parent
7b57e64ff6
commit
316d32496c
@ -1,62 +0,0 @@
|
|||||||
use alloc::heap::{Alloc, AllocErr, Layout};
|
|
||||||
|
|
||||||
use core::sync::atomic::{AtomicUsize, Ordering};
|
|
||||||
|
|
||||||
/// A simple allocator that allocates memory linearly and ignores freed memory.
|
|
||||||
#[derive(Debug)]
|
|
||||||
pub struct BumpAllocator {
|
|
||||||
heap_start: usize,
|
|
||||||
heap_end: usize,
|
|
||||||
next: AtomicUsize,
|
|
||||||
}
|
|
||||||
|
|
||||||
impl BumpAllocator {
|
|
||||||
pub const fn new(heap_start: usize, heap_end: usize) -> Self {
|
|
||||||
Self { heap_start, heap_end, next: AtomicUsize::new(heap_start) }
|
|
||||||
}
|
|
||||||
}
|
|
||||||
|
|
||||||
unsafe impl<'a> Alloc for &'a BumpAllocator {
|
|
||||||
unsafe fn alloc(&mut self, layout: Layout) -> Result<*mut u8, AllocErr> {
|
|
||||||
loop {
|
|
||||||
// load current state of the `next` field
|
|
||||||
let current_next = self.next.load(Ordering::Relaxed);
|
|
||||||
let alloc_start = align_up(current_next, layout.align());
|
|
||||||
let alloc_end = alloc_start.saturating_add(layout.size());
|
|
||||||
|
|
||||||
if alloc_end <= self.heap_end {
|
|
||||||
// update the `next` pointer if it still has the value `current_next`
|
|
||||||
let next_now = self.next.compare_and_swap(current_next, alloc_end,
|
|
||||||
Ordering::Relaxed);
|
|
||||||
if next_now == current_next {
|
|
||||||
// next address was successfully updated, allocation succeeded
|
|
||||||
return Ok(alloc_start as *mut u8);
|
|
||||||
}
|
|
||||||
} else {
|
|
||||||
return Err(AllocErr::Exhausted{ request: layout })
|
|
||||||
}
|
|
||||||
}
|
|
||||||
}
|
|
||||||
|
|
||||||
unsafe fn dealloc(&mut self, ptr: *mut u8, layout: Layout) {
|
|
||||||
// do nothing, leak memory
|
|
||||||
}
|
|
||||||
}
|
|
||||||
|
|
||||||
/// Align downwards. Returns the greatest x with alignment `align`
|
|
||||||
/// so that x <= addr. The alignment must be a power of 2.
|
|
||||||
pub fn align_down(addr: usize, align: usize) -> usize {
|
|
||||||
if align.is_power_of_two() {
|
|
||||||
addr & !(align - 1)
|
|
||||||
} else if align == 0 {
|
|
||||||
addr
|
|
||||||
} else {
|
|
||||||
panic!("`align` must be a power of 2");
|
|
||||||
}
|
|
||||||
}
|
|
||||||
|
|
||||||
/// Align upwards. Returns the smallest x with alignment `align`
|
|
||||||
/// so that x >= addr. The alignment must be a power of 2.
|
|
||||||
pub fn align_up(addr: usize, align: usize) -> usize {
|
|
||||||
align_down(addr + align - 1, align)
|
|
||||||
}
|
|
Loading…
Reference in new issue