1 //! This module has a map which can be iterated in a deterministic order. See the [`IndexedMap`].
3 use crate::prelude::{HashMap, hash_map};
5 use alloc::slice::Iter;
8 use core::ops::{Bound, RangeBounds};
10 /// A map which can be iterated in a deterministic order.
12 /// This would traditionally be accomplished by simply using a [`BTreeMap`], however B-Trees
13 /// generally have very slow lookups. Because we use a nodes+channels map while finding routes
14 /// across the network graph, our network graph backing map must be as performant as possible.
15 /// However, because peers expect to sync the network graph from us (and we need to support that
16 /// without holding a lock on the graph for the duration of the sync or dumping the entire graph
17 /// into our outbound message queue), we need an iterable map with a consistent iteration order we
18 /// can jump to a starting point on.
20 /// Thus, we have a custom data structure here - its API mimics that of Rust's [`BTreeMap`], but is
21 /// actually backed by a [`HashMap`], with some additional tracking to ensure we can iterate over
22 /// keys in the order defined by [`Ord`].
24 /// [`BTreeMap`]: alloc::collections::BTreeMap
25 #[derive(Clone, Debug, Eq)]
26 pub struct IndexedMap<K: Hash + Ord, V> {
31 impl<K: Clone + Hash + Ord, V> IndexedMap<K, V> {
32 /// Constructs a new, empty map
33 pub fn new() -> Self {
41 /// Fetches the element with the given `key`, if one exists.
42 pub fn get(&self, key: &K) -> Option<&V> {
46 /// Fetches a mutable reference to the element with the given `key`, if one exists.
47 pub fn get_mut(&mut self, key: &K) -> Option<&mut V> {
52 /// Returns true if an element with the given `key` exists in the map.
53 pub fn contains_key(&self, key: &K) -> bool {
54 self.map.contains_key(key)
57 /// Removes the element with the given `key`, returning it, if one exists.
58 pub fn remove(&mut self, key: &K) -> Option<V> {
59 let ret = self.map.remove(key);
60 if let Some(_) = ret {
61 let idx = self.keys.iter().position(|k| k == key).expect("map and keys must be consistent");
62 self.keys.remove(idx);
67 /// Inserts the given `key`/`value` pair into the map, returning the element that was
68 /// previously stored at the given `key`, if one exists.
69 pub fn insert(&mut self, key: K, value: V) -> Option<V> {
70 let ret = self.map.insert(key.clone(), value);
77 /// Returns an [`Entry`] for the given `key` in the map, allowing access to the value.
78 pub fn entry(&mut self, key: K) -> Entry<'_, K, V> {
79 match self.map.entry(key.clone()) {
80 hash_map::Entry::Vacant(entry) => {
81 Entry::Vacant(VacantEntry {
82 underlying_entry: entry,
87 hash_map::Entry::Occupied(entry) => {
88 Entry::Occupied(OccupiedEntry {
89 underlying_entry: entry,
96 /// Returns an iterator which iterates over the keys in the map, in a random order.
97 pub fn unordered_keys(&self) -> impl Iterator<Item = &K> {
101 /// Returns an iterator which iterates over the `key`/`value` pairs in a random order.
102 pub fn unordered_iter(&self) -> impl Iterator<Item = (&K, &V)> {
106 /// Returns an iterator which iterates over the `key`s and mutable references to `value`s in a
108 pub fn unordered_iter_mut(&mut self) -> impl Iterator<Item = (&K, &mut V)> {
112 /// Returns an iterator which iterates over the `key`/`value` pairs in a given range.
113 pub fn range<R: RangeBounds<K>>(&mut self, range: R) -> Range<K, V> {
114 self.keys.sort_unstable();
115 let start = match range.start_bound() {
116 Bound::Unbounded => 0,
117 Bound::Included(key) => self.keys.binary_search(key).unwrap_or_else(|index| index),
118 Bound::Excluded(key) => self.keys.binary_search(key).and_then(|index| Ok(index + 1)).unwrap_or_else(|index| index),
120 let end = match range.end_bound() {
121 Bound::Unbounded => self.keys.len(),
122 Bound::Included(key) => self.keys.binary_search(key).and_then(|index| Ok(index + 1)).unwrap_or_else(|index| index),
123 Bound::Excluded(key) => self.keys.binary_search(key).unwrap_or_else(|index| index),
127 inner_range: self.keys[start..end].iter(),
132 /// Returns the number of `key`/`value` pairs in the map
133 pub fn len(&self) -> usize {
137 /// Returns true if there are no elements in the map
138 pub fn is_empty(&self) -> bool {
143 impl<K: Hash + Ord + PartialEq, V: PartialEq> PartialEq for IndexedMap<K, V> {
144 fn eq(&self, other: &Self) -> bool {
145 self.map == other.map
149 /// An iterator over a range of values in an [`IndexedMap`]
150 pub struct Range<'a, K: Hash + Ord, V> {
151 inner_range: Iter<'a, K>,
152 map: &'a HashMap<K, V>,
154 impl<'a, K: Hash + Ord, V: 'a> Iterator for Range<'a, K, V> {
155 type Item = (&'a K, &'a V);
156 fn next(&mut self) -> Option<(&'a K, &'a V)> {
157 self.inner_range.next().map(|k| {
158 (k, self.map.get(k).expect("map and keys must be consistent"))
163 /// An [`Entry`] for a key which currently has no value
164 pub struct VacantEntry<'a, K: Hash + Ord, V> {
165 #[cfg(feature = "hashbrown")]
166 underlying_entry: hash_map::VacantEntry<'a, K, V, hash_map::DefaultHashBuilder>,
167 #[cfg(not(feature = "hashbrown"))]
168 underlying_entry: hash_map::VacantEntry<'a, K, V>,
170 keys: &'a mut Vec<K>,
173 /// An [`Entry`] for an existing key-value pair
174 pub struct OccupiedEntry<'a, K: Hash + Ord, V> {
175 #[cfg(feature = "hashbrown")]
176 underlying_entry: hash_map::OccupiedEntry<'a, K, V, hash_map::DefaultHashBuilder>,
177 #[cfg(not(feature = "hashbrown"))]
178 underlying_entry: hash_map::OccupiedEntry<'a, K, V>,
179 keys: &'a mut Vec<K>,
182 /// A mutable reference to a position in the map. This can be used to reference, add, or update the
183 /// value at a fixed key.
184 pub enum Entry<'a, K: Hash + Ord, V> {
185 /// A mutable reference to a position within the map where there is no value.
186 Vacant(VacantEntry<'a, K, V>),
187 /// A mutable reference to a position within the map where there is currently a value.
188 Occupied(OccupiedEntry<'a, K, V>),
191 impl<'a, K: Hash + Ord, V> VacantEntry<'a, K, V> {
192 /// Insert a value into the position described by this entry.
193 pub fn insert(self, value: V) -> &'a mut V {
194 self.keys.push(self.key);
195 self.underlying_entry.insert(value)
199 impl<'a, K: Hash + Ord, V> OccupiedEntry<'a, K, V> {
200 /// Remove the value at the position described by this entry.
201 pub fn remove_entry(self) -> (K, V) {
202 let res = self.underlying_entry.remove_entry();
203 let idx = self.keys.iter().position(|k| k == &res.0).expect("map and keys must be consistent");
204 self.keys.remove(idx);
208 /// Get a reference to the value at the position described by this entry.
209 pub fn get(&self) -> &V {
210 self.underlying_entry.get()
213 /// Get a mutable reference to the value at the position described by this entry.
214 pub fn get_mut(&mut self) -> &mut V {
215 self.underlying_entry.get_mut()
218 /// Consume this entry, returning a mutable reference to the value at the position described by
220 pub fn into_mut(self) -> &'a mut V {
221 self.underlying_entry.into_mut()