4038042eb0
These methods work very similarly to `Option`'s methods `as_ref` and `as_mut`. They are useful in several situation, particularly when calling other array methods (like `map`) on the result. Unfortunately, we can't easily call them `as_ref` and `as_mut` as that would shadow those methods on slices, thus being a breaking change (that is likely to affect a lot of code).
579 lines
17 KiB
Rust
579 lines
17 KiB
Rust
//! Implementations of things like `Eq` for fixed-length arrays
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//! up to a certain length. Eventually, we should be able to generalize
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//! to all lengths.
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//!
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//! *[See also the array primitive type](../../std/primitive.array.html).*
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#![stable(feature = "core_array", since = "1.36.0")]
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use crate::borrow::{Borrow, BorrowMut};
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use crate::cmp::Ordering;
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use crate::convert::{Infallible, TryFrom};
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use crate::fmt;
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use crate::hash::{self, Hash};
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use crate::marker::Unsize;
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use crate::mem::MaybeUninit;
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use crate::ops::{Index, IndexMut};
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use crate::slice::{Iter, IterMut};
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mod iter;
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#[unstable(feature = "array_value_iter", issue = "65798")]
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pub use iter::IntoIter;
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/// Converts a reference to `T` into a reference to an array of length 1 (without copying).
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#[unstable(feature = "array_from_ref", issue = "77101")]
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pub fn from_ref<T>(s: &T) -> &[T; 1] {
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// SAFETY: Converting `&T` to `&[T; 1]` is sound.
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unsafe { &*(s as *const T).cast::<[T; 1]>() }
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}
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/// Converts a mutable reference to `T` into a mutable reference to an array of length 1 (without copying).
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#[unstable(feature = "array_from_ref", issue = "77101")]
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pub fn from_mut<T>(s: &mut T) -> &mut [T; 1] {
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// SAFETY: Converting `&mut T` to `&mut [T; 1]` is sound.
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unsafe { &mut *(s as *mut T).cast::<[T; 1]>() }
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}
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/// Utility trait implemented only on arrays of fixed size
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///
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/// This trait can be used to implement other traits on fixed-size arrays
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/// without causing much metadata bloat.
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///
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/// The trait is marked unsafe in order to restrict implementors to fixed-size
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/// arrays. User of this trait can assume that implementors have the exact
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/// layout in memory of a fixed size array (for example, for unsafe
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/// initialization).
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///
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/// Note that the traits [`AsRef`] and [`AsMut`] provide similar methods for types that
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/// may not be fixed-size arrays. Implementors should prefer those traits
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/// instead.
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#[unstable(feature = "fixed_size_array", issue = "27778")]
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pub unsafe trait FixedSizeArray<T> {
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/// Converts the array to immutable slice
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#[unstable(feature = "fixed_size_array", issue = "27778")]
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fn as_slice(&self) -> &[T];
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/// Converts the array to mutable slice
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#[unstable(feature = "fixed_size_array", issue = "27778")]
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fn as_mut_slice(&mut self) -> &mut [T];
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}
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#[unstable(feature = "fixed_size_array", issue = "27778")]
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unsafe impl<T, A: Unsize<[T]>> FixedSizeArray<T> for A {
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#[inline]
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fn as_slice(&self) -> &[T] {
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self
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}
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#[inline]
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fn as_mut_slice(&mut self) -> &mut [T] {
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self
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}
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}
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/// The error type returned when a conversion from a slice to an array fails.
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#[stable(feature = "try_from", since = "1.34.0")]
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#[derive(Debug, Copy, Clone)]
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pub struct TryFromSliceError(());
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#[stable(feature = "core_array", since = "1.36.0")]
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impl fmt::Display for TryFromSliceError {
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#[inline]
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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fmt::Display::fmt(self.__description(), f)
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}
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}
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impl TryFromSliceError {
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#[unstable(
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feature = "array_error_internals",
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reason = "available through Error trait and this method should not \
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be exposed publicly",
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issue = "none"
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)]
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#[inline]
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#[doc(hidden)]
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pub fn __description(&self) -> &str {
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"could not convert slice to array"
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}
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}
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#[stable(feature = "try_from_slice_error", since = "1.36.0")]
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impl From<Infallible> for TryFromSliceError {
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fn from(x: Infallible) -> TryFromSliceError {
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match x {}
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}
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<T, const N: usize> AsRef<[T]> for [T; N] {
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#[inline]
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fn as_ref(&self) -> &[T] {
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&self[..]
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}
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<T, const N: usize> AsMut<[T]> for [T; N] {
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#[inline]
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fn as_mut(&mut self) -> &mut [T] {
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&mut self[..]
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}
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}
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#[stable(feature = "array_borrow", since = "1.4.0")]
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impl<T, const N: usize> Borrow<[T]> for [T; N] {
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fn borrow(&self) -> &[T] {
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self
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}
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}
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#[stable(feature = "array_borrow", since = "1.4.0")]
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impl<T, const N: usize> BorrowMut<[T]> for [T; N] {
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fn borrow_mut(&mut self) -> &mut [T] {
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self
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}
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}
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#[stable(feature = "try_from", since = "1.34.0")]
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impl<T, const N: usize> TryFrom<&[T]> for [T; N]
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where
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T: Copy,
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{
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type Error = TryFromSliceError;
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fn try_from(slice: &[T]) -> Result<[T; N], TryFromSliceError> {
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<&Self>::try_from(slice).map(|r| *r)
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}
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}
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#[stable(feature = "try_from", since = "1.34.0")]
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impl<'a, T, const N: usize> TryFrom<&'a [T]> for &'a [T; N] {
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type Error = TryFromSliceError;
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fn try_from(slice: &[T]) -> Result<&[T; N], TryFromSliceError> {
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if slice.len() == N {
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let ptr = slice.as_ptr() as *const [T; N];
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// SAFETY: ok because we just checked that the length fits
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unsafe { Ok(&*ptr) }
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} else {
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Err(TryFromSliceError(()))
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}
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}
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}
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#[stable(feature = "try_from", since = "1.34.0")]
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impl<'a, T, const N: usize> TryFrom<&'a mut [T]> for &'a mut [T; N] {
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type Error = TryFromSliceError;
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fn try_from(slice: &mut [T]) -> Result<&mut [T; N], TryFromSliceError> {
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if slice.len() == N {
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let ptr = slice.as_mut_ptr() as *mut [T; N];
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// SAFETY: ok because we just checked that the length fits
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unsafe { Ok(&mut *ptr) }
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} else {
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Err(TryFromSliceError(()))
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}
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}
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<T: Hash, const N: usize> Hash for [T; N] {
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fn hash<H: hash::Hasher>(&self, state: &mut H) {
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Hash::hash(&self[..], state)
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}
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<T: fmt::Debug, const N: usize> fmt::Debug for [T; N] {
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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fmt::Debug::fmt(&&self[..], f)
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}
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<'a, T, const N: usize> IntoIterator for &'a [T; N] {
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type Item = &'a T;
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type IntoIter = Iter<'a, T>;
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fn into_iter(self) -> Iter<'a, T> {
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self.iter()
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}
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<'a, T, const N: usize> IntoIterator for &'a mut [T; N] {
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type Item = &'a mut T;
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type IntoIter = IterMut<'a, T>;
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fn into_iter(self) -> IterMut<'a, T> {
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self.iter_mut()
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}
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}
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#[stable(feature = "index_trait_on_arrays", since = "1.50.0")]
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impl<T, I, const N: usize> Index<I> for [T; N]
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where
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[T]: Index<I>,
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{
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type Output = <[T] as Index<I>>::Output;
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#[inline]
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fn index(&self, index: I) -> &Self::Output {
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Index::index(self as &[T], index)
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}
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}
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#[stable(feature = "index_trait_on_arrays", since = "1.50.0")]
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impl<T, I, const N: usize> IndexMut<I> for [T; N]
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where
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[T]: IndexMut<I>,
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{
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#[inline]
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fn index_mut(&mut self, index: I) -> &mut Self::Output {
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IndexMut::index_mut(self as &mut [T], index)
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}
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<A, B, const N: usize> PartialEq<[B; N]> for [A; N]
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where
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A: PartialEq<B>,
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{
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#[inline]
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fn eq(&self, other: &[B; N]) -> bool {
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self[..] == other[..]
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}
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#[inline]
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fn ne(&self, other: &[B; N]) -> bool {
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self[..] != other[..]
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}
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<A, B, const N: usize> PartialEq<[B]> for [A; N]
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where
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A: PartialEq<B>,
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{
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#[inline]
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fn eq(&self, other: &[B]) -> bool {
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self[..] == other[..]
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}
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#[inline]
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fn ne(&self, other: &[B]) -> bool {
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self[..] != other[..]
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}
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<A, B, const N: usize> PartialEq<[A; N]> for [B]
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where
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B: PartialEq<A>,
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{
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#[inline]
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fn eq(&self, other: &[A; N]) -> bool {
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self[..] == other[..]
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}
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#[inline]
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fn ne(&self, other: &[A; N]) -> bool {
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self[..] != other[..]
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}
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<A, B, const N: usize> PartialEq<&[B]> for [A; N]
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where
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A: PartialEq<B>,
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{
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#[inline]
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fn eq(&self, other: &&[B]) -> bool {
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self[..] == other[..]
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}
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#[inline]
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fn ne(&self, other: &&[B]) -> bool {
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self[..] != other[..]
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}
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<A, B, const N: usize> PartialEq<[A; N]> for &[B]
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where
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B: PartialEq<A>,
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{
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#[inline]
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fn eq(&self, other: &[A; N]) -> bool {
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self[..] == other[..]
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}
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#[inline]
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fn ne(&self, other: &[A; N]) -> bool {
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self[..] != other[..]
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}
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<A, B, const N: usize> PartialEq<&mut [B]> for [A; N]
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where
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A: PartialEq<B>,
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{
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#[inline]
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fn eq(&self, other: &&mut [B]) -> bool {
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self[..] == other[..]
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}
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#[inline]
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fn ne(&self, other: &&mut [B]) -> bool {
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self[..] != other[..]
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}
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}
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|
#[stable(feature = "rust1", since = "1.0.0")]
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impl<A, B, const N: usize> PartialEq<[A; N]> for &mut [B]
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|
where
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B: PartialEq<A>,
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{
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#[inline]
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fn eq(&self, other: &[A; N]) -> bool {
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self[..] == other[..]
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}
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#[inline]
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fn ne(&self, other: &[A; N]) -> bool {
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self[..] != other[..]
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}
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}
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// NOTE: some less important impls are omitted to reduce code bloat
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// __impl_slice_eq2! { [A; $N], &'b [B; $N] }
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// __impl_slice_eq2! { [A; $N], &'b mut [B; $N] }
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|
#[stable(feature = "rust1", since = "1.0.0")]
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impl<T: Eq, const N: usize> Eq for [T; N] {}
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<T: PartialOrd, const N: usize> PartialOrd for [T; N] {
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#[inline]
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fn partial_cmp(&self, other: &[T; N]) -> Option<Ordering> {
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PartialOrd::partial_cmp(&&self[..], &&other[..])
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}
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#[inline]
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fn lt(&self, other: &[T; N]) -> bool {
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PartialOrd::lt(&&self[..], &&other[..])
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}
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#[inline]
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fn le(&self, other: &[T; N]) -> bool {
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PartialOrd::le(&&self[..], &&other[..])
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}
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#[inline]
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fn ge(&self, other: &[T; N]) -> bool {
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PartialOrd::ge(&&self[..], &&other[..])
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}
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#[inline]
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fn gt(&self, other: &[T; N]) -> bool {
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PartialOrd::gt(&&self[..], &&other[..])
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}
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}
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/// Implements comparison of arrays [lexicographically](Ord#lexicographical-comparison).
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<T: Ord, const N: usize> Ord for [T; N] {
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#[inline]
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fn cmp(&self, other: &[T; N]) -> Ordering {
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Ord::cmp(&&self[..], &&other[..])
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}
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}
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|
// The Default impls cannot be done with const generics because `[T; 0]` doesn't
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// require Default to be implemented, and having different impl blocks for
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// different numbers isn't supported yet.
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|
macro_rules! array_impl_default {
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{$n:expr, $t:ident $($ts:ident)*} => {
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#[stable(since = "1.4.0", feature = "array_default")]
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|
impl<T> Default for [T; $n] where T: Default {
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|
fn default() -> [T; $n] {
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[$t::default(), $($ts::default()),*]
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|
}
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}
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array_impl_default!{($n - 1), $($ts)*}
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};
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|
{$n:expr,} => {
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|
#[stable(since = "1.4.0", feature = "array_default")]
|
|
impl<T> Default for [T; $n] {
|
|
fn default() -> [T; $n] { [] }
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|
}
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|
};
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|
}
|
|
|
|
array_impl_default! {32, T T T T T T T T T T T T T T T T T T T T T T T T T T T T T T T T}
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|
|
#[lang = "array"]
|
|
impl<T, const N: usize> [T; N] {
|
|
/// Returns an array of the same size as `self`, with function `f` applied to each element
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|
/// in order.
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|
///
|
|
/// # Examples
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|
///
|
|
/// ```
|
|
/// #![feature(array_map)]
|
|
/// let x = [1, 2, 3];
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|
/// let y = x.map(|v| v + 1);
|
|
/// assert_eq!(y, [2, 3, 4]);
|
|
///
|
|
/// let x = [1, 2, 3];
|
|
/// let mut temp = 0;
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|
/// let y = x.map(|v| { temp += 1; v * temp });
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|
/// assert_eq!(y, [1, 4, 9]);
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|
///
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|
/// let x = ["Ferris", "Bueller's", "Day", "Off"];
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|
/// let y = x.map(|v| v.len());
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|
/// assert_eq!(y, [6, 9, 3, 3]);
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|
/// ```
|
|
#[unstable(feature = "array_map", issue = "75243")]
|
|
pub fn map<F, U>(self, mut f: F) -> [U; N]
|
|
where
|
|
F: FnMut(T) -> U,
|
|
{
|
|
struct Guard<T, const N: usize> {
|
|
dst: *mut T,
|
|
initialized: usize,
|
|
}
|
|
|
|
impl<T, const N: usize> Drop for Guard<T, N> {
|
|
fn drop(&mut self) {
|
|
debug_assert!(self.initialized <= N);
|
|
|
|
let initialized_part =
|
|
crate::ptr::slice_from_raw_parts_mut(self.dst, self.initialized);
|
|
// SAFETY: this raw slice will contain only initialized objects
|
|
// that's why, it is allowed to drop it.
|
|
unsafe {
|
|
crate::ptr::drop_in_place(initialized_part);
|
|
}
|
|
}
|
|
}
|
|
let mut dst = MaybeUninit::uninit_array::<N>();
|
|
let mut guard: Guard<U, N> =
|
|
Guard { dst: MaybeUninit::slice_as_mut_ptr(&mut dst), initialized: 0 };
|
|
for (src, dst) in IntoIter::new(self).zip(&mut dst) {
|
|
dst.write(f(src));
|
|
guard.initialized += 1;
|
|
}
|
|
// FIXME: Convert to crate::mem::transmute once it works with generics.
|
|
// unsafe { crate::mem::transmute::<[MaybeUninit<U>; N], [U; N]>(dst) }
|
|
crate::mem::forget(guard);
|
|
// SAFETY: At this point we've properly initialized the whole array
|
|
// and we just need to cast it to the correct type.
|
|
unsafe { crate::mem::transmute_copy::<_, [U; N]>(&dst) }
|
|
}
|
|
|
|
/// 'Zips up' two arrays into a single array of pairs.
|
|
///
|
|
/// `zip()` returns a new array where every element is a tuple where the
|
|
/// first element comes from the first array, and the second element comes
|
|
/// from the second array. In other words, it zips two arrays together,
|
|
/// into a single one.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// #![feature(array_zip)]
|
|
/// let x = [1, 2, 3];
|
|
/// let y = [4, 5, 6];
|
|
/// let z = x.zip(y);
|
|
/// assert_eq!(z, [(1, 4), (2, 5), (3, 6)]);
|
|
/// ```
|
|
#[unstable(feature = "array_zip", issue = "80094")]
|
|
pub fn zip<U>(self, rhs: [U; N]) -> [(T, U); N] {
|
|
let mut dst = MaybeUninit::uninit_array::<N>();
|
|
for (i, (lhs, rhs)) in IntoIter::new(self).zip(IntoIter::new(rhs)).enumerate() {
|
|
dst[i].write((lhs, rhs));
|
|
}
|
|
// FIXME: Convert to crate::mem::transmute once it works with generics.
|
|
// unsafe { crate::mem::transmute::<[MaybeUninit<U>; N], [U; N]>(dst) }
|
|
// SAFETY: At this point we've properly initialized the whole array
|
|
// and we just need to cast it to the correct type.
|
|
unsafe { crate::mem::transmute_copy::<_, [(T, U); N]>(&dst) }
|
|
}
|
|
|
|
/// Returns a slice containing the entire array. Equivalent to `&s[..]`.
|
|
#[unstable(feature = "array_methods", issue = "76118")]
|
|
pub fn as_slice(&self) -> &[T] {
|
|
self
|
|
}
|
|
|
|
/// Returns a mutable slice containing the entire array. Equivalent to
|
|
/// `&mut s[..]`.
|
|
#[unstable(feature = "array_methods", issue = "76118")]
|
|
pub fn as_mut_slice(&mut self) -> &mut [T] {
|
|
self
|
|
}
|
|
|
|
/// Borrows each element and returns an array of references with the same
|
|
/// size as `self`.
|
|
///
|
|
///
|
|
/// # Example
|
|
///
|
|
/// ```
|
|
/// #![feature(array_methods)]
|
|
///
|
|
/// let floats = [3.1, 2.7, -1.0];
|
|
/// let float_refs: [&f64; 3] = floats.each_ref();
|
|
/// assert_eq!(float_refs, [&3.1, &2.7, &-1.0]);
|
|
/// ```
|
|
///
|
|
/// This method is particularly useful if combined with other methods, like
|
|
/// [`map`](#method.map). This way, you can can avoid moving the original
|
|
/// array if its elements are not `Copy`.
|
|
///
|
|
/// ```
|
|
/// #![feature(array_methods, array_map)]
|
|
///
|
|
/// let strings = ["Ferris".to_string(), "♥".to_string(), "Rust".to_string()];
|
|
/// let is_ascii = strings.each_ref().map(|s| s.is_ascii());
|
|
/// assert_eq!(is_ascii, [true, false, true]);
|
|
///
|
|
/// // We can still access the original array: it has not been moved.
|
|
/// assert_eq!(strings.len(), 3);
|
|
/// ```
|
|
#[unstable(feature = "array_methods", issue = "76118")]
|
|
pub fn each_ref(&self) -> [&T; N] {
|
|
// Unlike in `map`, we don't need a guard here, as dropping a reference
|
|
// is a noop.
|
|
let mut out = MaybeUninit::uninit_array::<N>();
|
|
for (src, dst) in self.iter().zip(&mut out) {
|
|
dst.write(src);
|
|
}
|
|
|
|
// SAFETY: All elements of `dst` are properly initialized and
|
|
// `MaybeUninit<T>` has the same layout as `T`, so this cast is valid.
|
|
unsafe { (&mut out as *mut _ as *mut [&T; N]).read() }
|
|
}
|
|
|
|
/// Borrows each element mutably and returns an array of mutable references
|
|
/// with the same size as `self`.
|
|
///
|
|
///
|
|
/// # Example
|
|
///
|
|
/// ```
|
|
/// #![feature(array_methods)]
|
|
///
|
|
/// let mut floats = [3.1, 2.7, -1.0];
|
|
/// let float_refs: [&mut f64; 3] = floats.each_mut();
|
|
/// *float_refs[0] = 0.0;
|
|
/// assert_eq!(float_refs, [&mut 0.0, &mut 2.7, &mut -1.0]);
|
|
/// assert_eq!(floats, [0.0, 2.7, -1.0]);
|
|
/// ```
|
|
#[unstable(feature = "array_methods", issue = "76118")]
|
|
pub fn each_mut(&mut self) -> [&mut T; N] {
|
|
// Unlike in `map`, we don't need a guard here, as dropping a reference
|
|
// is a noop.
|
|
let mut out = MaybeUninit::uninit_array::<N>();
|
|
for (src, dst) in self.iter_mut().zip(&mut out) {
|
|
dst.write(src);
|
|
}
|
|
|
|
// SAFETY: All elements of `dst` are properly initialized and
|
|
// `MaybeUninit<T>` has the same layout as `T`, so this cast is valid.
|
|
unsafe { (&mut out as *mut _ as *mut [&mut T; N]).read() }
|
|
}
|
|
}
|