Implement ReadableArgs on (BestBlock, OutputSweeper)

.. and allow to query the best currently known block.

This allows to detect from which block to resume chain syncing.

Author: tnull

lightning/src/util/sweep.rs

@@ -507,6 +507,12 @@ where
 		self.sweeper_state.lock().unwrap().outputs.clone()
 	}
 
+	/// Gets the latest best block which was connected either via the [`Listen`] or
+	/// [`Confirm`] interfaces.
+	pub fn current_best_block(&self) -> BestBlock {
+		self.sweeper_state.lock().unwrap().best_block
+	}
+
 	fn regenerate_spend_if_necessary(
 		&self, sweeper_state: &mut SweeperState,
 	) -> Option<Transaction> {
@@ -798,3 +804,56 @@ where
 		})
 	}
 }
+
+impl<B: Deref, F: Deref, K: Deref, L: Deref>
+	ReadableArgs<(
+		B,
+		Option<F>,
+		K,
+		L,
+		Box<
+			dyn Fn(&[&SpendableOutputDescriptor]) -> Result<Transaction, ()>
+				+ Send
+				+ Sync
+				+ 'static,
+		>,
+	)> for (BestBlock, OutputSweeper<B, F, K, L>)
+where
+	B::Target: BroadcasterInterface,
+	F::Target: Filter + Sync + Send,
+	K::Target: KVStore,
+	L::Target: Logger,
+{
+	#[inline]
+	fn read<R: io::Read>(
+		reader: &mut R,
+		args: (
+			B,
+			Option<F>,
+			K,
+			L,
+			Box<
+				dyn Fn(&[&SpendableOutputDescriptor]) -> Result<Transaction, ()>
+					+ Send
+					+ Sync
+					+ 'static,
+			>,
+		),
+	) -> Result<Self, DecodeError> {
+		let (broadcaster, chain_data_source, kv_store, logger, spend_outputs_callback) = args;
+		let state = SweeperState::read(reader)?;
+		let best_block = state.best_block;
+		let sweeper_state = Mutex::new(state);
+		Ok((
+			best_block,
+			OutputSweeper {
+				sweeper_state,
+				broadcaster,
+				kv_store,
+				chain_data_source,
+				logger,
+				spend_outputs_callback,
+			},
+		))
+	}
+}