Commit 1edd0337 authored by Asahi Lina's avatar Asahi Lina Committed by Miguel Ojeda
Browse files

rust: sync: arc: Implement Arc<dyn Any + Send + Sync>::downcast() 

This mirrors the standard library's alloc::sync::Arc::downcast().

Based on the Rust standard library implementation, ver 1.62.0,
licensed under "Apache-2.0 OR MIT", from:

    https://github.com/rust-lang/rust/tree/1.62.0/library/alloc/src

For copyright details, please see:

    https://github.com/rust-lang/rust/blob/1.62.0/COPYRIGHT



Reviewed-by: default avatarMartin Rodriguez Reboredo <yakoyoku@gmail.com>
Reviewed-by: default avatarAndreas Hindborg <a.hindborg@samsung.com>
Reviewed-by: default avatarVincenzo Palazzo <vincenzopalazzodev@gmail.com>
Reviewed-by: default avatarGary Guo <gary@garyguo.net>
Signed-off-by: default avatarAsahi Lina <lina@asahilina.net>
Link: https://lore.kernel.org/r/20230224-rust-arc-v2-1-5c97a865b276@asahilina.net


[ Moved `mod std_vendor;` up. ]
Signed-off-by: default avatarMiguel Ojeda <ojeda@kernel.org>
parent 39867fec

rust/kernel/sync/arc.rs

+2 −0
Original line number Diff line number Diff line
@@ -30,6 +30,8 @@ use core::{ 
    ptr::NonNull,

};



mod std_vendor;



/// A reference-counted pointer to an instance of `T`.

///

/// The reference count is incremented when new instances of [`Arc`] are created, and decremented

rust/kernel/sync/arc/std_vendor.rs

0 → 100644
+28 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: Apache-2.0 OR MIT



//! The contents of this file come from the Rust standard library, hosted in

//! the <https://github.com/rust-lang/rust> repository, licensed under

//! "Apache-2.0 OR MIT" and adapted for kernel use. For copyright details,

//! see <https://github.com/rust-lang/rust/blob/master/COPYRIGHT>.



use crate::sync::{arc::ArcInner, Arc};

use core::any::Any;



impl Arc<dyn Any + Send + Sync> {

    /// Attempt to downcast the `Arc<dyn Any + Send + Sync>` to a concrete type.

    pub fn downcast<T>(self) -> core::result::Result<Arc<T>, Self>

    where

        T: Any + Send + Sync,

    {

        if (*self).is::<T>() {

            // SAFETY: We have just checked that the type is correct, so we can cast the pointer.

            unsafe {

                let ptr = self.ptr.cast::<ArcInner<T>>();

                core::mem::forget(self);

                Ok(Arc::from_inner(ptr))

            }

        } else {

            Err(self)

        }

    }

}