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
Signed-off-by: Asahi Lina <lina@asahilina.net>
---
rust/kernel/sync/arc.rs | 22 ++++++++++++++++++++++
1 file changed, 22 insertions(+)
diff --git a/rust/kernel/sync/arc.rs b/rust/kernel/sync/arc.rs
index a94e303217c6..752bd7c4699e 100644
--- a/rust/kernel/sync/arc.rs
+++ b/rust/kernel/sync/arc.rs
@@ -22,6 +22,7 @@ use crate::{
};
use alloc::boxed::Box;
use core::{
+ any::Any,
fmt,
marker::{PhantomData, Unsize},
mem::{ManuallyDrop, MaybeUninit},
@@ -220,6 +221,27 @@ impl<T: 'static> ForeignOwnable for Arc<T> {
}
}
+impl Arc<dyn Any + Send + Sync> {
+ /// Attempt to downcast the `Arc<dyn Any + Send + Sync>` to a concrete type.
+ // Based on the Rust standard library implementation, ver 1.62.0, which is
+ // Apache-2.0 OR MIT.
+ 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)
+ }
+ }
+}
+
impl<T: ?Sized> Deref for Arc<T> {
type Target = T;
--
2.35.1> 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 > > Signed-off-by: Asahi Lina <lina@asahilina.net> > --- Reviewed-by: Vincenzo Palazzo <vincenzopalazzodev@gmail.com>
Asahi Lina <lina@asahilina.net> writes:
> 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
>
> Signed-off-by: Asahi Lina <lina@asahilina.net>
> ---
Reviewed-by: Andreas Hindborg <a.hindborg@samsung.com>
> rust/kernel/sync/arc.rs | 22 ++++++++++++++++++++++
> 1 file changed, 22 insertions(+)
>
> diff --git a/rust/kernel/sync/arc.rs b/rust/kernel/sync/arc.rs
> index a94e303217c6..752bd7c4699e 100644
> --- a/rust/kernel/sync/arc.rs
> +++ b/rust/kernel/sync/arc.rs
> @@ -22,6 +22,7 @@ use crate::{
> };
> use alloc::boxed::Box;
> use core::{
> + any::Any,
> fmt,
> marker::{PhantomData, Unsize},
> mem::{ManuallyDrop, MaybeUninit},
> @@ -220,6 +221,27 @@ impl<T: 'static> ForeignOwnable for Arc<T> {
> }
> }
>
> +impl Arc<dyn Any + Send + Sync> {
> + /// Attempt to downcast the `Arc<dyn Any + Send + Sync>` to a concrete type.
> + // Based on the Rust standard library implementation, ver 1.62.0, which is
> + // Apache-2.0 OR MIT.
> + 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)
> + }
> + }
> +}
> +
> impl<T: ?Sized> Deref for Arc<T> {
> type Target = T;
On Fri, 24 Feb 2023 16:59:33 +0900
Asahi Lina <lina@asahilina.net> wrote:
> 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
>
> Signed-off-by: Asahi Lina <lina@asahilina.net>
Reviewed-by: Gary Guo <gary@garyguo.net>
> ---
> rust/kernel/sync/arc.rs | 22 ++++++++++++++++++++++
> 1 file changed, 22 insertions(+)
>
> diff --git a/rust/kernel/sync/arc.rs b/rust/kernel/sync/arc.rs
> index a94e303217c6..752bd7c4699e 100644
> --- a/rust/kernel/sync/arc.rs
> +++ b/rust/kernel/sync/arc.rs
> @@ -22,6 +22,7 @@ use crate::{
> };
> use alloc::boxed::Box;
> use core::{
> + any::Any,
> fmt,
> marker::{PhantomData, Unsize},
> mem::{ManuallyDrop, MaybeUninit},
> @@ -220,6 +221,27 @@ impl<T: 'static> ForeignOwnable for Arc<T> {
> }
> }
>
> +impl Arc<dyn Any + Send + Sync> {
> + /// Attempt to downcast the `Arc<dyn Any + Send + Sync>` to a concrete type.
> + // Based on the Rust standard library implementation, ver 1.62.0, which is
> + // Apache-2.0 OR MIT.
> + 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)
> + }
> + }
> +}
> +
> impl<T: ?Sized> Deref for Arc<T> {
> type Target = T;
>
>
On Fri, Feb 24, 2023 at 05:09:47PM +0900, Asahi Lina wrote:
> 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
>
> Signed-off-by: Asahi Lina <lina@asahilina.net>
> ---
> rust/kernel/sync/arc.rs | 22 ++++++++++++++++++++++
> 1 file changed, 22 insertions(+)
>
> diff --git a/rust/kernel/sync/arc.rs b/rust/kernel/sync/arc.rs
> index a94e303217c6..752bd7c4699e 100644
> --- a/rust/kernel/sync/arc.rs
> +++ b/rust/kernel/sync/arc.rs
> @@ -22,6 +22,7 @@ use crate::{
> };
> use alloc::boxed::Box;
> use core::{
> + any::Any,
> fmt,
> marker::{PhantomData, Unsize},
> mem::{ManuallyDrop, MaybeUninit},
> @@ -220,6 +221,27 @@ impl<T: 'static> ForeignOwnable for Arc<T> {
> }
> }
>
> +impl Arc<dyn Any + Send + Sync> {
> + /// Attempt to downcast the `Arc<dyn Any + Send + Sync>` to a concrete type.
> + // Based on the Rust standard library implementation, ver 1.62.0, which is
> + // Apache-2.0 OR MIT.
> + 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);
I see, we cast the inner pointer of the `Arc` to the target type which
is wrapped in an `ArcInner` that is then used for another `Arc`. This is
important as this new value now owns the pointer and, by consequence,
it is safe to forget the passed `Arc` as it won't leak the pointer.
Thus, this method is safe.
> + Ok(Arc::from_inner(ptr))
> + }
> + } else {
> + Err(self)
> + }
> + }
> +}
> +
> impl<T: ?Sized> Deref for Arc<T> {
> type Target = T;
Reviewed-by: Martin Rodriguez Reboredo <yakoyoku@gmail.com>
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