1 // Copyright 2021 Google LLC
2 //
3 // Licensed under the Apache License, Version 2.0 (the "License");
4 // you may not use this file except in compliance with the License.
5 // You may obtain a copy of the License at
6 //
7 // http://www.apache.org/licenses/LICENSE-2.0
8 //
9 // Unless required by applicable law or agreed to in writing, software
10 // distributed under the License is distributed on an "AS IS" BASIS,
11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 // See the License for the specific language governing permissions and
13 // limitations under the License.
14
15 use core::mem;
16 use core::mem::MaybeUninit;
17 use core::ops::Deref;
18 use core::pin::Pin;
19
20 use crate::new;
21 use crate::new::New;
22
23 /// A copy constructible type: a destination-aware `Clone`.
24 ///
25 /// # Safety
26 ///
27 /// After [`CopyNew::copy_new()`] is called:
28 /// - `this` must have been initialized.
29 pub unsafe trait CopyNew: Sized {
30 /// Copy-construct `src` into `this`, effectively re-pinning it at a new
31 /// location.
32 ///
33 /// # Safety
34 ///
35 /// The same safety requirements of [`New::new()`] apply.
copy_new(src: &Self, this: Pin<&mut MaybeUninit<Self>>)36 unsafe fn copy_new(src: &Self, this: Pin<&mut MaybeUninit<Self>>);
37 }
38
39 /// Returns a new `New` that uses a copy constructor.
40 #[inline]
copy<P>(ptr: P) -> impl New<Output = P::Target> where P: Deref, P::Target: CopyNew,41 pub fn copy<P>(ptr: P) -> impl New<Output = P::Target>
42 where
43 P: Deref,
44 P::Target: CopyNew,
45 {
46 unsafe {
47 new::by_raw(move |this| {
48 CopyNew::copy_new(&*ptr, this);
49
50 // Because `*ptr` is still intact, we can drop it normally.
51 mem::drop(ptr)
52 })
53 }
54 }
55