100 lines
3.6 KiB
Rust
100 lines
3.6 KiB
Rust
use alloc::alloc::{GlobalAlloc, Layout};
|
|
use core::{mem, ptr};
|
|
use super::Locked;
|
|
|
|
struct ListNode {
|
|
next: Option<&'static mut ListNode>,
|
|
}
|
|
|
|
/// The block sizes to use.
|
|
///
|
|
/// The sizes must each be a power of 2 because they are also used as
|
|
/// the block alignment (alignments must be always powers of 2).
|
|
const BLOCK_SIZES: &[usize] = &[8, 16, 32, 64, 128, 256, 512, 1024, 2048];
|
|
|
|
pub struct FixedSizeBlockAllocator {
|
|
list_heads: [Option<&'static mut ListNode>; BLOCK_SIZES.len()],
|
|
fallback_allocator: linked_list_allocator::Heap,
|
|
}
|
|
|
|
impl FixedSizeBlockAllocator {
|
|
/// Creates an empty FixedSizeBlockAllocator.
|
|
pub const fn new() -> Self {
|
|
FixedSizeBlockAllocator {
|
|
list_heads: [None; BLOCK_SIZES.len()],
|
|
fallback_allocator: linked_list_allocator::Heap::empty(),
|
|
}
|
|
}
|
|
|
|
/// Initialize the allocator with the given heap bounds.
|
|
///
|
|
/// This function is unsafe because the caller must guarantee that the given
|
|
/// heap bounds are valid and that the heap is unused. This method must be
|
|
/// called only once.
|
|
pub unsafe fn init(&mut self, heap_start: usize, heap_size: usize) {
|
|
self.fallback_allocator.init(heap_start, heap_size);
|
|
}
|
|
|
|
/// Allocates using the fallback allocator.
|
|
fn fallback_alloc(&mut self, layout: Layout) -> *mut u8 {
|
|
match self.fallback_allocator.allocate_first_fit(layout) {
|
|
Ok(ptr) => ptr.as_ptr(),
|
|
Err(_) => ptr::null_mut(),
|
|
}
|
|
}
|
|
}
|
|
|
|
fn list_index(layout: &Layout) -> Option<usize> {
|
|
let required_block_size = layout.size().max(layout.align());
|
|
BLOCK_SIZES.iter().position(|&s| s >= required_block_size)
|
|
}
|
|
|
|
unsafe impl GlobalAlloc for Locked<FixedSizeBlockAllocator> {
|
|
unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
|
|
let mut allocator = self.lock();
|
|
match list_index(&layout) {
|
|
Some(index) => {
|
|
match allocator.list_heads[index].take() {
|
|
Some(node) => {
|
|
allocator.list_heads[index] = node.next.take();
|
|
node as *mut ListNode as *mut u8
|
|
}
|
|
None => {
|
|
// no block exists in list => allocate new block
|
|
let block_size = BLOCK_SIZES[index];
|
|
|
|
// only works if all block sizes are a power of 2
|
|
let block_align = block_size;
|
|
let layout = Layout::from_size_align(block_size, block_align)
|
|
.unwrap();
|
|
allocator.fallback_alloc(layout)
|
|
}
|
|
}
|
|
},
|
|
None => allocator.fallback_alloc(layout),
|
|
}
|
|
}
|
|
|
|
unsafe fn dealloc(&self, ptr: *mut u8, layout: Layout) {
|
|
let mut allocator = self.lock();
|
|
match list_index(&layout) {
|
|
Some(index) => {
|
|
let new_node = ListNode {
|
|
next: allocator.list_heads[index].take(),
|
|
};
|
|
|
|
// verify that block has size and alignment required for storing node
|
|
assert!(mem::size_of::<ListNode>() <= BLOCK_SIZES[index]);
|
|
assert!(mem::align_of::<ListNode>() <= BLOCK_SIZES[index]);
|
|
|
|
let new_node_ptr = ptr as *mut ListNode;
|
|
new_node_ptr.write(new_node);
|
|
allocator.list_heads[index] = Some(&mut *new_node_ptr);
|
|
}
|
|
None => {
|
|
let ptr = ptr::NonNull::new(ptr).unwrap();
|
|
allocator.fallback_allocator.deallocate(ptr, layout);
|
|
}
|
|
}
|
|
}
|
|
} |