/rust/registry/src/index.crates.io-1949cf8c6b5b557f/managed-0.8.0/src/slice.rs
Line | Count | Source |
1 | | use core::ops::{Deref, DerefMut}; |
2 | | use core::fmt; |
3 | | |
4 | | #[cfg(feature = "std")] |
5 | | use std::boxed::Box; |
6 | | #[cfg(all(feature = "alloc", not(feature = "std")))] |
7 | | use alloc::boxed::Box; |
8 | | #[cfg(feature = "std")] |
9 | | use std::vec::Vec; |
10 | | #[cfg(all(feature = "alloc", not(feature = "std")))] |
11 | | use alloc::vec::Vec; |
12 | | |
13 | | /// A managed slice. |
14 | | /// |
15 | | /// This enum can be used to represent exclusive access to slices of objects. |
16 | | /// In Rust, exclusive access to an object is obtained by either owning the object, |
17 | | /// or owning a mutable pointer to the object; hence, "managed". |
18 | | /// |
19 | | /// The purpose of this enum is providing good ergonomics with `std` present while making |
20 | | /// it possible to avoid having a heap at all (which of course means that `std` is not present). |
21 | | /// To achieve this, the variants other than `Borrowed` are only available when the corresponding |
22 | | /// feature is opted in. |
23 | | /// |
24 | | /// A function that requires a managed object should be generic over an `Into<ManagedSlice<'a, T>>` |
25 | | /// argument; then, it will be possible to pass either a `Vec<T>`, or a `&'a mut [T]` |
26 | | /// without any conversion at the call site. |
27 | | /// |
28 | | /// See also [Managed](enum.Managed.html). |
29 | | pub enum ManagedSlice<'a, T: 'a> { |
30 | | /// Borrowed variant. |
31 | | Borrowed(&'a mut [T]), |
32 | | /// Owned variant, only available with the `std` or `alloc` feature enabled. |
33 | | #[cfg(any(feature = "std", feature = "alloc"))] |
34 | | Owned(Vec<T>) |
35 | | } |
36 | | |
37 | | impl<'a, T: 'a> fmt::Debug for ManagedSlice<'a, T> |
38 | | where T: fmt::Debug { |
39 | | fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { |
40 | | match self { |
41 | | &ManagedSlice::Borrowed(ref x) => write!(f, "Borrowed({:?})", x), |
42 | | #[cfg(any(feature = "std", feature = "alloc"))] |
43 | | &ManagedSlice::Owned(ref x) => write!(f, "Owned({:?})", x) |
44 | | } |
45 | | } |
46 | | } |
47 | | |
48 | | impl<'a, T: 'a> From<&'a mut [T]> for ManagedSlice<'a, T> { |
49 | | fn from(value: &'a mut [T]) -> Self { |
50 | | ManagedSlice::Borrowed(value) |
51 | | } |
52 | | } |
53 | | |
54 | | macro_rules! from_unboxed_slice { |
55 | | ($n:expr) => ( |
56 | | impl<'a, T> From<[T; $n]> for ManagedSlice<'a, T> { |
57 | | #[inline] |
58 | | fn from(value: [T; $n]) -> Self { |
59 | | ManagedSlice::Owned((Box::new(value) as Box<[T]>).into_vec()) |
60 | | } |
61 | | } |
62 | | ); |
63 | | ($n:expr, $( $r:expr ),*) => ( |
64 | | from_unboxed_slice!($n); |
65 | | from_unboxed_slice!($( $r ),*); |
66 | | ) |
67 | | } |
68 | | |
69 | | #[cfg(any(feature = "std", feature = "alloc"))] |
70 | | from_unboxed_slice!(0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, |
71 | | 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31); |
72 | | |
73 | | #[cfg(any(feature = "std", feature = "alloc"))] |
74 | | impl<'a, T: 'a> From<Vec<T>> for ManagedSlice<'a, T> { |
75 | | fn from(value: Vec<T>) -> Self { |
76 | | ManagedSlice::Owned(value) |
77 | | } |
78 | | } |
79 | | |
80 | | impl<'a, T: 'a> Deref for ManagedSlice<'a, T> { |
81 | | type Target = [T]; |
82 | | |
83 | 0 | fn deref(&self) -> &Self::Target { |
84 | 0 | match self { |
85 | 0 | &ManagedSlice::Borrowed(ref value) => value, |
86 | | #[cfg(any(feature = "std", feature = "alloc"))] |
87 | 0 | &ManagedSlice::Owned(ref value) => value |
88 | | } |
89 | 0 | } |
90 | | } |
91 | | |
92 | | impl<'a, T: 'a> DerefMut for ManagedSlice<'a, T> { |
93 | 0 | fn deref_mut(&mut self) -> &mut Self::Target { |
94 | 0 | match self { |
95 | 0 | &mut ManagedSlice::Borrowed(ref mut value) => value, |
96 | | #[cfg(any(feature = "std", feature = "alloc"))] |
97 | 0 | &mut ManagedSlice::Owned(ref mut value) => value |
98 | | } |
99 | 0 | } |
100 | | } |