Change sort_and_filter_channels return type to a Box containing an

iterator

Author: upjohnc

lightning-invoice/src/utils.rs

@@ -241,7 +241,7 @@ where
 	for PhantomRouteHints { channels, phantom_scid, real_node_pubkey } in phantom_route_hints {
 		log_trace!(logger, "Generating phantom route hints for node {}",
 			log_pubkey!(real_node_pubkey));
-		let mut route_hints = sort_and_filter_channels(channels, amt_msat, &logger);
+		let mut route_hints: Vec<RouteHint> = sort_and_filter_channels(channels, amt_msat, &logger).collect();
 
 		// If we have any public channel, the route hints from `sort_and_filter_channels` will be
 		// empty. In that case we create a RouteHint on which we will push a single hop with the
@@ -585,8 +585,13 @@ fn _create_invoice_from_channelmanager_and_duration_since_epoch_with_payment_has
 /// * Sorted by lowest inbound capacity if an online channel with the minimum amount requested exists,
 ///   otherwise sort by highest inbound capacity to give the payment the best chance of succeeding.
 fn sort_and_filter_channels<L: Deref>(
-	channels: Vec<ChannelDetails>, min_inbound_capacity_msat: Option<u64>, logger: &L
-) -> Vec<RouteHint> where L::Target: Logger {
+    channels: Vec<ChannelDetails>,
+    min_inbound_capacity_msat: Option<u64>,
+    logger: &L,
+) -> Box<dyn Iterator<Item = RouteHint>>
+where
+    L::Target: Logger,
+{
 	let mut filtered_channels: HashMap<PublicKey, ChannelDetails> = HashMap::new();
 	let min_inbound_capacity = min_inbound_capacity_msat.unwrap_or(0);
 	let mut min_capacity_channel_exists = false;
@@ -612,7 +617,7 @@ fn sort_and_filter_channels<L: Deref>(
 				// look at the public channels instead.
 				log_trace!(logger, "Not including channels in invoice route hints on account of public channel {}",
 					log_bytes!(channel.channel_id));
-				return vec![]
+				return Box::new(vec![].into_iter());
 			}
 		}
 
@@ -672,7 +677,7 @@ fn sort_and_filter_channels<L: Deref>(
 		}
 	}
 
-	let route_hint_from_channel = |channel: ChannelDetails| {
+	fn route_hint_from_channel(channel: ChannelDetails) -> RouteHint {
 		let forwarding_info = channel.counterparty.forwarding_info.as_ref().unwrap();
 		RouteHint(vec![RouteHintHop {
 			src_node_id: channel.counterparty.node_id,
@@ -734,7 +739,8 @@ fn sort_and_filter_channels<L: Deref>(
 			} else {
 				b.inbound_capacity_msat.cmp(&a.inbound_capacity_msat)
 			}});
-		eligible_channels.into_iter().take(3).map(route_hint_from_channel).collect::<Vec<RouteHint>>()
+
+		Box::new(eligible_channels.into_iter().take(3).map(route_hint_from_channel))
 }
 
 /// prefer_current_channel chooses a channel to use for route hints between a currently selected and candidate