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use core::ptr::{self};
/// Returns the two slices that cover the `VecDeque`'s valid range
pub trait RingSlices: Sized {
fn slice(self, from: usize, to: usize) -> Self;
fn split_at(self, i: usize) -> (Self, Self);
fn ring_slices(buf: Self, head: usize, tail: usize) -> (Self, Self) {
let contiguous = tail <= head;
if contiguous {
let (empty, buf) = buf.split_at(0);
(buf.slice(tail, head), empty)
} else {
let (mid, right) = buf.split_at(tail);
let (left, _) = mid.split_at(head);
(right, left)
}
}
}
impl<T> RingSlices for &[T] {
fn slice(self, from: usize, to: usize) -> Self {
&self[from..to]
}
fn split_at(self, i: usize) -> (Self, Self) {
(*self).split_at(i)
}
}
impl<T> RingSlices for &mut [T] {
fn slice(self, from: usize, to: usize) -> Self {
&mut self[from..to]
}
fn split_at(self, i: usize) -> (Self, Self) {
(*self).split_at_mut(i)
}
}
impl<T> RingSlices for *mut [T] {
fn slice(self, from: usize, to: usize) -> Self {
assert!(from <= to && to < self.len());
// Not using `get_unchecked_mut` to keep this a safe operation.
let len = to - from;
ptr::slice_from_raw_parts_mut(self.as_mut_ptr().wrapping_add(from), len)
}
fn split_at(self, mid: usize) -> (Self, Self) {
let len = self.len();
let ptr = self.as_mut_ptr();
assert!(mid <= len);
(
ptr::slice_from_raw_parts_mut(ptr, mid),
ptr::slice_from_raw_parts_mut(ptr.wrapping_add(mid), len - mid),
)
}
}
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