Struct mnemos_alloc::heap::MnemosAlloc

pub struct MnemosAlloc<U> {
    allocator: U,
}

Mnemos Allocator

This is a wrapper type over an implementor of UnderlyingAllocator.

This “inherits” any of the behaviors and safety requirements of the chosen UnderlyingAllocator, and in addition has two major special behaviors that are intended to help respond gracefully to ephemeral Out of Memory conditions

• On alloc:
  • We check whether allocation is inhibited. If it is - a nullptr is returned, regardless of whether there is sufficient room to allocate the requested amount.
  • If we are NOT inhibited, but are now out of memory (the underlying allocator returned a nullptr), we inhibit further allocations until the next deallocation occurs
• On dealloc:
  • The “inhibit allocations” flag is cleared
  • If any tasks are waiting on the “OOM” queue, they are ALL awoken if the inhibit flag was previously set

These two details are intended to allow the “async allocation aware” types defined in crate::containers to yield if allocation is not currently possible.

By wrapping the UnderlyingAllocator, we allow non-async-aware allocations (like those through alloc::alloc::alloc() or alloc::alloc::dealloc()) to trigger these behaviors. However, non-async-aware allocations are still subject to normal OOM handling, which typically means panicking.

Fields

allocator: U

Implementations

impl<U: UnderlyingAllocator> MnemosAlloc<U>

pub const fn new() -> Self

pub unsafe fn init(&self, start: NonNull<u8>, len: usize)

Trait Implementations

impl<U: UnderlyingAllocator> GlobalAlloc for MnemosAlloc<U>

unsafe fn alloc(&self, layout: Layout) -> *mut u8

Allocate memory as described by the given layout.

unsafe fn dealloc(&self, ptr: *mut u8, layout: Layout)

Deallocate the block of memory at the given ptr pointer with the given layout.

unsafe fn alloc_zeroed(&self, layout: Layout) -> *mut u8

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

unsafe fn realloc( &self, ptr: *mut u8, layout: Layout, new_size: usize ) -> *mut u8

Shrink or grow a block of memory to the given new_size in bytes. The block is described by the given ptr pointer and layout.