54 lines
1.6 KiB
Rust
54 lines
1.6 KiB
Rust
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use std::mem::size_of;
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use std::sync::atomic::{AtomicUsize, Ordering};
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pub(super) struct TempWasmAllocator {
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data: *mut u8,
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wasm_pointer: u32,
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currently_allocated: AtomicUsize,
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offset_high: AtomicUsize,
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}
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impl TempWasmAllocator {
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pub(super) fn new(data: *mut u8, wasm_pointer: u32) -> Self {
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Self {
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data,
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wasm_pointer,
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currently_allocated: AtomicUsize::new(0),
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offset_high: AtomicUsize::new(0),
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}
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}
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pub fn alloc<T>(&self) -> AllocatedObject<T> {
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self.currently_allocated.fetch_add(size_of::<T>(), Ordering::SeqCst);
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let ptr_offset = self.offset_high.fetch_add(size_of::<T>(), Ordering::SeqCst);
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let ptr = unsafe { self.data.add(ptr_offset) } as *mut T;
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AllocatedObject::<T> {
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ptr,
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wasm_pointer: self.wasm_pointer + ptr_offset as u32,
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allocator: self as *const TempWasmAllocator,
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}
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}
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pub fn drop<T>(&self) {
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self.currently_allocated.fetch_sub(size_of::<T>(), Ordering::SeqCst);
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// As soon as we've no longer allocated anything, we reset our allocating back to the start.
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if self.currently_allocated.load(Ordering::SeqCst) == 0 {
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self.offset_high.store(0, Ordering::SeqCst);
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}
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}
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}
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pub struct AllocatedObject<T> {
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pub ptr: *mut T,
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pub wasm_pointer: u32,
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allocator: *const TempWasmAllocator,
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}
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impl<T> Drop for AllocatedObject<T> {
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fn drop(&mut self) {
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unsafe {
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self.allocator.as_ref().unwrap().drop::<T>();
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}
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}
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}
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