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authorMiguel Ojeda <ojeda@kernel.org>2022-11-10 17:41:25 +0100
committerMiguel Ojeda <ojeda@kernel.org>2022-12-04 01:59:15 +0100
commitfeadd062871704b1de2111d06008ee24a8f03d02 (patch)
tree105dd87b80eff06d37c904f60a9b905e26229c76 /rust
parent51d3a25ab3a4f1dd701b17f7340e36de8600e41e (diff)
rust: alloc: add `Vec::try_with_capacity{,_in}()` constructors
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>
Diffstat (limited to 'rust')
-rw-r--r--rust/alloc/raw_vec.rs1
-rw-r--r--rust/alloc/vec/mod.rs89
2 files changed, 89 insertions, 1 deletions
diff --git a/rust/alloc/raw_vec.rs b/rust/alloc/raw_vec.rs
index c342f3843972..eb77db5def55 100644
--- a/rust/alloc/raw_vec.rs
+++ b/rust/alloc/raw_vec.rs
@@ -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)
diff --git a/rust/alloc/vec/mod.rs b/rust/alloc/vec/mod.rs
index 540787804cc2..8ac6c1e3b2a8 100644
--- a/rust/alloc/vec/mod.rs
+++ b/rust/alloc/vec/mod.rs
@@ -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