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authorObei Sideg <linux@obei.io>2024-01-29 06:45:27 +0000
committerMiguel Ojeda <ojeda@kernel.org>2024-02-25 19:17:31 +0100
commit5bc818419a551ab1fcdbff3c5d8b6043527d90dd (patch)
tree2b352fb034e0766029406e39072789197f54f0f7 /rust
parente3c3d34507c7a146de1c5ce01bd0b2c0018b2609 (diff)
rust: types: add `try_from_foreign()` method
Currently `ForeignOwnable::from_foreign()` only works for non-null pointers for the existing `impl`s (e.g. `Box`, `Arc`). In turn, this means callers may write code like: ```rust // `p` is a pointer that may be null. if p.is_null() { None } else { unsafe { Some(Self::from_foreign(ptr)) } } ``` Add a `try_from_foreign()` method to the trait with a default implementation that returns `None` if `ptr` is null, otherwise `Some(from_foreign(ptr))`, so that it can be used by callers instead. Link: https://github.com/Rust-for-Linux/linux/issues/1057 Signed-off-by: Obei Sideg <linux@obei.io> Reviewed-by: Alice Ryhl <aliceryhl@google.com> Reviewed-by: Trevor Gross <tmgross@umich.edu> Link: https://lore.kernel.org/r/0100018d53f737f8-80c1fe97-0019-40d7-ab69-b1b192785cd7-000000@email.amazonses.com [ Fixed intra-doc links, improved `SAFETY` comment and reworded commit. ] Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
Diffstat (limited to 'rust')
-rw-r--r--rust/kernel/types.rs19
1 files changed, 19 insertions, 0 deletions
diff --git a/rust/kernel/types.rs b/rust/kernel/types.rs
index 8aabe348b194..aa77bad9bce4 100644
--- a/rust/kernel/types.rs
+++ b/rust/kernel/types.rs
@@ -46,6 +46,25 @@ pub trait ForeignOwnable: Sized {
/// Additionally, all instances (if any) of values returned by [`ForeignOwnable::borrow`] for
/// this object must have been dropped.
unsafe fn from_foreign(ptr: *const core::ffi::c_void) -> Self;
+
+ /// Tries to convert a foreign-owned object back to a Rust-owned one.
+ ///
+ /// A convenience wrapper over [`ForeignOwnable::from_foreign`] that returns [`None`] if `ptr`
+ /// is null.
+ ///
+ /// # Safety
+ ///
+ /// `ptr` must either be null or satisfy the safety requirements for
+ /// [`ForeignOwnable::from_foreign`].
+ unsafe fn try_from_foreign(ptr: *const core::ffi::c_void) -> Option<Self> {
+ if ptr.is_null() {
+ None
+ } else {
+ // SAFETY: Since `ptr` is not null here, then `ptr` satisfies the safety requirements
+ // of `from_foreign` given the safety requirements of this function.
+ unsafe { Some(Self::from_foreign(ptr)) }
+ }
+ }
}
impl<T: 'static> ForeignOwnable for Box<T> {