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authorMiguel Ojeda <ojeda@kernel.org>2022-11-10 17:41:24 +0100
committerMiguel Ojeda <ojeda@kernel.org>2022-12-04 01:59:15 +0100
commit51d3a25ab3a4f1dd701b17f7340e36de8600e41e (patch)
treeb6634dc784239392b89db497403a7ac63ad1b956 /rust
parent25d176a4fad5841de1f85d2a4d69ce87416abc26 (diff)
rust: alloc: add `RawVec::try_with_capacity_in()` constructor
Add the `RawVec::try_with_capacity_in()` constructor as the fallible version of `RawVec::with_capacity_in()`. The implementation follows the original. The infallible constructor is implemented in terms of the private `RawVec::allocate_in()` constructor, thus also add the private `RawVec::try_allocate_in()` constructor following the other. It will be used to implement `Vec::try_with_capacity{,_in}()` in the next 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.rs34
1 files changed, 33 insertions, 1 deletions
diff --git a/rust/alloc/raw_vec.rs b/rust/alloc/raw_vec.rs
index daf5f2da7168..c342f3843972 100644
--- a/rust/alloc/raw_vec.rs
+++ b/rust/alloc/raw_vec.rs
@@ -20,11 +20,11 @@ use crate::collections::TryReserveErrorKind::*;
#[cfg(test)]
mod tests;
-#[cfg(not(no_global_oom_handling))]
enum AllocInit {
/// The contents of the new memory are uninitialized.
Uninitialized,
/// The new memory is guaranteed to be zeroed.
+ #[allow(dead_code)]
Zeroed,
}
@@ -133,6 +133,14 @@ impl<T, A: Allocator> RawVec<T, A> {
Self::allocate_in(capacity, AllocInit::Uninitialized, alloc)
}
+ /// 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)
+ }
+
/// Like `with_capacity_zeroed`, but parameterized over the choice
/// of allocator for the returned `RawVec`.
#[cfg(not(no_global_oom_handling))]
@@ -203,6 +211,30 @@ impl<T, A: Allocator> RawVec<T, A> {
}
}
+ fn try_allocate_in(capacity: usize, init: AllocInit, alloc: A) -> Result<Self, TryReserveError> {
+ // Don't allocate here because `Drop` will not deallocate when `capacity` is 0.
+ if mem::size_of::<T>() == 0 || capacity == 0 {
+ return Ok(Self::new_in(alloc));
+ }
+
+ let layout = Layout::array::<T>(capacity).map_err(|_| CapacityOverflow)?;
+ alloc_guard(layout.size())?;
+ let result = match init {
+ AllocInit::Uninitialized => alloc.allocate(layout),
+ AllocInit::Zeroed => alloc.allocate_zeroed(layout),
+ };
+ let ptr = result.map_err(|_| AllocError { layout, non_exhaustive: () })?;
+
+ // Allocators currently return a `NonNull<[u8]>` whose length
+ // matches the size requested. If that ever changes, the capacity
+ // here should change to `ptr.len() / mem::size_of::<T>()`.
+ Ok(Self {
+ ptr: unsafe { Unique::new_unchecked(ptr.cast().as_ptr()) },
+ cap: capacity,
+ alloc,
+ })
+ }
+
/// Reconstitutes a `RawVec` from a pointer, capacity, and allocator.
///
/// # Safety