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use core::marker::PhantomData;
use crate::{
Field,
type_lists::{
ConsSet,
GetPtr,
GetStride,
SculptSlice,
TupleSet,
},
};
/// Mutable reified lens into contiguous memory.
#[derive(Debug, PartialEq, Eq)]
pub struct LensSliceMut<'a, T>
where
T: TupleSet,
{
storage: T::ConsSlice,
len: usize,
_phantom: PhantomData<&'a ()>,
}
impl<'a, T> LensSliceMut<'a, T>
where
T: TupleSet,
{
#[inline]
pub(crate) const fn new(storage: T::ConsSlice, len: usize) -> Self {
Self {
storage,
len,
_phantom: PhantomData,
}
}
/// Split `self` into two mutable slice lenses.
///
/// `Lhs` is the tuple of fields that should appear in the left-hand
/// returned lens; the right-hand lens contains the remaining fields.
///
/// `Indices` is a single tuple-nested list of shrinking-list positions (one
/// per element of `Lhs`) and should be inferred; pass `_` at the call site.
#[expect(clippy::type_complexity, reason = "necessary type inference")]
#[inline]
pub fn split<Lhs, Indices>(
self,
) -> (
LensSliceMut<'a, Lhs>,
LensSliceMut<
'a,
<<T::ConsSlice as SculptSlice<Lhs::ConsSlice, Indices>>::Remainder as ConsSet>::Tuple,
>,
)
where
Lhs: TupleSet,
T::ConsSlice: SculptSlice<Lhs::ConsSlice, Indices>,
<T::ConsSlice as SculptSlice<Lhs::ConsSlice, Indices>>::Remainder: ConsSet<
Tuple: TupleSet<
ConsSlice = <T::ConsSlice as SculptSlice<Lhs::ConsSlice, Indices>>::Remainder,
>,
>,
{
let (lhs_storage, rem_storage) = self.storage.sculpt_slice();
(
LensSliceMut {
storage: lhs_storage,
len: self.len,
_phantom: PhantomData,
},
LensSliceMut {
storage: rem_storage,
len: self.len,
_phantom: PhantomData,
},
)
}
/// Returns a pointer to the first lensed element of a field.
#[inline]
pub fn as_ptr<Elt, Index>(&self) -> *const Elt::Type
where
Elt: Field + 'static,
T::ConsSlice: GetPtr<Elt, Index>,
{
self.storage.get_ptr().as_ptr()
}
/// Returns a mutable pointer to the first lensed element of a field.
#[inline]
pub fn as_mut_ptr<Elt, Index>(&mut self) -> *mut Elt::Type
where
Elt: Field + 'static,
T::ConsSlice: GetPtr<Elt, Index>,
{
self.storage.get_ptr().as_ptr()
}
/// Returns a shared reference to the `i`-th lensed element of a field, or
/// `None` if `i >= self.len()`.
#[inline]
#[must_use]
pub fn get<Elt, Index>(&self, i: usize) -> Option<&Elt::Type>
where
Elt: Field + 'static,
T::ConsSlice: GetPtr<Elt, Index> + GetStride<Elt, Index>,
{
if i < self.len {
// SAFETY: `i < self.len` checked above.
Some(unsafe { self.get_unchecked::<Elt, _>(i) })
} else {
None
}
}
/// Returns a shared reference to the `i`-th lensed element of a field,
/// without bounds checking.
///
/// # Safety
/// `i` must be `< self.len()`.
#[inline]
#[must_use]
pub unsafe fn get_unchecked<Elt, Index>(&self, i: usize) -> &Elt::Type
where
Elt: Field + 'static,
T::ConsSlice: GetPtr<Elt, Index> + GetStride<Elt, Index>,
{
let base: *const Elt::Type = self.storage.get_ptr().as_ptr();
let stride = self.storage.get_stride();
// SAFETY: By the caller's contract `i < self.len()`, so the offset
// `stride * i` lands inside the original slice. `Adapter` guarantees
// the resulting pointer is valid for reads of `Elt::Type` and
// properly aligned. Tying the returned reference to `&self`
// reborrows the lens shared for the call's lifetime, so no
// `&mut Elt::Type` to the same field can coexist.
unsafe { &*base.byte_add(stride * i) }
}
/// Returns a unique reference to the `i`-th lensed element of a field, or
/// `None` if `i >= self.len()`.
#[inline]
#[must_use]
pub fn get_mut<Elt, Index>(&mut self, i: usize) -> Option<&mut Elt::Type>
where
Elt: Field + 'static,
T::ConsSlice: GetPtr<Elt, Index> + GetStride<Elt, Index>,
{
if i < self.len {
// SAFETY: `i < self.len` checked above.
Some(unsafe { self.get_mut_unchecked::<Elt, _>(i) })
} else {
None
}
}
/// Returns a unique reference to the `i`-th lensed element of a field,
/// without bounds checking.
///
/// # Safety
/// `i` must be `< self.len()`.
#[inline]
#[must_use]
pub unsafe fn get_mut_unchecked<Elt, Index>(&mut self, i: usize) -> &mut Elt::Type
where
Elt: Field + 'static,
T::ConsSlice: GetPtr<Elt, Index> + GetStride<Elt, Index>,
{
let base: *mut Elt::Type = self.storage.get_ptr().as_ptr();
let stride = self.storage.get_stride();
// SAFETY: By the caller's contract `i < self.len()`, so the offset
// `stride * i` lands inside the original slice. `Adapter` guarantees
// the resulting pointer is valid for reads and writes of `Elt::Type`
// and properly aligned. `&mut self` reborrows the lens uniquely for
// the call's lifetime, so the returned `&mut` cannot alias any
// other reference reachable through the lens; the disjointness
// check at construction rules out aliasing through other fields.
unsafe { &mut *base.byte_add(stride * i) }
}
/// Returns the number of lensed elements.
#[inline]
pub const fn len(&self) -> usize {
self.len
}
/// Returns the number of bytes between lensed elements of a field.
#[inline]
pub fn stride<Elt, Index>(&self) -> usize
where
Elt: Field + 'static,
T::ConsSlice: GetStride<Elt, Index>,
{
self.storage.get_stride()
}
/// Returns `true` if the lens has a length of 0.
#[inline]
pub const fn is_empty(&self) -> bool {
self.len == 0
}
}