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use super::{
NodePtr,
iter::{ArrayLeftMostPtrIter, ArrayLeftMostPtrIterMut},
refs::Refs,
};
use crate::variant::Variant;
use core::fmt::Debug;
/// A constant number of left-aligned references.
///
/// It differs from [`RefsArray`] due to its additional requirement that:
/// * all Some references are to the left of all None references.
///
/// [`RefsArray`]: crate::RefsArray
pub struct RefsArrayLeftMost<const N: usize, V>
where
V: Variant,
{
array: [Option<NodePtr<V>>; N],
len: usize,
}
impl<const N: usize, V: Variant> Clone for RefsArrayLeftMost<N, V> {
fn clone(&self) -> Self {
Self {
array: self.array,
len: self.len,
}
}
}
impl<const N: usize, V: Variant> Debug for RefsArrayLeftMost<N, V> {
fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
f.debug_tuple("RefsArrayLeftMost")
.field(&self.array)
.finish()
}
}
impl<const N: usize, V> Refs for RefsArrayLeftMost<N, V>
where
V: Variant,
{
#[inline(always)]
fn empty() -> Self {
Self {
array: [const { None }; N],
len: 0,
}
}
#[inline(always)]
fn is_empty(&self) -> bool {
self.len == 0
}
#[inline(always)]
fn clear(&mut self) {
self.array
.iter_mut()
.take(self.len)
.for_each(|x| _ = x.take());
self.len = 0;
}
#[inline(always)]
fn remove_at(&mut self, ref_idx: usize) {
self.array[ref_idx] = None;
for i in (ref_idx + 1)..self.len {
self.array[i - 1] = self.array[i].take();
}
self.len -= 1;
}
#[inline(always)]
fn remove(&mut self, ptr: usize) -> Option<usize> {
let x = self.array.iter().enumerate().find(|x| match x.1 {
Some(x) => unsafe { x.ptr() as usize == ptr },
None => false,
});
match x {
Some((ref_idx, _)) => {
self.remove_at(ref_idx);
Some(ref_idx)
}
None => None,
}
}
}
impl<const N: usize, V: Variant> RefsArrayLeftMost<N, V> {
/// Returns the number of references.
pub fn len(&self) -> usize {
self.len
}
/// Returns true if the number of references is zero.
pub fn is_empty(&self) -> bool {
self.len == 0
}
/// Returns a reference to the node pointer at the `ref_idx` position of the references array.
pub fn get(&self, ref_idx: usize) -> Option<NodePtr<V>> {
match ref_idx < N {
true => self.array[ref_idx],
false => None,
}
}
/// Returns the optional node pointers as a slice such that:
/// * length of the slice is equal to `self.len()`,
/// * all elements of the slice are of `Some` variant, and hence,
/// * can be safely unwrapped to access the node pointer.
pub fn as_slice(&self) -> &[Option<NodePtr<V>>] {
&self.array[..self.len]
}
/// Creates an iterator over node pointers of the references collection.
pub fn iter(&self) -> ArrayLeftMostPtrIter<'_, V> {
let slice = &self.array[..self.len];
ArrayLeftMostPtrIter::new(slice.iter())
}
/// Creates a mutable iterator over node pointers of the references collection.
pub fn iter_mut(&mut self) -> ArrayLeftMostPtrIterMut<'_, V> {
let slice = &mut self.array[..self.len];
ArrayLeftMostPtrIterMut::new(slice.iter_mut())
}
/// Returns whether or not the collection has room for another reference.
pub fn has_room(&self) -> bool {
self.len < N
}
/// Pushes the node references to the end of the references collection.
///
/// # Panics
///
/// Panics if the array already has `N` references; i.e., when `self.has_room()` is false.
pub fn push(&mut self, node_ptr: NodePtr<V>) {
self.assert_has_room_for::<1>();
self.array[self.len] = Some(node_ptr);
self.len += 1;
}
/// Inserts the reference with the given `node_ptr` to the given `position` of the references collection.
pub fn insert(&mut self, position: usize, node_ptr: NodePtr<V>) {
for q in (position..self.len).rev() {
self.array[q + 1] = self.array[q];
}
self.array[position] = Some(node_ptr);
self.len += 1;
}
/// Inserts the reference with the given `node_ptr` just before the given `pivot_ptr` the reference if it exists;
/// and returns the position that the new reference is inserted to.
///
/// Does nothing leaving the children unchanged if the `pivot_ptr` reference does not exists, and returns None.
pub fn push_before(&mut self, pivot_ptr: NodePtr<V>, node_ptr: NodePtr<V>) -> Option<usize> {
self.assert_has_room_for::<1>();
let position = self.iter().position(|x| *x == pivot_ptr);
if let Some(p) = position {
self.insert(p, node_ptr);
}
position
}
/// Inserts the reference with the given `node_ptr` just after the given `pivot_ptr` the reference if it exists;
/// and returns the position that the new reference is inserted to.
///
/// Does nothing leaving the children unchanged if the `pivot_ptr` reference does not exists, and returns None.
pub fn push_after(&mut self, pivot_ptr: NodePtr<V>, node_ptr: NodePtr<V>) -> Option<usize> {
self.assert_has_room_for::<1>();
let position = self.iter().position(|x| *x == pivot_ptr);
if let Some(p) = position {
self.insert(p + 1, node_ptr);
}
position
}
/// Replaces the node reference `old_node_ptr` with the `new_node_ptr` and returns
/// the position of the reference.
///
/// Does nothing and returns None if the `old_node_ptr` is absent.
pub fn replace_with(
&mut self,
old_node_ptr: NodePtr<V>,
new_node_ptr: NodePtr<V>,
) -> Option<usize> {
let position = self.iter().position(|x| *x == old_node_ptr);
if let Some(p) = position {
self.array[p] = Some(new_node_ptr);
}
position
}
/// If both pointers `ptr_a` and `ptr_b` exist as children, this method swaps their positions
/// and returns `(pos_a, pos_b)` where `pos_a` (`pos_b`) is the original (before the swap) position
/// of the child `ptr_a` (`ptr_b`).
///
/// Does nothing and returns None if either of the pointers is absent.
pub fn swap(&mut self, ptr_a: NodePtr<V>, ptr_b: NodePtr<V>) -> Option<(usize, usize)> {
let (pos_a, pos_b) = {
let mut a = None;
let mut b = None;
for (i, x) in self.array[..self.len].iter().enumerate() {
match *x {
x if x == Some(ptr_a) => {
a = Some(i);
if b.is_some() {
break;
}
}
x if x == Some(ptr_b) => {
b = Some(i);
if a.is_some() {
break;
}
}
_ => {}
}
}
match (a, b) {
(Some(a), Some(b)) => Some((a, b)),
_ => None,
}
}?;
self.array[pos_a] = Some(ptr_b);
self.array[pos_b] = Some(ptr_a);
Some((pos_a, pos_b))
}
// helpers
fn assert_has_room_for<const P: usize>(&self) {
assert!(
self.len + P <= N,
"Pushing the {}-th reference to array-backed references with maximum of {} elements.",
N + P,
N
);
}
}