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
use cell::Cell;
use ptr;
use sync::Arc;
use sys_common;
use sys_common::mutex::Mutex;
pub struct Lazy<T> {
lock: Mutex,
ptr: Cell<*mut Arc<T>>,
init: fn() -> Arc<T>,
}
unsafe impl<T> Sync for Lazy<T> {}
impl<T: Send + Sync + 'static> Lazy<T> {
pub const fn new(init: fn() -> Arc<T>) -> Lazy<T> {
Lazy {
lock: Mutex::new(),
ptr: Cell::new(ptr::null_mut()),
init,
}
}
pub fn get(&'static self) -> Option<Arc<T>> {
unsafe {
self.lock.lock();
let ptr = self.ptr.get();
let ret = if ptr.is_null() {
Some(self.init())
} else if ptr as usize == 1 {
None
} else {
Some((*ptr).clone())
};
self.lock.unlock();
return ret
}
}
unsafe fn init(&'static self) -> Arc<T> {
let registered = sys_common::at_exit(move || {
self.lock.lock();
let ptr = self.ptr.get();
self.ptr.set(1 as *mut _);
self.lock.unlock();
drop(Box::from_raw(ptr))
});
let ret = (self.init)();
if registered.is_ok() {
self.ptr.set(Box::into_raw(Box::new(ret.clone())));
}
ret
}
}