62 lines
1.7 KiB
Rust
62 lines
1.7 KiB
Rust
use super::{align_up, Locked};
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use alloc::alloc::{GlobalAlloc, Layout};
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use core::ptr;
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pub struct BumpAllocator {
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heap_start: usize,
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heap_end: usize,
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next: usize,
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allocations: usize,
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}
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impl BumpAllocator {
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/// Creates a new empty bump allocator.
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pub const fn new() -> Self {
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BumpAllocator {
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heap_start: 0,
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heap_end: 0,
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next: 0,
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allocations: 0,
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}
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}
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/// Initializes the bump allocator with the given heap bounds.
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///
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/// This method is unsafe because the caller must ensure that the given
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/// memory range is unused. Also, this method must be called only once.
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pub unsafe fn init(&mut self, heap_start: usize, heap_size: usize) {
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self.heap_start = heap_start;
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self.heap_end = heap_start.saturating_add(heap_size);
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self.next = heap_start;
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}
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}
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unsafe impl GlobalAlloc for Locked<BumpAllocator> {
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unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
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let mut bump = self.lock(); // get a mutable reference
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let alloc_start = align_up(bump.next, layout.align());
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let alloc_end = match alloc_start.checked_add(layout.size()) {
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Some(end) => end,
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None => return ptr::null_mut(),
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};
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if alloc_end > bump.heap_end {
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ptr::null_mut() // out of memory
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} else {
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bump.next = alloc_end;
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bump.allocations += 1;
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alloc_start as *mut u8
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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 mut bump = self.lock(); // get a mutable reference
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bump.allocations -= 1;
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if bump.allocations == 0 {
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bump.next = bump.heap_start;
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}
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}
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}
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