1 // Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 //! Slice management and manipulation
13 //! For more details `std::slice`.
15 #![stable(feature = "rust1", since = "1.0.0")]
17 // How this module is organized.
19 // The library infrastructure for slices is fairly messy. There's
20 // a lot of stuff defined here. Let's keep it clean.
22 // Since slices don't support inherent methods; all operations
23 // on them are defined on traits, which are then reexported from
24 // the prelude for convenience. So there are a lot of traits here.
26 // The layout of this file is thus:
28 // * Slice-specific 'extension' traits and their implementations. This
29 // is where most of the slice API resides.
30 // * Implementations of a few common traits with important slice ops.
31 // * Definitions of a bunch of iterators.
33 // * The `raw` and `bytes` submodules.
34 // * Boilerplate trait implementations.
37 use cmp::{Ordering, PartialEq, PartialOrd, Eq, Ord};
38 use cmp::Ordering::{Less, Equal, Greater};
41 use intrinsics::assume;
43 use ops::{FnMut, self, Index};
46 use option::Option::{None, Some};
48 use result::Result::{Ok, Err};
51 use marker::{Copy, Send, Sync, self};
53 // Avoid conflicts with *both* the Slice trait (buggy) and the `slice::raw` module.
54 use raw::Slice as RawSlice;
61 /// Extension methods for slices.
62 #[unstable(feature = "core_slice_ext",
63 reason = "stable interface provided by `impl [T]` in later crates",
65 #[allow(missing_docs)] // documented elsewhere
69 #[stable(feature = "core", since = "1.6.0")]
70 fn split_at(&self, mid: usize) -> (&[Self::Item], &[Self::Item]);
71 #[stable(feature = "core", since = "1.6.0")]
72 fn iter(&self) -> Iter<Self::Item>;
73 #[stable(feature = "core", since = "1.6.0")]
74 fn split<P>(&self, pred: P) -> Split<Self::Item, P>
75 where P: FnMut(&Self::Item) -> bool;
76 #[stable(feature = "core", since = "1.6.0")]
77 fn splitn<P>(&self, n: usize, pred: P) -> SplitN<Self::Item, P>
78 where P: FnMut(&Self::Item) -> bool;
79 #[stable(feature = "core", since = "1.6.0")]
80 fn rsplitn<P>(&self, n: usize, pred: P) -> RSplitN<Self::Item, P>
81 where P: FnMut(&Self::Item) -> bool;
82 #[stable(feature = "core", since = "1.6.0")]
83 fn windows(&self, size: usize) -> Windows<Self::Item>;
84 #[stable(feature = "core", since = "1.6.0")]
85 fn chunks(&self, size: usize) -> Chunks<Self::Item>;
86 #[stable(feature = "core", since = "1.6.0")]
87 fn get(&self, index: usize) -> Option<&Self::Item>;
88 #[stable(feature = "core", since = "1.6.0")]
89 fn first(&self) -> Option<&Self::Item>;
90 #[stable(feature = "core", since = "1.6.0")]
91 fn split_first(&self) -> Option<(&Self::Item, &[Self::Item])>;
92 #[stable(feature = "core", since = "1.6.0")]
93 fn split_last(&self) -> Option<(&Self::Item, &[Self::Item])>;
94 #[stable(feature = "core", since = "1.6.0")]
95 fn last(&self) -> Option<&Self::Item>;
96 #[stable(feature = "core", since = "1.6.0")]
97 unsafe fn get_unchecked(&self, index: usize) -> &Self::Item;
98 #[stable(feature = "core", since = "1.6.0")]
99 fn as_ptr(&self) -> *const Self::Item;
100 #[stable(feature = "core", since = "1.6.0")]
101 fn binary_search(&self, x: &Self::Item) -> Result<usize, usize>
102 where Self::Item: Ord;
103 #[stable(feature = "core", since = "1.6.0")]
104 fn binary_search_by<F>(&self, f: F) -> Result<usize, usize>
105 where F: FnMut(&Self::Item) -> Ordering;
106 #[stable(feature = "core", since = "1.6.0")]
107 fn len(&self) -> usize;
108 #[stable(feature = "core", since = "1.6.0")]
109 fn is_empty(&self) -> bool { self.len() == 0 }
110 #[stable(feature = "core", since = "1.6.0")]
111 fn get_mut(&mut self, index: usize) -> Option<&mut Self::Item>;
112 #[stable(feature = "core", since = "1.6.0")]
113 fn iter_mut(&mut self) -> IterMut<Self::Item>;
114 #[stable(feature = "core", since = "1.6.0")]
115 fn first_mut(&mut self) -> Option<&mut Self::Item>;
116 #[stable(feature = "core", since = "1.6.0")]
117 fn split_first_mut(&mut self) -> Option<(&mut Self::Item, &mut [Self::Item])>;
118 #[stable(feature = "core", since = "1.6.0")]
119 fn split_last_mut(&mut self) -> Option<(&mut Self::Item, &mut [Self::Item])>;
120 #[stable(feature = "core", since = "1.6.0")]
121 fn last_mut(&mut self) -> Option<&mut Self::Item>;
122 #[stable(feature = "core", since = "1.6.0")]
123 fn split_mut<P>(&mut self, pred: P) -> SplitMut<Self::Item, P>
124 where P: FnMut(&Self::Item) -> bool;
125 #[stable(feature = "core", since = "1.6.0")]
126 fn splitn_mut<P>(&mut self, n: usize, pred: P) -> SplitNMut<Self::Item, P>
127 where P: FnMut(&Self::Item) -> bool;
128 #[stable(feature = "core", since = "1.6.0")]
129 fn rsplitn_mut<P>(&mut self, n: usize, pred: P) -> RSplitNMut<Self::Item, P>
130 where P: FnMut(&Self::Item) -> bool;
131 #[stable(feature = "core", since = "1.6.0")]
132 fn chunks_mut(&mut self, chunk_size: usize) -> ChunksMut<Self::Item>;
133 #[stable(feature = "core", since = "1.6.0")]
134 fn swap(&mut self, a: usize, b: usize);
135 #[stable(feature = "core", since = "1.6.0")]
136 fn split_at_mut(&mut self, mid: usize) -> (&mut [Self::Item], &mut [Self::Item]);
137 #[stable(feature = "core", since = "1.6.0")]
138 fn reverse(&mut self);
139 #[stable(feature = "core", since = "1.6.0")]
140 unsafe fn get_unchecked_mut(&mut self, index: usize) -> &mut Self::Item;
141 #[stable(feature = "core", since = "1.6.0")]
142 fn as_mut_ptr(&mut self) -> *mut Self::Item;
144 #[stable(feature = "core", since = "1.6.0")]
145 fn contains(&self, x: &Self::Item) -> bool where Self::Item: PartialEq;
147 #[stable(feature = "core", since = "1.6.0")]
148 fn starts_with(&self, needle: &[Self::Item]) -> bool where Self::Item: PartialEq;
150 #[stable(feature = "core", since = "1.6.0")]
151 fn ends_with(&self, needle: &[Self::Item]) -> bool where Self::Item: PartialEq;
153 #[stable(feature = "clone_from_slice", since = "1.7.0")]
154 fn clone_from_slice(&mut self, &[Self::Item]) where Self::Item: Clone;
155 #[unstable(feature = "copy_from_slice", issue = "31755")]
156 fn copy_from_slice(&mut self, src: &[Self::Item]) where Self::Item: Copy;
159 // Use macros to be generic over const/mut
160 macro_rules! slice_offset {
161 ($ptr:expr, $by:expr) => {{
163 if size_from_ptr(ptr) == 0 {
164 ::intrinsics::arith_offset(ptr as *mut i8, $by) as *mut _
171 macro_rules! slice_ref {
174 if size_from_ptr(ptr) == 0 {
175 // Use a non-null pointer value
183 #[unstable(feature = "core_slice_ext",
184 reason = "stable interface provided by `impl [T]` in later crates",
186 impl<T> SliceExt for [T] {
190 fn split_at(&self, mid: usize) -> (&[T], &[T]) {
191 (&self[..mid], &self[mid..])
195 fn iter(&self) -> Iter<T> {
197 let p = if mem::size_of::<T>() == 0 {
200 let p = self.as_ptr();
201 assume(!p.is_null());
207 end: slice_offset!(p, self.len() as isize),
208 _marker: marker::PhantomData
214 fn split<P>(&self, pred: P) -> Split<T, P> where P: FnMut(&T) -> bool {
223 fn splitn<P>(&self, n: usize, pred: P) -> SplitN<T, P> where
224 P: FnMut(&T) -> bool,
227 inner: GenericSplitN {
228 iter: self.split(pred),
236 fn rsplitn<P>(&self, n: usize, pred: P) -> RSplitN<T, P> where
237 P: FnMut(&T) -> bool,
240 inner: GenericSplitN {
241 iter: self.split(pred),
249 fn windows(&self, size: usize) -> Windows<T> {
251 Windows { v: self, size: size }
255 fn chunks(&self, size: usize) -> Chunks<T> {
257 Chunks { v: self, size: size }
261 fn get(&self, index: usize) -> Option<&T> {
262 if index < self.len() { Some(&self[index]) } else { None }
266 fn first(&self) -> Option<&T> {
267 if self.is_empty() { None } else { Some(&self[0]) }
271 fn split_first(&self) -> Option<(&T, &[T])> {
272 if self.is_empty() { None } else { Some((&self[0], &self[1..])) }
276 fn split_last(&self) -> Option<(&T, &[T])> {
277 let len = self.len();
278 if len == 0 { None } else { Some((&self[len - 1], &self[..(len - 1)])) }
282 fn last(&self) -> Option<&T> {
283 if self.is_empty() { None } else { Some(&self[self.len() - 1]) }
287 unsafe fn get_unchecked(&self, index: usize) -> &T {
288 &*(self.as_ptr().offset(index as isize))
292 fn as_ptr(&self) -> *const T {
293 self as *const [T] as *const T
296 fn binary_search_by<F>(&self, mut f: F) -> Result<usize, usize> where
297 F: FnMut(&T) -> Ordering
299 let mut base = 0usize;
303 let (head, tail) = s.split_at(s.len() >> 1);
309 base += head.len() + 1;
313 Equal => return Ok(base + head.len()),
319 fn len(&self) -> usize { self.repr().len }
322 fn get_mut(&mut self, index: usize) -> Option<&mut T> {
323 if index < self.len() { Some(&mut self[index]) } else { None }
327 fn split_at_mut(&mut self, mid: usize) -> (&mut [T], &mut [T]) {
328 let len = self.len();
329 let ptr = self.as_mut_ptr();
334 (from_raw_parts_mut(ptr, mid),
335 from_raw_parts_mut(ptr.offset(mid as isize), len - mid))
340 fn iter_mut(&mut self) -> IterMut<T> {
342 let p = if mem::size_of::<T>() == 0 {
345 let p = self.as_mut_ptr();
346 assume(!p.is_null());
352 end: slice_offset!(p, self.len() as isize),
353 _marker: marker::PhantomData
359 fn last_mut(&mut self) -> Option<&mut T> {
360 let len = self.len();
361 if len == 0 { return None; }
362 Some(&mut self[len - 1])
366 fn first_mut(&mut self) -> Option<&mut T> {
367 if self.is_empty() { None } else { Some(&mut self[0]) }
371 fn split_first_mut(&mut self) -> Option<(&mut T, &mut [T])> {
372 if self.is_empty() { None } else {
373 let split = self.split_at_mut(1);
374 Some((&mut split.0[0], split.1))
379 fn split_last_mut(&mut self) -> Option<(&mut T, &mut [T])> {
380 let len = self.len();
381 if len == 0 { None } else {
382 let split = self.split_at_mut(len - 1);
383 Some((&mut split.1[0], split.0))
388 fn split_mut<P>(&mut self, pred: P) -> SplitMut<T, P> where P: FnMut(&T) -> bool {
389 SplitMut { v: self, pred: pred, finished: false }
393 fn splitn_mut<P>(&mut self, n: usize, pred: P) -> SplitNMut<T, P> where
397 inner: GenericSplitN {
398 iter: self.split_mut(pred),
406 fn rsplitn_mut<P>(&mut self, n: usize, pred: P) -> RSplitNMut<T, P> where
407 P: FnMut(&T) -> bool,
410 inner: GenericSplitN {
411 iter: self.split_mut(pred),
419 fn chunks_mut(&mut self, chunk_size: usize) -> ChunksMut<T> {
420 assert!(chunk_size > 0);
421 ChunksMut { v: self, chunk_size: chunk_size }
425 fn swap(&mut self, a: usize, b: usize) {
427 // Can't take two mutable loans from one vector, so instead just cast
428 // them to their raw pointers to do the swap
429 let pa: *mut T = &mut self[a];
430 let pb: *mut T = &mut self[b];
435 fn reverse(&mut self) {
436 let mut i: usize = 0;
439 // Unsafe swap to avoid the bounds check in safe swap.
441 let pa: *mut T = self.get_unchecked_mut(i);
442 let pb: *mut T = self.get_unchecked_mut(ln - i - 1);
450 unsafe fn get_unchecked_mut(&mut self, index: usize) -> &mut T {
451 &mut *self.as_mut_ptr().offset(index as isize)
455 fn as_mut_ptr(&mut self) -> *mut T {
456 self as *mut [T] as *mut T
460 fn contains(&self, x: &T) -> bool where T: PartialEq {
461 self.iter().any(|elt| *x == *elt)
465 fn starts_with(&self, needle: &[T]) -> bool where T: PartialEq {
466 let n = needle.len();
467 self.len() >= n && needle == &self[..n]
471 fn ends_with(&self, needle: &[T]) -> bool where T: PartialEq {
472 let (m, n) = (self.len(), needle.len());
473 m >= n && needle == &self[m-n..]
476 fn binary_search(&self, x: &T) -> Result<usize, usize> where T: Ord {
477 self.binary_search_by(|p| p.cmp(x))
481 fn clone_from_slice(&mut self, src: &[T]) where T: Clone {
482 assert!(self.len() == src.len(),
483 "destination and source slices have different lengths");
484 // NOTE: We need to explicitly slice them to the same length
485 // for bounds checking to be elided, and the optimizer will
486 // generate memcpy for simple cases (for example T = u8).
487 let len = self.len();
488 let src = &src[..len];
490 self[i].clone_from(&src[i]);
495 fn copy_from_slice(&mut self, src: &[T]) where T: Copy {
496 assert!(self.len() == src.len(),
497 "destination and source slices have different lengths");
499 ptr::copy_nonoverlapping(
500 src.as_ptr(), self.as_mut_ptr(), self.len());
505 #[stable(feature = "rust1", since = "1.0.0")]
506 impl<T> ops::Index<usize> for [T] {
509 fn index(&self, index: usize) -> &T {
510 assert!(index < self.len());
511 unsafe { self.get_unchecked(index) }
515 #[stable(feature = "rust1", since = "1.0.0")]
516 impl<T> ops::IndexMut<usize> for [T] {
518 fn index_mut(&mut self, index: usize) -> &mut T {
519 assert!(index < self.len());
520 unsafe { self.get_unchecked_mut(index) }
526 fn slice_index_len_fail(index: usize, len: usize) -> ! {
527 panic!("index {} out of range for slice of length {}", index, len);
532 fn slice_index_order_fail(index: usize, end: usize) -> ! {
533 panic!("slice index starts at {} but ends at {}", index, end);
536 // FIXME implement indexing with inclusive ranges
538 /// Implements slicing with syntax `&self[begin .. end]`.
540 /// Returns a slice of self for the index range [`begin`..`end`).
542 /// This operation is `O(1)`.
546 /// Requires that `begin <= end` and `end <= self.len()`,
547 /// otherwise slicing will panic.
548 #[stable(feature = "rust1", since = "1.0.0")]
549 impl<T> ops::Index<ops::Range<usize>> for [T] {
553 fn index(&self, index: ops::Range<usize>) -> &[T] {
554 if index.start > index.end {
555 slice_index_order_fail(index.start, index.end);
556 } else if index.end > self.len() {
557 slice_index_len_fail(index.end, self.len());
561 self.as_ptr().offset(index.start as isize),
562 index.end - index.start
568 /// Implements slicing with syntax `&self[.. end]`.
570 /// Returns a slice of self from the beginning until but not including
573 /// Equivalent to `&self[0 .. end]`
574 #[stable(feature = "rust1", since = "1.0.0")]
575 impl<T> ops::Index<ops::RangeTo<usize>> for [T] {
579 fn index(&self, index: ops::RangeTo<usize>) -> &[T] {
580 self.index(0 .. index.end)
584 /// Implements slicing with syntax `&self[begin ..]`.
586 /// Returns a slice of self from and including the index `begin` until the end.
588 /// Equivalent to `&self[begin .. self.len()]`
589 #[stable(feature = "rust1", since = "1.0.0")]
590 impl<T> ops::Index<ops::RangeFrom<usize>> for [T] {
594 fn index(&self, index: ops::RangeFrom<usize>) -> &[T] {
595 self.index(index.start .. self.len())
599 /// Implements slicing with syntax `&self[..]`.
601 /// Returns a slice of the whole slice. This operation can not panic.
603 /// Equivalent to `&self[0 .. self.len()]`
604 #[stable(feature = "rust1", since = "1.0.0")]
605 impl<T> ops::Index<RangeFull> for [T] {
609 fn index(&self, _index: RangeFull) -> &[T] {
614 #[unstable(feature = "inclusive_range", reason = "recently added, follows RFC", issue = "28237")]
615 impl<T> ops::Index<ops::RangeInclusive<usize>> for [T] {
619 fn index(&self, index: ops::RangeInclusive<usize>) -> &[T] {
621 ops::RangeInclusive::Empty { .. } => &[],
622 ops::RangeInclusive::NonEmpty { end, .. } if end == usize::max_value() =>
623 panic!("attempted to index slice up to maximum usize"),
624 ops::RangeInclusive::NonEmpty { start, end } =>
625 self.index(start .. end+1)
629 #[unstable(feature = "inclusive_range", reason = "recently added, follows RFC", issue = "28237")]
630 impl<T> ops::Index<ops::RangeToInclusive<usize>> for [T] {
634 fn index(&self, index: ops::RangeToInclusive<usize>) -> &[T] {
635 // SNAP 4d3eebf change this to `0...index.end`
636 self.index(ops::RangeInclusive::NonEmpty { start: 0, end: index.end })
640 /// Implements mutable slicing with syntax `&mut self[begin .. end]`.
642 /// Returns a slice of self for the index range [`begin`..`end`).
644 /// This operation is `O(1)`.
648 /// Requires that `begin <= end` and `end <= self.len()`,
649 /// otherwise slicing will panic.
650 #[stable(feature = "rust1", since = "1.0.0")]
651 impl<T> ops::IndexMut<ops::Range<usize>> for [T] {
653 fn index_mut(&mut self, index: ops::Range<usize>) -> &mut [T] {
654 if index.start > index.end {
655 slice_index_order_fail(index.start, index.end);
656 } else if index.end > self.len() {
657 slice_index_len_fail(index.end, self.len());
661 self.as_mut_ptr().offset(index.start as isize),
662 index.end - index.start
668 /// Implements mutable slicing with syntax `&mut self[.. end]`.
670 /// Returns a slice of self from the beginning until but not including
673 /// Equivalent to `&mut self[0 .. end]`
674 #[stable(feature = "rust1", since = "1.0.0")]
675 impl<T> ops::IndexMut<ops::RangeTo<usize>> for [T] {
677 fn index_mut(&mut self, index: ops::RangeTo<usize>) -> &mut [T] {
678 self.index_mut(0 .. index.end)
682 /// Implements mutable slicing with syntax `&mut self[begin ..]`.
684 /// Returns a slice of self from and including the index `begin` until the end.
686 /// Equivalent to `&mut self[begin .. self.len()]`
687 #[stable(feature = "rust1", since = "1.0.0")]
688 impl<T> ops::IndexMut<ops::RangeFrom<usize>> for [T] {
690 fn index_mut(&mut self, index: ops::RangeFrom<usize>) -> &mut [T] {
691 let len = self.len();
692 self.index_mut(index.start .. len)
696 /// Implements mutable slicing with syntax `&mut self[..]`.
698 /// Returns a slice of the whole slice. This operation can not panic.
700 /// Equivalent to `&mut self[0 .. self.len()]`
701 #[stable(feature = "rust1", since = "1.0.0")]
702 impl<T> ops::IndexMut<RangeFull> for [T] {
704 fn index_mut(&mut self, _index: RangeFull) -> &mut [T] {
709 #[unstable(feature = "inclusive_range", reason = "recently added, follows RFC", issue = "28237")]
710 impl<T> ops::IndexMut<ops::RangeInclusive<usize>> for [T] {
712 fn index_mut(&mut self, index: ops::RangeInclusive<usize>) -> &mut [T] {
714 ops::RangeInclusive::Empty { .. } => &mut [],
715 ops::RangeInclusive::NonEmpty { end, .. } if end == usize::max_value() =>
716 panic!("attempted to index slice up to maximum usize"),
717 ops::RangeInclusive::NonEmpty { start, end } =>
718 self.index_mut(start .. end+1)
722 #[unstable(feature = "inclusive_range", reason = "recently added, follows RFC", issue = "28237")]
723 impl<T> ops::IndexMut<ops::RangeToInclusive<usize>> for [T] {
725 fn index_mut(&mut self, index: ops::RangeToInclusive<usize>) -> &mut [T] {
726 // SNAP 4d3eebf change this to `0...index.end`
727 self.index_mut(ops::RangeInclusive::NonEmpty { start: 0, end: index.end })
731 ////////////////////////////////////////////////////////////////////////////////
733 ////////////////////////////////////////////////////////////////////////////////
735 #[stable(feature = "rust1", since = "1.0.0")]
736 impl<'a, T> Default for &'a [T] {
737 fn default() -> &'a [T] { &[] }
740 #[stable(feature = "mut_slice_default", since = "1.5.0")]
741 impl<'a, T> Default for &'a mut [T] {
742 fn default() -> &'a mut [T] { &mut [] }
749 #[stable(feature = "rust1", since = "1.0.0")]
750 impl<'a, T> IntoIterator for &'a [T] {
752 type IntoIter = Iter<'a, T>;
754 fn into_iter(self) -> Iter<'a, T> {
759 #[stable(feature = "rust1", since = "1.0.0")]
760 impl<'a, T> IntoIterator for &'a mut [T] {
761 type Item = &'a mut T;
762 type IntoIter = IterMut<'a, T>;
764 fn into_iter(self) -> IterMut<'a, T> {
770 fn size_from_ptr<T>(_: *const T) -> usize {
774 // The shared definition of the `Iter` and `IterMut` iterators
775 macro_rules! iterator {
776 (struct $name:ident -> $ptr:ty, $elem:ty) => {
777 #[stable(feature = "rust1", since = "1.0.0")]
778 impl<'a, T> Iterator for $name<'a, T> {
782 fn next(&mut self) -> Option<$elem> {
783 // could be implemented with slices, but this avoids bounds checks
785 if mem::size_of::<T>() != 0 {
786 assume(!self.ptr.is_null());
787 assume(!self.end.is_null());
789 if self.ptr == self.end {
793 self.ptr = slice_offset!(self.ptr, 1);
794 Some(slice_ref!(old))
800 fn size_hint(&self) -> (usize, Option<usize>) {
801 let diff = (self.end as usize).wrapping_sub(self.ptr as usize);
802 let size = mem::size_of::<T>();
803 let exact = diff / (if size == 0 {1} else {size});
808 fn count(self) -> usize {
813 fn nth(&mut self, n: usize) -> Option<$elem> {
814 // Call helper method. Can't put the definition here because mut versus const.
819 fn last(mut self) -> Option<$elem> {
824 #[stable(feature = "rust1", since = "1.0.0")]
825 impl<'a, T> DoubleEndedIterator for $name<'a, T> {
827 fn next_back(&mut self) -> Option<$elem> {
828 // could be implemented with slices, but this avoids bounds checks
830 if mem::size_of::<T>() != 0 {
831 assume(!self.ptr.is_null());
832 assume(!self.end.is_null());
834 if self.end == self.ptr {
837 self.end = slice_offset!(self.end, -1);
838 Some(slice_ref!(self.end))
846 macro_rules! make_slice {
847 ($start: expr, $end: expr) => {{
849 let diff = ($end as usize).wrapping_sub(start as usize);
850 if size_from_ptr(start) == 0 {
851 // use a non-null pointer value
852 unsafe { from_raw_parts(1 as *const _, diff) }
854 let len = diff / size_from_ptr(start);
855 unsafe { from_raw_parts(start, len) }
860 macro_rules! make_mut_slice {
861 ($start: expr, $end: expr) => {{
863 let diff = ($end as usize).wrapping_sub(start as usize);
864 if size_from_ptr(start) == 0 {
865 // use a non-null pointer value
866 unsafe { from_raw_parts_mut(1 as *mut _, diff) }
868 let len = diff / size_from_ptr(start);
869 unsafe { from_raw_parts_mut(start, len) }
874 /// Immutable slice iterator
875 #[stable(feature = "rust1", since = "1.0.0")]
876 pub struct Iter<'a, T: 'a> {
879 _marker: marker::PhantomData<&'a T>,
882 #[stable(feature = "rust1", since = "1.0.0")]
883 unsafe impl<'a, T: Sync> Sync for Iter<'a, T> {}
884 #[stable(feature = "rust1", since = "1.0.0")]
885 unsafe impl<'a, T: Sync> Send for Iter<'a, T> {}
887 impl<'a, T> Iter<'a, T> {
888 /// View the underlying data as a subslice of the original data.
890 /// This has the same lifetime as the original slice, and so the
891 /// iterator can continue to be used while this exists.
892 #[stable(feature = "iter_to_slice", since = "1.4.0")]
893 pub fn as_slice(&self) -> &'a [T] {
894 make_slice!(self.ptr, self.end)
897 // Helper function for Iter::nth
898 fn iter_nth(&mut self, n: usize) -> Option<&'a T> {
899 match self.as_slice().get(n) {
900 Some(elem_ref) => unsafe {
901 self.ptr = slice_offset!(self.ptr, (n as isize).wrapping_add(1));
912 iterator!{struct Iter -> *const T, &'a T}
914 #[stable(feature = "rust1", since = "1.0.0")]
915 impl<'a, T> ExactSizeIterator for Iter<'a, T> {}
917 #[stable(feature = "rust1", since = "1.0.0")]
918 impl<'a, T> Clone for Iter<'a, T> {
919 fn clone(&self) -> Iter<'a, T> { Iter { ptr: self.ptr, end: self.end, _marker: self._marker } }
922 /// Mutable slice iterator.
923 #[stable(feature = "rust1", since = "1.0.0")]
924 pub struct IterMut<'a, T: 'a> {
927 _marker: marker::PhantomData<&'a mut T>,
930 #[stable(feature = "rust1", since = "1.0.0")]
931 unsafe impl<'a, T: Sync> Sync for IterMut<'a, T> {}
932 #[stable(feature = "rust1", since = "1.0.0")]
933 unsafe impl<'a, T: Send> Send for IterMut<'a, T> {}
935 impl<'a, T> IterMut<'a, T> {
936 /// View the underlying data as a subslice of the original data.
938 /// To avoid creating `&mut` references that alias, this is forced
939 /// to consume the iterator. Consider using the `Slice` and
940 /// `SliceMut` implementations for obtaining slices with more
941 /// restricted lifetimes that do not consume the iterator.
942 #[stable(feature = "iter_to_slice", since = "1.4.0")]
943 pub fn into_slice(self) -> &'a mut [T] {
944 make_mut_slice!(self.ptr, self.end)
947 // Helper function for IterMut::nth
948 fn iter_nth(&mut self, n: usize) -> Option<&'a mut T> {
949 match make_mut_slice!(self.ptr, self.end).get_mut(n) {
950 Some(elem_ref) => unsafe {
951 self.ptr = slice_offset!(self.ptr, (n as isize).wrapping_add(1));
962 iterator!{struct IterMut -> *mut T, &'a mut T}
964 #[stable(feature = "rust1", since = "1.0.0")]
965 impl<'a, T> ExactSizeIterator for IterMut<'a, T> {}
967 /// An internal abstraction over the splitting iterators, so that
968 /// splitn, splitn_mut etc can be implemented once.
970 trait SplitIter: DoubleEndedIterator {
971 /// Mark the underlying iterator as complete, extracting the remaining
972 /// portion of the slice.
973 fn finish(&mut self) -> Option<Self::Item>;
976 /// An iterator over subslices separated by elements that match a predicate
978 #[stable(feature = "rust1", since = "1.0.0")]
979 pub struct Split<'a, T:'a, P> where P: FnMut(&T) -> bool {
985 // FIXME(#19839) Remove in favor of `#[derive(Clone)]`
986 #[stable(feature = "rust1", since = "1.0.0")]
987 impl<'a, T, P> Clone for Split<'a, T, P> where P: Clone + FnMut(&T) -> bool {
988 fn clone(&self) -> Split<'a, T, P> {
991 pred: self.pred.clone(),
992 finished: self.finished,
997 #[stable(feature = "rust1", since = "1.0.0")]
998 impl<'a, T, P> Iterator for Split<'a, T, P> where P: FnMut(&T) -> bool {
1002 fn next(&mut self) -> Option<&'a [T]> {
1003 if self.finished { return None; }
1005 match self.v.iter().position(|x| (self.pred)(x)) {
1006 None => self.finish(),
1008 let ret = Some(&self.v[..idx]);
1009 self.v = &self.v[idx + 1..];
1016 fn size_hint(&self) -> (usize, Option<usize>) {
1020 (1, Some(self.v.len() + 1))
1025 #[stable(feature = "rust1", since = "1.0.0")]
1026 impl<'a, T, P> DoubleEndedIterator for Split<'a, T, P> where P: FnMut(&T) -> bool {
1028 fn next_back(&mut self) -> Option<&'a [T]> {
1029 if self.finished { return None; }
1031 match self.v.iter().rposition(|x| (self.pred)(x)) {
1032 None => self.finish(),
1034 let ret = Some(&self.v[idx + 1..]);
1035 self.v = &self.v[..idx];
1042 impl<'a, T, P> SplitIter for Split<'a, T, P> where P: FnMut(&T) -> bool {
1044 fn finish(&mut self) -> Option<&'a [T]> {
1045 if self.finished { None } else { self.finished = true; Some(self.v) }
1049 /// An iterator over the subslices of the vector which are separated
1050 /// by elements that match `pred`.
1051 #[stable(feature = "rust1", since = "1.0.0")]
1052 pub struct SplitMut<'a, T:'a, P> where P: FnMut(&T) -> bool {
1058 impl<'a, T, P> SplitIter for SplitMut<'a, T, P> where P: FnMut(&T) -> bool {
1060 fn finish(&mut self) -> Option<&'a mut [T]> {
1064 self.finished = true;
1065 Some(mem::replace(&mut self.v, &mut []))
1070 #[stable(feature = "rust1", since = "1.0.0")]
1071 impl<'a, T, P> Iterator for SplitMut<'a, T, P> where P: FnMut(&T) -> bool {
1072 type Item = &'a mut [T];
1075 fn next(&mut self) -> Option<&'a mut [T]> {
1076 if self.finished { return None; }
1078 let idx_opt = { // work around borrowck limitations
1079 let pred = &mut self.pred;
1080 self.v.iter().position(|x| (*pred)(x))
1083 None => self.finish(),
1085 let tmp = mem::replace(&mut self.v, &mut []);
1086 let (head, tail) = tmp.split_at_mut(idx);
1087 self.v = &mut tail[1..];
1094 fn size_hint(&self) -> (usize, Option<usize>) {
1098 // if the predicate doesn't match anything, we yield one slice
1099 // if it matches every element, we yield len+1 empty slices.
1100 (1, Some(self.v.len() + 1))
1105 #[stable(feature = "rust1", since = "1.0.0")]
1106 impl<'a, T, P> DoubleEndedIterator for SplitMut<'a, T, P> where
1107 P: FnMut(&T) -> bool,
1110 fn next_back(&mut self) -> Option<&'a mut [T]> {
1111 if self.finished { return None; }
1113 let idx_opt = { // work around borrowck limitations
1114 let pred = &mut self.pred;
1115 self.v.iter().rposition(|x| (*pred)(x))
1118 None => self.finish(),
1120 let tmp = mem::replace(&mut self.v, &mut []);
1121 let (head, tail) = tmp.split_at_mut(idx);
1123 Some(&mut tail[1..])
1129 /// An private iterator over subslices separated by elements that
1130 /// match a predicate function, splitting at most a fixed number of
1132 struct GenericSplitN<I> {
1138 impl<T, I: SplitIter<Item=T>> Iterator for GenericSplitN<I> {
1142 fn next(&mut self) -> Option<T> {
1145 1 => { self.count -= 1; self.iter.finish() }
1148 if self.invert {self.iter.next_back()} else {self.iter.next()}
1154 fn size_hint(&self) -> (usize, Option<usize>) {
1155 let (lower, upper_opt) = self.iter.size_hint();
1156 (lower, upper_opt.map(|upper| cmp::min(self.count, upper)))
1160 /// An iterator over subslices separated by elements that match a predicate
1161 /// function, limited to a given number of splits.
1162 #[stable(feature = "rust1", since = "1.0.0")]
1163 pub struct SplitN<'a, T: 'a, P> where P: FnMut(&T) -> bool {
1164 inner: GenericSplitN<Split<'a, T, P>>
1167 /// An iterator over subslices separated by elements that match a
1168 /// predicate function, limited to a given number of splits, starting
1169 /// from the end of the slice.
1170 #[stable(feature = "rust1", since = "1.0.0")]
1171 pub struct RSplitN<'a, T: 'a, P> where P: FnMut(&T) -> bool {
1172 inner: GenericSplitN<Split<'a, T, P>>
1175 /// An iterator over subslices separated by elements that match a predicate
1176 /// function, limited to a given number of splits.
1177 #[stable(feature = "rust1", since = "1.0.0")]
1178 pub struct SplitNMut<'a, T: 'a, P> where P: FnMut(&T) -> bool {
1179 inner: GenericSplitN<SplitMut<'a, T, P>>
1182 /// An iterator over subslices separated by elements that match a
1183 /// predicate function, limited to a given number of splits, starting
1184 /// from the end of the slice.
1185 #[stable(feature = "rust1", since = "1.0.0")]
1186 pub struct RSplitNMut<'a, T: 'a, P> where P: FnMut(&T) -> bool {
1187 inner: GenericSplitN<SplitMut<'a, T, P>>
1190 macro_rules! forward_iterator {
1191 ($name:ident: $elem:ident, $iter_of:ty) => {
1192 #[stable(feature = "rust1", since = "1.0.0")]
1193 impl<'a, $elem, P> Iterator for $name<'a, $elem, P> where
1194 P: FnMut(&T) -> bool
1196 type Item = $iter_of;
1199 fn next(&mut self) -> Option<$iter_of> {
1204 fn size_hint(&self) -> (usize, Option<usize>) {
1205 self.inner.size_hint()
1211 forward_iterator! { SplitN: T, &'a [T] }
1212 forward_iterator! { RSplitN: T, &'a [T] }
1213 forward_iterator! { SplitNMut: T, &'a mut [T] }
1214 forward_iterator! { RSplitNMut: T, &'a mut [T] }
1216 /// An iterator over overlapping subslices of length `size`.
1217 #[stable(feature = "rust1", since = "1.0.0")]
1218 pub struct Windows<'a, T:'a> {
1223 // FIXME(#19839) Remove in favor of `#[derive(Clone)]`
1224 #[stable(feature = "rust1", since = "1.0.0")]
1225 impl<'a, T> Clone for Windows<'a, T> {
1226 fn clone(&self) -> Windows<'a, T> {
1234 #[stable(feature = "rust1", since = "1.0.0")]
1235 impl<'a, T> Iterator for Windows<'a, T> {
1236 type Item = &'a [T];
1239 fn next(&mut self) -> Option<&'a [T]> {
1240 if self.size > self.v.len() {
1243 let ret = Some(&self.v[..self.size]);
1244 self.v = &self.v[1..];
1250 fn size_hint(&self) -> (usize, Option<usize>) {
1251 if self.size > self.v.len() {
1254 let size = self.v.len() - self.size + 1;
1260 fn count(self) -> usize {
1265 fn nth(&mut self, n: usize) -> Option<Self::Item> {
1266 let (end, overflow) = self.size.overflowing_add(n);
1267 if end > self.v.len() || overflow {
1271 let nth = &self.v[n..end];
1272 self.v = &self.v[n+1..];
1278 fn last(self) -> Option<Self::Item> {
1279 if self.size > self.v.len() {
1282 let start = self.v.len() - self.size;
1283 Some(&self.v[start..])
1288 #[stable(feature = "rust1", since = "1.0.0")]
1289 impl<'a, T> DoubleEndedIterator for Windows<'a, T> {
1291 fn next_back(&mut self) -> Option<&'a [T]> {
1292 if self.size > self.v.len() {
1295 let ret = Some(&self.v[self.v.len()-self.size..]);
1296 self.v = &self.v[..self.v.len()-1];
1302 #[stable(feature = "rust1", since = "1.0.0")]
1303 impl<'a, T> ExactSizeIterator for Windows<'a, T> {}
1305 /// An iterator over a slice in (non-overlapping) chunks (`size` elements at a
1308 /// When the slice len is not evenly divided by the chunk size, the last slice
1309 /// of the iteration will be the remainder.
1310 #[stable(feature = "rust1", since = "1.0.0")]
1311 pub struct Chunks<'a, T:'a> {
1316 // FIXME(#19839) Remove in favor of `#[derive(Clone)]`
1317 #[stable(feature = "rust1", since = "1.0.0")]
1318 impl<'a, T> Clone for Chunks<'a, T> {
1319 fn clone(&self) -> Chunks<'a, T> {
1327 #[stable(feature = "rust1", since = "1.0.0")]
1328 impl<'a, T> Iterator for Chunks<'a, T> {
1329 type Item = &'a [T];
1332 fn next(&mut self) -> Option<&'a [T]> {
1333 if self.v.is_empty() {
1336 let chunksz = cmp::min(self.v.len(), self.size);
1337 let (fst, snd) = self.v.split_at(chunksz);
1344 fn size_hint(&self) -> (usize, Option<usize>) {
1345 if self.v.is_empty() {
1348 let n = self.v.len() / self.size;
1349 let rem = self.v.len() % self.size;
1350 let n = if rem > 0 { n+1 } else { n };
1356 fn count(self) -> usize {
1361 fn nth(&mut self, n: usize) -> Option<Self::Item> {
1362 let (start, overflow) = n.overflowing_mul(self.size);
1363 if start >= self.v.len() || overflow {
1367 let end = match start.checked_add(self.size) {
1368 Some(sum) => cmp::min(self.v.len(), sum),
1369 None => self.v.len(),
1371 let nth = &self.v[start..end];
1372 self.v = &self.v[end..];
1378 fn last(self) -> Option<Self::Item> {
1379 if self.v.is_empty() {
1382 let start = (self.v.len() - 1) / self.size * self.size;
1383 Some(&self.v[start..])
1388 #[stable(feature = "rust1", since = "1.0.0")]
1389 impl<'a, T> DoubleEndedIterator for Chunks<'a, T> {
1391 fn next_back(&mut self) -> Option<&'a [T]> {
1392 if self.v.is_empty() {
1395 let remainder = self.v.len() % self.size;
1396 let chunksz = if remainder != 0 { remainder } else { self.size };
1397 let (fst, snd) = self.v.split_at(self.v.len() - chunksz);
1404 #[stable(feature = "rust1", since = "1.0.0")]
1405 impl<'a, T> ExactSizeIterator for Chunks<'a, T> {}
1407 /// An iterator over a slice in (non-overlapping) mutable chunks (`size`
1408 /// elements at a time). When the slice len is not evenly divided by the chunk
1409 /// size, the last slice of the iteration will be the remainder.
1410 #[stable(feature = "rust1", since = "1.0.0")]
1411 pub struct ChunksMut<'a, T:'a> {
1416 #[stable(feature = "rust1", since = "1.0.0")]
1417 impl<'a, T> Iterator for ChunksMut<'a, T> {
1418 type Item = &'a mut [T];
1421 fn next(&mut self) -> Option<&'a mut [T]> {
1422 if self.v.is_empty() {
1425 let sz = cmp::min(self.v.len(), self.chunk_size);
1426 let tmp = mem::replace(&mut self.v, &mut []);
1427 let (head, tail) = tmp.split_at_mut(sz);
1434 fn size_hint(&self) -> (usize, Option<usize>) {
1435 if self.v.is_empty() {
1438 let n = self.v.len() / self.chunk_size;
1439 let rem = self.v.len() % self.chunk_size;
1440 let n = if rem > 0 { n + 1 } else { n };
1446 fn count(self) -> usize {
1451 fn nth(&mut self, n: usize) -> Option<&'a mut [T]> {
1452 let (start, overflow) = n.overflowing_mul(self.chunk_size);
1453 if start >= self.v.len() || overflow {
1457 let end = match start.checked_add(self.chunk_size) {
1458 Some(sum) => cmp::min(self.v.len(), sum),
1459 None => self.v.len(),
1461 let tmp = mem::replace(&mut self.v, &mut []);
1462 let (head, tail) = tmp.split_at_mut(end);
1463 let (_, nth) = head.split_at_mut(start);
1470 fn last(self) -> Option<Self::Item> {
1471 if self.v.is_empty() {
1474 let start = (self.v.len() - 1) / self.chunk_size * self.chunk_size;
1475 Some(&mut self.v[start..])
1480 #[stable(feature = "rust1", since = "1.0.0")]
1481 impl<'a, T> DoubleEndedIterator for ChunksMut<'a, T> {
1483 fn next_back(&mut self) -> Option<&'a mut [T]> {
1484 if self.v.is_empty() {
1487 let remainder = self.v.len() % self.chunk_size;
1488 let sz = if remainder != 0 { remainder } else { self.chunk_size };
1489 let tmp = mem::replace(&mut self.v, &mut []);
1490 let tmp_len = tmp.len();
1491 let (head, tail) = tmp.split_at_mut(tmp_len - sz);
1498 #[stable(feature = "rust1", since = "1.0.0")]
1499 impl<'a, T> ExactSizeIterator for ChunksMut<'a, T> {}
1505 /// Forms a slice from a pointer and a length.
1507 /// The `len` argument is the number of **elements**, not the number of bytes.
1511 /// This function is unsafe as there is no guarantee that the given pointer is
1512 /// valid for `len` elements, nor whether the lifetime inferred is a suitable
1513 /// lifetime for the returned slice.
1515 /// `p` must be non-null, even for zero-length slices.
1519 /// The lifetime for the returned slice is inferred from its usage. To
1520 /// prevent accidental misuse, it's suggested to tie the lifetime to whichever
1521 /// source lifetime is safe in the context, such as by providing a helper
1522 /// function taking the lifetime of a host value for the slice, or by explicit
1530 /// // manifest a slice out of thin air!
1531 /// let ptr = 0x1234 as *const usize;
1534 /// let slice = slice::from_raw_parts(ptr, amt);
1538 #[stable(feature = "rust1", since = "1.0.0")]
1539 pub unsafe fn from_raw_parts<'a, T>(p: *const T, len: usize) -> &'a [T] {
1540 mem::transmute(RawSlice { data: p, len: len })
1543 /// Performs the same functionality as `from_raw_parts`, except that a mutable
1544 /// slice is returned.
1546 /// This function is unsafe for the same reasons as `from_raw_parts`, as well
1547 /// as not being able to provide a non-aliasing guarantee of the returned
1550 #[stable(feature = "rust1", since = "1.0.0")]
1551 pub unsafe fn from_raw_parts_mut<'a, T>(p: *mut T, len: usize) -> &'a mut [T] {
1552 mem::transmute(RawSlice { data: p, len: len })
1559 /// Operations on `[u8]`.
1560 #[unstable(feature = "slice_bytes", reason = "needs review",
1562 #[rustc_deprecated(reason = "unidiomatic functions not pulling their weight",
1564 #[allow(deprecated)]
1567 use slice::SliceExt;
1569 /// A trait for operations on mutable `[u8]`s.
1570 pub trait MutableByteVector {
1571 /// Sets all bytes of the receiver to the given value.
1572 fn set_memory(&mut self, value: u8);
1575 impl MutableByteVector for [u8] {
1577 fn set_memory(&mut self, value: u8) {
1578 unsafe { ptr::write_bytes(self.as_mut_ptr(), value, self.len()) };
1582 /// Copies data from `src` to `dst`
1584 /// Panics if the length of `dst` is less than the length of `src`.
1586 pub fn copy_memory(src: &[u8], dst: &mut [u8]) {
1587 let len_src = src.len();
1588 assert!(dst.len() >= len_src);
1589 // `dst` is unaliasable, so we know statically it doesn't overlap
1592 ptr::copy_nonoverlapping(src.as_ptr(),
1602 // Boilerplate traits
1605 #[stable(feature = "rust1", since = "1.0.0")]
1606 impl<A, B> PartialEq<[B]> for [A] where A: PartialEq<B> {
1607 fn eq(&self, other: &[B]) -> bool {
1608 if self.len() != other.len() {
1612 for i in 0..self.len() {
1613 if !self[i].eq(&other[i]) {
1620 fn ne(&self, other: &[B]) -> bool {
1621 if self.len() != other.len() {
1625 for i in 0..self.len() {
1626 if self[i].ne(&other[i]) {
1635 #[stable(feature = "rust1", since = "1.0.0")]
1636 impl<T: Eq> Eq for [T] {}
1638 #[stable(feature = "rust1", since = "1.0.0")]
1639 impl<T: Ord> Ord for [T] {
1640 fn cmp(&self, other: &[T]) -> Ordering {
1641 let l = cmp::min(self.len(), other.len());
1643 // Slice to the loop iteration range to enable bound check
1644 // elimination in the compiler
1645 let lhs = &self[..l];
1646 let rhs = &other[..l];
1649 match lhs[i].cmp(&rhs[i]) {
1650 Ordering::Equal => (),
1651 non_eq => return non_eq,
1655 self.len().cmp(&other.len())
1659 #[stable(feature = "rust1", since = "1.0.0")]
1660 impl<T: PartialOrd> PartialOrd for [T] {
1661 fn partial_cmp(&self, other: &[T]) -> Option<Ordering> {
1662 let l = cmp::min(self.len(), other.len());
1664 // Slice to the loop iteration range to enable bound check
1665 // elimination in the compiler
1666 let lhs = &self[..l];
1667 let rhs = &other[..l];
1670 match lhs[i].partial_cmp(&rhs[i]) {
1671 Some(Ordering::Equal) => (),
1672 non_eq => return non_eq,
1676 self.len().partial_cmp(&other.len())