1// Extracted from the scopeguard crate
2use core::{
3 mem,
4 ops::{Deref, DerefMut},
5 ptr,
6};
7
8pub struct ScopeGuard<T, F>
9where
10 F: FnMut(&mut T),
11{
12 dropfn: F,
13 value: T,
14}
15
16#[inline]
17pub fn guard<T, F>(value: T, dropfn: F) -> ScopeGuard<T, F>
18where
19 F: FnMut(&mut T),
20{
21 ScopeGuard { dropfn, value }
22}
23
24impl<T, F> ScopeGuard<T, F>
25where
26 F: FnMut(&mut T),
27{
28 #[inline]
29 pub fn into_inner(guard: Self) -> T {
30 // Cannot move out of Drop-implementing types, so
31 // ptr::read the value and forget the guard.
32 unsafe {
33 let value: T = ptr::read(&guard.value);
34 // read the closure so that it is dropped, and assign it to a local
35 // variable to ensure that it is only dropped after the guard has
36 // been forgotten. (In case the Drop impl of the closure, or that
37 // of any consumed captured variable, panics).
38 let _dropfn: F = ptr::read(&guard.dropfn);
39 mem::forget(guard);
40 value
41 }
42 }
43}
44
45impl<T, F> Deref for ScopeGuard<T, F>
46where
47 F: FnMut(&mut T),
48{
49 type Target = T;
50 #[inline]
51 fn deref(&self) -> &T {
52 &self.value
53 }
54}
55
56impl<T, F> DerefMut for ScopeGuard<T, F>
57where
58 F: FnMut(&mut T),
59{
60 #[inline]
61 fn deref_mut(&mut self) -> &mut T {
62 &mut self.value
63 }
64}
65
66impl<T, F> Drop for ScopeGuard<T, F>
67where
68 F: FnMut(&mut T),
69{
70 #[inline]
71 fn drop(&mut self) {
72 (self.dropfn)(&mut self.value);
73 }
74}
75