1 | //! Utilities for the array primitive type. |
2 | //! |
3 | //! *[See also the array primitive type](array).* |
4 | |
5 | #![stable (feature = "core_array" , since = "1.36.0" )] |
6 | |
7 | use crate::borrow::{Borrow, BorrowMut}; |
8 | use crate::cmp::Ordering; |
9 | use crate::convert::Infallible; |
10 | use crate::error::Error; |
11 | use crate::fmt; |
12 | use crate::hash::{self, Hash}; |
13 | use crate::iter::UncheckedIterator; |
14 | use crate::mem::{self, MaybeUninit}; |
15 | use crate::ops::{ |
16 | ChangeOutputType, ControlFlow, FromResidual, Index, IndexMut, NeverShortCircuit, Residual, Try, |
17 | }; |
18 | use crate::slice::{Iter, IterMut}; |
19 | |
20 | mod ascii; |
21 | mod drain; |
22 | mod equality; |
23 | mod iter; |
24 | |
25 | pub(crate) use drain::drain_array_with; |
26 | |
27 | #[stable (feature = "array_value_iter" , since = "1.51.0" )] |
28 | pub use iter::IntoIter; |
29 | |
30 | /// Creates an array of type [T; N], where each element `T` is the returned value from `cb` |
31 | /// using that element's index. |
32 | /// |
33 | /// # Arguments |
34 | /// |
35 | /// * `cb`: Callback where the passed argument is the current array index. |
36 | /// |
37 | /// # Example |
38 | /// |
39 | /// ```rust |
40 | /// // type inference is helping us here, the way `from_fn` knows how many |
41 | /// // elements to produce is the length of array down there: only arrays of |
42 | /// // equal lengths can be compared, so the const generic parameter `N` is |
43 | /// // inferred to be 5, thus creating array of 5 elements. |
44 | /// |
45 | /// let array = core::array::from_fn(|i| i); |
46 | /// // indexes are: 0 1 2 3 4 |
47 | /// assert_eq!(array, [0, 1, 2, 3, 4]); |
48 | /// |
49 | /// let array2: [usize; 8] = core::array::from_fn(|i| i * 2); |
50 | /// // indexes are: 0 1 2 3 4 5 6 7 |
51 | /// assert_eq!(array2, [0, 2, 4, 6, 8, 10, 12, 14]); |
52 | /// |
53 | /// let bool_arr = core::array::from_fn::<_, 5, _>(|i| i % 2 == 0); |
54 | /// // indexes are: 0 1 2 3 4 |
55 | /// assert_eq!(bool_arr, [true, false, true, false, true]); |
56 | /// ``` |
57 | #[inline ] |
58 | #[stable (feature = "array_from_fn" , since = "1.63.0" )] |
59 | pub fn from_fn<T, const N: usize, F>(cb: F) -> [T; N] |
60 | where |
61 | F: FnMut(usize) -> T, |
62 | { |
63 | try_from_fn(cb:NeverShortCircuit::wrap_mut_1(cb)).0 |
64 | } |
65 | |
66 | /// Creates an array `[T; N]` where each fallible array element `T` is returned by the `cb` call. |
67 | /// Unlike [`from_fn`], where the element creation can't fail, this version will return an error |
68 | /// if any element creation was unsuccessful. |
69 | /// |
70 | /// The return type of this function depends on the return type of the closure. |
71 | /// If you return `Result<T, E>` from the closure, you'll get a `Result<[T; N], E>`. |
72 | /// If you return `Option<T>` from the closure, you'll get an `Option<[T; N]>`. |
73 | /// |
74 | /// # Arguments |
75 | /// |
76 | /// * `cb`: Callback where the passed argument is the current array index. |
77 | /// |
78 | /// # Example |
79 | /// |
80 | /// ```rust |
81 | /// #![feature(array_try_from_fn)] |
82 | /// |
83 | /// let array: Result<[u8; 5], _> = std::array::try_from_fn(|i| i.try_into()); |
84 | /// assert_eq!(array, Ok([0, 1, 2, 3, 4])); |
85 | /// |
86 | /// let array: Result<[i8; 200], _> = std::array::try_from_fn(|i| i.try_into()); |
87 | /// assert!(array.is_err()); |
88 | /// |
89 | /// let array: Option<[_; 4]> = std::array::try_from_fn(|i| i.checked_add(100)); |
90 | /// assert_eq!(array, Some([100, 101, 102, 103])); |
91 | /// |
92 | /// let array: Option<[_; 4]> = std::array::try_from_fn(|i| i.checked_sub(100)); |
93 | /// assert_eq!(array, None); |
94 | /// ``` |
95 | #[inline ] |
96 | #[unstable (feature = "array_try_from_fn" , issue = "89379" )] |
97 | pub fn try_from_fn<R, const N: usize, F>(cb: F) -> ChangeOutputType<R, [R::Output; N]> |
98 | where |
99 | F: FnMut(usize) -> R, |
100 | R: Try, |
101 | R::Residual: Residual<[R::Output; N]>, |
102 | { |
103 | let mut array: [MaybeUninit<::Output>; N] = MaybeUninit::uninit_array::<N>(); |
104 | match try_from_fn_erased(&mut array, generator:cb) { |
105 | ControlFlow::Break(r: ::Residual) => FromResidual::from_residual(r), |
106 | ControlFlow::Continue(()) => { |
107 | // SAFETY: All elements of the array were populated. |
108 | try { unsafe { MaybeUninit::array_assume_init(array) } } |
109 | } |
110 | } |
111 | } |
112 | |
113 | /// Converts a reference to `T` into a reference to an array of length 1 (without copying). |
114 | #[stable (feature = "array_from_ref" , since = "1.53.0" )] |
115 | #[rustc_const_stable (feature = "const_array_from_ref_shared" , since = "1.63.0" )] |
116 | pub const fn from_ref<T>(s: &T) -> &[T; 1] { |
117 | // SAFETY: Converting `&T` to `&[T; 1]` is sound. |
118 | unsafe { &*(s as *const T).cast::<[T; 1]>() } |
119 | } |
120 | |
121 | /// Converts a mutable reference to `T` into a mutable reference to an array of length 1 (without copying). |
122 | #[stable (feature = "array_from_ref" , since = "1.53.0" )] |
123 | #[rustc_const_unstable (feature = "const_array_from_ref" , issue = "90206" )] |
124 | pub const fn from_mut<T>(s: &mut T) -> &mut [T; 1] { |
125 | // SAFETY: Converting `&mut T` to `&mut [T; 1]` is sound. |
126 | unsafe { &mut *(s as *mut T).cast::<[T; 1]>() } |
127 | } |
128 | |
129 | /// The error type returned when a conversion from a slice to an array fails. |
130 | #[stable (feature = "try_from" , since = "1.34.0" )] |
131 | #[derive (Debug, Copy, Clone)] |
132 | pub struct TryFromSliceError(()); |
133 | |
134 | #[stable (feature = "core_array" , since = "1.36.0" )] |
135 | impl fmt::Display for TryFromSliceError { |
136 | #[inline ] |
137 | fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
138 | #[allow (deprecated)] |
139 | self.description().fmt(f) |
140 | } |
141 | } |
142 | |
143 | #[stable (feature = "try_from" , since = "1.34.0" )] |
144 | impl Error for TryFromSliceError { |
145 | #[allow (deprecated)] |
146 | fn description(&self) -> &str { |
147 | "could not convert slice to array" |
148 | } |
149 | } |
150 | |
151 | #[stable (feature = "try_from_slice_error" , since = "1.36.0" )] |
152 | impl From<Infallible> for TryFromSliceError { |
153 | fn from(x: Infallible) -> TryFromSliceError { |
154 | match x {} |
155 | } |
156 | } |
157 | |
158 | #[stable (feature = "rust1" , since = "1.0.0" )] |
159 | impl<T, const N: usize> AsRef<[T]> for [T; N] { |
160 | #[inline ] |
161 | fn as_ref(&self) -> &[T] { |
162 | &self[..] |
163 | } |
164 | } |
165 | |
166 | #[stable (feature = "rust1" , since = "1.0.0" )] |
167 | impl<T, const N: usize> AsMut<[T]> for [T; N] { |
168 | #[inline ] |
169 | fn as_mut(&mut self) -> &mut [T] { |
170 | &mut self[..] |
171 | } |
172 | } |
173 | |
174 | #[stable (feature = "array_borrow" , since = "1.4.0" )] |
175 | impl<T, const N: usize> Borrow<[T]> for [T; N] { |
176 | fn borrow(&self) -> &[T] { |
177 | self |
178 | } |
179 | } |
180 | |
181 | #[stable (feature = "array_borrow" , since = "1.4.0" )] |
182 | impl<T, const N: usize> BorrowMut<[T]> for [T; N] { |
183 | fn borrow_mut(&mut self) -> &mut [T] { |
184 | self |
185 | } |
186 | } |
187 | |
188 | /// Tries to create an array `[T; N]` by copying from a slice `&[T]`. Succeeds if |
189 | /// `slice.len() == N`. |
190 | /// |
191 | /// ``` |
192 | /// let bytes: [u8; 3] = [1, 0, 2]; |
193 | /// |
194 | /// let bytes_head: [u8; 2] = <[u8; 2]>::try_from(&bytes[0..2]).unwrap(); |
195 | /// assert_eq!(1, u16::from_le_bytes(bytes_head)); |
196 | /// |
197 | /// let bytes_tail: [u8; 2] = bytes[1..3].try_into().unwrap(); |
198 | /// assert_eq!(512, u16::from_le_bytes(bytes_tail)); |
199 | /// ``` |
200 | #[stable (feature = "try_from" , since = "1.34.0" )] |
201 | impl<T, const N: usize> TryFrom<&[T]> for [T; N] |
202 | where |
203 | T: Copy, |
204 | { |
205 | type Error = TryFromSliceError; |
206 | |
207 | #[inline ] |
208 | fn try_from(slice: &[T]) -> Result<[T; N], TryFromSliceError> { |
209 | <&Self>::try_from(slice).copied() |
210 | } |
211 | } |
212 | |
213 | /// Tries to create an array `[T; N]` by copying from a mutable slice `&mut [T]`. |
214 | /// Succeeds if `slice.len() == N`. |
215 | /// |
216 | /// ``` |
217 | /// let mut bytes: [u8; 3] = [1, 0, 2]; |
218 | /// |
219 | /// let bytes_head: [u8; 2] = <[u8; 2]>::try_from(&mut bytes[0..2]).unwrap(); |
220 | /// assert_eq!(1, u16::from_le_bytes(bytes_head)); |
221 | /// |
222 | /// let bytes_tail: [u8; 2] = (&mut bytes[1..3]).try_into().unwrap(); |
223 | /// assert_eq!(512, u16::from_le_bytes(bytes_tail)); |
224 | /// ``` |
225 | #[stable (feature = "try_from_mut_slice_to_array" , since = "1.59.0" )] |
226 | impl<T, const N: usize> TryFrom<&mut [T]> for [T; N] |
227 | where |
228 | T: Copy, |
229 | { |
230 | type Error = TryFromSliceError; |
231 | |
232 | #[inline ] |
233 | fn try_from(slice: &mut [T]) -> Result<[T; N], TryFromSliceError> { |
234 | <Self>::try_from(&*slice) |
235 | } |
236 | } |
237 | |
238 | /// Tries to create an array ref `&[T; N]` from a slice ref `&[T]`. Succeeds if |
239 | /// `slice.len() == N`. |
240 | /// |
241 | /// ``` |
242 | /// let bytes: [u8; 3] = [1, 0, 2]; |
243 | /// |
244 | /// let bytes_head: &[u8; 2] = <&[u8; 2]>::try_from(&bytes[0..2]).unwrap(); |
245 | /// assert_eq!(1, u16::from_le_bytes(*bytes_head)); |
246 | /// |
247 | /// let bytes_tail: &[u8; 2] = bytes[1..3].try_into().unwrap(); |
248 | /// assert_eq!(512, u16::from_le_bytes(*bytes_tail)); |
249 | /// ``` |
250 | #[stable (feature = "try_from" , since = "1.34.0" )] |
251 | impl<'a, T, const N: usize> TryFrom<&'a [T]> for &'a [T; N] { |
252 | type Error = TryFromSliceError; |
253 | |
254 | #[inline ] |
255 | fn try_from(slice: &'a [T]) -> Result<&'a [T; N], TryFromSliceError> { |
256 | if slice.len() == N { |
257 | let ptr: *const [T; N] = slice.as_ptr() as *const [T; N]; |
258 | // SAFETY: ok because we just checked that the length fits |
259 | unsafe { Ok(&*ptr) } |
260 | } else { |
261 | Err(TryFromSliceError(())) |
262 | } |
263 | } |
264 | } |
265 | |
266 | /// Tries to create a mutable array ref `&mut [T; N]` from a mutable slice ref |
267 | /// `&mut [T]`. Succeeds if `slice.len() == N`. |
268 | /// |
269 | /// ``` |
270 | /// let mut bytes: [u8; 3] = [1, 0, 2]; |
271 | /// |
272 | /// let bytes_head: &mut [u8; 2] = <&mut [u8; 2]>::try_from(&mut bytes[0..2]).unwrap(); |
273 | /// assert_eq!(1, u16::from_le_bytes(*bytes_head)); |
274 | /// |
275 | /// let bytes_tail: &mut [u8; 2] = (&mut bytes[1..3]).try_into().unwrap(); |
276 | /// assert_eq!(512, u16::from_le_bytes(*bytes_tail)); |
277 | /// ``` |
278 | #[stable (feature = "try_from" , since = "1.34.0" )] |
279 | impl<'a, T, const N: usize> TryFrom<&'a mut [T]> for &'a mut [T; N] { |
280 | type Error = TryFromSliceError; |
281 | |
282 | #[inline ] |
283 | fn try_from(slice: &'a mut [T]) -> Result<&'a mut [T; N], TryFromSliceError> { |
284 | if slice.len() == N { |
285 | let ptr: *mut [T; N] = slice.as_mut_ptr() as *mut [T; N]; |
286 | // SAFETY: ok because we just checked that the length fits |
287 | unsafe { Ok(&mut *ptr) } |
288 | } else { |
289 | Err(TryFromSliceError(())) |
290 | } |
291 | } |
292 | } |
293 | |
294 | /// The hash of an array is the same as that of the corresponding slice, |
295 | /// as required by the `Borrow` implementation. |
296 | /// |
297 | /// ``` |
298 | /// use std::hash::BuildHasher; |
299 | /// |
300 | /// let b = std::hash::RandomState::new(); |
301 | /// let a: [u8; 3] = [0xa8, 0x3c, 0x09]; |
302 | /// let s: &[u8] = &[0xa8, 0x3c, 0x09]; |
303 | /// assert_eq!(b.hash_one(a), b.hash_one(s)); |
304 | /// ``` |
305 | #[stable (feature = "rust1" , since = "1.0.0" )] |
306 | impl<T: Hash, const N: usize> Hash for [T; N] { |
307 | fn hash<H: hash::Hasher>(&self, state: &mut H) { |
308 | Hash::hash(&self[..], state) |
309 | } |
310 | } |
311 | |
312 | #[stable (feature = "rust1" , since = "1.0.0" )] |
313 | impl<T: fmt::Debug, const N: usize> fmt::Debug for [T; N] { |
314 | fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
315 | fmt::Debug::fmt(&&self[..], f) |
316 | } |
317 | } |
318 | |
319 | #[stable (feature = "rust1" , since = "1.0.0" )] |
320 | impl<'a, T, const N: usize> IntoIterator for &'a [T; N] { |
321 | type Item = &'a T; |
322 | type IntoIter = Iter<'a, T>; |
323 | |
324 | fn into_iter(self) -> Iter<'a, T> { |
325 | self.iter() |
326 | } |
327 | } |
328 | |
329 | #[stable (feature = "rust1" , since = "1.0.0" )] |
330 | impl<'a, T, const N: usize> IntoIterator for &'a mut [T; N] { |
331 | type Item = &'a mut T; |
332 | type IntoIter = IterMut<'a, T>; |
333 | |
334 | fn into_iter(self) -> IterMut<'a, T> { |
335 | self.iter_mut() |
336 | } |
337 | } |
338 | |
339 | #[stable (feature = "index_trait_on_arrays" , since = "1.50.0" )] |
340 | impl<T, I, const N: usize> Index<I> for [T; N] |
341 | where |
342 | [T]: Index<I>, |
343 | { |
344 | type Output = <[T] as Index<I>>::Output; |
345 | |
346 | #[inline ] |
347 | fn index(&self, index: I) -> &Self::Output { |
348 | Index::index(self as &[T], index) |
349 | } |
350 | } |
351 | |
352 | #[stable (feature = "index_trait_on_arrays" , since = "1.50.0" )] |
353 | impl<T, I, const N: usize> IndexMut<I> for [T; N] |
354 | where |
355 | [T]: IndexMut<I>, |
356 | { |
357 | #[inline ] |
358 | fn index_mut(&mut self, index: I) -> &mut Self::Output { |
359 | IndexMut::index_mut(self as &mut [T], index) |
360 | } |
361 | } |
362 | |
363 | /// Implements comparison of arrays [lexicographically](Ord#lexicographical-comparison). |
364 | #[stable (feature = "rust1" , since = "1.0.0" )] |
365 | impl<T: PartialOrd, const N: usize> PartialOrd for [T; N] { |
366 | #[inline ] |
367 | fn partial_cmp(&self, other: &[T; N]) -> Option<Ordering> { |
368 | PartialOrd::partial_cmp(&&self[..], &&other[..]) |
369 | } |
370 | #[inline ] |
371 | fn lt(&self, other: &[T; N]) -> bool { |
372 | PartialOrd::lt(&&self[..], &&other[..]) |
373 | } |
374 | #[inline ] |
375 | fn le(&self, other: &[T; N]) -> bool { |
376 | PartialOrd::le(&&self[..], &&other[..]) |
377 | } |
378 | #[inline ] |
379 | fn ge(&self, other: &[T; N]) -> bool { |
380 | PartialOrd::ge(&&self[..], &&other[..]) |
381 | } |
382 | #[inline ] |
383 | fn gt(&self, other: &[T; N]) -> bool { |
384 | PartialOrd::gt(&&self[..], &&other[..]) |
385 | } |
386 | } |
387 | |
388 | /// Implements comparison of arrays [lexicographically](Ord#lexicographical-comparison). |
389 | #[stable (feature = "rust1" , since = "1.0.0" )] |
390 | impl<T: Ord, const N: usize> Ord for [T; N] { |
391 | #[inline ] |
392 | fn cmp(&self, other: &[T; N]) -> Ordering { |
393 | Ord::cmp(&&self[..], &&other[..]) |
394 | } |
395 | } |
396 | |
397 | #[stable (feature = "copy_clone_array_lib" , since = "1.58.0" )] |
398 | impl<T: Copy, const N: usize> Copy for [T; N] {} |
399 | |
400 | #[stable (feature = "copy_clone_array_lib" , since = "1.58.0" )] |
401 | impl<T: Clone, const N: usize> Clone for [T; N] { |
402 | #[inline ] |
403 | fn clone(&self) -> Self { |
404 | SpecArrayClone::clone(self) |
405 | } |
406 | |
407 | #[inline ] |
408 | fn clone_from(&mut self, other: &Self) { |
409 | self.clone_from_slice(src:other); |
410 | } |
411 | } |
412 | |
413 | trait SpecArrayClone: Clone { |
414 | fn clone<const N: usize>(array: &[Self; N]) -> [Self; N]; |
415 | } |
416 | |
417 | impl<T: Clone> SpecArrayClone for T { |
418 | #[inline ] |
419 | default fn clone<const N: usize>(array: &[T; N]) -> [T; N] { |
420 | from_trusted_iterator(iter:array.iter().cloned()) |
421 | } |
422 | } |
423 | |
424 | impl<T: Copy> SpecArrayClone for T { |
425 | #[inline ] |
426 | fn clone<const N: usize>(array: &[T; N]) -> [T; N] { |
427 | *array |
428 | } |
429 | } |
430 | |
431 | // The Default impls cannot be done with const generics because `[T; 0]` doesn't |
432 | // require Default to be implemented, and having different impl blocks for |
433 | // different numbers isn't supported yet. |
434 | |
435 | macro_rules! array_impl_default { |
436 | {$n:expr, $t:ident $($ts:ident)*} => { |
437 | #[stable(since = "1.4.0" , feature = "array_default" )] |
438 | impl<T> Default for [T; $n] where T: Default { |
439 | fn default() -> [T; $n] { |
440 | [$t::default(), $($ts::default()),*] |
441 | } |
442 | } |
443 | array_impl_default!{($n - 1), $($ts)*} |
444 | }; |
445 | {$n:expr,} => { |
446 | #[stable(since = "1.4.0" , feature = "array_default" )] |
447 | impl<T> Default for [T; $n] { |
448 | fn default() -> [T; $n] { [] } |
449 | } |
450 | }; |
451 | } |
452 | |
453 | 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} |
454 | |
455 | impl<T, const N: usize> [T; N] { |
456 | /// Returns an array of the same size as `self`, with function `f` applied to each element |
457 | /// in order. |
458 | /// |
459 | /// If you don't necessarily need a new fixed-size array, consider using |
460 | /// [`Iterator::map`] instead. |
461 | /// |
462 | /// |
463 | /// # Note on performance and stack usage |
464 | /// |
465 | /// Unfortunately, usages of this method are currently not always optimized |
466 | /// as well as they could be. This mainly concerns large arrays, as mapping |
467 | /// over small arrays seem to be optimized just fine. Also note that in |
468 | /// debug mode (i.e. without any optimizations), this method can use a lot |
469 | /// of stack space (a few times the size of the array or more). |
470 | /// |
471 | /// Therefore, in performance-critical code, try to avoid using this method |
472 | /// on large arrays or check the emitted code. Also try to avoid chained |
473 | /// maps (e.g. `arr.map(...).map(...)`). |
474 | /// |
475 | /// In many cases, you can instead use [`Iterator::map`] by calling `.iter()` |
476 | /// or `.into_iter()` on your array. `[T; N]::map` is only necessary if you |
477 | /// really need a new array of the same size as the result. Rust's lazy |
478 | /// iterators tend to get optimized very well. |
479 | /// |
480 | /// |
481 | /// # Examples |
482 | /// |
483 | /// ``` |
484 | /// let x = [1, 2, 3]; |
485 | /// let y = x.map(|v| v + 1); |
486 | /// assert_eq!(y, [2, 3, 4]); |
487 | /// |
488 | /// let x = [1, 2, 3]; |
489 | /// let mut temp = 0; |
490 | /// let y = x.map(|v| { temp += 1; v * temp }); |
491 | /// assert_eq!(y, [1, 4, 9]); |
492 | /// |
493 | /// let x = ["Ferris" , "Bueller's" , "Day" , "Off" ]; |
494 | /// let y = x.map(|v| v.len()); |
495 | /// assert_eq!(y, [6, 9, 3, 3]); |
496 | /// ``` |
497 | #[stable (feature = "array_map" , since = "1.55.0" )] |
498 | pub fn map<F, U>(self, f: F) -> [U; N] |
499 | where |
500 | F: FnMut(T) -> U, |
501 | { |
502 | self.try_map(NeverShortCircuit::wrap_mut_1(f)).0 |
503 | } |
504 | |
505 | /// A fallible function `f` applied to each element on array `self` in order to |
506 | /// return an array the same size as `self` or the first error encountered. |
507 | /// |
508 | /// The return type of this function depends on the return type of the closure. |
509 | /// If you return `Result<T, E>` from the closure, you'll get a `Result<[T; N], E>`. |
510 | /// If you return `Option<T>` from the closure, you'll get an `Option<[T; N]>`. |
511 | /// |
512 | /// # Examples |
513 | /// |
514 | /// ``` |
515 | /// #![feature(array_try_map)] |
516 | /// |
517 | /// let a = ["1" , "2" , "3" ]; |
518 | /// let b = a.try_map(|v| v.parse::<u32>()).unwrap().map(|v| v + 1); |
519 | /// assert_eq!(b, [2, 3, 4]); |
520 | /// |
521 | /// let a = ["1" , "2a" , "3" ]; |
522 | /// let b = a.try_map(|v| v.parse::<u32>()); |
523 | /// assert!(b.is_err()); |
524 | /// |
525 | /// use std::num::NonZero; |
526 | /// |
527 | /// let z = [1, 2, 0, 3, 4]; |
528 | /// assert_eq!(z.try_map(NonZero::new), None); |
529 | /// |
530 | /// let a = [1, 2, 3]; |
531 | /// let b = a.try_map(NonZero::new); |
532 | /// let c = b.map(|x| x.map(NonZero::get)); |
533 | /// assert_eq!(c, Some(a)); |
534 | /// ``` |
535 | #[unstable (feature = "array_try_map" , issue = "79711" )] |
536 | pub fn try_map<F, R>(self, f: F) -> ChangeOutputType<R, [R::Output; N]> |
537 | where |
538 | F: FnMut(T) -> R, |
539 | R: Try, |
540 | R::Residual: Residual<[R::Output; N]>, |
541 | { |
542 | drain_array_with(self, |iter| try_from_trusted_iterator(iter.map(f))) |
543 | } |
544 | |
545 | /// Returns a slice containing the entire array. Equivalent to `&s[..]`. |
546 | #[stable (feature = "array_as_slice" , since = "1.57.0" )] |
547 | #[rustc_const_stable (feature = "array_as_slice" , since = "1.57.0" )] |
548 | pub const fn as_slice(&self) -> &[T] { |
549 | self |
550 | } |
551 | |
552 | /// Returns a mutable slice containing the entire array. Equivalent to |
553 | /// `&mut s[..]`. |
554 | #[stable (feature = "array_as_slice" , since = "1.57.0" )] |
555 | pub fn as_mut_slice(&mut self) -> &mut [T] { |
556 | self |
557 | } |
558 | |
559 | /// Borrows each element and returns an array of references with the same |
560 | /// size as `self`. |
561 | /// |
562 | /// |
563 | /// # Example |
564 | /// |
565 | /// ``` |
566 | /// let floats = [3.1, 2.7, -1.0]; |
567 | /// let float_refs: [&f64; 3] = floats.each_ref(); |
568 | /// assert_eq!(float_refs, [&3.1, &2.7, &-1.0]); |
569 | /// ``` |
570 | /// |
571 | /// This method is particularly useful if combined with other methods, like |
572 | /// [`map`](#method.map). This way, you can avoid moving the original |
573 | /// array if its elements are not [`Copy`]. |
574 | /// |
575 | /// ``` |
576 | /// let strings = ["Ferris" .to_string(), "♥" .to_string(), "Rust" .to_string()]; |
577 | /// let is_ascii = strings.each_ref().map(|s| s.is_ascii()); |
578 | /// assert_eq!(is_ascii, [true, false, true]); |
579 | /// |
580 | /// // We can still access the original array: it has not been moved. |
581 | /// assert_eq!(strings.len(), 3); |
582 | /// ``` |
583 | #[stable (feature = "array_methods" , since = "1.77.0" )] |
584 | pub fn each_ref(&self) -> [&T; N] { |
585 | from_trusted_iterator(self.iter()) |
586 | } |
587 | |
588 | /// Borrows each element mutably and returns an array of mutable references |
589 | /// with the same size as `self`. |
590 | /// |
591 | /// |
592 | /// # Example |
593 | /// |
594 | /// ``` |
595 | /// |
596 | /// let mut floats = [3.1, 2.7, -1.0]; |
597 | /// let float_refs: [&mut f64; 3] = floats.each_mut(); |
598 | /// *float_refs[0] = 0.0; |
599 | /// assert_eq!(float_refs, [&mut 0.0, &mut 2.7, &mut -1.0]); |
600 | /// assert_eq!(floats, [0.0, 2.7, -1.0]); |
601 | /// ``` |
602 | #[stable (feature = "array_methods" , since = "1.77.0" )] |
603 | pub fn each_mut(&mut self) -> [&mut T; N] { |
604 | from_trusted_iterator(self.iter_mut()) |
605 | } |
606 | |
607 | /// Divides one array reference into two at an index. |
608 | /// |
609 | /// The first will contain all indices from `[0, M)` (excluding |
610 | /// the index `M` itself) and the second will contain all |
611 | /// indices from `[M, N)` (excluding the index `N` itself). |
612 | /// |
613 | /// # Panics |
614 | /// |
615 | /// Panics if `M > N`. |
616 | /// |
617 | /// # Examples |
618 | /// |
619 | /// ``` |
620 | /// #![feature(split_array)] |
621 | /// |
622 | /// let v = [1, 2, 3, 4, 5, 6]; |
623 | /// |
624 | /// { |
625 | /// let (left, right) = v.split_array_ref::<0>(); |
626 | /// assert_eq!(left, &[]); |
627 | /// assert_eq!(right, &[1, 2, 3, 4, 5, 6]); |
628 | /// } |
629 | /// |
630 | /// { |
631 | /// let (left, right) = v.split_array_ref::<2>(); |
632 | /// assert_eq!(left, &[1, 2]); |
633 | /// assert_eq!(right, &[3, 4, 5, 6]); |
634 | /// } |
635 | /// |
636 | /// { |
637 | /// let (left, right) = v.split_array_ref::<6>(); |
638 | /// assert_eq!(left, &[1, 2, 3, 4, 5, 6]); |
639 | /// assert_eq!(right, &[]); |
640 | /// } |
641 | /// ``` |
642 | #[unstable ( |
643 | feature = "split_array" , |
644 | reason = "return type should have array as 2nd element" , |
645 | issue = "90091" |
646 | )] |
647 | #[inline ] |
648 | pub fn split_array_ref<const M: usize>(&self) -> (&[T; M], &[T]) { |
649 | (&self[..]).split_first_chunk::<M>().unwrap() |
650 | } |
651 | |
652 | /// Divides one mutable array reference into two at an index. |
653 | /// |
654 | /// The first will contain all indices from `[0, M)` (excluding |
655 | /// the index `M` itself) and the second will contain all |
656 | /// indices from `[M, N)` (excluding the index `N` itself). |
657 | /// |
658 | /// # Panics |
659 | /// |
660 | /// Panics if `M > N`. |
661 | /// |
662 | /// # Examples |
663 | /// |
664 | /// ``` |
665 | /// #![feature(split_array)] |
666 | /// |
667 | /// let mut v = [1, 0, 3, 0, 5, 6]; |
668 | /// let (left, right) = v.split_array_mut::<2>(); |
669 | /// assert_eq!(left, &mut [1, 0][..]); |
670 | /// assert_eq!(right, &mut [3, 0, 5, 6]); |
671 | /// left[1] = 2; |
672 | /// right[1] = 4; |
673 | /// assert_eq!(v, [1, 2, 3, 4, 5, 6]); |
674 | /// ``` |
675 | #[unstable ( |
676 | feature = "split_array" , |
677 | reason = "return type should have array as 2nd element" , |
678 | issue = "90091" |
679 | )] |
680 | #[inline ] |
681 | pub fn split_array_mut<const M: usize>(&mut self) -> (&mut [T; M], &mut [T]) { |
682 | (&mut self[..]).split_first_chunk_mut::<M>().unwrap() |
683 | } |
684 | |
685 | /// Divides one array reference into two at an index from the end. |
686 | /// |
687 | /// The first will contain all indices from `[0, N - M)` (excluding |
688 | /// the index `N - M` itself) and the second will contain all |
689 | /// indices from `[N - M, N)` (excluding the index `N` itself). |
690 | /// |
691 | /// # Panics |
692 | /// |
693 | /// Panics if `M > N`. |
694 | /// |
695 | /// # Examples |
696 | /// |
697 | /// ``` |
698 | /// #![feature(split_array)] |
699 | /// |
700 | /// let v = [1, 2, 3, 4, 5, 6]; |
701 | /// |
702 | /// { |
703 | /// let (left, right) = v.rsplit_array_ref::<0>(); |
704 | /// assert_eq!(left, &[1, 2, 3, 4, 5, 6]); |
705 | /// assert_eq!(right, &[]); |
706 | /// } |
707 | /// |
708 | /// { |
709 | /// let (left, right) = v.rsplit_array_ref::<2>(); |
710 | /// assert_eq!(left, &[1, 2, 3, 4]); |
711 | /// assert_eq!(right, &[5, 6]); |
712 | /// } |
713 | /// |
714 | /// { |
715 | /// let (left, right) = v.rsplit_array_ref::<6>(); |
716 | /// assert_eq!(left, &[]); |
717 | /// assert_eq!(right, &[1, 2, 3, 4, 5, 6]); |
718 | /// } |
719 | /// ``` |
720 | #[unstable ( |
721 | feature = "split_array" , |
722 | reason = "return type should have array as 2nd element" , |
723 | issue = "90091" |
724 | )] |
725 | #[inline ] |
726 | pub fn rsplit_array_ref<const M: usize>(&self) -> (&[T], &[T; M]) { |
727 | (&self[..]).split_last_chunk::<M>().unwrap() |
728 | } |
729 | |
730 | /// Divides one mutable array reference into two at an index from the end. |
731 | /// |
732 | /// The first will contain all indices from `[0, N - M)` (excluding |
733 | /// the index `N - M` itself) and the second will contain all |
734 | /// indices from `[N - M, N)` (excluding the index `N` itself). |
735 | /// |
736 | /// # Panics |
737 | /// |
738 | /// Panics if `M > N`. |
739 | /// |
740 | /// # Examples |
741 | /// |
742 | /// ``` |
743 | /// #![feature(split_array)] |
744 | /// |
745 | /// let mut v = [1, 0, 3, 0, 5, 6]; |
746 | /// let (left, right) = v.rsplit_array_mut::<4>(); |
747 | /// assert_eq!(left, &mut [1, 0]); |
748 | /// assert_eq!(right, &mut [3, 0, 5, 6][..]); |
749 | /// left[1] = 2; |
750 | /// right[1] = 4; |
751 | /// assert_eq!(v, [1, 2, 3, 4, 5, 6]); |
752 | /// ``` |
753 | #[unstable ( |
754 | feature = "split_array" , |
755 | reason = "return type should have array as 2nd element" , |
756 | issue = "90091" |
757 | )] |
758 | #[inline ] |
759 | pub fn rsplit_array_mut<const M: usize>(&mut self) -> (&mut [T], &mut [T; M]) { |
760 | (&mut self[..]).split_last_chunk_mut::<M>().unwrap() |
761 | } |
762 | } |
763 | |
764 | /// Populate an array from the first `N` elements of `iter` |
765 | /// |
766 | /// # Panics |
767 | /// |
768 | /// If the iterator doesn't actually have enough items. |
769 | /// |
770 | /// By depending on `TrustedLen`, however, we can do that check up-front (where |
771 | /// it easily optimizes away) so it doesn't impact the loop that fills the array. |
772 | #[inline ] |
773 | fn from_trusted_iterator<T, const N: usize>(iter: impl UncheckedIterator<Item = T>) -> [T; N] { |
774 | try_from_trusted_iterator(iter:iter.map(NeverShortCircuit)).0 |
775 | } |
776 | |
777 | #[inline ] |
778 | fn try_from_trusted_iterator<T, R, const N: usize>( |
779 | iter: impl UncheckedIterator<Item = R>, |
780 | ) -> ChangeOutputType<R, [T; N]> |
781 | where |
782 | R: Try<Output = T>, |
783 | R::Residual: Residual<[T; N]>, |
784 | { |
785 | assert!(iter.size_hint().0 >= N); |
786 | fn next<T>(mut iter: impl UncheckedIterator<Item = T>) -> impl FnMut(usize) -> T { |
787 | move |_| { |
788 | // SAFETY: We know that `from_fn` will call this at most N times, |
789 | // and we checked to ensure that we have at least that many items. |
790 | unsafe { iter.next_unchecked() } |
791 | } |
792 | } |
793 | |
794 | try_from_fn(cb:next(iter)) |
795 | } |
796 | |
797 | /// Version of [`try_from_fn`] using a passed-in slice in order to avoid |
798 | /// needing to monomorphize for every array length. |
799 | /// |
800 | /// This takes a generator rather than an iterator so that *at the type level* |
801 | /// it never needs to worry about running out of items. When combined with |
802 | /// an infallible `Try` type, that means the loop canonicalizes easily, allowing |
803 | /// it to optimize well. |
804 | /// |
805 | /// It would be *possible* to unify this and [`iter_next_chunk_erased`] into one |
806 | /// function that does the union of both things, but last time it was that way |
807 | /// it resulted in poor codegen from the "are there enough source items?" checks |
808 | /// not optimizing away. So if you give it a shot, make sure to watch what |
809 | /// happens in the codegen tests. |
810 | #[inline ] |
811 | fn try_from_fn_erased<T, R>( |
812 | buffer: &mut [MaybeUninit<T>], |
813 | mut generator: impl FnMut(usize) -> R, |
814 | ) -> ControlFlow<R::Residual> |
815 | where |
816 | R: Try<Output = T>, |
817 | { |
818 | let mut guard: Guard<'_, T> = Guard { array_mut: buffer, initialized: 0 }; |
819 | |
820 | while guard.initialized < guard.array_mut.len() { |
821 | let item: T = generator(guard.initialized).branch()?; |
822 | |
823 | // SAFETY: The loop condition ensures we have space to push the item |
824 | unsafe { guard.push_unchecked(item) }; |
825 | } |
826 | |
827 | mem::forget(guard); |
828 | ControlFlow::Continue(()) |
829 | } |
830 | |
831 | /// Panic guard for incremental initialization of arrays. |
832 | /// |
833 | /// Disarm the guard with `mem::forget` once the array has been initialized. |
834 | /// |
835 | /// # Safety |
836 | /// |
837 | /// All write accesses to this structure are unsafe and must maintain a correct |
838 | /// count of `initialized` elements. |
839 | /// |
840 | /// To minimize indirection fields are still pub but callers should at least use |
841 | /// `push_unchecked` to signal that something unsafe is going on. |
842 | struct Guard<'a, T> { |
843 | /// The array to be initialized. |
844 | pub array_mut: &'a mut [MaybeUninit<T>], |
845 | /// The number of items that have been initialized so far. |
846 | pub initialized: usize, |
847 | } |
848 | |
849 | impl<T> Guard<'_, T> { |
850 | /// Adds an item to the array and updates the initialized item counter. |
851 | /// |
852 | /// # Safety |
853 | /// |
854 | /// No more than N elements must be initialized. |
855 | #[inline ] |
856 | pub unsafe fn push_unchecked(&mut self, item: T) { |
857 | // SAFETY: If `initialized` was correct before and the caller does not |
858 | // invoke this method more than N times then writes will be in-bounds |
859 | // and slots will not be initialized more than once. |
860 | unsafe { |
861 | self.array_mut.get_unchecked_mut(self.initialized).write(val:item); |
862 | self.initialized = self.initialized.unchecked_add(1); |
863 | } |
864 | } |
865 | } |
866 | |
867 | impl<T> Drop for Guard<'_, T> { |
868 | fn drop(&mut self) { |
869 | debug_assert!(self.initialized <= self.array_mut.len()); |
870 | |
871 | // SAFETY: this slice will contain only initialized objects. |
872 | unsafe { |
873 | crate::ptr::drop_in_place(to_drop:MaybeUninit::slice_assume_init_mut( |
874 | self.array_mut.get_unchecked_mut(..self.initialized), |
875 | )); |
876 | } |
877 | } |
878 | } |
879 | |
880 | /// Pulls `N` items from `iter` and returns them as an array. If the iterator |
881 | /// yields fewer than `N` items, `Err` is returned containing an iterator over |
882 | /// the already yielded items. |
883 | /// |
884 | /// Since the iterator is passed as a mutable reference and this function calls |
885 | /// `next` at most `N` times, the iterator can still be used afterwards to |
886 | /// retrieve the remaining items. |
887 | /// |
888 | /// If `iter.next()` panicks, all items already yielded by the iterator are |
889 | /// dropped. |
890 | /// |
891 | /// Used for [`Iterator::next_chunk`]. |
892 | #[inline ] |
893 | pub(crate) fn iter_next_chunk<T, const N: usize>( |
894 | iter: &mut impl Iterator<Item = T>, |
895 | ) -> Result<[T; N], IntoIter<T, N>> { |
896 | let mut array: [MaybeUninit; N] = MaybeUninit::uninit_array::<N>(); |
897 | let r: Result<(), usize> = iter_next_chunk_erased(&mut array, iter); |
898 | match r { |
899 | Ok(()) => { |
900 | // SAFETY: All elements of `array` were populated. |
901 | Ok(unsafe { MaybeUninit::array_assume_init(array) }) |
902 | } |
903 | Err(initialized: usize) => { |
904 | // SAFETY: Only the first `initialized` elements were populated |
905 | Err(unsafe { IntoIter::new_unchecked(buffer:array, initialized:0..initialized) }) |
906 | } |
907 | } |
908 | } |
909 | |
910 | /// Version of [`iter_next_chunk`] using a passed-in slice in order to avoid |
911 | /// needing to monomorphize for every array length. |
912 | /// |
913 | /// Unfortunately this loop has two exit conditions, the buffer filling up |
914 | /// or the iterator running out of items, making it tend to optimize poorly. |
915 | #[inline ] |
916 | fn iter_next_chunk_erased<T>( |
917 | buffer: &mut [MaybeUninit<T>], |
918 | iter: &mut impl Iterator<Item = T>, |
919 | ) -> Result<(), usize> { |
920 | let mut guard: Guard<'_, T> = Guard { array_mut: buffer, initialized: 0 }; |
921 | while guard.initialized < guard.array_mut.len() { |
922 | let Some(item: T) = iter.next() else { |
923 | // Unlike `try_from_fn_erased`, we want to keep the partial results, |
924 | // so we need to defuse the guard instead of using `?`. |
925 | let initialized: usize = guard.initialized; |
926 | mem::forget(guard); |
927 | return Err(initialized); |
928 | }; |
929 | |
930 | // SAFETY: The loop condition ensures we have space to push the item |
931 | unsafe { guard.push_unchecked(item) }; |
932 | } |
933 | |
934 | mem::forget(guard); |
935 | Ok(()) |
936 | } |
937 | |