1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
|
use {crate::unreachable_unchecked, alloc::vec::Vec, core::mem::replace};
#[derive(Debug)]
enum Entry<T> {
Vacant(usize),
Occupied(T),
}
#[derive(Debug)]
pub(crate) struct Slab<T> {
next_vacant: usize,
entries: Vec<Entry<T>>,
}
impl<T> Slab<T> {
pub fn new() -> Self {
Slab {
next_vacant: !0,
entries: Vec::new(),
}
}
/// Inserts value into this linked vec and returns index
/// at which value can be accessed in constant time.
pub fn insert(&mut self, value: T) -> usize {
if self.next_vacant >= self.entries.len() {
self.entries.push(Entry::Occupied(value));
self.entries.len() - 1
} else {
match *unsafe { self.entries.get_unchecked(self.next_vacant) } {
Entry::Vacant(next_vacant) => {
unsafe {
*self.entries.get_unchecked_mut(self.next_vacant) = Entry::Occupied(value);
}
replace(&mut self.next_vacant, next_vacant)
}
_ => unsafe { unreachable_unchecked() },
}
}
}
pub fn len(&self) -> usize {
self.entries.len()
}
pub unsafe fn get_unchecked(&self, index: usize) -> &T {
debug_assert!(index < self.len());
match self.entries.get_unchecked(index) {
Entry::Occupied(value) => value,
_ => unreachable_unchecked(),
}
}
pub unsafe fn get_unchecked_mut(&mut self, index: usize) -> &mut T {
debug_assert!(index < self.len());
match self.entries.get_unchecked_mut(index) {
Entry::Occupied(value) => value,
_ => unreachable_unchecked(),
}
}
pub fn get(&self, index: usize) -> &T {
match self.entries.get(index) {
Some(Entry::Occupied(value)) => value,
_ => panic!("Invalid index"),
}
}
pub fn get_mut(&mut self, index: usize) -> &mut T {
match self.entries.get_mut(index) {
Some(Entry::Occupied(value)) => value,
_ => panic!("Invalid index"),
}
}
pub unsafe fn remove_unchecked(&mut self, index: usize) -> T {
let entry = replace(
self.entries.get_unchecked_mut(index),
Entry::Vacant(self.next_vacant),
);
self.next_vacant = index;
match entry {
Entry::Occupied(value) => value,
_ => unreachable_unchecked(),
}
}
pub fn remove(&mut self, index: usize) -> T {
match self.entries.get_mut(index) {
Some(Entry::Occupied(_)) => unsafe { self.remove_unchecked(index) },
_ => panic!("Invalid index"),
}
}
}
|
