Replace BTreeSet in IndexedMap with sorted Vec

The `Vec` is sorted not on `IndexedMap::insert`, but on
`IndexedMap::range` to avoid unnecessary work while reading a network
graph.

Author: alecchendev

fuzz/src/indexedmap.rs

@@ -13,7 +13,7 @@ use hashbrown::HashSet;
 
 use crate::utils::test_logger;
 
-fn check_eq(btree: &BTreeMap<u8, u8>, indexed: &IndexedMap<u8, u8>) {
+fn check_eq(btree: &BTreeMap<u8, u8>, indexed: &mut IndexedMap<u8, u8>) {
 	assert_eq!(btree.len(), indexed.len());
 	assert_eq!(btree.is_empty(), indexed.is_empty());
 
@@ -91,15 +91,15 @@ pub fn do_test(data: &[u8]) {
 		let prev_value_i = indexed.insert(tuple[0], tuple[1]);
 		assert_eq!(prev_value_b, prev_value_i);
 	}
-	check_eq(&btree, &indexed);
+	check_eq(&btree, &mut indexed);
 
 	// Now, modify the maps in all the ways we have to do so, checking that the maps remain
 	// equivalent as we go.
 	for (k, v) in indexed.unordered_iter_mut() {
 		*v = *k;
 		*btree.get_mut(k).unwrap() = *k;
 	}
-	check_eq(&btree, &indexed);
+	check_eq(&btree, &mut indexed);
 
 	for k in 0..=255 {
 		match btree.entry(k) {
@@ -124,7 +124,7 @@ pub fn do_test(data: &[u8]) {
 			},
 		}
 	}
-	check_eq(&btree, &indexed);
+	check_eq(&btree, &mut indexed);
 }
 
 pub fn indexedmap_test<Out: test_logger::Output>(data: &[u8], _out: Out) {

lightning/src/routing/gossip.rs

@@ -390,7 +390,7 @@ where U::Target: UtxoLookup, L::Target: Logger
 	}
 
 	fn get_next_channel_announcement(&self, starting_point: u64) -> Option<(ChannelAnnouncement, Option<ChannelUpdate>, Option<ChannelUpdate>)> {
-		let channels = self.network_graph.channels.read().unwrap();
+		let mut channels = self.network_graph.channels.write().unwrap();
 		for (_, ref chan) in channels.range(starting_point..) {
 			if chan.announcement_message.is_some() {
 				let chan_announcement = chan.announcement_message.clone().unwrap();
@@ -412,7 +412,7 @@ where U::Target: UtxoLookup, L::Target: Logger
 	}
 
 	fn get_next_node_announcement(&self, starting_point: Option<&NodeId>) -> Option<NodeAnnouncement> {
-		let nodes = self.network_graph.nodes.read().unwrap();
+		let mut nodes = self.network_graph.nodes.write().unwrap();
 		let iter = if let Some(node_id) = starting_point {
 				nodes.range((Bound::Excluded(node_id), Bound::Unbounded))
 			} else {
@@ -572,7 +572,7 @@ where U::Target: UtxoLookup, L::Target: Logger
 		// (has at least one update). A peer may still want to know the channel
 		// exists even if its not yet routable.
 		let mut batches: Vec<Vec<u64>> = vec![Vec::with_capacity(MAX_SCIDS_PER_REPLY)];
-		let channels = self.network_graph.channels.read().unwrap();
+		let mut channels = self.network_graph.channels.write().unwrap();
 		for (_, ref chan) in channels.range(inclusive_start_scid.unwrap()..exclusive_end_scid.unwrap()) {
 			if let Some(chan_announcement) = &chan.announcement_message {
 				// Construct a new batch if last one is full

lightning/src/util/indexed_map.rs

@@ -1,10 +1,11 @@
 //! This module has a map which can be iterated in a deterministic order. See the [`IndexedMap`].
 
 use crate::prelude::{HashMap, hash_map};
-use alloc::collections::{BTreeSet, btree_set};
+use alloc::vec::Vec;
+use alloc::slice::Iter;
 use core::hash::Hash;
 use core::cmp::Ord;
-use core::ops::RangeBounds;
+use core::ops::{Bound, RangeBounds};
 
 /// A map which can be iterated in a deterministic order.
 ///
@@ -21,19 +22,18 @@ use core::ops::RangeBounds;
 /// keys in the order defined by [`Ord`].
 ///
 /// [`BTreeMap`]: alloc::collections::BTreeMap
-#[derive(Clone, Debug, PartialEq, Eq)]
+#[derive(Clone, Debug, Eq)]
 pub struct IndexedMap<K: Hash + Ord, V> {
 	map: HashMap<K, V>,
-	// TODO: Explore swapping this for a sorted vec (that is only sorted on first range() call)
-	keys: BTreeSet<K>,
+	keys: Vec<K>,
 }
 
 impl<K: Clone + Hash + Ord, V> IndexedMap<K, V> {
 	/// Constructs a new, empty map
 	pub fn new() -> Self {
 		Self {
 			map: HashMap::new(),
-			keys: BTreeSet::new(),
+			keys: Vec::new(),
 		}
 	}
 
@@ -58,7 +58,8 @@ impl<K: Clone + Hash + Ord, V> IndexedMap<K, V> {
 	pub fn remove(&mut self, key: &K) -> Option<V> {
 		let ret = self.map.remove(key);
 		if let Some(_) = ret {
-			assert!(self.keys.remove(key), "map and keys must be consistent");
+			let idx = self.keys.iter().position(|k| k == key).expect("map and keys must be consistent");
+			self.keys.remove(idx);
 		}
 		ret
 	}
@@ -68,7 +69,7 @@ impl<K: Clone + Hash + Ord, V> IndexedMap<K, V> {
 	pub fn insert(&mut self, key: K, value: V) -> Option<V> {
 		let ret = self.map.insert(key.clone(), value);
 		if ret.is_none() {
-			assert!(self.keys.insert(key), "map and keys must be consistent");
+			self.keys.push(key);
 		}
 		ret
 	}
@@ -109,9 +110,21 @@ impl<K: Clone + Hash + Ord, V> IndexedMap<K, V> {
 	}
 
 	/// Returns an iterator which iterates over the `key`/`value` pairs in a given range.
-	pub fn range<R: RangeBounds<K>>(&self, range: R) -> Range<K, V> {
+	pub fn range<R: RangeBounds<K>>(&mut self, range: R) -> Range<K, V> {
+		self.keys.sort();
+		let start = match range.start_bound() {
+			Bound::Unbounded => 0,
+			Bound::Included(key) => self.keys.binary_search(key).unwrap_or_else(|index| index),
+			Bound::Excluded(key) => self.keys.binary_search(key).and_then(|index| Ok(index + 1)).unwrap_or_else(|index| index),
+		};
+		let end = match range.end_bound() {
+			Bound::Unbounded => self.keys.len(),
+			Bound::Included(key) => self.keys.binary_search(key).and_then(|index| Ok(index + 1)).unwrap_or_else(|index| index),
+			Bound::Excluded(key) => self.keys.binary_search(key).unwrap_or_else(|index| index),
+		};
+
 		Range {
-			inner_range: self.keys.range(range),
+			inner_range: self.keys[start..end].iter(),
 			map: &self.map,
 		}
 	}
@@ -127,9 +140,15 @@ impl<K: Clone + Hash + Ord, V> IndexedMap<K, V> {
 	}
 }
 
+impl<K: Hash + Ord + PartialEq, V: PartialEq> PartialEq for IndexedMap<K, V> {
+	fn eq(&self, other: &Self) -> bool {
+		self.map == other.map && self.keys.iter().all(|item| self.keys.contains(item))
+	}
+}
+
 /// An iterator over a range of values in an [`IndexedMap`]
 pub struct Range<'a, K: Hash + Ord, V> {
-	inner_range: btree_set::Range<'a, K>,
+	inner_range: Iter<'a, K>,
 	map: &'a HashMap<K, V>,
 }
 impl<'a, K: Hash + Ord, V: 'a> Iterator for Range<'a, K, V> {
@@ -148,7 +167,7 @@ pub struct VacantEntry<'a, K: Hash + Ord, V> {
 	#[cfg(not(feature = "hashbrown"))]
 	underlying_entry: hash_map::VacantEntry<'a, K, V>,
 	key: K,
-	keys: &'a mut BTreeSet<K>,
+	keys: &'a mut Vec<K>,
 }
 
 /// An [`Entry`] for an existing key-value pair
@@ -157,7 +176,7 @@ pub struct OccupiedEntry<'a, K: Hash + Ord, V> {
 	underlying_entry: hash_map::OccupiedEntry<'a, K, V, hash_map::DefaultHashBuilder>,
 	#[cfg(not(feature = "hashbrown"))]
 	underlying_entry: hash_map::OccupiedEntry<'a, K, V>,
-	keys: &'a mut BTreeSet<K>,
+	keys: &'a mut Vec<K>,
 }
 
 /// A mutable reference to a position in the map. This can be used to reference, add, or update the
@@ -172,7 +191,7 @@ pub enum Entry<'a, K: Hash + Ord, V> {
 impl<'a, K: Hash + Ord, V> VacantEntry<'a, K, V> {
 	/// Insert a value into the position described by this entry.
 	pub fn insert(self, value: V) -> &'a mut V {
-		assert!(self.keys.insert(self.key), "map and keys must be consistent");
+		self.keys.push(self.key);
 		self.underlying_entry.insert(value)
 	}
 }
@@ -181,7 +200,8 @@ impl<'a, K: Hash + Ord, V> OccupiedEntry<'a, K, V> {
 	/// Remove the value at the position described by this entry.
 	pub fn remove_entry(self) -> (K, V) {
 		let res = self.underlying_entry.remove_entry();
-		assert!(self.keys.remove(&res.0), "map and keys must be consistent");
+		let idx = self.keys.iter().position(|k| k == &res.0).expect("map and keys must be consistent");
+		self.keys.remove(idx);
 		res
 	}