This commit introduces a new method to the public API, under
`vec_split_at_spare` feature gate:
```rust
impl<T, A: Allocator> impl Vec<T, A> {
pub fn split_at_spare_mut(&mut self) -> (&mut [T], &mut [MaybeUninit<T>]);
}
```
The method returns 2 slices, one slice references the content of the vector,
and the other references the remaining spare capacity.
The method was previously implemented while adding `Vec::extend_from_within`,
and used to implement `Vec::spare_capacity_mut` (as the later is just a
subset of former one).
add `Vec::extend_from_within` method under `vec_extend_from_within` feature gate
Implement <https://github.com/rust-lang/rfcs/pull/2714>
### tl;dr
This PR adds a `extend_from_within` method to `Vec` which allows copying elements from a range to the end:
```rust
#![feature(vec_extend_from_within)]
let mut vec = vec![0, 1, 2, 3, 4];
vec.extend_from_within(2..);
assert_eq!(vec, [0, 1, 2, 3, 4, 2, 3, 4]);
vec.extend_from_within(..2);
assert_eq!(vec, [0, 1, 2, 3, 4, 2, 3, 4, 0, 1]);
vec.extend_from_within(4..8);
assert_eq!(vec, [0, 1, 2, 3, 4, 2, 3, 4, 0, 1, 4, 2, 3, 4]);
```
### Implementation notes
Originally I've copied `@Shnatsel's` [implementation](690742a0de/src/lib.rs (L74)) with some minor changes to support other ranges:
```rust
pub fn append_from_within<R>(&mut self, src: R)
where
T: Copy,
R: RangeBounds<usize>,
{
let len = self.len();
let Range { start, end } = src.assert_len(len);;
let count = end - start;
self.reserve(count);
unsafe {
// This is safe because `reserve()` above succeeded,
// so `self.len() + count` did not overflow usize
ptr::copy_nonoverlapping(
self.get_unchecked(src.start),
self.as_mut_ptr().add(len),
count,
);
self.set_len(len + count);
}
}
```
But then I've realized that this duplicates most of the code from (private) `Vec::append_elements`, so I've used it instead.
Then I've applied `@KodrAus` suggestions from https://github.com/rust-lang/rust/pull/79015#issuecomment-727200852.
Implement <https://github.com/rust-lang/rfcs/pull/2714>, changes from the RFC:
- Rename the method `append_from_within` => `extend_from_within`
- Loose :Copy bound => :Clone
- Specialize in case of :Copy
This commit also adds `Vec::split_at_spare` private method and use it to implement
`Vec::spare_capacity_mut` and `Vec::extend_from_within`. This method returns 2
slices - initialized elements (same as `&mut vec[..]`) and uninitialized but
allocated space (same as `vec.spare_capacity_mut()`).
Fix broken links with `--document-private-items` in the standard library
As it was suggested in #81037 `SpecFromIter` is not
in the scope and therefore we get a warning when we try to
do document private intems in `rust/library/alloc/`.
This addresses #81037 by adding the trait in the scope as ```@jyn514```
suggested and also adding an `allow(unused_imports)` flag so that
the compiler does not complain, Since the trait is not used
per se in the code, it's just needed to have properly documented
docs.
Visualize vector while differentiating between stack and heap.
Inspired by cheats.rs, as this is probably the first place beginner go,
they could understand stack and heap, length and capacity with this. Not
sure if adding this means we should add to other places too.
Superseeds #76066
As it was suggested in #81037 `SpecFromIter` is not
in the scope and therefore (even it should fail),
we get a warning when we try do document private
intems in `rust/library/alloc/`.
This fixes#81037 by adding the trait in the scope
and also adding an `allow(unused_imports)` flag so that
the compiler does not complain, Since the trait is not used
per se in the code, it's just needed to have properly documented
docs.
Remove unstable deprecated Vec::remove_item
Closes#40062
The `Vec::remove_item` method was deprecated in `1.46.0` (in August of 2020). This PR now removes that unstable method entirely.
