Struct SharedAllocator

pub struct SharedAllocator(/* private fields */);

An allocator implementing std::alloc::Allocator which allocates items in linux shared memory.

Implementations

impl SharedAllocator

pub fn new(shmid_path: &str, size: usize) -> Self

Construct an alloctor storing the shared memory id in a file at shmid_path.

Constructing multiple allocators with the same shmid_path will use the same shared memory.

After constructing the first allocator of a given shmid_path constructing new allocators with the same shmid_path is the same as cloning the original allocator.

Allocators with the same shmid_path across processes access the same memory although are unaware of the presence of items created with allocators from other processes. If 2 or more processes are allocating items in the same shared memory it is likely memory will be corrupted.

When constructing an allocator with the same shmid_path as an existing allocator the value of size will not be used for allocating shared memory but rather attaching shared memory. As such if the value shoould not be larger than the shared memory initially allocated (by the first allocator constructed with the shmid_path)

This library does not currently implement a mechanism for communicating the layout of the shared memory between allocators in different processes. You have to do this manually, in the example of the simplest use case, 1 process stores a large object in shared memory, when this process wishes to handoff to a newer process it sends the address of this object in the shared memory over a std::os::unix::net::UnixDatagram to the new process, which can pickup this object more quickly than if it had to be serialized and sent over a std::os::unix::net::UnixStream for example

Panics

For a whole lot of reasons. This is not a production ready library, it is a toy, treat it as such.

Trait Implementations

impl Allocator for SharedAllocator

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.

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.

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 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 Clone for SharedAllocator

fn clone(&self) -> SharedAllocator

Returns a duplicate of the value.

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

Performs copy-assignment from source.