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use super::{Bucket, Entries, IndexSet, IntoIter, Iter};
use crate::util::try_simplify_range;
use alloc::boxed::Box;
use alloc::vec::Vec;
use core::cmp::Ordering;
use core::fmt;
use core::hash::{Hash, Hasher};
use core::ops::{self, Bound, Index, RangeBounds};
/// A dynamically-sized slice of values in an [`IndexSet`].
///
/// This supports indexed operations much like a `[T]` slice,
/// but not any hashed operations on the values.
///
/// Unlike `IndexSet`, `Slice` does consider the order for [`PartialEq`]
/// and [`Eq`], and it also implements [`PartialOrd`], [`Ord`], and [`Hash`].
#[repr(transparent)]
pub struct Slice<T> {
pub(crate) entries: [Bucket<T>],
}
// SAFETY: `Slice<T>` is a transparent wrapper around `[Bucket<T>]`,
// and reference lifetimes are bound together in function signatures.
#[allow(unsafe_code)]
impl<T> Slice<T> {
pub(super) const fn from_slice(entries: &[Bucket<T>]) -> &Self {
unsafe { &*(entries as *const [Bucket<T>] as *const Self) }
}
pub(super) fn from_boxed(entries: Box<[Bucket<T>]>) -> Box<Self> {
unsafe { Box::from_raw(Box::into_raw(entries) as *mut Self) }
}
fn into_boxed(self: Box<Self>) -> Box<[Bucket<T>]> {
unsafe { Box::from_raw(Box::into_raw(self) as *mut [Bucket<T>]) }
}
}
impl<T> Slice<T> {
pub(crate) fn into_entries(self: Box<Self>) -> Vec<Bucket<T>> {
self.into_boxed().into_vec()
}
/// Returns an empty slice.
pub const fn new<'a>() -> &'a Self {
Self::from_slice(&[])
}
/// Return the number of elements in the set slice.
pub const fn len(&self) -> usize {
self.entries.len()
}
/// Returns true if the set slice contains no elements.
pub const fn is_empty(&self) -> bool {
self.entries.is_empty()
}
/// Get a value by index.
///
/// Valid indices are *0 <= index < self.len()*
pub fn get_index(&self, index: usize) -> Option<&T> {
self.entries.get(index).map(Bucket::key_ref)
}
/// Returns a slice of values in the given range of indices.
///
/// Valid indices are *0 <= index < self.len()*
pub fn get_range<R: RangeBounds<usize>>(&self, range: R) -> Option<&Self> {
let range = try_simplify_range(range, self.entries.len())?;
self.entries.get(range).map(Self::from_slice)
}
/// Get the first value.
pub fn first(&self) -> Option<&T> {
self.entries.first().map(Bucket::key_ref)
}
/// Get the last value.
pub fn last(&self) -> Option<&T> {
self.entries.last().map(Bucket::key_ref)
}
/// Divides one slice into two at an index.
///
/// ***Panics*** if `index > len`.
pub fn split_at(&self, index: usize) -> (&Self, &Self) {
let (first, second) = self.entries.split_at(index);
(Self::from_slice(first), Self::from_slice(second))
}
/// Returns the first value and the rest of the slice,
/// or `None` if it is empty.
pub fn split_first(&self) -> Option<(&T, &Self)> {
if let [first, rest @ ..] = &self.entries {
Some((&first.key, Self::from_slice(rest)))
} else {
None
}
}
/// Returns the last value and the rest of the slice,
/// or `None` if it is empty.
pub fn split_last(&self) -> Option<(&T, &Self)> {
if let [rest @ .., last] = &self.entries {
Some((&last.key, Self::from_slice(rest)))
} else {
None
}
}
/// Return an iterator over the values of the set slice.
pub fn iter(&self) -> Iter<'_, T> {
Iter::new(&self.entries)
}
/// Search over a sorted set for a value.
///
/// Returns the position where that value is present, or the position where it can be inserted
/// to maintain the sort. See [`slice::binary_search`] for more details.
///
/// Computes in **O(log(n))** time, which is notably less scalable than looking the value up in
/// the set this is a slice from using [`IndexSet::get_index_of`], but this can also position
/// missing values.
pub fn binary_search(&self, x: &T) -> Result<usize, usize>
where
T: Ord,
{
self.binary_search_by(|p| p.cmp(x))
}
/// Search over a sorted set with a comparator function.
///
/// Returns the position where that value is present, or the position where it can be inserted
/// to maintain the sort. See [`slice::binary_search_by`] for more details.
///
/// Computes in **O(log(n))** time.
#[inline]
pub fn binary_search_by<'a, F>(&'a self, mut f: F) -> Result<usize, usize>
where
F: FnMut(&'a T) -> Ordering,
{
self.entries.binary_search_by(move |a| f(&a.key))
}
/// Search over a sorted set with an extraction function.
///
/// Returns the position where that value is present, or the position where it can be inserted
/// to maintain the sort. See [`slice::binary_search_by_key`] for more details.
///
/// Computes in **O(log(n))** time.
#[inline]
pub fn binary_search_by_key<'a, B, F>(&'a self, b: &B, mut f: F) -> Result<usize, usize>
where
F: FnMut(&'a T) -> B,
B: Ord,
{
self.binary_search_by(|k| f(k).cmp(b))
}
/// Returns the index of the partition point of a sorted set according to the given predicate
/// (the index of the first element of the second partition).
///
/// See [`slice::partition_point`] for more details.
///
/// Computes in **O(log(n))** time.
#[must_use]
pub fn partition_point<P>(&self, mut pred: P) -> usize
where
P: FnMut(&T) -> bool,
{
self.entries.partition_point(move |a| pred(&a.key))
}
}
impl<'a, T> IntoIterator for &'a Slice<T> {
type IntoIter = Iter<'a, T>;
type Item = &'a T;
fn into_iter(self) -> Self::IntoIter {
self.iter()
}
}
impl<T> IntoIterator for Box<Slice<T>> {
type IntoIter = IntoIter<T>;
type Item = T;
fn into_iter(self) -> Self::IntoIter {
IntoIter::new(self.into_entries())
}
}
impl<T> Default for &'_ Slice<T> {
fn default() -> Self {
Slice::from_slice(&[])
}
}
impl<T> Default for Box<Slice<T>> {
fn default() -> Self {
Slice::from_boxed(Box::default())
}
}
impl<T: Clone> Clone for Box<Slice<T>> {
fn clone(&self) -> Self {
Slice::from_boxed(self.entries.to_vec().into_boxed_slice())
}
}
impl<T: Copy> From<&Slice<T>> for Box<Slice<T>> {
fn from(slice: &Slice<T>) -> Self {
Slice::from_boxed(Box::from(&slice.entries))
}
}
impl<T: fmt::Debug> fmt::Debug for Slice<T> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_list().entries(self).finish()
}
}
impl<T: PartialEq> PartialEq for Slice<T> {
fn eq(&self, other: &Self) -> bool {
self.len() == other.len() && self.iter().eq(other)
}
}
impl<T: Eq> Eq for Slice<T> {}
impl<T: PartialOrd> PartialOrd for Slice<T> {
fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
self.iter().partial_cmp(other)
}
}
impl<T: Ord> Ord for Slice<T> {
fn cmp(&self, other: &Self) -> Ordering {
self.iter().cmp(other)
}
}
impl<T: Hash> Hash for Slice<T> {
fn hash<H: Hasher>(&self, state: &mut H) {
self.len().hash(state);
for value in self {
value.hash(state);
}
}
}
impl<T> Index<usize> for Slice<T> {
type Output = T;
fn index(&self, index: usize) -> &Self::Output {
&self.entries[index].key
}
}
// We can't have `impl<I: RangeBounds<usize>> Index<I>` because that conflicts with `Index<usize>`.
// Instead, we repeat the implementations for all the core range types.
macro_rules! impl_index {
($($range:ty),*) => {$(
impl<T, S> Index<$range> for IndexSet<T, S> {
type Output = Slice<T>;
fn index(&self, range: $range) -> &Self::Output {
Slice::from_slice(&self.as_entries()[range])
}
}
impl<T> Index<$range> for Slice<T> {
type Output = Self;
fn index(&self, range: $range) -> &Self::Output {
Slice::from_slice(&self.entries[range])
}
}
)*}
}
impl_index!(
ops::Range<usize>,
ops::RangeFrom<usize>,
ops::RangeFull,
ops::RangeInclusive<usize>,
ops::RangeTo<usize>,
ops::RangeToInclusive<usize>,
(Bound<usize>, Bound<usize>)
);
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn slice_index() {
fn check(vec_slice: &[i32], set_slice: &Slice<i32>, sub_slice: &Slice<i32>) {
assert_eq!(set_slice as *const _, sub_slice as *const _);
itertools::assert_equal(vec_slice, set_slice);
}
let vec: Vec<i32> = (0..10).map(|i| i * i).collect();
let set: IndexSet<i32> = vec.iter().cloned().collect();
let slice = set.as_slice();
// RangeFull
check(&vec[..], &set[..], &slice[..]);
for i in 0usize..10 {
// Index
assert_eq!(vec[i], set[i]);
assert_eq!(vec[i], slice[i]);
// RangeFrom
check(&vec[i..], &set[i..], &slice[i..]);
// RangeTo
check(&vec[..i], &set[..i], &slice[..i]);
// RangeToInclusive
check(&vec[..=i], &set[..=i], &slice[..=i]);
// (Bound<usize>, Bound<usize>)
let bounds = (Bound::Excluded(i), Bound::Unbounded);
check(&vec[i + 1..], &set[bounds], &slice[bounds]);
for j in i..=10 {
// Range
check(&vec[i..j], &set[i..j], &slice[i..j]);
}
for j in i..10 {
// RangeInclusive
check(&vec[i..=j], &set[i..=j], &slice[i..=j]);
}
}
}
}