liquidity: Allow setting process_events callback in c_bindings

To trigger message processing, we previously had the user set a callback
to `PeerHandler::process_events` via an `Fn()` callback. This is however
not supported by `c_bindings`.

Here, we therefore introduce as `ProcessMesssagesCallback` trait that
can be used via `LiquidityManager::set_process_msgs_callback_fn`, which
is exposed in `c_bindings`.

Author: tnull

lightning-liquidity/src/manager.rs

@@ -7,7 +7,7 @@ use crate::lsps0::ser::{
 	LSPS_MESSAGE_TYPE_ID,
 };
 use crate::lsps0::service::LSPS0ServiceHandler;
-use crate::message_queue::MessageQueue;
+use crate::message_queue::{MessageQueue, ProcessMessagesCallback};
 
 use crate::lsps1::client::{LSPS1ClientConfig, LSPS1ClientHandler};
 use crate::lsps1::msgs::LSPS1Message;
@@ -17,7 +17,7 @@ use crate::lsps1::service::{LSPS1ServiceConfig, LSPS1ServiceHandler};
 use crate::lsps2::client::{LSPS2ClientConfig, LSPS2ClientHandler};
 use crate::lsps2::msgs::LSPS2Message;
 use crate::lsps2::service::{LSPS2ServiceConfig, LSPS2ServiceHandler};
-use crate::prelude::{new_hash_map, new_hash_set, HashMap, HashSet, ToString, Vec};
+use crate::prelude::{new_hash_map, new_hash_set, Box, HashMap, HashSet, ToString, Vec};
 use crate::sync::{Arc, Mutex, RwLock};
 
 use lightning::chain::{self, BestBlock, Confirm, Filter, Listen};
@@ -310,74 +310,27 @@ where {
 	/// let process_msgs_pm = Arc::clone(&my_peer_manager);
 	/// let process_msgs_callback = move || process_msgs_pm.process_events();
 	///
-	/// my_liquidity_manager.set_process_msgs_callback(process_msgs_callback);
+	/// my_liquidity_manager.set_process_msgs_callback(Box::new(process_msgs_callback));
 	/// # }
 	/// ```
 	///
 	/// [`PeerManager::process_events`]: lightning::ln::peer_handler::PeerManager::process_events
-	#[cfg(feature = "std")]
-	pub fn set_process_msgs_callback(&self, callback: impl Fn() + Send + Sync + 'static) {
-		self.pending_messages.set_process_msgs_callback(callback)
+	pub fn set_process_msgs_callback(&self, callback: Box<dyn ProcessMessagesCallback>) {
+		self.pending_messages.set_process_msgs_callback(callback);
 	}
 
 	/// Allows to set a callback that will be called after new messages are pushed to the message
 	/// queue.
 	///
-	/// Usually, you'll want to use this to call [`PeerManager::process_events`] to clear the
-	/// message queue. For example:
+	/// C bindings don't (currently) know how to map `Box<dyn Trait>`, and while it could add the
+	/// following wrapper, doing it in the bindings is currently much more work than simply doing it
+	/// here.
 	///
-	/// ```
-	/// # use lightning::io;
-	/// # use lightning_liquidity::LiquidityManager;
-	/// # use std::sync::{Arc, RwLock};
-	/// # use std::sync::atomic::{AtomicBool, Ordering};
-	/// # use std::time::SystemTime;
-	/// # struct MyStore {}
-	/// # impl lightning::util::persist::KVStore for MyStore {
-	/// #     fn read(&self, primary_namespace: &str, secondary_namespace: &str, key: &str) -> io::Result<Vec<u8>> { Ok(Vec::new()) }
-	/// #     fn write(&self, primary_namespace: &str, secondary_namespace: &str, key: &str, buf: &[u8]) -> io::Result<()> { Ok(()) }
-	/// #     fn remove(&self, primary_namespace: &str, secondary_namespace: &str, key: &str, lazy: bool) -> io::Result<()> { Ok(()) }
-	/// #     fn list(&self, primary_namespace: &str, secondary_namespace: &str) -> io::Result<Vec<String>> { Ok(Vec::new()) }
-	/// # }
-	/// # struct MyEntropySource {}
-	/// # impl lightning::sign::EntropySource for MyEntropySource {
-	/// #     fn get_secure_random_bytes(&self) -> [u8; 32] { [0u8; 32] }
-	/// # }
-	/// # struct MyEventHandler {}
-	/// # impl MyEventHandler {
-	/// #     async fn handle_event(&self, _: lightning::events::Event) {}
-	/// # }
-	/// # #[derive(Eq, PartialEq, Clone, Hash)]
-	/// # struct MySocketDescriptor {}
-	/// # impl lightning::ln::peer_handler::SocketDescriptor for MySocketDescriptor {
-	/// #     fn send_data(&mut self, _data: &[u8], _resume_read: bool) -> usize { 0 }
-	/// #     fn disconnect_socket(&mut self) {}
-	/// # }
-	/// # type MyBroadcaster = dyn lightning::chain::chaininterface::BroadcasterInterface;
-	/// # type MyFeeEstimator = dyn lightning::chain::chaininterface::FeeEstimator;
-	/// # type MyNodeSigner = dyn lightning::sign::NodeSigner;
-	/// # type MyUtxoLookup = dyn lightning::routing::utxo::UtxoLookup;
-	/// # type MyFilter = dyn lightning::chain::Filter;
-	/// # type MyLogger = dyn lightning::util::logger::Logger;
-	/// # type MyChainMonitor = lightning::chain::chainmonitor::ChainMonitor<lightning::sign::InMemorySigner, Arc<MyFilter>, Arc<MyBroadcaster>, Arc<MyFeeEstimator>, Arc<MyLogger>, Arc<MyStore>>;
-	/// # type MyPeerManager = lightning::ln::peer_handler::SimpleArcPeerManager<MySocketDescriptor, MyChainMonitor, MyBroadcaster, MyFeeEstimator, Arc<MyUtxoLookup>, MyLogger>;
-	/// # type MyNetworkGraph = lightning::routing::gossip::NetworkGraph<Arc<MyLogger>>;
-	/// # type MyGossipSync = lightning::routing::gossip::P2PGossipSync<Arc<MyNetworkGraph>, Arc<MyUtxoLookup>, Arc<MyLogger>>;
-	/// # type MyChannelManager = lightning::ln::channelmanager::SimpleArcChannelManager<MyChainMonitor, MyBroadcaster, MyFeeEstimator, MyLogger>;
-	/// # type MyScorer = RwLock<lightning::routing::scoring::ProbabilisticScorer<Arc<MyNetworkGraph>, Arc<MyLogger>>>;
-	/// # type MyLiquidityManager = LiquidityManager<Arc<MyEntropySource>, Arc<MyChannelManager>, Arc<MyFilter>>;
-	/// # fn setup_background_processing(my_persister: Arc<MyStore>, my_event_handler: Arc<MyEventHandler>, my_chain_monitor: Arc<MyChainMonitor>, my_channel_manager: Arc<MyChannelManager>, my_logger: Arc<MyLogger>, my_peer_manager: Arc<MyPeerManager>, my_liquidity_manager: Arc<MyLiquidityManager>) {
-	/// let process_msgs_pm = Arc::clone(&my_peer_manager);
-	/// let process_msgs_callback = move || process_msgs_pm.process_events();
-	///
-	/// my_liquidity_manager.set_process_msgs_callback(process_msgs_callback);
-	/// # }
-	/// ```
-	///
-	/// [`PeerManager::process_events`]: lightning::ln::peer_handler::PeerManager::process_events
-	#[cfg(not(feature = "std"))]
-	pub fn set_process_msgs_callback(&self, callback: impl Fn() + 'static) {
-		self.pending_messages.set_process_msgs_callback(callback)
+	/// Hence we simply allow setting a callback function that will be set via
+	/// [`Self::set_process_msgs_callback`] internally.
+	#[cfg(c_bindings)]
+	pub fn set_process_msgs_callback_fn<F: 'static + ProcessMessagesCallback>(&self, callback: F) {
+		self.set_process_msgs_callback(Box::new(callback));
 	}
 
 	/// Blocks the current thread until next event is ready and returns it.

lightning-liquidity/src/message_queue.rs

@@ -11,10 +11,7 @@ use bitcoin::secp256k1::PublicKey;
 /// [`LiquidityManager`]: crate::LiquidityManager
 pub struct MessageQueue {
 	queue: Mutex<VecDeque<(PublicKey, LSPSMessage)>>,
-	#[cfg(feature = "std")]
-	process_msgs_callback: RwLock<Option<Box<dyn Fn() + Send + Sync + 'static>>>,
-	#[cfg(not(feature = "std"))]
-	process_msgs_callback: RwLock<Option<Box<dyn Fn() + 'static>>>,
+	process_msgs_callback: RwLock<Option<Box<dyn ProcessMessagesCallback>>>,
 }
 
 impl MessageQueue {
@@ -24,14 +21,8 @@ impl MessageQueue {
 		Self { queue, process_msgs_callback }
 	}
 
-	#[cfg(feature = "std")]
-	pub(crate) fn set_process_msgs_callback(&self, callback: impl Fn() + Send + Sync + 'static) {
-		*self.process_msgs_callback.write().unwrap() = Some(Box::new(callback));
-	}
-
-	#[cfg(not(feature = "std"))]
-	pub(crate) fn set_process_msgs_callback(&self, callback: impl Fn() + 'static) {
-		*self.process_msgs_callback.write().unwrap() = Some(Box::new(callback));
+	pub(crate) fn set_process_msgs_callback(&self, callback: Box<dyn ProcessMessagesCallback>) {
+		*self.process_msgs_callback.write().unwrap() = Some(callback);
 	}
 
 	pub(crate) fn get_and_clear_pending_msgs(&self) -> Vec<(PublicKey, LSPSMessage)> {
@@ -45,7 +36,28 @@ impl MessageQueue {
 		}
 
 		if let Some(process_msgs_callback) = self.process_msgs_callback.read().unwrap().as_ref() {
-			(process_msgs_callback)()
+			process_msgs_callback.call()
 		}
 	}
 }
+
+macro_rules! define_callback { ($($bounds: path),*) => {
+/// A callback which will be called to trigger network message processing.
+///
+/// Usually, this should call [`PeerHandler::process_events`].
+///
+/// [`PeerManager::process_events`]: lightning::ln::peer_handler::PeerManager::process_events
+pub trait ProcessMessagesCallback : $($bounds +)* {
+	/// The method which is called.
+	fn call(&self);
+}
+
+impl<F: Fn() $(+ $bounds)*> ProcessMessagesCallback for F {
+	fn call(&self) { (self)(); }
+}
+} }
+
+#[cfg(feature = "std")]
+define_callback!(Send, Sync);
+#[cfg(not(feature = "std"))]
+define_callback!();

lightning-liquidity/tests/common/mod.rs

@@ -478,7 +478,10 @@ pub(crate) fn create_liquidity_node(
 
 	let process_msgs_flag = Arc::clone(&check_msgs_processed);
 	let process_msgs_callback = move || process_msgs_flag.store(true, Ordering::Release);
-	liquidity_manager.set_process_msgs_callback(process_msgs_callback);
+	#[cfg(not(c_bindings))]
+	liquidity_manager.set_process_msgs_callback(Box::new(process_msgs_callback));
+	#[cfg(c_bindings)]
+	liquidity_manager.set_process_msgs_callback_fn(process_msgs_callback);
 
 	Node {
 		channel_manager,