Module layout 

The different layouts used by ArcSlice and ArcSliceMut.

A layout defines how the data is stored, impacting memory size and the behavior of some operations like clone.

Almost all layouts are compatible with each other: ArcSlice::with_layout and ArcSliceMut::with_layout allows to update the layout used, often at zero cost. See FromLayout.

ArcSlice and ArcSliceMut have a default layout, which can be overridden using crate features.

Which layout to choose

The default layout, ArcLayout, should support most of the use cases efficiently. The other layouts are designed to support some particular buffers without allocating an inner Arc:

• BoxedSliceLayout and VecLayout are intended for boxed slice/vector buffers, and should be used only when clones are unlikely;
• RawLayout should be used with Arc and other raw buffers.

Since layout primarily affects ArcSlice/ArcSliceMut instantiation, libraries generally don’t need to worry about it: they can either accept the default layout or use a generic one in public APIs, and expose the most appropriate layout in their return types. Libraries should not override the default layout using [crate features], as it would impact every other crates.
Binaries should use the default layout, adapting it to the use case using [crate features].

In any case, layout choice is primarily a performance concern and should be supported by measurement.

Layouts summary

Layout	ArcSlice size	static/empty slices support	arbitrary buffers support	cloning may allocate	optimized for
ArcLayout	3 * size_of::<usize>()	yes (optional)	yes (optional)	no	regular ArcSlice
BoxedSliceLayout	3 * size_of::<usize>()	yes	yes	yes	Box<[T]>
VecLayout	4 * size_of::<usize>()	yes	yes	yes	Vec<T>
RawLayout	4 * size_of::<usize>()	yes	yes	no	RawBuffer

Structs

ArcLayout

The default and most optimized layout.

BoxedSliceLayout

Enables storing a boxed slice into an ArcSlice without requiring the allocation of an inner Arc, as long as there is a single instance.

RawLayoutraw-buffer

Enables storing a RawBuffer, without requiring the allocation of an inner Arc.

VecLayout

Enables storing a vector into an ArcSlice without requiring the allocation of an inner Arc, as long as there is a single instance.

Traits

AnyBufferLayout

A layout that supports arbitrary buffers, such as Vec, shared memory regions, ffi buffers, etc.

CloneNoAllocLayout

A layout that supports clone without allocating.

FromLayout

A layout that can be converted from another one.

Layout

A layout, which defines how ArcSlice data is stored.

LayoutMut

A layout, which defines how ArcSliceMut data is stored.

StaticLayout

A layout that supports static slices without inner Arc allocation.

TruncateNoAllocLayout

A layout that supports truncate without allocating.

Type Aliases

DefaultLayout

Default layout used by ArcSlice.

DefaultLayoutMut

Default layout used by ArcSliceMut.