/// }

///

/// impl Gadget {

/// /// Construct a reference counted Gadget.

/// /// Constructs a reference counted Gadget.

/// fn new() -> Arc<Self> {

/// // `me` is a `Weak<Gadget>` pointing at the new allocation of the

/// // `Arc` we're constructing.

/// })

/// }

///

/// /// Return a reference counted pointer to Self.

/// /// Returns a reference counted pointer to Self.

/// fn me(&self) -> Arc<Self> {

/// self.me.upgrade().unwrap()

/// }

}

impl<A: Allocator> Arc<dyn Any + Send + Sync, A> {

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

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

///

/// # Examples

///

#[cfg(not(no_global_oom_handling))]

#[stable(feature = "shared_from_slice", since = "1.21.0")]

impl<T: Clone> From<&[T]> for Arc<[T]> {

/// Allocate a reference-counted slice and fill it by cloning `v`'s items.

/// Allocates a reference-counted slice and fills it by cloning `v`'s items.

///

/// # Example

///

#[cfg(not(no_global_oom_handling))]

#[stable(feature = "shared_from_slice", since = "1.21.0")]

impl From<&str> for Arc<str> {

/// Allocate a reference-counted `str` and copy `v` into it.

/// Allocates a reference-counted `str` and copies `v` into it.

///

/// # Example

///

#[cfg(not(no_global_oom_handling))]

#[stable(feature = "shared_from_slice", since = "1.21.0")]

impl From<String> for Arc<str> {

/// Allocate a reference-counted `str` and copy `v` into it.

/// Allocates a reference-counted `str` and copies `v` into it.

///

/// # Example

///

#[cfg(not(no_global_oom_handling))]

#[stable(feature = "shared_from_slice", since = "1.21.0")]

impl<T, A: Allocator + Clone> From<Vec<T, A>> for Arc<[T], A> {

/// Allocate a reference-counted slice and move `v`'s items into it.

/// Allocates a reference-counted slice and moves `v`'s items into it.

///

/// # Example

///

B: ToOwned + ?Sized,

Arc<B>: From<&'a B> + From<B::Owned>,

{

/// Create an atomically reference-counted pointer from

/// a clone-on-write pointer by copying its content.

/// Creates an atomically reference-counted pointer from a clone-on-write

/// pointer by copying its content.

///

/// # Example

///

#[stable(feature = "pin", since = "1.33.0")]

impl<T: ?Sized, A: Allocator> Unpin for Arc<T, A> {}

/// Get the offset within an `ArcInner` for the payload behind a pointer.

/// Gets the offset within an `ArcInner` for the payload behind a pointer.

///

/// # Safety

///

layout.size() + layout.padding_needed_for(align)

}

/// A unique owning pointer to a [`ArcInner`] **that does not imply the contents are initialized,**

/// A unique owning pointer to an [`ArcInner`] **that does not imply the contents are initialized,**

/// but will deallocate it (without dropping the value) when dropped.

///

/// This is a helper for [`Arc::make_mut()`] to ensure correct cleanup on panic.

#[cfg(not(no_global_oom_handling))]

impl<T: ?Sized, A: Allocator> UniqueArcUninit<T, A> {

/// Allocate a ArcInner with layout suitable to contain `for_value` or a clone of it.

/// Allocates an ArcInner with layout suitable to contain `for_value` or a clone of it.

fn new(for_value: &T, alloc: A) -> UniqueArcUninit<T, A> {

let layout = Layout::for_value(for_value);

let ptr = unsafe {