// SPDX-License-Identifier: Apache-2.0 OR MIT
#[cfg(not(no_global_oom_handling))]
use super::AsVecIntoIter;
use crate::alloc::{Allocator, Global};
#[cfg(not(no_global_oom_handling))]
use crate::collections::VecDeque;
use crate::raw_vec::RawVec;
use core::array;
use core::fmt;
use core::iter::{
FusedIterator, InPlaceIterable, SourceIter, TrustedLen, TrustedRandomAccessNoCoerce,
};
use core::marker::PhantomData;
use core::mem::{self, ManuallyDrop, MaybeUninit, SizedTypeProperties};
use core::num::NonZeroUsize;
#[cfg(not(no_global_oom_handling))]
use core::ops::Deref;
use core::ptr::{self, NonNull};
use core::slice::{self};
/// An iterator that moves out of a vector.
///
/// This `struct` is created by the `into_iter` method on [`Vec`](super::Vec)
/// (provided by the [`IntoIterator`] trait).
///
/// # Example
///
/// ```
/// let v = vec![0, 1, 2];
/// let iter: std::vec::IntoIter<_> = v.into_iter();
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[rustc_insignificant_dtor]
pub struct IntoIter<
T,
#[unstable(feature = "allocator_api", issue = "32838")] A: Allocator = Global,
> {
pub(super) buf: NonNull<T>,
pub(super) phantom: PhantomData<T>,
pub(super) cap: usize,
// the drop impl reconstructs a RawVec from buf, cap and alloc
// to avoid dropping the allocator twice we need to wrap it into ManuallyDrop
pub(super) alloc: ManuallyDrop<A>,
pub(super) ptr: *const T,
pub(super) end: *const T, // If T is a ZST, this is actually ptr+len. This encoding is picked so that
// ptr == end is a quick test for the Iterator being empty, that works
// for both ZST and non-ZST.
}
#[stable(feature = "vec_intoiter_debug", since = "1.13.0")]
impl<T: fmt::Debug, A: Allocator> fmt::Debug for IntoIter<T, A> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_tuple("IntoIter").field(&self.as_slice()).finish()
}
}
impl<T, A: Allocator> IntoIter<T, A> {
/// Returns the remaining items of this iterator as a slice.
///
/// # Examples
///
/// ```
/// let vec = vec!['a', 'b', 'c'];
/// let mut into_iter = vec.into_iter();
/// assert_eq!(into_iter.as_slice(), &['a', 'b', 'c']);
/// let _ = into_iter.next().unwrap();
/// assert_eq!(into_iter.as_slice(), &['b', 'c']);
/// ```
#[stable(feature = "vec_into_iter_as_slice", since = "1.15.0")]
pub fn as_slice(&self) -> &[T] {
unsafe { slice::from_raw_parts(self.ptr, self.len()) }
}
/// Returns the remaining items of this iterator as a mutable slice.
///
/// # Examples
///
/// ```
/// let vec = vec!['a', 'b', 'c'];
/// let mut into_iter = vec.into_iter();
/// assert_eq!(into_iter.as_slice(), &['a', 'b', 'c']);
/// into_iter.as_mut_slice()[2] = 'z';
/// assert_eq!(into_iter.next().unwrap(), 'a');
/// assert_eq!(into_iter.next().unwrap(), 'b');
/// assert_eq!(into_iter.next().unwrap(), 'z');
/// ```
#[stable(feature = "vec_into_iter_as_slice", since = "1.15.0")]
pub fn as_mut_slice(&mut self) -> &mut [T] {
unsafe { &mut *self.as_raw_mut_slice() }
}
/// Returns a reference to the underlying allocator.
#[unstable(feature = "allocator_api", issue = "32838")]
#[inline]
pub fn allocator(&self) -> &A {
&self.alloc
}
fn as_raw_mut_slice(&mut self) -> *mut [T] {
ptr::slice_from_raw_parts_mut(self.ptr as *mut T, self.len())
}
/// Drops remaining elements and relinquishes the backing allocation.
/// This method guarantees it won't panic before relinquishing
/// the backing allocation.
///
/// This is roughly equivalent to the following, but more efficient
///
/// ```
/// # let mut into_iter = Vec::<u8>::with_capacity(10).into_iter();
/// let mut into_iter = std::mem::replace(&mut into_iter, Vec::new().into_iter());
/// (&mut into_iter).for_each(drop);
/// std::mem::forget(into_iter);
/// ```
///
/// This method is used by in-place iteration, refer to the vec::in_place_collect
/// documentation for an overview.
#[cfg(not(no_global_oom_handling))]
pub(super) fn forget_allocation_drop_remaining(&mut self) {
let remaining = self.as_raw_mut_slice();
// overwrite the individual fields instead of creating a new
// struct and then overwriting &mut self.
// this creates less assembly
self.cap = 0;
self.buf = unsafe { NonNull::new_unchecked(RawVec::NEW.ptr()) };
self.ptr = self.buf.as_ptr();
self.end = self.buf.as_ptr();
// Dropping the remaining elements can panic, so this needs to be
// done only after updating the other fields.
unsafe {
ptr::drop_in_place(remaining);
}
}
/// Forgets to Drop the remaining elements while still allowing the backing allocation to be freed.
pub(crate) fn forget_remaining_elements(&mut self) {
// For th ZST case, it is crucial that we mutate `end` here, not `ptr`.
// `ptr` must stay aligned, while `end` may be unaligned.
self.end = self.ptr;
}
#[cfg(not(no_global_oom_handling))]
#[inline]
pub(crate) fn into_vecdeque(self) -> VecDeque<T, A> {
// Keep our `Drop` impl from dropping the elements and the allocator
let mut this = ManuallyDrop::new(self);
// SAFETY: This allocation originally came from a `Vec`, so it passes
// all those checks. We have `this.buf` ≤ `this.ptr` ≤ `this.end`,
// so the `sub_ptr`s below cannot wrap, and will produce a well-formed
// range. `end` ≤ `buf + cap`, so the range will be in-bounds.
// Taking `alloc` is ok because nothing else is going to look at it,
// since our `Drop` impl isn't going to run so there's no more code.
unsafe {
let buf = this.buf.as_ptr();
let initialized = if T::IS_ZST {
// All the pointers are the same for ZSTs, so it's fine to
// say that they're all at the beginning of the "allocation".
0..this.len()
} else {
this.ptr.sub_ptr(buf)..this.end.sub_ptr(buf)
};
let cap = this.cap;
let alloc = ManuallyDrop::take(&mut this.alloc);
VecDeque::from_contiguous_raw_parts_in(buf, initialized, cap, alloc)
}
}
}
#[stable(feature = "vec_intoiter_as_ref", since = "1.46.0")]
impl<T, A: Allocator> AsRef<[T]> for IntoIter<T, A> {
fn as_ref(&self) -> &[T] {
self.as_slice()
}
}
#[stable(feature = "rust1", since = "1.0.0")]
unsafe impl<T: Send, A: Allocator + Send> Send for IntoIter<T, A> {}
#[stable(feature = "rust1", since = "1.0.0")]
unsafe impl<T: Sync, A: Allocator + Sync> Sync for IntoIter<T, A> {}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T, A: Allocator> Iterator for IntoIter<T, A> {
type Item = T;
#[inline]
fn next(&mut self) -> Option<T> {
if self.ptr == self.end {
None
} else if T::IS_ZST {
// `ptr` has to stay where it is to remain aligned, so we reduce the length by 1 by
// reducing the `end`.
self.end = self.end.wrapping_byte_sub(1);
// Make up a value of this ZST.
Some(unsafe { mem::zeroed() })
} else {
let old = self.ptr;
self.ptr = unsafe { self.ptr.add(1) };
Some(unsafe { ptr::read(old) })
}
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
let exact = if T::IS_ZST {
self.end.addr().wrapping_sub(self.ptr.addr())
} else {
unsafe { self.end.sub_ptr(self.ptr) }
};
(exact, Some(exact))
}
#[inline]
fn advance_by(&mut self, n: usize) -> Result<(), NonZeroUsize> {
let step_size = self.len().min(n);
let to_drop = ptr::slice_from_raw_parts_mut(self.ptr as *mut T, step_size);
if T::IS_ZST {
// See `next` for why we sub `end` here.
self.end = self.end.wrapping_byte_sub(step_size);
} else {
// SAFETY: the min() above ensures that step_size is in bounds
self.ptr = unsafe { self.ptr.add(step_size) };
}
// SAFETY: the min() above ensures that step_size is in bounds
unsafe {
ptr::drop_in_place(to_drop);
}
NonZeroUsize::new(n - step_size).map_or(Ok(()), Err)
}
#[inline]
fn count(self) -> usize {
self.len()
}
#[inline]
fn next_chunk<const N: usize>(&mut self) -> Result<[T; N], core::array::IntoIter<T, N>> {
let mut raw_ary = MaybeUninit::uninit_array();
let len = self.len();
if T::IS_ZST {
if len < N {
self.forget_remaining_elements();
// Safety: ZSTs can be conjured ex nihilo, only the amount has to be correct
return Err(unsafe { array::IntoIter::new_unchecked(raw_ary, 0..len) });
}
self.end = self.end.wrapping_byte_sub(N);
// Safety: ditto
return Ok(unsafe { raw_ary.transpose().assume_init() });
}
if len < N {
// Safety: `len` indicates that this many elements are available and we just checked that
// it fits into the array.
unsafe {
ptr::copy_nonoverlapping(self.ptr, raw_ary.as_mut_ptr() as *mut T, len);
self.forget_remaining_elements();
return Err(array::IntoIter::new_unchecked(raw_ary, 0..len));
}
}
// Safety: `len` is larger than the array size. Copy a fixed amount here to fully initialize
// the array.
return unsafe {
ptr::copy_nonoverlapping(self.ptr, raw_ary.as_mut_ptr() as *mut T, N);
self.ptr = self.ptr.add(N);
Ok(raw_ary.transpose().assume_init())
};
}
unsafe fn __iterator_get_unchecked(&mut self, i: usize) -> Self::Item
where
Self: TrustedRandomAccessNoCoerce,
{
// SAFETY: the caller must guarantee that `i` is in bounds of the
// `Vec<T>`, so `i` cannot overflow an `isize`, and the `self.ptr.add(i)`
// is guaranteed to pointer to an element of the `Vec<T>` and
// thus guaranteed to be valid to dereference.
//
// Also note the implementation of `Self: TrustedRandomAccess` requires
// that `T: Copy` so reading elements from the buffer doesn't invalidate
// them for `Drop`.
unsafe {
if T::IS_ZST { mem::zeroed() } else { ptr::read(self.ptr.add(i)) }
}
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T, A: Allocator> DoubleEndedIterator for IntoIter<T, A> {
#[inline]
fn next_back(&mut self) -> Option<T> {
if self.end == self.ptr {
None
} else if T::IS_ZST {
// See above for why 'ptr.offset' isn't used
self.end = self.end.wrapping_byte_sub(1);
// Make up a value of this ZST.
Some(unsafe { mem::zeroed() })
} else {
self.end = unsafe { self.end.sub(1) };
Some(unsafe { ptr::read(self.end) })
}
}
#[inline]
fn advance_back_by(&mut self, n: usize) -> Result<(), NonZeroUsize> {
let step_size = self.len().min(n);
if T::IS_ZST {
// SAFETY: same as for advance_by()
self.end = self.end.wrapping_byte_sub(step_size);
} else {
// SAFETY: same as for advance_by()
self.end = unsafe { self.end.sub(step_size) };
}
let to_drop = ptr::slice_from_raw_parts_mut(self.end as *mut T, step_size);
// SAFETY: same as for advance_by()
unsafe {
ptr::drop_in_place(to_drop);
}
NonZeroUsize::new(n - step_size).map_or(Ok(()), Err)
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T, A: Allocator> ExactSizeIterator for IntoIter<T, A> {
fn is_empty(&self) -> bool {
self.ptr == self.end
}
}
#[stable(feature = "fused", since = "1.26.0")]
impl<T, A: Allocator> FusedIterator for IntoIter<T, A> {}
#[unstable(feature = "trusted_len", issue = "37572")]
unsafe impl<T, A: Allocator> TrustedLen for IntoIter<T, A> {}
#[stable(feature = "default_iters", since = "1.70.0")]
impl<T, A> Default for IntoIter<T, A>
where
A: Allocator + Default,
{
/// Creates an empty `vec::IntoIter`.
///
/// ```
/// # use std::vec;
/// let iter: vec::IntoIter<u8> = Default::default();
/// assert_eq!(iter.len(), 0);
/// assert_eq!(iter.as_slice(), &[]);
/// ```
fn default() -> Self {
super::Vec::new_in(Default::default()).into_iter()
}
}
#[doc(hidden)]
#[unstable(issue = "none", feature = "std_internals")]
#[rustc_unsafe_specialization_marker]
pub trait NonDrop {}
// T: Copy as approximation for !Drop since get_unchecked does not advance self.ptr
// and thus we can't implement drop-handling
#[unstable(issue = "none", feature = "std_internals")]
impl<T: Copy> NonDrop for T {}
#[doc(hidden)]
#[unstable(issue = "none", feature = "std_internals")]
// TrustedRandomAccess (without NoCoerce) must not be implemented because
// subtypes/supertypes of `T` might not be `NonDrop`
unsafe impl<T, A: Allocator> TrustedRandomAccessNoCoerce for IntoIter<T, A>
where
T: NonDrop,
{
const MAY_HAVE_SIDE_EFFECT: bool = false;
}
#[cfg(not(no_global_oom_handling))]
#[stable(feature = "vec_into_iter_clone", since = "1.8.0")]
impl<T: Clone, A: Allocator + Clone> Clone for IntoIter<T, A> {
#[cfg(not(test))]
fn clone(&self) -> Self {
self.as_slice().to_vec_in(self.alloc.deref().clone()).into_iter()
}
#[cfg(test)]
fn clone(&self) -> Self {
crate::slice::to_vec(self.as_slice(), self.alloc.deref().clone()).into_iter()
}
}
#[stable(feature = "rust1", since = "1.0.0")]
unsafe impl<#[may_dangle] T, A: Allocator> Drop for IntoIter<T, A> {
fn drop(&mut self) {
struct DropGuard<'a, T, A: Allocator>(&'a mut IntoIter<T, A>);
impl<T, A: Allocator> Drop for DropGuard<'_, T, A> {
fn drop(&mut self) {
unsafe {
// `IntoIter::alloc` is not used anymore after this and will be dropped by RawVec
let alloc = ManuallyDrop::take(&mut self.0.alloc);
// RawVec handles deallocation
let _ = RawVec::from_raw_parts_in(self.0.buf.as_ptr(), self.0.cap, alloc);
}
}
}
let guard = DropGuard(self);
// destroy the remaining elements
unsafe {
ptr::drop_in_place(guard.0.as_raw_mut_slice());
}
// now `guard` will be dropped and do the rest
}
}
// In addition to the SAFETY invariants of the following three unsafe traits
// also refer to the vec::in_place_collect module documentation to get an overview
#[unstable(issue = "none", feature = "inplace_iteration")]
#[doc(hidden)]
unsafe impl<T, A: Allocator> InPlaceIterable for IntoIter<T, A> {}
#[unstable(issue = "none", feature = "inplace_iteration")]
#[doc(hidden)]
unsafe impl<T, A: Allocator> SourceIter for IntoIter<T, A> {
type Source = Self;
#[inline]
unsafe fn as_inner(&mut self) -> &mut Self::Source {
self
}
}
#[cfg(not(no_global_oom_handling))]
unsafe impl<T> AsVecIntoIter for IntoIter<T> {
type Item = T;
fn as_into_iter(&mut self) -> &mut IntoIter<Self::Item> {
self
}
}