Struct NoopAllocator 

pub struct NoopAllocator<'a>(/* private fields */);

An Allocator that does nothing.

Specifically:

• allocate and allocate_zeroed will return Err for any non-zero-sized allocation requests
• deallocate is a no-op, and does not require that ptr be “currently allocated”, or fit layout.
• shrink, grow, and grow_zeroed do not require that ptr be “currently allocated”, or fit old_layout, and will successfully return the original pointer unchanged (with the length of the new layout) if the ptr is aligned for the new layout and the new layout is smaller or the same size as the old layout.

This type is usable as an Allocator when you want to borrow an existing memory range for use in a single-allocation collection type, for example in Box or Vec.

Safety:

Many functions in this crate assume that impl Allocator for NoopAllocator<'_> as described above is sound, but feature(allocator_api) is unstable and the preconditions may change.

Implementations

impl<'a> NoopAllocator<'a>

pub const fn new() -> Self

Creates a new NoopAllocator<'a>.

Trait Implementations

impl Allocator for NoopAllocator<'_>

fn allocate(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocError>

🔬This is a nightly-only experimental API. (allocator_api)

Attempts to allocate a block of memory.

unsafe fn deallocate(&self, _ptr: NonNull<u8>, _layout: Layout)

🔬This is a nightly-only experimental API. (allocator_api)

Deallocates the memory referenced by ptr.

unsafe fn grow( &self, ptr: NonNull<u8>, old_layout: Layout, new_layout: Layout, ) -> Result<NonNull<[u8]>, AllocError>

🔬This is a nightly-only experimental API. (allocator_api)

Attempts to extend the memory block.

unsafe fn grow_zeroed( &self, ptr: NonNull<u8>, old_layout: Layout, new_layout: Layout, ) -> Result<NonNull<[u8]>, AllocError>

🔬This is a nightly-only experimental API. (allocator_api)

Behaves like grow, but also ensures that the new contents are set to zero before being returned.

unsafe fn shrink( &self, ptr: NonNull<u8>, old_layout: Layout, new_layout: Layout, ) -> Result<NonNull<[u8]>, AllocError>

🔬This is a nightly-only experimental API. (allocator_api)

Attempts to shrink the memory block.

fn allocate_zeroed(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocError>

🔬This is a nightly-only experimental API. (allocator_api)

Behaves like allocate, but also ensures that the returned memory is zero-initialized.

fn by_ref(&self) -> &Self

where Self: Sized,

🔬This is a nightly-only experimental API. (allocator_api)

Creates a “by reference” adapter for this instance of Allocator.

impl<'a> Default for NoopAllocator<'a>

fn default() -> Self

Returns the “default value” for a type.