| //! Utilities for the array primitive type. |
| //! |
| //! *[See also the array primitive type](array).* |
| |
| #![stable(feature = "core_array", since = "1.36.0")] |
| |
| use crate::borrow::{Borrow, BorrowMut}; |
| use crate::cmp::Ordering; |
| use crate::convert::{Infallible, TryFrom}; |
| use crate::error::Error; |
| use crate::fmt; |
| use crate::hash::{self, Hash}; |
| use crate::iter::UncheckedIterator; |
| use crate::mem::{self, MaybeUninit}; |
| use crate::ops::{ |
| ChangeOutputType, ControlFlow, FromResidual, Index, IndexMut, NeverShortCircuit, Residual, Try, |
| }; |
| use crate::slice::{Iter, IterMut}; |
| |
| mod ascii; |
| mod drain; |
| mod equality; |
| mod iter; |
| |
| pub(crate) use drain::drain_array_with; |
| |
| #[stable(feature = "array_value_iter", since = "1.51.0")] |
| pub use iter::IntoIter; |
| |
| /// Creates an array of type [T; N], where each element `T` is the returned value from `cb` |
| /// using that element's index. |
| /// |
| /// # Arguments |
| /// |
| /// * `cb`: Callback where the passed argument is the current array index. |
| /// |
| /// # Example |
| /// |
| /// ```rust |
| /// // type inference is helping us here, the way `from_fn` knows how many |
| /// // elements to produce is the length of array down there: only arrays of |
| /// // equal lengths can be compared, so the const generic parameter `N` is |
| /// // inferred to be 5, thus creating array of 5 elements. |
| /// |
| /// let array = core::array::from_fn(|i| i); |
| /// // indexes are: 0 1 2 3 4 |
| /// assert_eq!(array, [0, 1, 2, 3, 4]); |
| /// |
| /// let array2: [usize; 8] = core::array::from_fn(|i| i * 2); |
| /// // indexes are: 0 1 2 3 4 5 6 7 |
| /// assert_eq!(array2, [0, 2, 4, 6, 8, 10, 12, 14]); |
| /// |
| /// let bool_arr = core::array::from_fn::<_, 5, _>(|i| i % 2 == 0); |
| /// // indexes are: 0 1 2 3 4 |
| /// assert_eq!(bool_arr, [true, false, true, false, true]); |
| /// ``` |
| #[inline] |
| #[stable(feature = "array_from_fn", since = "1.63.0")] |
| pub fn from_fn<T, const N: usize, F>(cb: F) -> [T; N] |
| where |
| F: FnMut(usize) -> T, |
| { |
| try_from_fn(NeverShortCircuit::wrap_mut_1(cb)).0 |
| } |
| |
| /// Creates an array `[T; N]` where each fallible array element `T` is returned by the `cb` call. |
| /// Unlike [`from_fn`], where the element creation can't fail, this version will return an error |
| /// if any element creation was unsuccessful. |
| /// |
| /// The return type of this function depends on the return type of the closure. |
| /// If you return `Result<T, E>` from the closure, you'll get a `Result<[T; N], E>`. |
| /// If you return `Option<T>` from the closure, you'll get an `Option<[T; N]>`. |
| /// |
| /// # Arguments |
| /// |
| /// * `cb`: Callback where the passed argument is the current array index. |
| /// |
| /// # Example |
| /// |
| /// ```rust |
| /// #![feature(array_try_from_fn)] |
| /// |
| /// let array: Result<[u8; 5], _> = std::array::try_from_fn(|i| i.try_into()); |
| /// assert_eq!(array, Ok([0, 1, 2, 3, 4])); |
| /// |
| /// let array: Result<[i8; 200], _> = std::array::try_from_fn(|i| i.try_into()); |
| /// assert!(array.is_err()); |
| /// |
| /// let array: Option<[_; 4]> = std::array::try_from_fn(|i| i.checked_add(100)); |
| /// assert_eq!(array, Some([100, 101, 102, 103])); |
| /// |
| /// let array: Option<[_; 4]> = std::array::try_from_fn(|i| i.checked_sub(100)); |
| /// assert_eq!(array, None); |
| /// ``` |
| #[inline] |
| #[unstable(feature = "array_try_from_fn", issue = "89379")] |
| pub fn try_from_fn<R, const N: usize, F>(cb: F) -> ChangeOutputType<R, [R::Output; N]> |
| where |
| F: FnMut(usize) -> R, |
| R: Try, |
| R::Residual: Residual<[R::Output; N]>, |
| { |
| let mut array = MaybeUninit::uninit_array::<N>(); |
| match try_from_fn_erased(&mut array, cb) { |
| ControlFlow::Break(r) => FromResidual::from_residual(r), |
| ControlFlow::Continue(()) => { |
| // SAFETY: All elements of the array were populated. |
| try { unsafe { MaybeUninit::array_assume_init(array) } } |
| } |
| } |
| } |
| |
| /// Converts a reference to `T` into a reference to an array of length 1 (without copying). |
| #[stable(feature = "array_from_ref", since = "1.53.0")] |
| #[rustc_const_stable(feature = "const_array_from_ref_shared", since = "1.63.0")] |
| pub const fn from_ref<T>(s: &T) -> &[T; 1] { |
| // SAFETY: Converting `&T` to `&[T; 1]` is sound. |
| unsafe { &*(s as *const T).cast::<[T; 1]>() } |
| } |
| |
| /// Converts a mutable reference to `T` into a mutable reference to an array of length 1 (without copying). |
| #[stable(feature = "array_from_ref", since = "1.53.0")] |
| #[rustc_const_unstable(feature = "const_array_from_ref", issue = "90206")] |
| pub const fn from_mut<T>(s: &mut T) -> &mut [T; 1] { |
| // SAFETY: Converting `&mut T` to `&mut [T; 1]` is sound. |
| unsafe { &mut *(s as *mut T).cast::<[T; 1]>() } |
| } |
| |
| /// The error type returned when a conversion from a slice to an array fails. |
| #[stable(feature = "try_from", since = "1.34.0")] |
| #[derive(Debug, Copy, Clone)] |
| pub struct TryFromSliceError(()); |
| |
| #[stable(feature = "core_array", since = "1.36.0")] |
| impl fmt::Display for TryFromSliceError { |
| #[inline] |
| fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
| #[allow(deprecated)] |
| self.description().fmt(f) |
| } |
| } |
| |
| #[stable(feature = "try_from", since = "1.34.0")] |
| impl Error for TryFromSliceError { |
| #[allow(deprecated)] |
| fn description(&self) -> &str { |
| "could not convert slice to array" |
| } |
| } |
| |
| #[stable(feature = "try_from_slice_error", since = "1.36.0")] |
| impl From<Infallible> for TryFromSliceError { |
| fn from(x: Infallible) -> TryFromSliceError { |
| match x {} |
| } |
| } |
| |
| #[stable(feature = "rust1", since = "1.0.0")] |
| impl<T, const N: usize> AsRef<[T]> for [T; N] { |
| #[inline] |
| fn as_ref(&self) -> &[T] { |
| &self[..] |
| } |
| } |
| |
| #[stable(feature = "rust1", since = "1.0.0")] |
| impl<T, const N: usize> AsMut<[T]> for [T; N] { |
| #[inline] |
| fn as_mut(&mut self) -> &mut [T] { |
| &mut self[..] |
| } |
| } |
| |
| #[stable(feature = "array_borrow", since = "1.4.0")] |
| impl<T, const N: usize> Borrow<[T]> for [T; N] { |
| fn borrow(&self) -> &[T] { |
| self |
| } |
| } |
| |
| #[stable(feature = "array_borrow", since = "1.4.0")] |
| impl<T, const N: usize> BorrowMut<[T]> for [T; N] { |
| fn borrow_mut(&mut self) -> &mut [T] { |
| self |
| } |
| } |
| |
| /// Tries to create an array `[T; N]` by copying from a slice `&[T]`. Succeeds if |
| /// `slice.len() == N`. |
| /// |
| /// ``` |
| /// let bytes: [u8; 3] = [1, 0, 2]; |
| /// |
| /// let bytes_head: [u8; 2] = <[u8; 2]>::try_from(&bytes[0..2]).unwrap(); |
| /// assert_eq!(1, u16::from_le_bytes(bytes_head)); |
| /// |
| /// let bytes_tail: [u8; 2] = bytes[1..3].try_into().unwrap(); |
| /// assert_eq!(512, u16::from_le_bytes(bytes_tail)); |
| /// ``` |
| #[stable(feature = "try_from", since = "1.34.0")] |
| impl<T, const N: usize> TryFrom<&[T]> for [T; N] |
| where |
| T: Copy, |
| { |
| type Error = TryFromSliceError; |
| |
| #[inline] |
| fn try_from(slice: &[T]) -> Result<[T; N], TryFromSliceError> { |
| <&Self>::try_from(slice).map(|r| *r) |
| } |
| } |
| |
| /// Tries to create an array `[T; N]` by copying from a mutable slice `&mut [T]`. |
| /// Succeeds if `slice.len() == N`. |
| /// |
| /// ``` |
| /// let mut bytes: [u8; 3] = [1, 0, 2]; |
| /// |
| /// let bytes_head: [u8; 2] = <[u8; 2]>::try_from(&mut bytes[0..2]).unwrap(); |
| /// assert_eq!(1, u16::from_le_bytes(bytes_head)); |
| /// |
| /// let bytes_tail: [u8; 2] = (&mut bytes[1..3]).try_into().unwrap(); |
| /// assert_eq!(512, u16::from_le_bytes(bytes_tail)); |
| /// ``` |
| #[stable(feature = "try_from_mut_slice_to_array", since = "1.59.0")] |
| impl<T, const N: usize> TryFrom<&mut [T]> for [T; N] |
| where |
| T: Copy, |
| { |
| type Error = TryFromSliceError; |
| |
| #[inline] |
| fn try_from(slice: &mut [T]) -> Result<[T; N], TryFromSliceError> { |
| <Self>::try_from(&*slice) |
| } |
| } |
| |
| /// Tries to create an array ref `&[T; N]` from a slice ref `&[T]`. Succeeds if |
| /// `slice.len() == N`. |
| /// |
| /// ``` |
| /// let bytes: [u8; 3] = [1, 0, 2]; |
| /// |
| /// let bytes_head: &[u8; 2] = <&[u8; 2]>::try_from(&bytes[0..2]).unwrap(); |
| /// assert_eq!(1, u16::from_le_bytes(*bytes_head)); |
| /// |
| /// let bytes_tail: &[u8; 2] = bytes[1..3].try_into().unwrap(); |
| /// assert_eq!(512, u16::from_le_bytes(*bytes_tail)); |
| /// ``` |
| #[stable(feature = "try_from", since = "1.34.0")] |
| impl<'a, T, const N: usize> TryFrom<&'a [T]> for &'a [T; N] { |
| type Error = TryFromSliceError; |
| |
| #[inline] |
| fn try_from(slice: &'a [T]) -> Result<&'a [T; N], TryFromSliceError> { |
| if slice.len() == N { |
| let ptr = slice.as_ptr() as *const [T; N]; |
| // SAFETY: ok because we just checked that the length fits |
| unsafe { Ok(&*ptr) } |
| } else { |
| Err(TryFromSliceError(())) |
| } |
| } |
| } |
| |
| /// Tries to create a mutable array ref `&mut [T; N]` from a mutable slice ref |
| /// `&mut [T]`. Succeeds if `slice.len() == N`. |
| /// |
| /// ``` |
| /// let mut bytes: [u8; 3] = [1, 0, 2]; |
| /// |
| /// let bytes_head: &mut [u8; 2] = <&mut [u8; 2]>::try_from(&mut bytes[0..2]).unwrap(); |
| /// assert_eq!(1, u16::from_le_bytes(*bytes_head)); |
| /// |
| /// let bytes_tail: &mut [u8; 2] = (&mut bytes[1..3]).try_into().unwrap(); |
| /// assert_eq!(512, u16::from_le_bytes(*bytes_tail)); |
| /// ``` |
| #[stable(feature = "try_from", since = "1.34.0")] |
| impl<'a, T, const N: usize> TryFrom<&'a mut [T]> for &'a mut [T; N] { |
| type Error = TryFromSliceError; |
| |
| #[inline] |
| fn try_from(slice: &'a mut [T]) -> Result<&'a mut [T; N], TryFromSliceError> { |
| if slice.len() == N { |
| let ptr = slice.as_mut_ptr() as *mut [T; N]; |
| // SAFETY: ok because we just checked that the length fits |
| unsafe { Ok(&mut *ptr) } |
| } else { |
| Err(TryFromSliceError(())) |
| } |
| } |
| } |
| |
| /// The hash of an array is the same as that of the corresponding slice, |
| /// as required by the `Borrow` implementation. |
| /// |
| /// ``` |
| /// use std::hash::BuildHasher; |
| /// |
| /// let b = std::collections::hash_map::RandomState::new(); |
| /// let a: [u8; 3] = [0xa8, 0x3c, 0x09]; |
| /// let s: &[u8] = &[0xa8, 0x3c, 0x09]; |
| /// assert_eq!(b.hash_one(a), b.hash_one(s)); |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| impl<T: Hash, const N: usize> Hash for [T; N] { |
| fn hash<H: hash::Hasher>(&self, state: &mut H) { |
| Hash::hash(&self[..], state) |
| } |
| } |
| |
| #[stable(feature = "rust1", since = "1.0.0")] |
| impl<T: fmt::Debug, const N: usize> fmt::Debug for [T; N] { |
| fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
| fmt::Debug::fmt(&&self[..], f) |
| } |
| } |
| |
| #[stable(feature = "rust1", since = "1.0.0")] |
| impl<'a, T, const N: usize> IntoIterator for &'a [T; N] { |
| type Item = &'a T; |
| type IntoIter = Iter<'a, T>; |
| |
| fn into_iter(self) -> Iter<'a, T> { |
| self.iter() |
| } |
| } |
| |
| #[stable(feature = "rust1", since = "1.0.0")] |
| impl<'a, T, const N: usize> IntoIterator for &'a mut [T; N] { |
| type Item = &'a mut T; |
| type IntoIter = IterMut<'a, T>; |
| |
| fn into_iter(self) -> IterMut<'a, T> { |
| self.iter_mut() |
| } |
| } |
| |
| #[stable(feature = "index_trait_on_arrays", since = "1.50.0")] |
| impl<T, I, const N: usize> Index<I> for [T; N] |
| where |
| [T]: Index<I>, |
| { |
| type Output = <[T] as Index<I>>::Output; |
| |
| #[inline] |
| fn index(&self, index: I) -> &Self::Output { |
| Index::index(self as &[T], index) |
| } |
| } |
| |
| #[stable(feature = "index_trait_on_arrays", since = "1.50.0")] |
| impl<T, I, const N: usize> IndexMut<I> for [T; N] |
| where |
| [T]: IndexMut<I>, |
| { |
| #[inline] |
| fn index_mut(&mut self, index: I) -> &mut Self::Output { |
| IndexMut::index_mut(self as &mut [T], index) |
| } |
| } |
| |
| #[stable(feature = "rust1", since = "1.0.0")] |
| impl<T: PartialOrd, const N: usize> PartialOrd for [T; N] { |
| #[inline] |
| fn partial_cmp(&self, other: &[T; N]) -> Option<Ordering> { |
| PartialOrd::partial_cmp(&&self[..], &&other[..]) |
| } |
| #[inline] |
| fn lt(&self, other: &[T; N]) -> bool { |
| PartialOrd::lt(&&self[..], &&other[..]) |
| } |
| #[inline] |
| fn le(&self, other: &[T; N]) -> bool { |
| PartialOrd::le(&&self[..], &&other[..]) |
| } |
| #[inline] |
| fn ge(&self, other: &[T; N]) -> bool { |
| PartialOrd::ge(&&self[..], &&other[..]) |
| } |
| #[inline] |
| fn gt(&self, other: &[T; N]) -> bool { |
| PartialOrd::gt(&&self[..], &&other[..]) |
| } |
| } |
| |
| /// Implements comparison of arrays [lexicographically](Ord#lexicographical-comparison). |
| #[stable(feature = "rust1", since = "1.0.0")] |
| impl<T: Ord, const N: usize> Ord for [T; N] { |
| #[inline] |
| fn cmp(&self, other: &[T; N]) -> Ordering { |
| Ord::cmp(&&self[..], &&other[..]) |
| } |
| } |
| |
| #[stable(feature = "copy_clone_array_lib", since = "1.58.0")] |
| impl<T: Copy, const N: usize> Copy for [T; N] {} |
| |
| #[stable(feature = "copy_clone_array_lib", since = "1.58.0")] |
| impl<T: Clone, const N: usize> Clone for [T; N] { |
| #[inline] |
| fn clone(&self) -> Self { |
| SpecArrayClone::clone(self) |
| } |
| |
| #[inline] |
| fn clone_from(&mut self, other: &Self) { |
| self.clone_from_slice(other); |
| } |
| } |
| |
| trait SpecArrayClone: Clone { |
| fn clone<const N: usize>(array: &[Self; N]) -> [Self; N]; |
| } |
| |
| impl<T: Clone> SpecArrayClone for T { |
| #[inline] |
| default fn clone<const N: usize>(array: &[T; N]) -> [T; N] { |
| from_trusted_iterator(array.iter().cloned()) |
| } |
| } |
| |
| impl<T: Copy> SpecArrayClone for T { |
| #[inline] |
| fn clone<const N: usize>(array: &[T; N]) -> [T; N] { |
| *array |
| } |
| } |
| |
| // The Default impls cannot be done with const generics because `[T; 0]` doesn't |
| // require Default to be implemented, and having different impl blocks for |
| // different numbers isn't supported yet. |
| |
| macro_rules! array_impl_default { |
| {$n:expr, $t:ident $($ts:ident)*} => { |
| #[stable(since = "1.4.0", feature = "array_default")] |
| impl<T> Default for [T; $n] where T: Default { |
| fn default() -> [T; $n] { |
| [$t::default(), $($ts::default()),*] |
| } |
| } |
| array_impl_default!{($n - 1), $($ts)*} |
| }; |
| {$n:expr,} => { |
| #[stable(since = "1.4.0", feature = "array_default")] |
| impl<T> Default for [T; $n] { |
| fn default() -> [T; $n] { [] } |
| } |
| }; |
| } |
| |
| 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} |
| |
| impl<T, const N: usize> [T; N] { |
| /// Returns an array of the same size as `self`, with function `f` applied to each element |
| /// in order. |
| /// |
| /// If you don't necessarily need a new fixed-size array, consider using |
| /// [`Iterator::map`] instead. |
| /// |
| /// |
| /// # Note on performance and stack usage |
| /// |
| /// Unfortunately, usages of this method are currently not always optimized |
| /// as well as they could be. This mainly concerns large arrays, as mapping |
| /// over small arrays seem to be optimized just fine. Also note that in |
| /// debug mode (i.e. without any optimizations), this method can use a lot |
| /// of stack space (a few times the size of the array or more). |
| /// |
| /// Therefore, in performance-critical code, try to avoid using this method |
| /// on large arrays or check the emitted code. Also try to avoid chained |
| /// maps (e.g. `arr.map(...).map(...)`). |
| /// |
| /// In many cases, you can instead use [`Iterator::map`] by calling `.iter()` |
| /// or `.into_iter()` on your array. `[T; N]::map` is only necessary if you |
| /// really need a new array of the same size as the result. Rust's lazy |
| /// iterators tend to get optimized very well. |
| /// |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// let x = [1, 2, 3]; |
| /// let y = x.map(|v| v + 1); |
| /// assert_eq!(y, [2, 3, 4]); |
| /// |
| /// let x = [1, 2, 3]; |
| /// let mut temp = 0; |
| /// let y = x.map(|v| { temp += 1; v * temp }); |
| /// assert_eq!(y, [1, 4, 9]); |
| /// |
| /// let x = ["Ferris", "Bueller's", "Day", "Off"]; |
| /// let y = x.map(|v| v.len()); |
| /// assert_eq!(y, [6, 9, 3, 3]); |
| /// ``` |
| #[stable(feature = "array_map", since = "1.55.0")] |
| pub fn map<F, U>(self, f: F) -> [U; N] |
| where |
| F: FnMut(T) -> U, |
| { |
| self.try_map(NeverShortCircuit::wrap_mut_1(f)).0 |
| } |
| |
| /// A fallible function `f` applied to each element on array `self` in order to |
| /// return an array the same size as `self` or the first error encountered. |
| /// |
| /// The return type of this function depends on the return type of the closure. |
| /// If you return `Result<T, E>` from the closure, you'll get a `Result<[T; N], E>`. |
| /// If you return `Option<T>` from the closure, you'll get an `Option<[T; N]>`. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// #![feature(array_try_map)] |
| /// let a = ["1", "2", "3"]; |
| /// let b = a.try_map(|v| v.parse::<u32>()).unwrap().map(|v| v + 1); |
| /// assert_eq!(b, [2, 3, 4]); |
| /// |
| /// let a = ["1", "2a", "3"]; |
| /// let b = a.try_map(|v| v.parse::<u32>()); |
| /// assert!(b.is_err()); |
| /// |
| /// use std::num::NonZeroU32; |
| /// let z = [1, 2, 0, 3, 4]; |
| /// assert_eq!(z.try_map(NonZeroU32::new), None); |
| /// let a = [1, 2, 3]; |
| /// let b = a.try_map(NonZeroU32::new); |
| /// let c = b.map(|x| x.map(NonZeroU32::get)); |
| /// assert_eq!(c, Some(a)); |
| /// ``` |
| #[unstable(feature = "array_try_map", issue = "79711")] |
| pub fn try_map<F, R>(self, f: F) -> ChangeOutputType<R, [R::Output; N]> |
| where |
| F: FnMut(T) -> R, |
| R: Try, |
| R::Residual: Residual<[R::Output; N]>, |
| { |
| drain_array_with(self, |iter| try_from_trusted_iterator(iter.map(f))) |
| } |
| |
| /// Returns a slice containing the entire array. Equivalent to `&s[..]`. |
| #[stable(feature = "array_as_slice", since = "1.57.0")] |
| #[rustc_const_stable(feature = "array_as_slice", since = "1.57.0")] |
| pub const fn as_slice(&self) -> &[T] { |
| self |
| } |
| |
| /// Returns a mutable slice containing the entire array. Equivalent to |
| /// `&mut s[..]`. |
| #[stable(feature = "array_as_slice", since = "1.57.0")] |
| 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 avoid moving the original |
| /// array if its elements are not [`Copy`]. |
| /// |
| /// ``` |
| /// #![feature(array_methods)] |
| /// |
| /// 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] { |
| from_trusted_iterator(self.iter()) |
| } |
| |
| /// 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] { |
| from_trusted_iterator(self.iter_mut()) |
| } |
| |
| /// Divides one array reference into two at an index. |
| /// |
| /// The first will contain all indices from `[0, M)` (excluding |
| /// the index `M` itself) and the second will contain all |
| /// indices from `[M, N)` (excluding the index `N` itself). |
| /// |
| /// # Panics |
| /// |
| /// Panics if `M > N`. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// #![feature(split_array)] |
| /// |
| /// let v = [1, 2, 3, 4, 5, 6]; |
| /// |
| /// { |
| /// let (left, right) = v.split_array_ref::<0>(); |
| /// assert_eq!(left, &[]); |
| /// assert_eq!(right, &[1, 2, 3, 4, 5, 6]); |
| /// } |
| /// |
| /// { |
| /// let (left, right) = v.split_array_ref::<2>(); |
| /// assert_eq!(left, &[1, 2]); |
| /// assert_eq!(right, &[3, 4, 5, 6]); |
| /// } |
| /// |
| /// { |
| /// let (left, right) = v.split_array_ref::<6>(); |
| /// assert_eq!(left, &[1, 2, 3, 4, 5, 6]); |
| /// assert_eq!(right, &[]); |
| /// } |
| /// ``` |
| #[unstable( |
| feature = "split_array", |
| reason = "return type should have array as 2nd element", |
| issue = "90091" |
| )] |
| #[inline] |
| pub fn split_array_ref<const M: usize>(&self) -> (&[T; M], &[T]) { |
| (&self[..]).split_array_ref::<M>() |
| } |
| |
| /// Divides one mutable array reference into two at an index. |
| /// |
| /// The first will contain all indices from `[0, M)` (excluding |
| /// the index `M` itself) and the second will contain all |
| /// indices from `[M, N)` (excluding the index `N` itself). |
| /// |
| /// # Panics |
| /// |
| /// Panics if `M > N`. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// #![feature(split_array)] |
| /// |
| /// let mut v = [1, 0, 3, 0, 5, 6]; |
| /// let (left, right) = v.split_array_mut::<2>(); |
| /// assert_eq!(left, &mut [1, 0][..]); |
| /// assert_eq!(right, &mut [3, 0, 5, 6]); |
| /// left[1] = 2; |
| /// right[1] = 4; |
| /// assert_eq!(v, [1, 2, 3, 4, 5, 6]); |
| /// ``` |
| #[unstable( |
| feature = "split_array", |
| reason = "return type should have array as 2nd element", |
| issue = "90091" |
| )] |
| #[inline] |
| pub fn split_array_mut<const M: usize>(&mut self) -> (&mut [T; M], &mut [T]) { |
| (&mut self[..]).split_array_mut::<M>() |
| } |
| |
| /// Divides one array reference into two at an index from the end. |
| /// |
| /// The first will contain all indices from `[0, N - M)` (excluding |
| /// the index `N - M` itself) and the second will contain all |
| /// indices from `[N - M, N)` (excluding the index `N` itself). |
| /// |
| /// # Panics |
| /// |
| /// Panics if `M > N`. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// #![feature(split_array)] |
| /// |
| /// let v = [1, 2, 3, 4, 5, 6]; |
| /// |
| /// { |
| /// let (left, right) = v.rsplit_array_ref::<0>(); |
| /// assert_eq!(left, &[1, 2, 3, 4, 5, 6]); |
| /// assert_eq!(right, &[]); |
| /// } |
| /// |
| /// { |
| /// let (left, right) = v.rsplit_array_ref::<2>(); |
| /// assert_eq!(left, &[1, 2, 3, 4]); |
| /// assert_eq!(right, &[5, 6]); |
| /// } |
| /// |
| /// { |
| /// let (left, right) = v.rsplit_array_ref::<6>(); |
| /// assert_eq!(left, &[]); |
| /// assert_eq!(right, &[1, 2, 3, 4, 5, 6]); |
| /// } |
| /// ``` |
| #[unstable( |
| feature = "split_array", |
| reason = "return type should have array as 2nd element", |
| issue = "90091" |
| )] |
| #[inline] |
| pub fn rsplit_array_ref<const M: usize>(&self) -> (&[T], &[T; M]) { |
| (&self[..]).rsplit_array_ref::<M>() |
| } |
| |
| /// Divides one mutable array reference into two at an index from the end. |
| /// |
| /// The first will contain all indices from `[0, N - M)` (excluding |
| /// the index `N - M` itself) and the second will contain all |
| /// indices from `[N - M, N)` (excluding the index `N` itself). |
| /// |
| /// # Panics |
| /// |
| /// Panics if `M > N`. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// #![feature(split_array)] |
| /// |
| /// let mut v = [1, 0, 3, 0, 5, 6]; |
| /// let (left, right) = v.rsplit_array_mut::<4>(); |
| /// assert_eq!(left, &mut [1, 0]); |
| /// assert_eq!(right, &mut [3, 0, 5, 6][..]); |
| /// left[1] = 2; |
| /// right[1] = 4; |
| /// assert_eq!(v, [1, 2, 3, 4, 5, 6]); |
| /// ``` |
| #[unstable( |
| feature = "split_array", |
| reason = "return type should have array as 2nd element", |
| issue = "90091" |
| )] |
| #[inline] |
| pub fn rsplit_array_mut<const M: usize>(&mut self) -> (&mut [T], &mut [T; M]) { |
| (&mut self[..]).rsplit_array_mut::<M>() |
| } |
| } |
| |
| /// Populate an array from the first `N` elements of `iter` |
| /// |
| /// # Panics |
| /// |
| /// If the iterator doesn't actually have enough items. |
| /// |
| /// By depending on `TrustedLen`, however, we can do that check up-front (where |
| /// it easily optimizes away) so it doesn't impact the loop that fills the array. |
| #[inline] |
| fn from_trusted_iterator<T, const N: usize>(iter: impl UncheckedIterator<Item = T>) -> [T; N] { |
| try_from_trusted_iterator(iter.map(NeverShortCircuit)).0 |
| } |
| |
| #[inline] |
| fn try_from_trusted_iterator<T, R, const N: usize>( |
| iter: impl UncheckedIterator<Item = R>, |
| ) -> ChangeOutputType<R, [T; N]> |
| where |
| R: Try<Output = T>, |
| R::Residual: Residual<[T; N]>, |
| { |
| assert!(iter.size_hint().0 >= N); |
| fn next<T>(mut iter: impl UncheckedIterator<Item = T>) -> impl FnMut(usize) -> T { |
| move |_| { |
| // SAFETY: We know that `from_fn` will call this at most N times, |
| // and we checked to ensure that we have at least that many items. |
| unsafe { iter.next_unchecked() } |
| } |
| } |
| |
| try_from_fn(next(iter)) |
| } |
| |
| /// Version of [`try_from_fn`] using a passed-in slice in order to avoid |
| /// needing to monomorphize for every array length. |
| /// |
| /// This takes a generator rather than an iterator so that *at the type level* |
| /// it never needs to worry about running out of items. When combined with |
| /// an infallible `Try` type, that means the loop canonicalizes easily, allowing |
| /// it to optimize well. |
| /// |
| /// It would be *possible* to unify this and [`iter_next_chunk_erased`] into one |
| /// function that does the union of both things, but last time it was that way |
| /// it resulted in poor codegen from the "are there enough source items?" checks |
| /// not optimizing away. So if you give it a shot, make sure to watch what |
| /// happens in the codegen tests. |
| #[inline] |
| fn try_from_fn_erased<T, R>( |
| buffer: &mut [MaybeUninit<T>], |
| mut generator: impl FnMut(usize) -> R, |
| ) -> ControlFlow<R::Residual> |
| where |
| R: Try<Output = T>, |
| { |
| let mut guard = Guard { array_mut: buffer, initialized: 0 }; |
| |
| while guard.initialized < guard.array_mut.len() { |
| let item = generator(guard.initialized).branch()?; |
| |
| // SAFETY: The loop condition ensures we have space to push the item |
| unsafe { guard.push_unchecked(item) }; |
| } |
| |
| mem::forget(guard); |
| ControlFlow::Continue(()) |
| } |
| |
| /// Panic guard for incremental initialization of arrays. |
| /// |
| /// Disarm the guard with `mem::forget` once the array has been initialized. |
| /// |
| /// # Safety |
| /// |
| /// All write accesses to this structure are unsafe and must maintain a correct |
| /// count of `initialized` elements. |
| /// |
| /// To minimize indirection fields are still pub but callers should at least use |
| /// `push_unchecked` to signal that something unsafe is going on. |
| struct Guard<'a, T> { |
| /// The array to be initialized. |
| pub array_mut: &'a mut [MaybeUninit<T>], |
| /// The number of items that have been initialized so far. |
| pub initialized: usize, |
| } |
| |
| impl<T> Guard<'_, T> { |
| /// Adds an item to the array and updates the initialized item counter. |
| /// |
| /// # Safety |
| /// |
| /// No more than N elements must be initialized. |
| #[inline] |
| pub unsafe fn push_unchecked(&mut self, item: T) { |
| // SAFETY: If `initialized` was correct before and the caller does not |
| // invoke this method more than N times then writes will be in-bounds |
| // and slots will not be initialized more than once. |
| unsafe { |
| self.array_mut.get_unchecked_mut(self.initialized).write(item); |
| self.initialized = self.initialized.unchecked_add(1); |
| } |
| } |
| } |
| |
| impl<T> Drop for Guard<'_, T> { |
| fn drop(&mut self) { |
| debug_assert!(self.initialized <= self.array_mut.len()); |
| |
| // SAFETY: this slice will contain only initialized objects. |
| unsafe { |
| crate::ptr::drop_in_place(MaybeUninit::slice_assume_init_mut( |
| self.array_mut.get_unchecked_mut(..self.initialized), |
| )); |
| } |
| } |
| } |
| |
| /// Pulls `N` items from `iter` and returns them as an array. If the iterator |
| /// yields fewer than `N` items, `Err` is returned containing an iterator over |
| /// the already yielded items. |
| /// |
| /// Since the iterator is passed as a mutable reference and this function calls |
| /// `next` at most `N` times, the iterator can still be used afterwards to |
| /// retrieve the remaining items. |
| /// |
| /// If `iter.next()` panicks, all items already yielded by the iterator are |
| /// dropped. |
| /// |
| /// Used for [`Iterator::next_chunk`]. |
| #[inline] |
| pub(crate) fn iter_next_chunk<T, const N: usize>( |
| iter: &mut impl Iterator<Item = T>, |
| ) -> Result<[T; N], IntoIter<T, N>> { |
| let mut array = MaybeUninit::uninit_array::<N>(); |
| let r = iter_next_chunk_erased(&mut array, iter); |
| match r { |
| Ok(()) => { |
| // SAFETY: All elements of `array` were populated. |
| Ok(unsafe { MaybeUninit::array_assume_init(array) }) |
| } |
| Err(initialized) => { |
| // SAFETY: Only the first `initialized` elements were populated |
| Err(unsafe { IntoIter::new_unchecked(array, 0..initialized) }) |
| } |
| } |
| } |
| |
| /// Version of [`iter_next_chunk`] using a passed-in slice in order to avoid |
| /// needing to monomorphize for every array length. |
| /// |
| /// Unfortunately this loop has two exit conditions, the buffer filling up |
| /// or the iterator running out of items, making it tend to optimize poorly. |
| #[inline] |
| fn iter_next_chunk_erased<T>( |
| buffer: &mut [MaybeUninit<T>], |
| iter: &mut impl Iterator<Item = T>, |
| ) -> Result<(), usize> { |
| let mut guard = Guard { array_mut: buffer, initialized: 0 }; |
| while guard.initialized < guard.array_mut.len() { |
| let Some(item) = iter.next() else { |
| // Unlike `try_from_fn_erased`, we want to keep the partial results, |
| // so we need to defuse the guard instead of using `?`. |
| let initialized = guard.initialized; |
| mem::forget(guard); |
| return Err(initialized); |
| }; |
| |
| // SAFETY: The loop condition ensures we have space to push the item |
| unsafe { guard.push_unchecked(item) }; |
| } |
| |
| mem::forget(guard); |
| Ok(()) |
| } |