Struct backdrop_arc::OffsetArc

#[repr(transparent)]
pub struct OffsetArc<T, S>where
    S: BackdropStrategy<Box<ArcInner<T>>>,{ /* private fields */ }

An Arc, except it holds a pointer to the T instead of to the entire ArcInner.

An OffsetArc<T, S> has the same layout and ABI as a non-null const T* in C, and may be used in FFI function signatures.

 Arc<T, S>    OffsetArc<T, S>
  |          |
  v          v
 ---------------------
| RefCount | T (data) | [ArcInner<T>]
 ---------------------

This means that this is a direct pointer to its contained data (and can be read from by both C++ and Rust), but we can also convert it to a “regular” Arc<T, S> by removing the offset.

This is very useful if you have an Arc-containing struct shared between Rust and C++, and wish for C++ to be able to read the data behind the Arc without incurring an FFI call overhead.

Implementations

impl<T, S> OffsetArc<T, S>where S: BackdropStrategy<Box<ArcInner<T>>>,

pub fn with_arc<F, U>(&self, f: F) -> Uwhere F: FnOnce(&Arc<T, S>) -> U,

Temporarily converts |self| into a bonafide Arc and exposes it to the provided callback. The refcount is not modified.

pub fn make_mut(&mut self) -> &mut Twhere T: Clone,

If uniquely owned, provide a mutable reference Else create a copy, and mutate that

This is functionally the same thing as Arc::make_mut

pub fn clone_arc(&self) -> Arc<T, S>

Clone it as an Arc

pub fn borrow_arc(&self) -> ArcBorrow<'_, T>

Produce a pointer to the data that can be converted back to an Arc

Trait Implementations

impl<T, S> Clone for OffsetArc<T, S>where S: BackdropStrategy<Box<ArcInner<T>>>,

fn clone(&self) -> Self

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<T: Debug, S> Debug for OffsetArc<T, S>where S: BackdropStrategy<Box<ArcInner<T>>>,

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<T, S> Deref for OffsetArc<T, S>where S: BackdropStrategy<Box<ArcInner<T>>>,

type Target = T

The resulting type after dereferencing.

fn deref(&self) -> &Self::Target

Dereferences the value.

impl<T, S> Drop for OffsetArc<T, S>where S: BackdropStrategy<Box<ArcInner<T>>>,

fn drop(&mut self)

Executes the destructor for this type.

impl<T: PartialEq, S> PartialEq<OffsetArc<T, S>> for OffsetArc<T, S>where S: BackdropStrategy<Box<ArcInner<T>>>,

fn eq(&self, other: &OffsetArc<T, S>) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &OffsetArc<T, S>) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<T: Eq, S> Eq for OffsetArc<T, S>where S: BackdropStrategy<Box<ArcInner<T>>> + Eq,

impl<T: Sync + Send, S> Send for OffsetArc<T, S>where S: BackdropStrategy<Box<ArcInner<T>>>,

impl<T, S> StructuralEq for OffsetArc<T, S>where S: BackdropStrategy<Box<ArcInner<T>>>,

impl<T: Sync + Send, S> Sync for OffsetArc<T, S>where S: BackdropStrategy<Box<ArcInner<T>>>,