1use std::fmt::{self, Debug};
2use std::thread::{self, ThreadId};
3
4/// ThreadBound is a Sync-maker and Send-maker that allows accessing a value
5/// of type T only from the original thread on which the ThreadBound was
6/// constructed.
7pub struct ThreadBound<T> {
8 value: T,
9 thread_id: ThreadId,
10}
11
12unsafe impl<T> Sync for ThreadBound<T> {}
13
14// Send bound requires Copy, as otherwise Drop could run in the wrong place.
15unsafe impl<T: Copy> Send for ThreadBound<T> {}
16
17impl<T> ThreadBound<T> {
18 pub fn new(value: T) -> Self {
19 ThreadBound {
20 value,
21 thread_id: thread::current().id(),
22 }
23 }
24
25 pub fn get(&self) -> Option<&T> {
26 if thread::current().id() == self.thread_id {
27 Some(&self.value)
28 } else {
29 None
30 }
31 }
32}
33
34impl<T: Debug> Debug for ThreadBound<T> {
35 fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
36 match self.get() {
37 Some(value) => Debug::fmt(value, formatter),
38 None => formatter.write_str("unknown"),
39 }
40 }
41}
42