning = { version = "0.0.114", path = "../lightning" }
-futures-util = { version = "0.3" }
 tokio = { version = "1.0", features = [ "io-util", "net", "time" ], optional = true }
 serde_json = { version = "1.0", optional = true }
 chunked_transfer = { version = "1.4", optional = true }

lightning-block-sync/src/rest.rs

@@ -7,32 +7,34 @@ use crate::http::{BinaryResponse, HttpEndpoint, HttpClient, JsonResponse};
 use bitcoin::hash_types::BlockHash;
 use bitcoin::hashes::hex::ToHex;
 
-use futures_util::lock::Mutex;
-
 use std::convert::TryFrom;
 use std::convert::TryInto;
+use std::sync::Mutex;
 
 /// A simple REST client for requesting resources using HTTP `GET`.
 pub struct RestClient {
 	endpoint: HttpEndpoint,
-	client: Mutex<HttpClient>,
+	client: Mutex<Option<HttpClient>>,
 }
 
 impl RestClient {
 	/// Creates a new REST client connected to the given endpoint.
 	///
 	/// The endpoint should contain the REST path component (e.g., http://127.0.0.1:8332/rest).
 	pub fn new(endpoint: HttpEndpoint) -> std::io::Result<Self> {
-		let client = Mutex::new(HttpClient::connect(&endpoint)?);
-		Ok(Self { endpoint, client })
+		Ok(Self { endpoint, client: Mutex::new(None) })
 	}
 
 	/// Requests a resource encoded in `F` format and interpreted as type `T`.
 	pub async fn request_resource<F, T>(&self, resource_path: &str) -> std::io::Result<T>
 	where F: TryFrom<Vec<u8>, Error = std::io::Error> + TryInto<T, Error = std::io::Error> {
 		let host = format!("{}:{}", self.endpoint.host(), self.endpoint.port());
 		let uri = format!("{}/{}", self.endpoint.path().trim_end_matches("/"), resource_path);
-		self.client.lock().await.get::<F>(&uri, &host).await?.try_into()
+		let mut client = if let Some(client) = self.client.lock().unwrap().take() { client }
+			else { HttpClient::connect(&self.endpoint)? };
+		let res = client.get::<F>(&uri, &host).await?.try_into();
+		*self.client.lock().unwrap() = Some(client);
+		res
 	}
 }
 

lightning-block-sync/src/rpc.rs

@@ -7,7 +7,7 @@ use crate::http::{HttpClient, HttpEndpoint, HttpError, JsonResponse};
 use bitcoin::hash_types::BlockHash;
 use bitcoin::hashes::hex::ToHex;
 
-use futures_util::lock::Mutex;
+use std::sync::Mutex;
 
 use serde_json;
 
@@ -41,7 +41,7 @@ impl Error for RpcError {}
 pub struct RpcClient {
 	basic_auth: String,
 	endpoint: HttpEndpoint,
-	client: Mutex<HttpClient>,
+	client: Mutex<Option<HttpClient>>,
 	id: AtomicUsize,
 }
 
@@ -50,11 +50,10 @@ impl RpcClient {
 	/// credentials should be a base64 encoding of a user name and password joined by a colon, as is
 	/// required for HTTP basic access authentication.
 	pub fn new(credentials: &str, endpoint: HttpEndpoint) -> std::io::Result<Self> {
-		let client = Mutex::new(HttpClient::connect(&endpoint)?);
 		Ok(Self {
 			basic_auth: "Basic ".to_string() + credentials,
 			endpoint,
-			client,
+			client: Mutex::new(None),
 			id: AtomicUsize::new(0),
 		})
 	}
@@ -73,7 +72,12 @@ impl RpcClient {
 			"id": &self.id.fetch_add(1, Ordering::AcqRel).to_string()
 		});
 
-		let mut response = match self.client.lock().await.post::<JsonResponse>(&uri, &host, &self.basic_auth, content).await {
+		let mut client = if let Some(client) = self.client.lock().unwrap().take() { client }
+			else { HttpClient::connect(&self.endpoint)? };
+		let http_response = client.post::<JsonResponse>(&uri, &host, &self.basic_auth, content).await;
+		*self.client.lock().unwrap() = Some(client);
+
+		let mut response = match http_response {
 			Ok(JsonResponse(response)) => response,
 			Err(e) if e.kind() == std::io::ErrorKind::Other => {
 				match e.get_ref().unwrap().downcast_ref::<HttpError>() {