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