use crate::base::*;
use core::alloc::{self, AllocError, Allocator};
use core::cmp::min;
use core::ptr::NonNull;
#[const_trait]
pub unsafe trait Params {
fn layout(&self) -> alloc::Layout;
}
pub struct CtParams<
const LAYOUT_SIZE: usize,
const LAYOUT_ALIGN: usize,
>(());
const fn is_power_of_two(x: usize) -> bool {
x != 0 && (x & (x - 1)) == 0
}
impl<
const LAYOUT_SIZE: usize,
const LAYOUT_ALIGN: usize,
> CtParams<LAYOUT_SIZE, LAYOUT_ALIGN> {
pub const fn new() -> Self {
assert!(LAYOUT_SIZE <= isize::MAX as usize);
assert!(LAYOUT_ALIGN <= isize::MAX as usize);
assert!(is_power_of_two(LAYOUT_ALIGN));
assert!(((LAYOUT_SIZE + LAYOUT_ALIGN - 1) / LAYOUT_ALIGN) * LAYOUT_ALIGN <= isize::MAX as usize);
CtParams(())
}
}
impl<
const LAYOUT_SIZE: usize,
const LAYOUT_ALIGN: usize,
> const Default for CtParams<LAYOUT_SIZE, LAYOUT_ALIGN> {
fn default() -> Self { CtParams::new() }
}
unsafe impl<
const LAYOUT_SIZE: usize,
const LAYOUT_ALIGN: usize,
> const Params for CtParams<LAYOUT_SIZE, LAYOUT_ALIGN> {
fn layout(&self) -> alloc::Layout {
unsafe { alloc::Layout::from_size_align_unchecked(LAYOUT_SIZE, LAYOUT_ALIGN) }
}
}
pub struct RtParams {
pub layout: alloc::Layout,
}
unsafe impl Params for RtParams {
fn layout(&self) -> alloc::Layout { self.layout }
}
pub struct LimitedUpTo<P: Params, A: Allocator> {
params: P,
base: A,
}
unsafe impl<P: Params, A: NonUnwinding> NonUnwinding for LimitedUpTo<P, A> { }
impl<P: Params, A: Allocator> LimitedUpTo<P, A> {
pub const fn new(params: P, base: A) -> Self {
LimitedUpTo { params, base }
}
fn manages(&self, layout: alloc::Layout) -> bool {
layout.size() <= self.params.layout().size() &&
layout.align() <= self.params.layout().align()
}
}
unsafe impl<P: Params, A: Allocator> Fallbackable for LimitedUpTo<P, A> {
unsafe fn has_allocated(&self, _ptr: NonNull<u8>, layout: alloc::Layout) -> bool {
self.manages(layout)
}
fn allows_fallback(&self, layout: alloc::Layout) -> bool {
!self.manages(layout)
}
}
unsafe impl<P: Params, A: Allocator> Allocator for LimitedUpTo<P, A> {
fn allocate(&self, layout: alloc::Layout) -> Result<NonNull<[u8]>, AllocError> {
if self.manages(layout) {
if let Ok(block) = self.base.allocate(layout) {
let len = min(block.len(), self.params.layout().size());
Ok(unsafe { NonNull::slice_from_raw_parts(NonNull::new_unchecked(block.as_mut_ptr()), len) })
} else {
Err(AllocError)
}
} else {
Err(AllocError)
}
}
fn allocate_zeroed(&self, layout: alloc::Layout) -> Result<NonNull<[u8]>, AllocError> {
if self.manages(layout) {
if let Ok(block) = self.base.allocate_zeroed(layout) {
let len = min(block.len(), self.params.layout().size());
Ok(unsafe { NonNull::slice_from_raw_parts(NonNull::new_unchecked(block.as_mut_ptr()), len) })
} else {
Err(AllocError)
}
} else {
Err(AllocError)
}
}
unsafe fn deallocate(&self, ptr: NonNull<u8>, layout: alloc::Layout) {
self.base.deallocate(ptr, layout);
}
unsafe fn grow(
&self,
ptr: NonNull<u8>,
old_layout: alloc::Layout,
new_layout: alloc::Layout
) -> Result<NonNull<[u8]>, AllocError> {
if self.manages(new_layout) {
if let Ok(block) = self.base.grow(ptr, old_layout, new_layout) {
let len = min(block.len(), self.params.layout().size());
Ok(NonNull::slice_from_raw_parts(NonNull::new_unchecked(block.as_mut_ptr()), len))
} else {
Err(AllocError)
}
} else {
Err(AllocError)
}
}
unsafe fn grow_zeroed(
&self,
ptr: NonNull<u8>,
old_layout: alloc::Layout,
new_layout: alloc::Layout
) -> Result<NonNull<[u8]>, AllocError> {
if self.manages(new_layout) {
if let Ok(block) = self.base.grow_zeroed(ptr, old_layout, new_layout) {
let len = min(block.len(), self.params.layout().size());
Ok(NonNull::slice_from_raw_parts(NonNull::new_unchecked(block.as_mut_ptr()), len))
} else {
Err(AllocError)
}
} else {
Err(AllocError)
}
}
unsafe fn shrink(
&self,
ptr: NonNull<u8>,
old_layout: alloc::Layout,
new_layout: alloc::Layout
) -> Result<NonNull<[u8]>, AllocError> {
if self.manages(new_layout) {
if let Ok(block) = self.base.shrink(ptr, old_layout, new_layout) {
let len = min(block.len(), self.params.layout().size());
Ok(NonNull::slice_from_raw_parts(NonNull::new_unchecked(block.as_mut_ptr()), len))
} else {
Err(AllocError)
}
} else {
Err(AllocError)
}
}
}