std_vendor.rs

 1// SPDX-License-Identifier: Apache-2.0 OR MIT
 2
 3//! Rust standard library vendored code.
 4//!
 5//! The contents of this file come from the Rust standard library, hosted in
 6//! the <https://github.com/rust-lang/rust> repository, licensed under
 7//! "Apache-2.0 OR MIT" and adapted for kernel use. For copyright details,
 8//! see <https://github.com/rust-lang/rust/blob/master/COPYRIGHT>.
 9
10use crate::sync::{arc::ArcInner, Arc};
11use core::any::Any;
12
13impl Arc<dyn Any + Send + Sync> {
14    /// Attempt to downcast the `Arc<dyn Any + Send + Sync>` to a concrete type.
15    pub fn downcast<T>(self) -> core::result::Result<Arc<T>, Self>
16    where
17        T: Any + Send + Sync,
18    {
19        if (*self).is::<T>() {
20            // SAFETY: We have just checked that the type is correct, so we can cast the pointer.
21            unsafe {
22                let ptr = self.ptr.cast::<ArcInner<T>>();
23                core::mem::forget(self);
24                Ok(Arc::from_inner(ptr))
25            }
26        } else {
27            Err(self)
28        }
29    }
30}