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use std::fmt::Debug;
use std::ops::{Add, Index, IndexMut};
/// A circular array that allows infinite pushes into a fixed-size array.
#[derive(Debug)]
pub struct CircularArray<const N: usize, T> {
arr: [T;N],
start: usize,
seq: usize,
}
impl<const N: usize, T> CircularArray<N, T> where T: Copy + Default + Debug {
pub fn new() -> Self {
Self {
arr: [T::default(); N],
start: 0,
seq: 0,
}
}
/// # example
/// ```
/// #[test]
/// #[allow(non_snake_case)]
/// fn test_Index_and_IndexMut() {
/// let mut arr = CircularArray::<3, u32>::new();
/// arr.push(0);
/// arr.push(0);
/// arr.push(0);
/// arr.push(0);
/// arr.push(0);
/// arr[0] = 1;
/// arr[1] = 2;
/// arr[2] = 3;
/// assert_eq!(arr[0], 1);
/// assert_eq!(arr[1], 2);
/// assert_eq!(arr[2], 3);
/// }
pub fn push(&mut self, item: T) {
if self.seq >= N {
self.arr[self.start] = item;
} else {
self.arr[self.seq] = item;
}
self.start = (self.start + 1) % N;
self.seq += 1;
}
/// ## Examples
/// ```
/// #[test]
/// fn test_to_array() {
/// let mut arr = CircularArray::<3, u32>::new();
/// arr.push(1);
/// arr.push(2);
/// arr.push(3);
/// assert_eq!(arr.to_array(), [1, 2, 3]);
/// arr.push(4);
/// assert_eq!(arr.to_array(), [2, 3, 4]);
/// }
/// ```
pub fn to_array(&self) -> [T;N] {
unsafe {
let mut arr = [T::default(); N];
let src_ptr = self.arr.as_ptr();
let dest_ptr = arr.as_mut_ptr();
if self.seq >= N && self.start > 0 {
std::ptr::copy_nonoverlapping(src_ptr.add(self.start), dest_ptr, N - self.start);
std::ptr::copy_nonoverlapping(src_ptr, dest_ptr.add(N - self.start), N - self.start);
} else {
std::ptr::copy_nonoverlapping(src_ptr, dest_ptr, N);
}
arr
}
}
}
impl<T, const N: usize> Index<usize> for CircularArray<N, T> where [T]: Index<usize>, T: Default + Copy
{
type Output = <[T] as Index<usize>>::Output;
#[inline]
fn index(&self, index: usize) -> &Self::Output {
if self.seq >= N {
&self.arr[(self.start + index) % N]
} else {
&self.arr[index]
}
}
}
impl<T, const N: usize> IndexMut<usize> for CircularArray<N, T>
where [T]: Index<usize>,
T: Default + Copy, usize: Add<usize> {
#[inline]
fn index_mut(&mut self, index: usize) -> &mut Self::Output {
if self.seq >= N {
&mut self.arr[(self.start + index) % N]
} else {
&mut self.arr[index]
}
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_push() {
let mut arr = CircularArray::<3, u32>::new();
arr.push(1);
arr.push(2);
arr.push(3);
assert_eq!(arr.arr, [1, 2, 3]);
arr.push(3);
assert_eq!(arr.arr, [2, 3, 4]);
}
#[test]
#[allow(non_snake_case)]
fn test_Index_and_IndexMut() {
let mut arr = CircularArray::<3, u32>::new();
arr.push(0);
arr.push(0);
arr.push(0);
arr.push(0);
arr.push(0);
arr[0] = 1;
arr[1] = 2;
arr[2] = 3;
assert_eq!(arr[0], 1);
assert_eq!(arr[1], 2);
assert_eq!(arr[2], 3);
}
#[test]
fn test_to_array() {
let mut arr = CircularArray::<3, u32>::new();
arr.push(1);
arr.push(2);
arr.push(3);
assert_eq!(arr.to_array(), [1, 2, 3]);
arr.push(4);
assert_eq!(arr.to_array(), [2, 3, 4]);
}
}