29 lines · rust
1// SPDX-License-Identifier: Apache-2.0 OR MIT2 3//! The contents of this file come from the Rust standard library, hosted in4//! the <https://github.com/rust-lang/rust> repository, licensed under5//! "Apache-2.0 OR MIT" and adapted for kernel use. For copyright details,6//! see <https://github.com/rust-lang/rust/blob/master/COPYRIGHT>.7 8use crate::sync::{arc::ArcInner, Arc};9use core::any::Any;10 11impl Arc<dyn Any + Send + Sync> {12 /// Attempt to downcast the `Arc<dyn Any + Send + Sync>` to a concrete type.13 pub fn downcast<T>(self) -> core::result::Result<Arc<T>, Self>14 where15 T: Any + Send + Sync,16 {17 if (*self).is::<T>() {18 // SAFETY: We have just checked that the type is correct, so we can cast the pointer.19 unsafe {20 let ptr = self.ptr.cast::<ArcInner<T>>();21 core::mem::forget(self);22 Ok(Arc::from_inner(ptr))23 }24 } else {25 Err(self)26 }27 }28}29