indexmap/set/
slice.rs

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1use super::{Bucket, IndexSet, IntoIter, Iter};
2use crate::util::{slice_eq, try_simplify_range};
3
4use alloc::boxed::Box;
5use alloc::vec::Vec;
6use core::cmp::Ordering;
7use core::fmt;
8use core::hash::{Hash, Hasher};
9use core::ops::{self, Bound, Index, RangeBounds};
10
11/// A dynamically-sized slice of values in an [`IndexSet`].
12///
13/// This supports indexed operations much like a `[T]` slice,
14/// but not any hashed operations on the values.
15///
16/// Unlike `IndexSet`, `Slice` does consider the order for [`PartialEq`]
17/// and [`Eq`], and it also implements [`PartialOrd`], [`Ord`], and [`Hash`].
18#[repr(transparent)]
19pub struct Slice<T> {
20    pub(crate) entries: [Bucket<T>],
21}
22
23// SAFETY: `Slice<T>` is a transparent wrapper around `[Bucket<T>]`,
24// and reference lifetimes are bound together in function signatures.
25#[allow(unsafe_code)]
26impl<T> Slice<T> {
27    pub(super) const fn from_slice(entries: &[Bucket<T>]) -> &Self {
28        unsafe { &*(entries as *const [Bucket<T>] as *const Self) }
29    }
30
31    pub(super) fn from_boxed(entries: Box<[Bucket<T>]>) -> Box<Self> {
32        unsafe { Box::from_raw(Box::into_raw(entries) as *mut Self) }
33    }
34
35    fn into_boxed(self: Box<Self>) -> Box<[Bucket<T>]> {
36        unsafe { Box::from_raw(Box::into_raw(self) as *mut [Bucket<T>]) }
37    }
38}
39
40impl<T> Slice<T> {
41    pub(crate) fn into_entries(self: Box<Self>) -> Vec<Bucket<T>> {
42        self.into_boxed().into_vec()
43    }
44
45    /// Returns an empty slice.
46    pub const fn new<'a>() -> &'a Self {
47        Self::from_slice(&[])
48    }
49
50    /// Return the number of elements in the set slice.
51    pub const fn len(&self) -> usize {
52        self.entries.len()
53    }
54
55    /// Returns true if the set slice contains no elements.
56    pub const fn is_empty(&self) -> bool {
57        self.entries.is_empty()
58    }
59
60    /// Get a value by index.
61    ///
62    /// Valid indices are `0 <= index < self.len()`.
63    pub fn get_index(&self, index: usize) -> Option<&T> {
64        self.entries.get(index).map(Bucket::key_ref)
65    }
66
67    /// Returns a slice of values in the given range of indices.
68    ///
69    /// Valid indices are `0 <= index < self.len()`.
70    pub fn get_range<R: RangeBounds<usize>>(&self, range: R) -> Option<&Self> {
71        let range = try_simplify_range(range, self.entries.len())?;
72        self.entries.get(range).map(Self::from_slice)
73    }
74
75    /// Get the first value.
76    pub fn first(&self) -> Option<&T> {
77        self.entries.first().map(Bucket::key_ref)
78    }
79
80    /// Get the last value.
81    pub fn last(&self) -> Option<&T> {
82        self.entries.last().map(Bucket::key_ref)
83    }
84
85    /// Divides one slice into two at an index.
86    ///
87    /// ***Panics*** if `index > len`.
88    #[track_caller]
89    pub fn split_at(&self, index: usize) -> (&Self, &Self) {
90        let (first, second) = self.entries.split_at(index);
91        (Self::from_slice(first), Self::from_slice(second))
92    }
93
94    /// Returns the first value and the rest of the slice,
95    /// or `None` if it is empty.
96    pub fn split_first(&self) -> Option<(&T, &Self)> {
97        if let [first, rest @ ..] = &self.entries {
98            Some((&first.key, Self::from_slice(rest)))
99        } else {
100            None
101        }
102    }
103
104    /// Returns the last value and the rest of the slice,
105    /// or `None` if it is empty.
106    pub fn split_last(&self) -> Option<(&T, &Self)> {
107        if let [rest @ .., last] = &self.entries {
108            Some((&last.key, Self::from_slice(rest)))
109        } else {
110            None
111        }
112    }
113
114    /// Return an iterator over the values of the set slice.
115    pub fn iter(&self) -> Iter<'_, T> {
116        Iter::new(&self.entries)
117    }
118
119    /// Search over a sorted set for a value.
120    ///
121    /// Returns the position where that value is present, or the position where it can be inserted
122    /// to maintain the sort. See [`slice::binary_search`] for more details.
123    ///
124    /// Computes in **O(log(n))** time, which is notably less scalable than looking the value up in
125    /// the set this is a slice from using [`IndexSet::get_index_of`], but this can also position
126    /// missing values.
127    pub fn binary_search(&self, x: &T) -> Result<usize, usize>
128    where
129        T: Ord,
130    {
131        self.binary_search_by(|p| p.cmp(x))
132    }
133
134    /// Search over a sorted set with a comparator function.
135    ///
136    /// Returns the position where that value is present, or the position where it can be inserted
137    /// to maintain the sort. See [`slice::binary_search_by`] for more details.
138    ///
139    /// Computes in **O(log(n))** time.
140    #[inline]
141    pub fn binary_search_by<'a, F>(&'a self, mut f: F) -> Result<usize, usize>
142    where
143        F: FnMut(&'a T) -> Ordering,
144    {
145        self.entries.binary_search_by(move |a| f(&a.key))
146    }
147
148    /// Search over a sorted set with an extraction function.
149    ///
150    /// Returns the position where that value is present, or the position where it can be inserted
151    /// to maintain the sort. See [`slice::binary_search_by_key`] for more details.
152    ///
153    /// Computes in **O(log(n))** time.
154    #[inline]
155    pub fn binary_search_by_key<'a, B, F>(&'a self, b: &B, mut f: F) -> Result<usize, usize>
156    where
157        F: FnMut(&'a T) -> B,
158        B: Ord,
159    {
160        self.binary_search_by(|k| f(k).cmp(b))
161    }
162
163    /// Returns the index of the partition point of a sorted set according to the given predicate
164    /// (the index of the first element of the second partition).
165    ///
166    /// See [`slice::partition_point`] for more details.
167    ///
168    /// Computes in **O(log(n))** time.
169    #[must_use]
170    pub fn partition_point<P>(&self, mut pred: P) -> usize
171    where
172        P: FnMut(&T) -> bool,
173    {
174        self.entries.partition_point(move |a| pred(&a.key))
175    }
176}
177
178impl<'a, T> IntoIterator for &'a Slice<T> {
179    type IntoIter = Iter<'a, T>;
180    type Item = &'a T;
181
182    fn into_iter(self) -> Self::IntoIter {
183        self.iter()
184    }
185}
186
187impl<T> IntoIterator for Box<Slice<T>> {
188    type IntoIter = IntoIter<T>;
189    type Item = T;
190
191    fn into_iter(self) -> Self::IntoIter {
192        IntoIter::new(self.into_entries())
193    }
194}
195
196impl<T> Default for &'_ Slice<T> {
197    fn default() -> Self {
198        Slice::from_slice(&[])
199    }
200}
201
202impl<T> Default for Box<Slice<T>> {
203    fn default() -> Self {
204        Slice::from_boxed(Box::default())
205    }
206}
207
208impl<T: Clone> Clone for Box<Slice<T>> {
209    fn clone(&self) -> Self {
210        Slice::from_boxed(self.entries.to_vec().into_boxed_slice())
211    }
212}
213
214impl<T: Copy> From<&Slice<T>> for Box<Slice<T>> {
215    fn from(slice: &Slice<T>) -> Self {
216        Slice::from_boxed(Box::from(&slice.entries))
217    }
218}
219
220impl<T: fmt::Debug> fmt::Debug for Slice<T> {
221    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
222        f.debug_list().entries(self).finish()
223    }
224}
225
226impl<T, U> PartialEq<Slice<U>> for Slice<T>
227where
228    T: PartialEq<U>,
229{
230    fn eq(&self, other: &Slice<U>) -> bool {
231        slice_eq(&self.entries, &other.entries, |b1, b2| b1.key == b2.key)
232    }
233}
234
235impl<T, U> PartialEq<[U]> for Slice<T>
236where
237    T: PartialEq<U>,
238{
239    fn eq(&self, other: &[U]) -> bool {
240        slice_eq(&self.entries, other, |b, o| b.key == *o)
241    }
242}
243
244impl<T, U> PartialEq<Slice<U>> for [T]
245where
246    T: PartialEq<U>,
247{
248    fn eq(&self, other: &Slice<U>) -> bool {
249        slice_eq(self, &other.entries, |o, b| *o == b.key)
250    }
251}
252
253impl<T, U, const N: usize> PartialEq<[U; N]> for Slice<T>
254where
255    T: PartialEq<U>,
256{
257    fn eq(&self, other: &[U; N]) -> bool {
258        <Self as PartialEq<[U]>>::eq(self, other)
259    }
260}
261
262impl<T, const N: usize, U> PartialEq<Slice<U>> for [T; N]
263where
264    T: PartialEq<U>,
265{
266    fn eq(&self, other: &Slice<U>) -> bool {
267        <[T] as PartialEq<Slice<U>>>::eq(self, other)
268    }
269}
270
271impl<T: Eq> Eq for Slice<T> {}
272
273impl<T: PartialOrd> PartialOrd for Slice<T> {
274    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
275        self.iter().partial_cmp(other)
276    }
277}
278
279impl<T: Ord> Ord for Slice<T> {
280    fn cmp(&self, other: &Self) -> Ordering {
281        self.iter().cmp(other)
282    }
283}
284
285impl<T: Hash> Hash for Slice<T> {
286    fn hash<H: Hasher>(&self, state: &mut H) {
287        self.len().hash(state);
288        for value in self {
289            value.hash(state);
290        }
291    }
292}
293
294impl<T> Index<usize> for Slice<T> {
295    type Output = T;
296
297    fn index(&self, index: usize) -> &Self::Output {
298        &self.entries[index].key
299    }
300}
301
302// We can't have `impl<I: RangeBounds<usize>> Index<I>` because that conflicts with `Index<usize>`.
303// Instead, we repeat the implementations for all the core range types.
304macro_rules! impl_index {
305    ($($range:ty),*) => {$(
306        impl<T, S> Index<$range> for IndexSet<T, S> {
307            type Output = Slice<T>;
308
309            fn index(&self, range: $range) -> &Self::Output {
310                Slice::from_slice(&self.as_entries()[range])
311            }
312        }
313
314        impl<T> Index<$range> for Slice<T> {
315            type Output = Self;
316
317            fn index(&self, range: $range) -> &Self::Output {
318                Slice::from_slice(&self.entries[range])
319            }
320        }
321    )*}
322}
323impl_index!(
324    ops::Range<usize>,
325    ops::RangeFrom<usize>,
326    ops::RangeFull,
327    ops::RangeInclusive<usize>,
328    ops::RangeTo<usize>,
329    ops::RangeToInclusive<usize>,
330    (Bound<usize>, Bound<usize>)
331);
332
333#[cfg(test)]
334mod tests {
335    use super::*;
336
337    #[test]
338    fn slice_index() {
339        fn check(vec_slice: &[i32], set_slice: &Slice<i32>, sub_slice: &Slice<i32>) {
340            assert_eq!(set_slice as *const _, sub_slice as *const _);
341            itertools::assert_equal(vec_slice, set_slice);
342        }
343
344        let vec: Vec<i32> = (0..10).map(|i| i * i).collect();
345        let set: IndexSet<i32> = vec.iter().cloned().collect();
346        let slice = set.as_slice();
347
348        // RangeFull
349        check(&vec[..], &set[..], &slice[..]);
350
351        for i in 0usize..10 {
352            // Index
353            assert_eq!(vec[i], set[i]);
354            assert_eq!(vec[i], slice[i]);
355
356            // RangeFrom
357            check(&vec[i..], &set[i..], &slice[i..]);
358
359            // RangeTo
360            check(&vec[..i], &set[..i], &slice[..i]);
361
362            // RangeToInclusive
363            check(&vec[..=i], &set[..=i], &slice[..=i]);
364
365            // (Bound<usize>, Bound<usize>)
366            let bounds = (Bound::Excluded(i), Bound::Unbounded);
367            check(&vec[i + 1..], &set[bounds], &slice[bounds]);
368
369            for j in i..=10 {
370                // Range
371                check(&vec[i..j], &set[i..j], &slice[i..j]);
372            }
373
374            for j in i..10 {
375                // RangeInclusive
376                check(&vec[i..=j], &set[i..=j], &slice[i..=j]);
377            }
378        }
379    }
380}
indexmap/set/slice.rs

indexmap/set/
slice.rs
