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DRY out as_flattened impls #146

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Sep 23, 2025
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DRY out as_flattened impls #146

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78 changes: 29 additions & 49 deletions src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -363,7 +363,7 @@ where
U: ArraySize,
V: ArraySize,
{
/// Takes a `&mut Array<Array<T, N>,M>`, and flattens it to a `&mut [T]`.
/// Takes a `&Array<Array<T, N>, >>`, and flattens it to a `&[T]`.
///
/// # Panics
///
Expand All @@ -376,33 +376,28 @@ where
/// # Examples
///
/// ```
/// use hybrid_array::{Array, typenum::U3};
/// use hybrid_array::{Array, typenum::{U0, U2, U3, U5, U10}};
///
/// fn add_5_to_all(slice: &mut [i32]) {
/// for i in slice {
/// *i += 5;
/// }
/// }
/// let a: Array<Array<usize, U3>, U2> = Array([Array([1, 2, 3]), Array([4, 5, 6])]);
/// assert_eq!(a.as_flattened(), &[1, 2, 3, 4, 5, 6]);
///
/// let mut array: Array<Array<i32, U3>, U3> = Array([Array([1_i32, 2, 3]), Array([4, 5, 6]), Array([7, 8, 9])]);
/// add_5_to_all(array.as_flattened_mut());
/// assert_eq!(array, Array([Array([6, 7, 8]), Array([9, 10, 11]), Array([12, 13, 14])]));
/// let b: Array<Array<usize, U2>, U3> = Array([Array([1, 2]), Array([3, 4]), Array([5, 6])]);
/// assert_eq!(a.as_flattened(), b.as_flattened());
///
/// let c: Array<[usize; 2], U3> = Array([[1, 2], [3, 4], [5, 6]]);
/// assert_eq!(a.as_flattened(), c.as_flattened());
///
/// let slice_of_empty_arrays: &Array<Array<i32, U5>, U0> = &Array::from_fn(|_| Array([1, 2, 3, 4, 5]));
/// assert!(slice_of_empty_arrays.as_flattened().is_empty());
///
/// let empty_slice_of_arrays: &Array<Array<u32, U10>, U0> = &Array([]);
/// assert!(empty_slice_of_arrays.as_flattened().is_empty());
/// ```
pub fn as_flattened_mut(&mut self) -> &mut [T] {
let len = if size_of::<T>() == 0 {
self.len()
.checked_mul(U::USIZE)
.expect("slice len overflow")
} else {
// SAFETY: `self.len() * N` cannot overflow because `self` is
// already in the address space.
unsafe { self.len().unchecked_mul(U::USIZE) }
};
// SAFETY: `[T]` is layout-identical to `[T; U]`
unsafe { slice::from_raw_parts_mut(self.as_mut_ptr().cast(), len) }
pub fn as_flattened(&self) -> &[T] {
Array::slice_as_flattened(self.as_slice())
}

/// Takes a `&Array<Array<T, N>, >>`, and flattens it to a `&[T]`.
/// Takes a `&mut Array<Array<T, N>,M>`, and flattens it to a `&mut [T]`.
///
/// # Panics
///
Expand All @@ -415,35 +410,20 @@ where
/// # Examples
///
/// ```
/// use hybrid_array::{Array, typenum::{U0, U2, U3, U5, U10}};
///
/// let a: Array<Array<usize, U3>, U2> = Array([Array([1, 2, 3]), Array([4, 5, 6])]);
/// assert_eq!(a.as_flattened(), &[1, 2, 3, 4, 5, 6]);
///
/// let b: Array<Array<usize, U2>, U3> = Array([Array([1, 2]), Array([3, 4]), Array([5, 6])]);
/// assert_eq!(a.as_flattened(), b.as_flattened());
///
/// let c: Array<[usize; 2], U3> = Array([[1, 2], [3, 4], [5, 6]]);
/// assert_eq!(a.as_flattened(), c.as_flattened());
/// use hybrid_array::{Array, typenum::U3};
///
/// let slice_of_empty_arrays: &Array<Array<i32, U5>, U0> = &Array::from_fn(|_| Array([1, 2, 3, 4, 5]));
/// assert!(slice_of_empty_arrays.as_flattened().is_empty());
/// fn add_5_to_all(slice: &mut [i32]) {
/// for i in slice {
/// *i += 5;
/// }
/// }
///
/// let empty_slice_of_arrays: &Array<Array<u32, U10>, U0> = &Array([]);
/// assert!(empty_slice_of_arrays.as_flattened().is_empty());
/// let mut array: Array<Array<i32, U3>, U3> = Array([Array([1_i32, 2, 3]), Array([4, 5, 6]), Array([7, 8, 9])]);
/// add_5_to_all(array.as_flattened_mut());
/// assert_eq!(array, Array([Array([6, 7, 8]), Array([9, 10, 11]), Array([12, 13, 14])]));
/// ```
pub fn as_flattened(&self) -> &[T] {
let len = if size_of::<T>() == 0 {
self.len()
.checked_mul(U::USIZE)
.expect("slice len overflow")
} else {
// SAFETY: `self.len() * N` cannot overflow because `self` is
// already in the address space.
unsafe { self.len().unchecked_mul(U::USIZE) }
};
// SAFETY: `[T]` is layout-identical to `[T; U]`
unsafe { slice::from_raw_parts(self.as_ptr().cast(), len) }
pub fn as_flattened_mut(&mut self) -> &mut [T] {
Array::slice_as_flattened_mut(self.as_mut_slice())
}
}

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