114 lines
3.3 KiB
Rust
114 lines
3.3 KiB
Rust
use super::{align_up, Locked};
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use alloc::alloc::{GlobalAlloc, Layout};
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use core::{mem, ptr};
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struct ListNode {
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size: usize,
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next: Option<&'static mut ListNode>,
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}
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impl ListNode {
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const fn new(size: usize) -> Self {
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ListNode { size, next: None }
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}
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fn start_addr(&self) -> usize {
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self as *const Self as usize
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}
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fn end_addr(&self) -> usize {
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self.start_addr() + self.size
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}
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}
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pub struct LinkedListAllocator {
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head: ListNode,
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}
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impl LinkedListAllocator {
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pub const fn new() -> Self {
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Self {
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head: ListNode::new(0),
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}
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}
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pub unsafe fn init(&mut self, heap_start: usize, heap_size: usize) {
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self.add_free_region(heap_start, heap_size);
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}
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unsafe fn add_free_region(&mut self, addr: usize, size: usize) {
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assert_eq!(align_up(addr, mem::align_of::<ListNode>()), addr);
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assert!(size >= mem::size_of::<ListNode>());
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let mut node = ListNode::new(size);
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node.next = self.head.next.take();
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let node_ptr = addr as *mut ListNode;
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node_ptr.write(node);
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self.head.next = Some(&mut *node_ptr)
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}
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fn find_region(&mut self, size: usize, align: usize) -> Option<(&'static mut ListNode, usize)> {
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let mut current = &mut self.head;
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while let Some(ref mut region) = current.next {
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if let Ok(alloc_start) = Self::alloc_from_region(®ion, size, align) {
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let next = region.next.take();
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let ret = Some((current.next.take().unwrap(), alloc_start));
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current.next = next;
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return ret;
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} else {
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current = current.next.as_mut().unwrap();
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}
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}
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None
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}
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fn alloc_from_region(region: &ListNode, size: usize, align: usize) -> Result<usize, ()> {
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let alloc_start = align_up(region.start_addr(), align);
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let alloc_end = alloc_start.checked_add(size).ok_or(())?;
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if alloc_end > region.end_addr() {
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}
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let excess_size = region.end_addr() - alloc_end;
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if excess_size > 0 && excess_size < mem::size_of::<ListNode>() {
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return Err(());
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}
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Ok(alloc_start)
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}
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fn size_align(layout: Layout) -> (usize, usize) {
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let layout = layout
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.align_to(mem::align_of::<ListNode>())
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.expect("adjusting alignment failed")
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.pad_to_align();
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let size = layout.size().max(mem::size_of::<ListNode>());
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(size, layout.align())
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}
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}
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unsafe impl GlobalAlloc for Locked<LinkedListAllocator> {
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unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
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let (size, align) = LinkedListAllocator::size_align(layout);
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let mut allocator = self.lock();
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if let Some((region, alloc_start)) = allocator.find_region(size, align) {
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let alloc_end = alloc_start.checked_add(size).expect("overflow");
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let excess_size = region.end_addr() - alloc_end;
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if excess_size > 0 {
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allocator.add_free_region(alloc_end, excess_size);
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}
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alloc_start as *mut u8
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} else {
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ptr::null_mut()
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}
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}
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unsafe fn dealloc(&self, ptr: *mut u8, layout: Layout) {
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let (size, _) = LinkedListAllocator::size_align(layout);
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self.lock().add_free_region(ptr as usize, size)
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}
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}
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