stackbox 0.2.2

`&own`ing references in stable Rust - no_std-friendly Box
Documentation 
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

//! Module that attemps to define a `Unique<T>` pointer:
//!
//!  - non-null, well-aligned & read-write dereferenceable,
//!    (for some _valid_ instance; wrap the `T` in a `MaybeUninit` to loosen
//!    that validity invariant)
//!  - unaliased,
//!  - covariant.
//!
//! When `Box` is available, `MD<Box<T>>` happens to satisfy all these
//! requirements, but for the dereferenceable one.
//!
//! Otherwise, `ptr::NonNull<T>` is the maximal covariant wrapper available
//! to stable Rust… đŸ˜©

#[allow(unused_imports)]
pub(crate) use ::core::ptr::*;

pub(crate) use __::Unique;

#[cfg(feature = "alloc")]
pub(crate) mod __ {
    use ::alloc::boxed::Box;
    use ::core::{mem::ManuallyDrop as MD, ptr};

    #[repr(transparent)]
    pub(crate) struct Unique<T: ?Sized>(MD<Box<T>>);

    impl<T: ?Sized> Unique<T> {
        #[inline]
        pub(crate) unsafe fn from_raw(ptr: *mut T) -> Unique<T> {
            Self(MD::new(Box::from_raw(ptr)))
        }

        #[inline]
        pub(crate) fn into_raw_nonnull(self: Unique<T>) -> ptr::NonNull<T> {
            Box::leak(MD::into_inner(self.0)).into()
        }

        #[inline]
        pub(crate) unsafe fn drop_in_place(this: &'_ mut Unique<T>) {
            ptr::drop_in_place::<T>(&mut **this)
        }
    }

    impl<T: ?Sized> ::core::ops::Deref for Unique<T> {
        type Target = T;

        #[inline]
        fn deref(self: &'_ Unique<T>) -> &'_ T {
            &**self.0
        }
    }

    impl<T: ?Sized> ::core::ops::DerefMut for Unique<T> {
        #[inline]
        fn deref_mut(self: &'_ mut Unique<T>) -> &'_ mut T {
            &mut **self.0
        }
    }
}

#[cfg(not(feature = "alloc"))]
pub(crate) mod __ {
    use ::core::ptr;

    #[repr(transparent)]
    pub(crate) struct Unique<T: ?Sized>(ptr::NonNull<T>);

    unsafe impl<T: Send + ?Sized> Send for Unique<T> {}
    unsafe impl<T: Sync + ?Sized> Sync for Unique<T> {}

    impl<T: ?Sized> Unique<T> {
        #[inline]
        pub(crate) unsafe fn from_raw(ptr: *mut T) -> Unique<T> {
            Self(ptr::NonNull::new_unchecked(ptr))
        }

        #[inline]
        pub(crate) fn into_raw_nonnull(self: Unique<T>) -> ptr::NonNull<T> {
            self.0
        }

        #[inline]
        pub(crate) unsafe fn drop_in_place(this: &'_ mut Unique<T>) {
            ptr::drop_in_place(this.0.as_ptr())
        }
    }

    impl<T: ?Sized> ::core::ops::Deref for Unique<T> {
        type Target = T;

        #[inline]
        fn deref(self: &'_ Unique<T>) -> &'_ T {
            unsafe { self.0.as_ref() }
        }
    }

    impl<T: ?Sized> ::core::ops::DerefMut for Unique<T> {
        #[inline]
        fn deref_mut(self: &'_ mut Unique<T>) -> &'_ mut T {
            unsafe { self.0.as_mut() }
        }
    }
}