1 // SPDX-License-Identifier: Apache-2.0 OR MIT 2 3 //! The contents of this file come from the Rust standard library, hosted in 4 //! the <https://github.com/rust-lang/rust> repository, licensed under 5 //! "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 8 use crate::sync::{arc::ArcInner, Arc}; 9 use core::any::Any; 10 11 impl 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 where 15 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