use crate::base::*;
use core::alloc::{self, AllocError, Allocator};
use core::ptr::{self, NonNull};
pub struct Fallbacked<A: Fallbackable, Fallback: Allocator>(pub A, pub Fallback);
unsafe impl<
A: NonUnwinding + Fallbackable,
Fallback: NonUnwinding
> NonUnwinding for Fallbacked<A, Fallback> { }
unsafe impl<A: Fallbackable, Fallback: Fallbackable> Fallbackable for Fallbacked<A, Fallback> {
unsafe fn has_allocated(&self, ptr: NonNull<u8>, layout: alloc::Layout) -> bool {
self.0.has_allocated(ptr, layout) || self.1.has_allocated(ptr, layout)
}
fn allows_fallback(&self, layout: alloc::Layout) -> bool {
self.0.allows_fallback(layout) && self.1.allows_fallback(layout)
}
}
unsafe impl<A: Fallbackable, Fallback: Allocator> Allocator for Fallbacked<A, Fallback> {
fn allocate(&self, layout: alloc::Layout) -> Result<NonNull<[u8]>, AllocError> {
if let Ok(block) = self.0.allocate(layout) {
Ok(block)
} else if self.0.allows_fallback(layout) {
self.1.allocate(layout)
} else {
Err(AllocError)
}
}
fn allocate_zeroed(&self, layout: alloc::Layout) -> Result<NonNull<[u8]>, AllocError> {
if let Ok(block) = self.0.allocate_zeroed(layout) {
Ok(block)
} else if self.0.allows_fallback(layout) {
self.1.allocate_zeroed(layout)
} else {
Err(AllocError)
}
}
unsafe fn deallocate(&self, ptr: NonNull<u8>, layout: alloc::Layout) {
if self.0.has_allocated(ptr, layout) {
self.0.deallocate(ptr, layout);
} else {
self.1.deallocate(ptr, layout);
}
}
unsafe fn grow(
&self,
ptr: NonNull<u8>,
old_layout: alloc::Layout,
new_layout: alloc::Layout
) -> Result<NonNull<[u8]>, AllocError> {
if self.0.has_allocated(ptr, old_layout) {
if let Ok(block) = self.0.grow(ptr, old_layout, new_layout) {
Ok(block)
} else if self.0.allows_fallback(new_layout) {
if let Ok(block) = self.1.allocate(new_layout) {
ptr::copy_nonoverlapping(ptr.as_ptr(), block.as_mut_ptr(), old_layout.size());
self.0.deallocate(ptr, old_layout);
Ok(block)
} else {
Err(AllocError)
}
} else {
Err(AllocError)
}
} else {
self.1.grow(ptr, old_layout, new_layout)
}
}
unsafe fn grow_zeroed(
&self,
ptr: NonNull<u8>,
old_layout: alloc::Layout,
new_layout: alloc::Layout
) -> Result<NonNull<[u8]>, AllocError> {
if self.0.has_allocated(ptr, old_layout) {
if let Ok(block) = self.0.grow_zeroed(ptr, old_layout, new_layout) {
Ok(block)
} else if self.0.allows_fallback(new_layout) {
if let Ok(block) = self.1.allocate_zeroed(new_layout) {
ptr::copy_nonoverlapping(ptr.as_ptr(), block.as_mut_ptr(), old_layout.size());
self.0.deallocate(ptr, old_layout);
Ok(block)
} else {
Err(AllocError)
}
} else {
Err(AllocError)
}
} else {
self.1.grow_zeroed(ptr, old_layout, new_layout)
}
}
unsafe fn shrink(
&self,
ptr: NonNull<u8>,
old_layout: alloc::Layout,
new_layout: alloc::Layout
) -> Result<NonNull<[u8]>, AllocError> {
if self.0.has_allocated(ptr, old_layout) {
if let Ok(block) = self.0.shrink(ptr, old_layout, new_layout) {
Ok(block)
} else if self.0.allows_fallback(new_layout) {
if let Ok(block) = self.1.allocate(new_layout) {
ptr::copy_nonoverlapping(ptr.as_ptr(), block.as_mut_ptr(), new_layout.size());
self.0.deallocate(ptr, old_layout);
Ok(block)
} else {
Err(AllocError)
}
} else {
Err(AllocError)
}
} else {
self.1.shrink(ptr, old_layout, new_layout)
}
}
}