luaur_common/records/
insertion_ordered_map.rs

1//! Node: `cxx:Record:Luau.Common:Common/include/Luau/InsertionOrderedMap.h:15:insertion_ordered_map`
2//! Source: `Common/include/Luau/InsertionOrderedMap.h:14-145` (hand-ported, complete API)
3//!
4//! A map preserving insertion order: pairs live in a Vec, an unordered index
5//! maps key -> position. `insert` is first-write-wins (a duplicate key is a
6//! no-op, matching C++). `erase` removes the pair and decrements every index
7//! after it, exactly like the C++ loop. C++ `operator[]` (find-or-default-
8//! insert) is `get_or_default`; C++ `find` returning an iterator maps to
9//! `find` returning the position, with `get`/`get_mut` for the common
10//! deref-the-iterator pattern.
11
12extern crate alloc;
13
14use crate::type_aliases::vec::vec;
15use std::collections::HashMap;
16use std::hash::Hash;
17
18#[derive(Debug, Clone)]
19pub struct InsertionOrderedMap<K, V>
20where
21    K: Eq + Hash + Clone,
22{
23    pub(crate) pairs: vec<K, V>,
24    pub(crate) indices: HashMap<K, usize>,
25}
26
27impl<K, V> InsertionOrderedMap<K, V>
28where
29    K: Eq + Hash + Clone,
30{
31    pub fn new() -> Self {
32        Self {
33            pairs: vec::new(),
34            indices: HashMap::new(),
35        }
36    }
37
38    pub fn insert(&mut self, k: K, v: V) {
39        if self.indices.contains_key(&k) {
40            return;
41        }
42        self.pairs.push((k.clone(), v));
43        self.indices.insert(k, self.pairs.len() - 1);
44    }
45
46    pub fn clear(&mut self) {
47        self.pairs.clear();
48        self.indices.clear();
49    }
50
51    pub fn size(&self) -> usize {
52        debug_assert_eq!(self.pairs.len(), self.indices.len());
53        self.pairs.len()
54    }
55
56    pub fn is_empty(&self) -> bool {
57        self.pairs.is_empty()
58    }
59
60    pub fn contains(&self, k: &K) -> bool {
61        self.indices.contains_key(k)
62    }
63
64    pub fn get(&self, k: &K) -> Option<&V> {
65        self.indices.get(k).map(|&i| &self.pairs[i].1)
66    }
67
68    pub fn get_mut(&mut self, k: &K) -> Option<&mut V> {
69        match self.indices.get(k) {
70            Some(&i) => Some(&mut self.pairs[i].1),
71            None => None,
72        }
73    }
74
75    /// C++ `operator[]`: returns the value for `k`, default-inserting it at
76    /// the back if absent.
77    pub fn get_or_default(&mut self, k: K) -> &mut V
78    where
79        V: Default,
80    {
81        if let Some(&i) = self.indices.get(&k) {
82            return &mut self.pairs[i].1;
83        }
84        self.pairs.push((k.clone(), V::default()));
85        self.indices.insert(k, self.pairs.len() - 1);
86        &mut self.pairs.last_mut().unwrap().1
87    }
88
89    /// C++ `find`: position of `k` in insertion order, or `None` (`end()`).
90    pub fn find(&self, k: &K) -> Option<usize> {
91        self.indices.get(k).copied()
92    }
93
94    /// C++ `erase(find(k))`: removes the pair and shifts every later index
95    /// down by one. Absent keys are a no-op (erasing `end()`).
96    pub fn erase(&mut self, k: &K) {
97        let Some(removed) = self.indices.remove(k) else {
98            return;
99        };
100        self.pairs.remove(removed);
101        for index in self.indices.values_mut() {
102            if *index > removed {
103                *index -= 1;
104            }
105        }
106    }
107
108    pub fn iter(&self) -> core::slice::Iter<'_, (K, V)> {
109        self.pairs.iter()
110    }
111
112    /// Values are mutable through iteration; keys are not (mutating a key
113    /// would desynchronize `indices` — C++ merely trusts you not to).
114    pub fn iter_mut(&mut self) -> impl Iterator<Item = (&K, &mut V)> {
115        self.pairs.iter_mut().map(|(k, v)| (&*k, v))
116    }
117}
118
119impl<'a, K, V> IntoIterator for &'a InsertionOrderedMap<K, V>
120where
121    K: Eq + Hash + Clone,
122{
123    type Item = &'a (K, V);
124    type IntoIter = core::slice::Iter<'a, (K, V)>;
125
126    fn into_iter(self) -> Self::IntoIter {
127        self.pairs.iter()
128    }
129}
130
131impl<K, V> Default for InsertionOrderedMap<K, V>
132where
133    K: Eq + Hash + Clone,
134{
135    fn default() -> Self {
136        Self::new()
137    }
138}
139
140#[cfg(test)]
141mod tests {
142    use super::InsertionOrderedMap;
143
144    // Behavioral oracle: mirrors the C++ semantics in
145    // Common/include/Luau/InsertionOrderedMap.h.
146    #[test]
147    fn insertion_order_preserved_and_duplicate_insert_is_noop() {
148        let mut m: InsertionOrderedMap<i32, &str> = InsertionOrderedMap::new();
149        m.insert(3, "c");
150        m.insert(1, "a");
151        m.insert(2, "b");
152        m.insert(1, "OVERWRITE"); // C++: duplicate key is a no-op
153        let keys: Vec<i32> = m.iter().map(|(k, _)| *k).collect();
154        assert_eq!(keys, vec![3, 1, 2]);
155        assert_eq!(m.get(&1), Some(&"a"));
156        assert_eq!(m.size(), 3);
157    }
158
159    #[test]
160    fn erase_reindexes_later_entries() {
161        let mut m: InsertionOrderedMap<i32, i32> = InsertionOrderedMap::new();
162        for k in [10, 20, 30, 40] {
163            m.insert(k, k * 2);
164        }
165        m.erase(&20);
166        assert_eq!(m.size(), 3);
167        assert_eq!(m.find(&10), Some(0));
168        assert_eq!(m.find(&30), Some(1));
169        assert_eq!(m.find(&40), Some(2));
170        assert_eq!(m.get(&40), Some(&80));
171        m.erase(&999); // erasing end() is a no-op
172        assert_eq!(m.size(), 3);
173    }
174
175    #[test]
176    fn get_or_default_matches_cpp_index_operator() {
177        let mut m: InsertionOrderedMap<i32, i32> = InsertionOrderedMap::new();
178        *m.get_or_default(5) = 50;
179        assert_eq!(m.get(&5), Some(&50));
180        *m.get_or_default(5) += 1; // existing: no new entry
181        assert_eq!(m.get(&5), Some(&51));
182        assert_eq!(m.size(), 1);
183    }
184}
luaur_common/records/insertion_ordered_map.rs

luaur_common/records/
insertion_ordered_map.rs
