1 #[cfg(not(no_global_oom_handling))]
2 use super::AsVecIntoIter;
3 use crate::alloc::{Allocator, Global};
4 #[cfg(not(no_global_oom_handling))]
5 use crate::collections::VecDeque;
6 use crate::raw_vec::RawVec;
10 FusedIterator, InPlaceIterable, SourceIter, TrustedLen, TrustedRandomAccessNoCoerce,
12 use core::marker::PhantomData;
13 use core::mem::{self, ManuallyDrop, MaybeUninit, SizedTypeProperties};
14 #[cfg(not(no_global_oom_handling))]
16 use core::ptr::{self, NonNull};
17 use core::slice::{self};
19 /// An iterator that moves out of a vector.
21 /// This `struct` is created by the `into_iter` method on [`Vec`](super::Vec)
22 /// (provided by the [`IntoIterator`] trait).
27 /// let v = vec![0, 1, 2];
28 /// let iter: std::vec::IntoIter<_> = v.into_iter();
30 #[stable(feature = "rust1", since = "1.0.0")]
31 #[rustc_insignificant_dtor]
34 #[unstable(feature = "allocator_api", issue = "32838")] A: Allocator = Global,
36 pub(super) buf: NonNull<T>,
37 pub(super) phantom: PhantomData<T>,
38 pub(super) cap: usize,
39 // the drop impl reconstructs a RawVec from buf, cap and alloc
40 // to avoid dropping the allocator twice we need to wrap it into ManuallyDrop
41 pub(super) alloc: ManuallyDrop<A>,
42 pub(super) ptr: *const T,
43 pub(super) end: *const T, // If T is a ZST, this is actually ptr+len. This encoding is picked so that
44 // ptr == end is a quick test for the Iterator being empty, that works
45 // for both ZST and non-ZST.
48 #[stable(feature = "vec_intoiter_debug", since = "1.13.0")]
49 impl<T: fmt::Debug, A: Allocator> fmt::Debug for IntoIter<T, A> {
50 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
51 f.debug_tuple("IntoIter").field(&self.as_slice()).finish()
55 impl<T, A: Allocator> IntoIter<T, A> {
56 /// Returns the remaining items of this iterator as a slice.
61 /// let vec = vec!['a', 'b', 'c'];
62 /// let mut into_iter = vec.into_iter();
63 /// assert_eq!(into_iter.as_slice(), &['a', 'b', 'c']);
64 /// let _ = into_iter.next().unwrap();
65 /// assert_eq!(into_iter.as_slice(), &['b', 'c']);
67 #[stable(feature = "vec_into_iter_as_slice", since = "1.15.0")]
68 pub fn as_slice(&self) -> &[T] {
69 unsafe { slice::from_raw_parts(self.ptr, self.len()) }
72 /// Returns the remaining items of this iterator as a mutable slice.
77 /// let vec = vec!['a', 'b', 'c'];
78 /// let mut into_iter = vec.into_iter();
79 /// assert_eq!(into_iter.as_slice(), &['a', 'b', 'c']);
80 /// into_iter.as_mut_slice()[2] = 'z';
81 /// assert_eq!(into_iter.next().unwrap(), 'a');
82 /// assert_eq!(into_iter.next().unwrap(), 'b');
83 /// assert_eq!(into_iter.next().unwrap(), 'z');
85 #[stable(feature = "vec_into_iter_as_slice", since = "1.15.0")]
86 pub fn as_mut_slice(&mut self) -> &mut [T] {
87 unsafe { &mut *self.as_raw_mut_slice() }
90 /// Returns a reference to the underlying allocator.
91 #[unstable(feature = "allocator_api", issue = "32838")]
93 pub fn allocator(&self) -> &A {
97 fn as_raw_mut_slice(&mut self) -> *mut [T] {
98 ptr::slice_from_raw_parts_mut(self.ptr as *mut T, self.len())
101 /// Drops remaining elements and relinquishes the backing allocation.
102 /// This method guarantees it won't panic before relinquishing
103 /// the backing allocation.
105 /// This is roughly equivalent to the following, but more efficient
108 /// # let mut into_iter = Vec::<u8>::with_capacity(10).into_iter();
109 /// let mut into_iter = std::mem::replace(&mut into_iter, Vec::new().into_iter());
110 /// (&mut into_iter).for_each(core::mem::drop);
111 /// std::mem::forget(into_iter);
114 /// This method is used by in-place iteration, refer to the vec::in_place_collect
115 /// documentation for an overview.
116 #[cfg(not(no_global_oom_handling))]
117 pub(super) fn forget_allocation_drop_remaining(&mut self) {
118 let remaining = self.as_raw_mut_slice();
120 // overwrite the individual fields instead of creating a new
121 // struct and then overwriting &mut self.
122 // this creates less assembly
124 self.buf = unsafe { NonNull::new_unchecked(RawVec::NEW.ptr()) };
125 self.ptr = self.buf.as_ptr();
126 self.end = self.buf.as_ptr();
128 // Dropping the remaining elements can panic, so this needs to be
129 // done only after updating the other fields.
131 ptr::drop_in_place(remaining);
135 /// Forgets to Drop the remaining elements while still allowing the backing allocation to be freed.
136 pub(crate) fn forget_remaining_elements(&mut self) {
137 // For th ZST case, it is crucial that we mutate `end` here, not `ptr`.
138 // `ptr` must stay aligned, while `end` may be unaligned.
142 #[cfg(not(no_global_oom_handling))]
144 pub(crate) fn into_vecdeque(self) -> VecDeque<T, A> {
145 // Keep our `Drop` impl from dropping the elements and the allocator
146 let mut this = ManuallyDrop::new(self);
148 // SAFETY: This allocation originally came from a `Vec`, so it passes
149 // all those checks. We have `this.buf` ≤ `this.ptr` ≤ `this.end`,
150 // so the `sub_ptr`s below cannot wrap, and will produce a well-formed
151 // range. `end` ≤ `buf + cap`, so the range will be in-bounds.
152 // Taking `alloc` is ok because nothing else is going to look at it,
153 // since our `Drop` impl isn't going to run so there's no more code.
155 let buf = this.buf.as_ptr();
156 let initialized = if T::IS_ZST {
157 // All the pointers are the same for ZSTs, so it's fine to
158 // say that they're all at the beginning of the "allocation".
161 this.ptr.sub_ptr(buf)..this.end.sub_ptr(buf)
164 let alloc = ManuallyDrop::take(&mut this.alloc);
165 VecDeque::from_contiguous_raw_parts_in(buf, initialized, cap, alloc)
170 #[stable(feature = "vec_intoiter_as_ref", since = "1.46.0")]
171 impl<T, A: Allocator> AsRef<[T]> for IntoIter<T, A> {
172 fn as_ref(&self) -> &[T] {
177 #[stable(feature = "rust1", since = "1.0.0")]
178 unsafe impl<T: Send, A: Allocator + Send> Send for IntoIter<T, A> {}
179 #[stable(feature = "rust1", since = "1.0.0")]
180 unsafe impl<T: Sync, A: Allocator + Sync> Sync for IntoIter<T, A> {}
182 #[stable(feature = "rust1", since = "1.0.0")]
183 impl<T, A: Allocator> Iterator for IntoIter<T, A> {
187 fn next(&mut self) -> Option<T> {
188 if self.ptr == self.end {
190 } else if T::IS_ZST {
191 // `ptr` has to stay where it is to remain aligned, so we reduce the length by 1 by
192 // reducing the `end`.
193 self.end = self.end.wrapping_byte_sub(1);
195 // Make up a value of this ZST.
196 Some(unsafe { mem::zeroed() })
199 self.ptr = unsafe { self.ptr.add(1) };
201 Some(unsafe { ptr::read(old) })
206 fn size_hint(&self) -> (usize, Option<usize>) {
207 let exact = if T::IS_ZST {
208 self.end.addr().wrapping_sub(self.ptr.addr())
210 unsafe { self.end.sub_ptr(self.ptr) }
216 fn advance_by(&mut self, n: usize) -> Result<(), usize> {
217 let step_size = self.len().min(n);
218 let to_drop = ptr::slice_from_raw_parts_mut(self.ptr as *mut T, step_size);
220 // See `next` for why we sub `end` here.
221 self.end = self.end.wrapping_byte_sub(step_size);
223 // SAFETY: the min() above ensures that step_size is in bounds
224 self.ptr = unsafe { self.ptr.add(step_size) };
226 // SAFETY: the min() above ensures that step_size is in bounds
228 ptr::drop_in_place(to_drop);
231 return Err(step_size);
237 fn count(self) -> usize {
242 fn next_chunk<const N: usize>(&mut self) -> Result<[T; N], core::array::IntoIter<T, N>> {
243 let mut raw_ary = MaybeUninit::uninit_array();
245 let len = self.len();
249 self.forget_remaining_elements();
250 // Safety: ZSTs can be conjured ex nihilo, only the amount has to be correct
251 return Err(unsafe { array::IntoIter::new_unchecked(raw_ary, 0..len) });
254 self.end = self.end.wrapping_byte_sub(N);
256 return Ok(unsafe { raw_ary.transpose().assume_init() });
260 // Safety: `len` indicates that this many elements are available and we just checked that
261 // it fits into the array.
263 ptr::copy_nonoverlapping(self.ptr, raw_ary.as_mut_ptr() as *mut T, len);
264 self.forget_remaining_elements();
265 return Err(array::IntoIter::new_unchecked(raw_ary, 0..len));
269 // Safety: `len` is larger than the array size. Copy a fixed amount here to fully initialize
272 ptr::copy_nonoverlapping(self.ptr, raw_ary.as_mut_ptr() as *mut T, N);
273 self.ptr = self.ptr.add(N);
274 Ok(raw_ary.transpose().assume_init())
278 unsafe fn __iterator_get_unchecked(&mut self, i: usize) -> Self::Item
280 Self: TrustedRandomAccessNoCoerce,
282 // SAFETY: the caller must guarantee that `i` is in bounds of the
283 // `Vec<T>`, so `i` cannot overflow an `isize`, and the `self.ptr.add(i)`
284 // is guaranteed to pointer to an element of the `Vec<T>` and
285 // thus guaranteed to be valid to dereference.
287 // Also note the implementation of `Self: TrustedRandomAccess` requires
288 // that `T: Copy` so reading elements from the buffer doesn't invalidate
291 if T::IS_ZST { mem::zeroed() } else { ptr::read(self.ptr.add(i)) }
296 #[stable(feature = "rust1", since = "1.0.0")]
297 impl<T, A: Allocator> DoubleEndedIterator for IntoIter<T, A> {
299 fn next_back(&mut self) -> Option<T> {
300 if self.end == self.ptr {
302 } else if T::IS_ZST {
303 // See above for why 'ptr.offset' isn't used
304 self.end = self.end.wrapping_byte_sub(1);
306 // Make up a value of this ZST.
307 Some(unsafe { mem::zeroed() })
309 self.end = unsafe { self.end.sub(1) };
311 Some(unsafe { ptr::read(self.end) })
316 fn advance_back_by(&mut self, n: usize) -> Result<(), usize> {
317 let step_size = self.len().min(n);
319 // SAFETY: same as for advance_by()
320 self.end = self.end.wrapping_byte_sub(step_size);
322 // SAFETY: same as for advance_by()
323 self.end = unsafe { self.end.sub(step_size) };
325 let to_drop = ptr::slice_from_raw_parts_mut(self.end as *mut T, step_size);
326 // SAFETY: same as for advance_by()
328 ptr::drop_in_place(to_drop);
331 return Err(step_size);
337 #[stable(feature = "rust1", since = "1.0.0")]
338 impl<T, A: Allocator> ExactSizeIterator for IntoIter<T, A> {
339 fn is_empty(&self) -> bool {
344 #[stable(feature = "fused", since = "1.26.0")]
345 impl<T, A: Allocator> FusedIterator for IntoIter<T, A> {}
347 #[unstable(feature = "trusted_len", issue = "37572")]
348 unsafe impl<T, A: Allocator> TrustedLen for IntoIter<T, A> {}
351 #[unstable(issue = "none", feature = "std_internals")]
352 #[rustc_unsafe_specialization_marker]
355 // T: Copy as approximation for !Drop since get_unchecked does not advance self.ptr
356 // and thus we can't implement drop-handling
357 #[unstable(issue = "none", feature = "std_internals")]
358 impl<T: Copy> NonDrop for T {}
361 #[unstable(issue = "none", feature = "std_internals")]
362 // TrustedRandomAccess (without NoCoerce) must not be implemented because
363 // subtypes/supertypes of `T` might not be `NonDrop`
364 unsafe impl<T, A: Allocator> TrustedRandomAccessNoCoerce for IntoIter<T, A>
368 const MAY_HAVE_SIDE_EFFECT: bool = false;
371 #[cfg(not(no_global_oom_handling))]
372 #[stable(feature = "vec_into_iter_clone", since = "1.8.0")]
373 impl<T: Clone, A: Allocator + Clone> Clone for IntoIter<T, A> {
375 fn clone(&self) -> Self {
376 self.as_slice().to_vec_in(self.alloc.deref().clone()).into_iter()
379 fn clone(&self) -> Self {
380 crate::slice::to_vec(self.as_slice(), self.alloc.deref().clone()).into_iter()
384 #[stable(feature = "rust1", since = "1.0.0")]
385 unsafe impl<#[may_dangle] T, A: Allocator> Drop for IntoIter<T, A> {
387 struct DropGuard<'a, T, A: Allocator>(&'a mut IntoIter<T, A>);
389 impl<T, A: Allocator> Drop for DropGuard<'_, T, A> {
392 // `IntoIter::alloc` is not used anymore after this and will be dropped by RawVec
393 let alloc = ManuallyDrop::take(&mut self.0.alloc);
394 // RawVec handles deallocation
395 let _ = RawVec::from_raw_parts_in(self.0.buf.as_ptr(), self.0.cap, alloc);
400 let guard = DropGuard(self);
401 // destroy the remaining elements
403 ptr::drop_in_place(guard.0.as_raw_mut_slice());
405 // now `guard` will be dropped and do the rest
409 // In addition to the SAFETY invariants of the following three unsafe traits
410 // also refer to the vec::in_place_collect module documentation to get an overview
411 #[unstable(issue = "none", feature = "inplace_iteration")]
413 unsafe impl<T, A: Allocator> InPlaceIterable for IntoIter<T, A> {}
415 #[unstable(issue = "none", feature = "inplace_iteration")]
417 unsafe impl<T, A: Allocator> SourceIter for IntoIter<T, A> {
421 unsafe fn as_inner(&mut self) -> &mut Self::Source {
426 #[cfg(not(no_global_oom_handling))]
427 unsafe impl<T> AsVecIntoIter for IntoIter<T> {
430 fn as_into_iter(&mut self) -> &mut IntoIter<Self::Item> {