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
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
use std::cell::UnsafeCell;
use std::fmt;
use std::sync::{Arc, Weak};
pub struct WeakSelf<T: ?Sized> {
cell: UnsafeCell<Option<Weak<T>>>
}
impl<T: ?Sized> WeakSelf<T> {
pub fn new() -> WeakSelf<T> {
WeakSelf {
cell: UnsafeCell::new(None)
}
}
pub fn init(&self, content: &Arc<T>) {
if Arc::strong_count(content) != 1 || Arc::weak_count(content) != 0 {
panic!("Exclusive access to Arc<T> is required while initializing WeakSelf<T>");
}
let weak = Arc::downgrade(content);
unsafe {
*self.cell.get() = Some(weak);
}
}
pub fn try_get(&self) -> Option<&Weak<T>> {
unsafe {
match *self.cell.get() {
Some(ref weak) => Some(&weak),
None => None
}
}
}
pub fn get(&self) -> Weak<T> {
self.try_get().expect("expected WeakSelf to be initialized").clone()
}
}
unsafe impl<T: ?Sized + Sync + Send> Sync for WeakSelf<T> {}
unsafe impl<T: ?Sized + Sync + Send> Send for WeakSelf<T> {}
impl<T: ?Sized + fmt::Debug> fmt::Debug for WeakSelf<T> {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
match self.try_get() {
None => { write!(f, "Empty WeakSelf<T>") }
Some(weak) => fmt::Debug::fmt(weak, f),
}
}
}
impl<T: ?Sized> Default for WeakSelf<T> {
fn default() -> Self {
WeakSelf::new()
}
}