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use core::mem::MaybeUninit;
use slice_trait::Slice;
use crate::padded::Padded;
#[const_trait]
pub trait SliceSpread<T>: Slice<Item = T>
{
/// Spreads elements equally across `M` slices.
/// Slices will have equal length only if the operand slice's length is divisible by `M`.
///
/// # Example
///
/// Take, for instance, that we want to divide a slice into odd and even elements:
///
/// ```rust
/// #![feature(generic_const_exprs)]
///
/// use slice_ops::ops::*;
///
/// let arr = [1, 2, 3];
/// let slice = arr.as_slice();
///
/// let [odd, even] = slice.spread();
///
/// assert_eq!(odd, [1, 3]);
/// assert_eq!(even, [2]);
/// ```
fn spread<const M: usize>(&self) -> [&[Padded<T, M>]; M]
where
[(); M - 1]:;
/// Spreads elements equally across `M` mutable slices.
/// Slices will have equal length only if the operand slice's length is divisible by `M`.
///
/// # Example
/// ```rust
/// #![feature(generic_const_exprs)]
///
/// use slice_ops::ops::*;
///
/// let mut arr = ["1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11", "12", "13", "14", "15"];
/// let slice = arr.as_mut_slice();
///
/// let [_, _, fizz] = slice.spread_mut::<3>();
/// assert_eq!(fizz, ["3", "6", "9", "12", "15"]);
/// for fizz in fizz.iter_mut()
/// {
/// **fizz = "fizz";
/// }
///
/// let [_, _, _, _, buzz] = slice.spread_mut::<5>();
/// assert_eq!(buzz, ["5", "10", "fizz"]);
/// for buzz in buzz.iter_mut()
/// {
/// if **buzz == "fizz"
/// {
/// **buzz = "fizzbuzz";
/// continue;
/// }
/// **buzz = "buzz";
/// }
///
/// assert_eq!(arr, ["1", "2", "fizz", "4", "buzz", "fizz", "7", "8", "fizz", "buzz", "11", "fizz", "13", "14", "fizzbuzz"]);
/// ```
fn spread_mut<const M: usize>(&mut self) -> [&mut [Padded<T, M>]; M]
where
[(); M - 1]:;
}
impl<T> SliceSpread<T> for [T]
{
fn spread<const M: usize>(&self) -> [&[Padded<T, M>]; M]
where
[(); M - 1]:
{
let len = self.len();
let ptr = self.as_ptr();
let mut spread: [MaybeUninit<&[Padded<T, M>]>; M] = MaybeUninit::uninit_array();
let mut i = 0;
while i < M
{
spread[i].write(unsafe {
core::slice::from_raw_parts(ptr.add(i).cast(), len/M + if len % M > i {1} else {0})
});
i += 1;
}
unsafe {
MaybeUninit::array_assume_init(spread)
}
}
fn spread_mut<const M: usize>(&mut self) -> [&mut [Padded<T, M>]; M]
where
[(); M - 1]:
{
let len = self.len();
let ptr = self.as_mut_ptr();
let mut spread: [MaybeUninit<&mut [Padded<T, M>]>; M] = MaybeUninit::uninit_array();
let mut i = 0;
while i < M
{
spread[i].write(unsafe {
core::slice::from_raw_parts_mut(ptr.add(i).cast(), len/M + if len % M > i {1} else {0})
});
i += 1;
}
unsafe {
MaybeUninit::array_assume_init(spread)
}
}
}
#[cfg(test)]
mod test
{
use crate::ops::SliceSpread;
#[test]
fn fizzbuzz()
{
let mut arr = ["1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11", "12", "13", "14", "15"];
let slice = arr.as_mut_slice();
let [_, _, fizz] = slice.spread_mut();
assert_eq!(fizz, ["3", "6", "9", "12", "15"]);
for fizz in fizz.iter_mut()
{
**fizz = "fizz";
}
let [_, _, _, _, buzz] = slice.spread_mut();
assert_eq!(buzz, ["5", "10", "fizz"]);
for buzz in buzz.iter_mut()
{
if **buzz == "fizz"
{
**buzz = "fizzbuzz";
continue;
}
**buzz = "buzz";
}
assert_eq!(
arr,
["1", "2", "fizz", "4", "buzz", "fizz", "7", "8", "fizz", "buzz", "11", "fizz", "13", "14", "fizzbuzz"]
);
}
}