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-rw-r--r--rust/alloc/vec/into_iter.rs78
1 files changed, 59 insertions, 19 deletions
diff --git a/rust/alloc/vec/into_iter.rs b/rust/alloc/vec/into_iter.rs
index f7a50e76691e..a8a2a8b66bfd 100644
--- a/rust/alloc/vec/into_iter.rs
+++ b/rust/alloc/vec/into_iter.rs
@@ -4,13 +4,13 @@
use super::AsVecIntoIter;
use crate::alloc::{Allocator, Global};
use crate::raw_vec::RawVec;
+use core::array;
use core::fmt;
-use core::intrinsics::arith_offset;
use core::iter::{
FusedIterator, InPlaceIterable, SourceIter, TrustedLen, TrustedRandomAccessNoCoerce,
};
use core::marker::PhantomData;
-use core::mem::{self, ManuallyDrop};
+use core::mem::{self, ManuallyDrop, MaybeUninit, SizedTypeProperties};
#[cfg(not(no_global_oom_handling))]
use core::ops::Deref;
use core::ptr::{self, NonNull};
@@ -97,13 +97,16 @@ impl<T, A: Allocator> IntoIter<T, A> {
}
/// 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(core::mem::drop);
- /// unsafe { core::ptr::write(&mut into_iter, Vec::new().into_iter()); }
+ /// std::mem::forget(into_iter);
/// ```
///
/// This method is used by in-place iteration, refer to the vec::in_place_collect
@@ -120,6 +123,8 @@ impl<T, A: Allocator> IntoIter<T, A> {
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);
}
@@ -150,19 +155,19 @@ impl<T, A: Allocator> Iterator for IntoIter<T, A> {
#[inline]
fn next(&mut self) -> Option<T> {
- if self.ptr as *const _ == self.end {
+ if self.ptr == self.end {
None
- } else if mem::size_of::<T>() == 0 {
+ } else if T::IS_ZST {
// purposefully don't use 'ptr.offset' because for
// vectors with 0-size elements this would return the
// same pointer.
- self.ptr = unsafe { arith_offset(self.ptr as *const i8, 1) as *mut T };
+ self.ptr = self.ptr.wrapping_byte_add(1);
// Make up a value of this ZST.
Some(unsafe { mem::zeroed() })
} else {
let old = self.ptr;
- self.ptr = unsafe { self.ptr.offset(1) };
+ self.ptr = unsafe { self.ptr.add(1) };
Some(unsafe { ptr::read(old) })
}
@@ -170,7 +175,7 @@ impl<T, A: Allocator> Iterator for IntoIter<T, A> {
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
- let exact = if mem::size_of::<T>() == 0 {
+ let exact = if T::IS_ZST {
self.end.addr().wrapping_sub(self.ptr.addr())
} else {
unsafe { self.end.sub_ptr(self.ptr) }
@@ -182,11 +187,11 @@ impl<T, A: Allocator> Iterator for IntoIter<T, A> {
fn advance_by(&mut self, n: usize) -> Result<(), usize> {
let step_size = self.len().min(n);
let to_drop = ptr::slice_from_raw_parts_mut(self.ptr as *mut T, step_size);
- if mem::size_of::<T>() == 0 {
+ if T::IS_ZST {
// SAFETY: due to unchecked casts of unsigned amounts to signed offsets the wraparound
// effectively results in unsigned pointers representing positions 0..usize::MAX,
// which is valid for ZSTs.
- self.ptr = unsafe { arith_offset(self.ptr as *const i8, step_size as isize) as *mut T }
+ self.ptr = self.ptr.wrapping_byte_add(step_size);
} else {
// SAFETY: the min() above ensures that step_size is in bounds
self.ptr = unsafe { self.ptr.add(step_size) };
@@ -206,6 +211,43 @@ impl<T, A: Allocator> Iterator for IntoIter<T, A> {
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.ptr = self.ptr.wrapping_byte_add(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,
@@ -219,7 +261,7 @@ impl<T, A: Allocator> Iterator for IntoIter<T, A> {
// that `T: Copy` so reading elements from the buffer doesn't invalidate
// them for `Drop`.
unsafe {
- if mem::size_of::<T>() == 0 { mem::zeroed() } else { ptr::read(self.ptr.add(i)) }
+ if T::IS_ZST { mem::zeroed() } else { ptr::read(self.ptr.add(i)) }
}
}
}
@@ -230,14 +272,14 @@ impl<T, A: Allocator> DoubleEndedIterator for IntoIter<T, A> {
fn next_back(&mut self) -> Option<T> {
if self.end == self.ptr {
None
- } else if mem::size_of::<T>() == 0 {
+ } else if T::IS_ZST {
// See above for why 'ptr.offset' isn't used
- self.end = unsafe { arith_offset(self.end as *const i8, -1) as *mut T };
+ 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.offset(-1) };
+ self.end = unsafe { self.end.sub(1) };
Some(unsafe { ptr::read(self.end) })
}
@@ -246,14 +288,12 @@ impl<T, A: Allocator> DoubleEndedIterator for IntoIter<T, A> {
#[inline]
fn advance_back_by(&mut self, n: usize) -> Result<(), usize> {
let step_size = self.len().min(n);
- if mem::size_of::<T>() == 0 {
+ if T::IS_ZST {
// SAFETY: same as for advance_by()
- self.end = unsafe {
- arith_offset(self.end as *const i8, step_size.wrapping_neg() as isize) as *mut T
- }
+ self.end = self.end.wrapping_byte_sub(step_size);
} else {
// SAFETY: same as for advance_by()
- self.end = unsafe { self.end.offset(step_size.wrapping_neg() as isize) };
+ 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()
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-22 03:22:44 +0000