Struct linked_list_allocator::Heap [] [src]

pub struct Heap {
    // some fields omitted

A fixed size heap backed by a linked list of free memory blocks.


impl Heap

const fn empty() -> Heap

Creates an empty heap. All allocate calls will return None.

unsafe fn new(heap_bottom: usize, heap_top: usize) -> Heap

Creates a new heap with the given bottom and top. Both addresses must be valid and the memory in the [heap_bottom, heap_top) range must not be used for anything else. This function is unsafe because it can cause undefined behavior if the given addresses are invalid.

fn allocate_first_fit(&mut self, size: usize, align: usize) -> Option<*mut u8>

Allocates a chunk of the given size with the given alignment. Returns a pointer to the beginning of that chunk if it was successful. Else it returns None. This function scans the list of free memory blocks and uses the first block that is big enough. The runtime is in O(n) where n is the number of free blocks, but it should be reasonably fast for small allocations.

unsafe fn deallocate(&mut self, ptr: *mut u8, size: usize, _align: usize)

Frees the given allocation. ptr must be a pointer returned by a call to the allocate_first_fit function with identical size and alignment. Undefined behavior may occur for invalid arguments, thus this function is unsafe.

This function walks the list of free memory blocks and inserts the freed block at the correct place. If the freed block is adjacent to another free block, the blocks are merged again. This operation is in O(n) since the list needs to be sorted by address.

fn bottom(&self) -> usize

Returns the bottom address of the heap.

fn top(&self) -> usize

Returns the top address of the heap.