Struct servo_arc::ThinArc

#[repr(C)]
pub struct ThinArc<H, T> {
    pub(crate) ptr: NonNull<ArcInner<HeaderSlice<HeaderWithLength<H>, [T; 0]>>>,
    pub(crate) phantom: PhantomData<(H, T)>,
}

A “thin” Arc containing dynamically sized data

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

When you create an Arc containing a dynamically sized type like HeaderSlice<H, [T]>, the Arc is represented on the stack as a “fat pointer”, where the length of the slice is stored alongside the Arc’s pointer. In some situations you may wish to have a thin pointer instead, perhaps for FFI compatibility or space efficiency.

Note that we use [T; 0] in order to have the right alignment for T.

ThinArc solves this by storing the length in the allocation itself, via HeaderSliceWithLength.

Fields

ptr: NonNull<ArcInner<HeaderSlice<HeaderWithLength<H>, [T; 0]>>>

phantom: PhantomData<(H, T)>

Implementations

impl<H, T> ThinArc<H, T>

pub fn with_arc<F, U>(&self, f: F) -> Uwhere
    F: FnOnce(&Arc<HeaderSlice<HeaderWithLength<H>, [T]>>) -> U,

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

pub fn from_header_and_iter<I>(header: H, items: I) -> Selfwhere
    I: Iterator<Item = T> + ExactSizeIterator,

Creates a ThinArc for a HeaderSlice using the given header struct and iterator to generate the slice.

pub unsafe fn static_from_header_and_iter<F, I>(
    alloc: F,
    header: H,
    items: I
) -> Selfwhere
    F: FnOnce(Layout) -> *mut u8,
    I: Iterator<Item = T> + ExactSizeIterator,

Create a static ThinArc for a HeaderSlice using the given header struct and iterator to generate the slice, placing it in the allocation provided by the specified alloc function.

alloc must return a pointer into a static allocation suitable for storing data with the Layout passed into it. The pointer returned by alloc will not be freed.

pub fn ptr(&self) -> *const c_void

Returns the address on the heap of the ThinArc itself – not the T within it – for memory reporting, and bindings.

pub fn heap_ptr(&self) -> *const c_void

If this is a static ThinArc, this returns null.

Trait Implementations

impl<H, T> Clone for ThinArc<H, T>

fn clone(&self) -> Self

Returns a copy of the value.

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

Performs copy-assignment from source.

impl<H: Debug, T: Debug> Debug for ThinArc<H, T>

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

Formats the value using the given formatter.

impl<H, T> Deref for ThinArc<H, T>

type Target = HeaderSlice<HeaderWithLength<H>, [T]>

The resulting type after dereferencing.

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

Dereferences the value.

impl<H, T> Drop for ThinArc<H, T>

fn drop(&mut self)

Executes the destructor for this type.

impl<H: PartialEq, T: PartialEq> PartialEq<ThinArc<H, T>> for ThinArc<H, T>

fn eq(&self, other: &ThinArc<H, T>) -> bool

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

fn ne(&self, other: &Rhs) -> bool

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

impl<H: Eq, T: Eq> Eq for ThinArc<H, T>

impl<H: Sync + Send, T: Sync + Send> Send for ThinArc<H, T>

impl<H: Sync + Send, T: Sync + Send> Sync for ThinArc<H, T>