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|
use core::alloc::{AllocError, Allocator, Layout};
use core::cell::Cell;
use core::mem::MaybeUninit;
use core::ptr::NonNull;
#[test]
fn uninitialized_zero_size_box() {
assert_eq!(
&*Box::<()>::new_uninit() as *const _,
NonNull::<MaybeUninit<()>>::dangling().as_ptr(),
);
assert_eq!(
Box::<[()]>::new_uninit_slice(4).as_ptr(),
NonNull::<MaybeUninit<()>>::dangling().as_ptr(),
);
assert_eq!(
Box::<[String]>::new_uninit_slice(0).as_ptr(),
NonNull::<MaybeUninit<String>>::dangling().as_ptr(),
);
}
#[derive(Clone, PartialEq, Eq, Debug)]
struct Dummy {
_data: u8,
}
#[test]
fn box_clone_and_clone_from_equivalence() {
for size in (0..8).map(|i| 2usize.pow(i)) {
let control = vec![Dummy { _data: 42 }; size].into_boxed_slice();
let clone = control.clone();
let mut copy = vec![Dummy { _data: 84 }; size].into_boxed_slice();
copy.clone_from(&control);
assert_eq!(control, clone);
assert_eq!(control, copy);
}
}
/// This test might give a false positive in case the box reallocates,
/// but the allocator keeps the original pointer.
///
/// On the other hand, it won't give a false negative: If it fails, then the
/// memory was definitely not reused.
#[test]
fn box_clone_from_ptr_stability() {
for size in (0..8).map(|i| 2usize.pow(i)) {
let control = vec![Dummy { _data: 42 }; size].into_boxed_slice();
let mut copy = vec![Dummy { _data: 84 }; size].into_boxed_slice();
let copy_raw = copy.as_ptr() as usize;
copy.clone_from(&control);
assert_eq!(copy.as_ptr() as usize, copy_raw);
}
}
#[test]
fn box_deref_lval() {
let x = Box::new(Cell::new(5));
x.set(1000);
assert_eq!(x.get(), 1000);
}
pub struct ConstAllocator;
unsafe impl const Allocator for ConstAllocator {
fn allocate(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocError> {
match layout.size() {
0 => Ok(NonNull::slice_from_raw_parts(layout.dangling(), 0)),
_ => unsafe {
let ptr = core::intrinsics::const_allocate(layout.size(), layout.align());
Ok(NonNull::new_unchecked(ptr as *mut [u8; 0] as *mut [u8]))
},
}
}
unsafe fn deallocate(&self, _ptr: NonNull<u8>, layout: Layout) {
match layout.size() {
0 => { /* do nothing */ }
_ => { /* do nothing too */ }
}
}
fn allocate_zeroed(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocError> {
let ptr = self.allocate(layout)?;
if layout.size() > 0 {
unsafe {
ptr.as_mut_ptr().write_bytes(0, layout.size());
}
}
Ok(ptr)
}
unsafe fn grow(
&self,
ptr: NonNull<u8>,
old_layout: Layout,
new_layout: Layout,
) -> Result<NonNull<[u8]>, AllocError> {
debug_assert!(
new_layout.size() >= old_layout.size(),
"`new_layout.size()` must be greater than or equal to `old_layout.size()`"
);
let new_ptr = self.allocate(new_layout)?;
if new_layout.size() > 0 {
// Safety: `new_ptr` is valid for writes and `ptr` for reads of
// `old_layout.size()`, because `new_layout.size() >=
// old_layout.size()` (which is an invariant that must be upheld by
// callers).
unsafe {
new_ptr.as_mut_ptr().copy_from_nonoverlapping(ptr.as_ptr(), old_layout.size());
}
// Safety: `ptr` is never used again is also an invariant which must
// be upheld by callers.
unsafe {
self.deallocate(ptr, old_layout);
}
}
Ok(new_ptr)
}
unsafe fn grow_zeroed(
&self,
ptr: NonNull<u8>,
old_layout: Layout,
new_layout: Layout,
) -> Result<NonNull<[u8]>, AllocError> {
// Safety: Invariants of `grow_zeroed` and `grow` are the same, and must
// be enforced by callers.
let new_ptr = unsafe { self.grow(ptr, old_layout, new_layout)? };
if new_layout.size() > 0 {
let old_size = old_layout.size();
let new_size = new_layout.size();
let raw_ptr = new_ptr.as_mut_ptr();
// Safety:
// - `grow` returned Ok, so the returned pointer must be valid for
// `new_size` bytes
// - `new_size` must be larger than `old_size`, which is an
// invariant which must be upheld by callers.
unsafe {
raw_ptr.add(old_size).write_bytes(0, new_size - old_size);
}
}
Ok(new_ptr)
}
unsafe fn shrink(
&self,
ptr: NonNull<u8>,
old_layout: Layout,
new_layout: Layout,
) -> Result<NonNull<[u8]>, AllocError> {
debug_assert!(
new_layout.size() <= old_layout.size(),
"`new_layout.size()` must be smaller than or equal to `old_layout.size()`"
);
let new_ptr = self.allocate(new_layout)?;
if new_layout.size() > 0 {
// Safety: `new_ptr` and `ptr` are valid for reads/writes of
// `new_layout.size()` because of the invariants of shrink, which
// include `new_layout.size()` being smaller than (or equal to)
// `old_layout.size()`.
unsafe {
new_ptr.as_mut_ptr().copy_from_nonoverlapping(ptr.as_ptr(), new_layout.size());
}
// Safety: `ptr` is never used again is also an invariant which must
// be upheld by callers.
unsafe {
self.deallocate(ptr, old_layout);
}
}
Ok(new_ptr)
}
fn by_ref(&self) -> &Self
where
Self: Sized,
{
self
}
}
|
