| use core::ops::{Deref, DerefMut}; |
| use core::fmt; |
| |
| #[cfg(feature = "std")] |
| use std::boxed::Box; |
| #[cfg(all(feature = "alloc", not(feature = "std")))] |
| use alloc::boxed::Box; |
| #[cfg(feature = "std")] |
| use std::vec::Vec; |
| #[cfg(all(feature = "alloc", not(feature = "std")))] |
| use alloc::vec::Vec; |
| |
| /// A managed slice. |
| /// |
| /// This enum can be used to represent exclusive access to slices of objects. |
| /// In Rust, exclusive access to an object is obtained by either owning the object, |
| /// or owning a mutable pointer to the object; hence, "managed". |
| /// |
| /// The purpose of this enum is providing good ergonomics with `std` present while making |
| /// it possible to avoid having a heap at all (which of course means that `std` is not present). |
| /// To achieve this, the variants other than `Borrowed` are only available when the corresponding |
| /// feature is opted in. |
| /// |
| /// A function that requires a managed object should be generic over an `Into<ManagedSlice<'a, T>>` |
| /// argument; then, it will be possible to pass either a `Vec<T>`, or a `&'a mut [T]` |
| /// without any conversion at the call site. |
| /// |
| /// See also [Managed](enum.Managed.html). |
| pub enum ManagedSlice<'a, T: 'a> { |
| /// Borrowed variant. |
| Borrowed(&'a mut [T]), |
| /// Owned variant, only available with the `std` or `alloc` feature enabled. |
| #[cfg(any(feature = "std", feature = "alloc"))] |
| Owned(Vec<T>) |
| } |
| |
| impl<'a, T: 'a> fmt::Debug for ManagedSlice<'a, T> |
| where T: fmt::Debug { |
| fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { |
| match self { |
| &ManagedSlice::Borrowed(ref x) => write!(f, "Borrowed({:?})", x), |
| #[cfg(any(feature = "std", feature = "alloc"))] |
| &ManagedSlice::Owned(ref x) => write!(f, "Owned({:?})", x) |
| } |
| } |
| } |
| |
| impl<'a, T: 'a> From<&'a mut [T]> for ManagedSlice<'a, T> { |
| fn from(value: &'a mut [T]) -> Self { |
| ManagedSlice::Borrowed(value) |
| } |
| } |
| |
| macro_rules! from_unboxed_slice { |
| ($n:expr) => ( |
| impl<'a, T> From<[T; $n]> for ManagedSlice<'a, T> { |
| #[inline] |
| fn from(value: [T; $n]) -> Self { |
| ManagedSlice::Owned((Box::new(value) as Box<[T]>).into_vec()) |
| } |
| } |
| ); |
| ($n:expr, $( $r:expr ),*) => ( |
| from_unboxed_slice!($n); |
| from_unboxed_slice!($( $r ),*); |
| ) |
| } |
| |
| #[cfg(any(feature = "std", feature = "alloc"))] |
| from_unboxed_slice!(0, 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); |
| |
| #[cfg(any(feature = "std", feature = "alloc"))] |
| impl<'a, T: 'a> From<Vec<T>> for ManagedSlice<'a, T> { |
| fn from(value: Vec<T>) -> Self { |
| ManagedSlice::Owned(value) |
| } |
| } |
| |
| impl<'a, T: 'a> Deref for ManagedSlice<'a, T> { |
| type Target = [T]; |
| |
| fn deref(&self) -> &Self::Target { |
| match self { |
| &ManagedSlice::Borrowed(ref value) => value, |
| #[cfg(any(feature = "std", feature = "alloc"))] |
| &ManagedSlice::Owned(ref value) => value |
| } |
| } |
| } |
| |
| impl<'a, T: 'a> DerefMut for ManagedSlice<'a, T> { |
| fn deref_mut(&mut self) -> &mut Self::Target { |
| match self { |
| &mut ManagedSlice::Borrowed(ref mut value) => value, |
| #[cfg(any(feature = "std", feature = "alloc"))] |
| &mut ManagedSlice::Owned(ref mut value) => value |
| } |
| } |
| } |