add functionality for BlockNotifier to unregister a previously registered listener, in order to no longer receive events

lightning/src/chain/chaininterface.rs

@@ -19,6 +19,7 @@ use std::sync::atomic::{AtomicUsize, Ordering};
 use std::collections::HashSet;
 use std::ops::Deref;
 use std::marker::PhantomData;
+use std::ptr;
 
 /// Used to give chain error details upstream
 pub enum ChainError {
@@ -252,11 +253,22 @@ impl<'a, CL: Deref<Target = ChainListener + 'a> + 'a> BlockNotifier<'a, CL> {
 	}
 
 	/// Register the given listener to receive events.
-	// TODO: unregister
 	pub fn register_listener(&self, listener: CL) {
 		let mut vec = self.listeners.lock().unwrap();
 		vec.push(listener);
 	}
+	/// Unregister the given listener to no longer
+	/// receive events.
+	///
+	/// If the same listener is registered multiple times, unregistering
+	/// will remove ALL occurrences of that listener. Comparison is done using
+	/// the pointer returned by the Deref trait implementation.
+	pub fn unregister_listener(&self, listener: CL) {
+		let mut vec = self.listeners.lock().unwrap();
+		// item is a ref to an abstract thing that dereferences to a ChainListener,
+		// so dereference it twice to get the ChainListener itself
+		vec.retain(|item | !ptr::eq(&(**item), &(*listener)));
+	}
 
 	/// Notify listeners that a block was connected given a full, unfiltered block.
 	///
@@ -376,3 +388,76 @@ impl ChainWatchInterfaceUtil {
 		watched.does_match_tx(tx)
 	}
 }
+
+#[cfg(test)]
+mod tests {
+	use ln::functional_test_utils::{create_node_cfgs};
+	use super::{BlockNotifier, ChainListener};
+	use std::ptr;
+
+	#[test]
+	fn register_listener_test() {
+		let node_cfgs = create_node_cfgs(1);
+		let block_notifier = BlockNotifier::new(node_cfgs[0].chain_monitor.clone());
+		assert_eq!(block_notifier.listeners.lock().unwrap().len(), 0);
+		let listener = &node_cfgs[0].chan_monitor.simple_monitor as &ChainListener;
+		block_notifier.register_listener(listener);
+		let vec = block_notifier.listeners.lock().unwrap();
+		assert_eq!(vec.len(), 1);
+		let item = vec.first().clone().unwrap();
+		assert!(ptr::eq(&(**item), &(*listener)));
+	}
+
+	#[test]
+	fn unregister_single_listener_test() {
+		let node_cfgs = create_node_cfgs(2);
+		let block_notifier = BlockNotifier::new(node_cfgs[0].chain_monitor.clone());
+		let listener1 = &node_cfgs[0].chan_monitor.simple_monitor as &ChainListener;
+		let listener2 = &node_cfgs[1].chan_monitor.simple_monitor as &ChainListener;
+		block_notifier.register_listener(listener1);
+		block_notifier.register_listener(listener2);
+		let vec = block_notifier.listeners.lock().unwrap();
+		assert_eq!(vec.len(), 2);
+		drop(vec);
+		block_notifier.unregister_listener(listener1);
+		let vec = block_notifier.listeners.lock().unwrap();
+		assert_eq!(vec.len(), 1);
+		let item = vec.first().clone().unwrap();
+		assert!(ptr::eq(&(**item), &(*listener2)));
+	}
+
+	#[test]
+	fn unregister_single_listener_ref_test() {
+		let node_cfgs = create_node_cfgs(2);
+		let block_notifier = BlockNotifier::new(node_cfgs[0].chain_monitor.clone());
+		block_notifier.register_listener(&node_cfgs[0].chan_monitor.simple_monitor as &ChainListener);
+		block_notifier.register_listener(&node_cfgs[1].chan_monitor.simple_monitor as &ChainListener);
+		let vec = block_notifier.listeners.lock().unwrap();
+		assert_eq!(vec.len(), 2);
+		drop(vec);
+		block_notifier.unregister_listener(&node_cfgs[0].chan_monitor.simple_monitor);
+		let vec = block_notifier.listeners.lock().unwrap();
+		assert_eq!(vec.len(), 1);
+		let item = vec.first().clone().unwrap();
+		assert!(ptr::eq(&(**item), &(*&node_cfgs[1].chan_monitor.simple_monitor)));
+	}
+
+	#[test]
+	fn unregister_multiple_of_the_same_listeners_test() {
+		let node_cfgs = create_node_cfgs(2);
+		let block_notifier = BlockNotifier::new(node_cfgs[0].chain_monitor.clone());
+		let listener1 = &node_cfgs[0].chan_monitor.simple_monitor as &ChainListener;
+		let listener2 = &node_cfgs[1].chan_monitor.simple_monitor as &ChainListener;
+		block_notifier.register_listener(listener1);
+		block_notifier.register_listener(listener1);
+		block_notifier.register_listener(listener2);
+		let vec = block_notifier.listeners.lock().unwrap();
+		assert_eq!(vec.len(), 3);
+		drop(vec);
+		block_notifier.unregister_listener(listener1);
+		let vec = block_notifier.listeners.lock().unwrap();
+		assert_eq!(vec.len(), 1);
+		let item = vec.first().clone().unwrap();
+		assert!(ptr::eq(&(**item), &(*listener2)));
+	}
+}

lightning/src/ln/mod.rs

@@ -27,7 +27,8 @@ mod onion_utils;
 mod wire;
 
 #[cfg(test)]
-#[macro_use] mod functional_test_utils;
+#[macro_use]
+pub(crate) mod functional_test_utils;
 #[cfg(test)]
 mod functional_tests;
 #[cfg(test)]