sharded_slab/
clear.rs

1use std::{collections, hash, ops::DerefMut, sync};
2
3/// Trait implemented by types which can be cleared in place, retaining any
4/// allocated memory.
5///
6/// This is essentially a generalization of methods on standard library
7/// collection types, including as [`Vec::clear`], [`String::clear`], and
8/// [`HashMap::clear`]. These methods drop all data stored in the collection,
9/// but retain the collection's heap allocation for future use. Types such as
10/// `BTreeMap`, whose `clear` methods drops allocations, should not
11/// implement this trait.
12///
13/// When implemented for types which do not own a heap allocation, `Clear`
14/// should reset the type in place if possible. If the type has an empty state
15/// or stores `Option`s, those values should be reset to the empty state. For
16/// "plain old data" types, which hold no pointers to other data and do not have
17/// an empty or initial state, it's okay for a `Clear` implementation to be a
18/// no-op. In that case, it essentially serves as a marker indicating that the
19/// type may be reused to store new data.
20///
21/// [`Vec::clear`]: https://doc.rust-lang.org/stable/std/vec/struct.Vec.html#method.clear
22/// [`String::clear`]: https://doc.rust-lang.org/stable/std/string/struct.String.html#method.clear
23/// [`HashMap::clear`]: https://doc.rust-lang.org/stable/std/collections/struct.HashMap.html#method.clear
24pub trait Clear {
25    /// Clear all data in `self`, retaining the allocated capacithy.
26    fn clear(&mut self);
27}
28
29impl<T> Clear for Option<T> {
30    fn clear(&mut self) {
31        let _ = self.take();
32    }
33}
34
35impl<T> Clear for Box<T>
36where
37    T: Clear,
38{
39    #[inline]
40    fn clear(&mut self) {
41        self.deref_mut().clear()
42    }
43}
44
45impl<T> Clear for Vec<T> {
46    #[inline]
47    fn clear(&mut self) {
48        Vec::clear(self)
49    }
50}
51
52impl<K, V, S> Clear for collections::HashMap<K, V, S>
53where
54    K: hash::Hash + Eq,
55    S: hash::BuildHasher,
56{
57    #[inline]
58    fn clear(&mut self) {
59        collections::HashMap::clear(self)
60    }
61}
62
63impl<T, S> Clear for collections::HashSet<T, S>
64where
65    T: hash::Hash + Eq,
66    S: hash::BuildHasher,
67{
68    #[inline]
69    fn clear(&mut self) {
70        collections::HashSet::clear(self)
71    }
72}
73
74impl Clear for String {
75    #[inline]
76    fn clear(&mut self) {
77        String::clear(self)
78    }
79}
80
81impl<T: Clear> Clear for sync::Mutex<T> {
82    #[inline]
83    fn clear(&mut self) {
84        self.get_mut().unwrap().clear();
85    }
86}
87
88impl<T: Clear> Clear for sync::RwLock<T> {
89    #[inline]
90    fn clear(&mut self) {
91        self.write().unwrap().clear();
92    }
93}
94
95#[cfg(all(loom, test))]
96impl<T: Clear> Clear for crate::sync::alloc::Track<T> {
97    fn clear(&mut self) {
98        self.get_mut().clear()
99    }
100}
sharded_slab/clear.rs

sharded_slab/
clear.rs
