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rust: alloc: add Vec::try_with_capacity{,_in}() constructors

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Add `Vec::try_with_capacity()` and `Vec::try_with_capacity_in()` as
the fallible versions of `Vec::with_capacity()` and
`Vec::with_capacity_in()`, respectively.

The implementations follow the originals and use the previously
added `RawVec::try_with_capacity_in()`.

In turn, `Vec::try_with_capacity()` will be used to implement
the `CString` type (which wraps a `Vec<u8>`) in a later patch.

Reviewed-by: Gary Guo <gary@garyguo.net>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
This commit is contained in:
Miguel Ojeda 2022-11-10 17:41:25 +01:00
parent 51d3a25ab3
commit feadd06287
2 changed files with 89 additions and 1 deletions
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1
rust/alloc/raw_vec.rs
View File

@ -135,7 +135,6 @@ impl<T, A: Allocator> RawVec<T, A> {
/// Like `try_with_capacity`, but parameterized over the choice of
/// allocator for the returned `RawVec`.
#[allow(dead_code)]
#[inline]
pub fn try_with_capacity_in(capacity: usize, alloc: A) -> Result<Self, TryReserveError> {
Self::try_allocate_in(capacity, AllocInit::Uninitialized, alloc)

89
rust/alloc/vec/mod.rs
View File

@ -472,6 +472,48 @@ impl<T> Vec<T> {
Self::with_capacity_in(capacity, Global)
}
/// Tries to construct a new, empty `Vec<T>` with the specified capacity.
///
/// The vector will be able to hold exactly `capacity` elements without
/// reallocating. If `capacity` is 0, the vector will not allocate.
///
/// It is important to note that although the returned vector has the
/// *capacity* specified, the vector will have a zero *length*. For an
/// explanation of the difference between length and capacity, see
/// *[Capacity and reallocation]*.
///
/// [Capacity and reallocation]: #capacity-and-reallocation
///
/// # Examples
///
/// ```
/// let mut vec = Vec::try_with_capacity(10).unwrap();
///
/// // The vector contains no items, even though it has capacity for more
/// assert_eq!(vec.len(), 0);
/// assert_eq!(vec.capacity(), 10);
///
/// // These are all done without reallocating...
/// for i in 0..10 {
/// vec.push(i);
/// }
/// assert_eq!(vec.len(), 10);
/// assert_eq!(vec.capacity(), 10);
///
/// // ...but this may make the vector reallocate
/// vec.push(11);
/// assert_eq!(vec.len(), 11);
/// assert!(vec.capacity() >= 11);
///
/// let mut result = Vec::try_with_capacity(usize::MAX);
/// assert!(result.is_err());
/// ```
#[inline]
#[stable(feature = "kernel", since = "1.0.0")]
pub fn try_with_capacity(capacity: usize) -> Result<Self, TryReserveError> {
Self::try_with_capacity_in(capacity, Global)
}
/// Creates a `Vec<T>` directly from the raw components of another vector.
///
/// # Safety
@ -617,6 +659,53 @@ impl<T, A: Allocator> Vec<T, A> {
Vec { buf: RawVec::with_capacity_in(capacity, alloc), len: 0 }
}
/// Tries to construct a new, empty `Vec<T, A>` with the specified capacity
/// with the provided allocator.
///
/// The vector will be able to hold exactly `capacity` elements without
/// reallocating. If `capacity` is 0, the vector will not allocate.
///
/// It is important to note that although the returned vector has the
/// *capacity* specified, the vector will have a zero *length*. For an
/// explanation of the difference between length and capacity, see
/// *[Capacity and reallocation]*.
///
/// [Capacity and reallocation]: #capacity-and-reallocation
///
/// # Examples
///
/// ```
/// #![feature(allocator_api)]
///
/// use std::alloc::System;
///
/// let mut vec = Vec::try_with_capacity_in(10, System).unwrap();
///
/// // The vector contains no items, even though it has capacity for more
/// assert_eq!(vec.len(), 0);
/// assert_eq!(vec.capacity(), 10);
///
/// // These are all done without reallocating...
/// for i in 0..10 {
/// vec.push(i);
/// }
/// assert_eq!(vec.len(), 10);
/// assert_eq!(vec.capacity(), 10);
///
/// // ...but this may make the vector reallocate
/// vec.push(11);
/// assert_eq!(vec.len(), 11);
/// assert!(vec.capacity() >= 11);
///
/// let mut result = Vec::try_with_capacity_in(usize::MAX, System);
/// assert!(result.is_err());
/// ```
#[inline]
#[stable(feature = "kernel", since = "1.0.0")]
pub fn try_with_capacity_in(capacity: usize, alloc: A) -> Result<Self, TryReserveError> {
Ok(Vec { buf: RawVec::try_with_capacity_in(capacity, alloc)?, len: 0 })
}
/// Creates a `Vec<T, A>` directly from the raw components of another vector.
///
/// # Safety