Crate servo_arc

Fork of Arc for Servo. This has the following advantages over std::sync::Arc:

• We don’t waste storage on the weak reference count.
• We don’t do extra RMU operations to handle the possibility of weak references.
• We can experiment with arena allocation (todo).
• We can add methods to support our custom use cases 1.
• We have support for dynamically-sized types (see from_header_and_iter).
• We have support for thin arcs to unsized types (see ThinArc).
• We have support for references to static data, which don’t do any refcounting.

Structs

Arc

An atomically reference counted shared pointer

ArcBorrow

A “borrowed Arc”. This is a pointer to a T that is known to have been allocated within an Arc.

ArcInner 🔒

The object allocated by an Arc

ArcUnion

A tagged union that can represent Arc<A> or Arc<B> while only consuming a single word. The type is also NonNull, and thus can be stored in an Option without increasing size.

HeaderSlice

Structure to allow Arc-managing some fixed-sized data and a variably-sized slice in a single allocation.

UniqueArc

An Arc that is known to be uniquely owned

Enums

ArcUnionBorrow

This represents a borrow of an ArcUnion.

Constants

MAX_REFCOUNT 🔒

A soft limit on the amount of references that may be made to an Arc.

STATIC_REFCOUNT 🔒

Special refcount value that means the data is not reference counted, and that the Arc is really acting as a read-only static reference.

Functions

data_offset 🔒

Computes the offset of the data field within ArcInner.

Type Aliases

ThinArc

This is functionally equivalent to Arc<(H, [T])>

ThinArcUnion

See ArcUnion. This is a version that works for ThinArcs.