1use core::hash::{BuildHasher, Hash};
2
3use super::{Equivalent, IndexSet};
4use crate::map::MutableKeys;
5
6/// Opt-in mutable access to [`IndexSet`] values.
7///
8/// These methods expose `&mut T`, mutable references to the value as it is stored
9/// in the set.
10/// You are allowed to modify the values in the set **if the modification
11/// does not change the value’s hash and equality**.
12///
13/// If values are modified erroneously, you can no longer look them up.
14/// This is sound (memory safe) but a logical error hazard (just like
15/// implementing `PartialEq`, `Eq`, or `Hash` incorrectly would be).
16///
17/// `use` this trait to enable its methods for `IndexSet`.
18///
19/// This trait is sealed and cannot be implemented for types outside this crate.
20pub trait MutableValues: private::Sealed {
21 type Value;
22
23 /// Return item index and mutable reference to the value
24 ///
25 /// Computes in **O(1)** time (average).
26 fn get_full_mut2<Q>(&mut self, value: &Q) -> Option<(usize, &mut Self::Value)>
27 where
28 Q: ?Sized + Hash + Equivalent<Self::Value>;
29
30 /// Return mutable reference to the value at an index.
31 ///
32 /// Valid indices are `0 <= index < self.len()`.
33 ///
34 /// Computes in **O(1)** time.
35 fn get_index_mut2(&mut self, index: usize) -> Option<&mut Self::Value>;
36
37 /// Scan through each value in the set and keep those where the
38 /// closure `keep` returns `true`.
39 ///
40 /// The values are visited in order, and remaining values keep their order.
41 ///
42 /// Computes in **O(n)** time (average).
43 fn retain2<F>(&mut self, keep: F)
44 where
45 F: FnMut(&mut Self::Value) -> bool;
46}
47
48/// Opt-in mutable access to [`IndexSet`] values.
49///
50/// See [`MutableValues`] for more information.
51impl<T, S> MutableValues for IndexSet<T, S>
52where
53 S: BuildHasher,
54{
55 type Value = T;
56
57 fn get_full_mut2<Q>(&mut self, value: &Q) -> Option<(usize, &mut T)>
58 where
59 Q: ?Sized + Hash + Equivalent<T>,
60 {
61 match self.map.get_full_mut2(value) {
62 Some((index, value, ())) => Some((index, value)),
63 None => None,
64 }
65 }
66
67 fn get_index_mut2(&mut self, index: usize) -> Option<&mut T> {
68 match self.map.get_index_mut2(index) {
69 Some((value, ())) => Some(value),
70 None => None,
71 }
72 }
73
74 fn retain2<F>(&mut self, mut keep: F)
75 where
76 F: FnMut(&mut T) -> bool,
77 {
78 self.map.retain2(move |value, ()| keep(value));
79 }
80}
81
82mod private {
83 pub trait Sealed {}
84
85 impl<T, S> Sealed for super::IndexSet<T, S> {}
86}
87