[PATCH 02/10] rust: alloc: introduce the `VecExt` trait

Wedson Almeida Filho
2024-03-25T19:54:57Z

From: Wedson Almeida Filho <walmeida@microsoft.com>

Make `try_with_capacity`, `try_push`, and `try_extend_from_slice`
methods available in `Vec` even though it doesn't implement them. It is
implemented with `try_reserve` and `push_within_capacity`.

This is in preparation for switching to the upstream `alloc` crate.

Suggested-by: Gary Guo <gary@garyguo.net>
Signed-off-by: Wedson Almeida Filho <walmeida@microsoft.com>
---
rust/kernel/alloc.rs | 1 +
rust/kernel/alloc/vecext.rs | 52 +++++++++++++++++++++++++++++++++++++
rust/kernel/lib.rs | 1 +
rust/kernel/prelude.rs | 2 ++
4 files changed, 56 insertions(+)
create mode 100644 rust/kernel/alloc/vecext.rs

diff --git a/rust/kernel/alloc.rs b/rust/kernel/alloc.rs
index ccd4149932c3..8ad57a2e693e 100644
--- a/rust/kernel/alloc.rs
+++ b/rust/kernel/alloc.rs
@@ -5,3 +5,4 @@
#[cfg(not(test))]
#[cfg(not(testlib))]
mod allocator;
+pub mod vecext;
diff --git a/rust/kernel/alloc/vecext.rs b/rust/kernel/alloc/vecext.rs
new file mode 100644
index 000000000000..59e92bab534e
--- /dev/null
+++ b/rust/kernel/alloc/vecext.rs
@@ -0,0 +1,52 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Extensions to [`Vec`] for fallible allocations.
+
+use alloc::{collections::TryReserveError, vec::Vec};
+use core::result::Result;
+
+/// Extensions to [`Vec`].
+pub trait VecExt<T>: Sized {
+ /// Creates a new [`Vec`] instance with at least the given capacity.
+ fn try_with_capacity(capacity: usize) -> Result<Self, TryReserveError>;
+
+ /// Appends an element to the back of the [`Vec`] instance.
+ fn try_push(&mut self, v: T) -> Result<(), TryReserveError>;
+
+ /// Pushes clones of the elements of slice into the [`Vec`] instance.
+ fn try_extend_from_slice(&mut self, other: &[T]) -> Result<(), TryReserveError>
+ where
+ T: Clone;
+}
+
+impl<T> VecExt<T> for Vec<T> {
+ fn try_with_capacity(capacity: usize) -> Result<Self, TryReserveError> {
+ let mut v = Vec::new();
+ v.try_reserve(capacity)?;
+ Ok(v)
+ }
+
+ fn try_push(&mut self, v: T) -> Result<(), TryReserveError> {
+ if let Err(retry) = self.push_within_capacity(v) {
+ self.try_reserve(1)?;
+ let _ = self.push_within_capacity(retry);
+ }
+ Ok(())
+ }
+
+ fn try_extend_from_slice(&mut self, other: &[T]) -> Result<(), TryReserveError>
+ where
+ T: Clone,
+ {
+ let extra_cap = self.capacity() - self.len();
+ if extra_cap > 0 {
+ self.try_reserve(extra_cap)?;
+ }
+
+ for item in other {
+ self.try_push(item.clone())?;
+ }
+
+ Ok(())
+ }
+}
diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index 51f30e55bd00..7f2841a18d05 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -19,6 +19,7 @@
#![feature(offset_of)]
#![feature(receiver_trait)]
#![feature(unsize)]
+#![feature(vec_push_within_capacity)]

// Ensure conditional compilation based on the kernel configuration works;
// otherwise we may silently break things like initcall handling.
diff --git a/rust/kernel/prelude.rs b/rust/kernel/prelude.rs
index ae21600970b3..a0177f195dec 100644
--- a/rust/kernel/prelude.rs
+++ b/rust/kernel/prelude.rs
@@ -14,6 +14,8 @@
#[doc(no_inline)]
pub use core::pin::Pin;

+pub use crate::alloc::vecext::VecExt;
+
#[doc(no_inline)]
pub use alloc::{boxed::Box, vec::Vec};

--
2.34.1