1use std::borrow::{Borrow, BorrowMut};
2use std::hash::Hash;
3use std::marker::PhantomData;
4use std::ops;
5
6use crate::fx::FxHashMap;
7pub use crate::undo_log::Snapshot;
8use crate::undo_log::{Rollback, Snapshots, UndoLogs, VecLog};
9
10#[cfg(test)]
11mod tests;
12
13pub type SnapshotMapStorage<K, V> = SnapshotMap<K, V, FxHashMap<K, V>, ()>;
14pub type SnapshotMapRef<'a, K, V, L> = SnapshotMap<K, V, &'a mut FxHashMap<K, V>, &'a mut L>;
15
16#[derive(Clone)]
17pub struct SnapshotMap<K, V, M = FxHashMap<K, V>, L = VecLog<UndoLog<K, V>>> {
18 map: M,
19 undo_log: L,
20 _marker: PhantomData<(K, V)>,
21}
22
23// HACK(eddyb) manual impl avoids `Default` bounds on `K` and `V`.
24impl<K, V, M, L> Default for SnapshotMap<K, V, M, L>
25where
26 M: Default,
27 L: Default,
28{
29 fn default() -> Self {
30 SnapshotMap { map: Default::default(), undo_log: Default::default(), _marker: PhantomData }
31 }
32}
33
34#[derive(Clone)]
35pub enum UndoLog<K, V> {
36 Inserted(K),
37 Overwrite(K, V),
38 Purged,
39}
40
41impl<K, V, M, L> SnapshotMap<K, V, M, L> {
42 #[inline]
43 pub fn with_log<L2>(&mut self, undo_log: L2) -> SnapshotMap<K, V, &mut M, L2> {
44 SnapshotMap { map: &mut self.map, undo_log, _marker: PhantomData }
45 }
46}
47
48impl<K, V, M, L> SnapshotMap<K, V, M, L>
49where
50 K: Hash + Clone + Eq,
51 M: BorrowMut<FxHashMap<K, V>> + Borrow<FxHashMap<K, V>>,
52 L: UndoLogs<UndoLog<K, V>>,
53{
54 pub fn clear(&mut self) {
55 self.map.borrow_mut().clear();
56 self.undo_log.clear();
57 }
58
59 pub fn insert(&mut self, key: K, value: V) -> bool {
60 match self.map.borrow_mut().insert(key.clone(), value) {
61 None => {
62 self.undo_log.push(UndoLog::Inserted(key));
63 true
64 }
65 Some(old_value) => {
66 self.undo_log.push(UndoLog::Overwrite(key, old_value));
67 false
68 }
69 }
70 }
71
72 pub fn remove(&mut self, key: K) -> bool {
73 match self.map.borrow_mut().remove(&key) {
74 Some(old_value) => {
75 self.undo_log.push(UndoLog::Overwrite(key, old_value));
76 true
77 }
78 None => false,
79 }
80 }
81
82 pub fn get(&self, key: &K) -> Option<&V> {
83 self.map.borrow().get(key)
84 }
85}
86
87impl<K, V> SnapshotMap<K, V>
88where
89 K: Hash + Clone + Eq,
90{
91 pub fn snapshot(&mut self) -> Snapshot {
92 self.undo_log.start_snapshot()
93 }
94
95 pub fn commit(&mut self, snapshot: Snapshot) {
96 self.undo_log.commit(snapshot)
97 }
98
99 pub fn rollback_to(&mut self, snapshot: Snapshot) {
100 let map: &mut HashMap = &mut self.map;
101 self.undo_log.rollback_to(|| map, snapshot)
102 }
103}
104
105impl<'k, K, V, M, L> ops::Index<&'k K> for SnapshotMap<K, V, M, L>
106where
107 K: Hash + Clone + Eq,
108 M: Borrow<FxHashMap<K, V>>,
109{
110 type Output = V;
111 fn index(&self, key: &'k K) -> &V {
112 &self.map.borrow()[key]
113 }
114}
115
116impl<K, V, M, L> Rollback<UndoLog<K, V>> for SnapshotMap<K, V, M, L>
117where
118 K: Eq + Hash,
119 M: Rollback<UndoLog<K, V>>,
120{
121 fn reverse(&mut self, undo: UndoLog<K, V>) {
122 self.map.reverse(undo)
123 }
124}
125
126impl<K, V> Rollback<UndoLog<K, V>> for FxHashMap<K, V>
127where
128 K: Eq + Hash,
129{
130 fn reverse(&mut self, undo: UndoLog<K, V>) {
131 match undo {
132 UndoLog::Inserted(key: K) => {
133 self.remove(&key);
134 }
135
136 UndoLog::Overwrite(key: K, old_value: V) => {
137 self.insert(k:key, v:old_value);
138 }
139
140 UndoLog::Purged => {}
141 }
142 }
143}
144

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