cranelift_bitset/
scalar.rs

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
//! Scalar bitsets.

use core::mem::size_of;
use core::ops::{Add, BitAnd, BitOr, Not, Shl, Shr, Sub};

/// A small bitset built on top of a single primitive integer type.
///
/// # Example
///
/// ```
/// use cranelift_bitset::ScalarBitSet;
///
/// // Create a new bitset backed with a `u32`.
/// let mut bitset = ScalarBitSet::<u32>::new();
///
/// // Bitsets are initially empty.
/// assert!(bitset.is_empty());
/// assert_eq!(bitset.len(), 0);
///
/// // Insert into the bitset.
/// bitset.insert(4);
/// bitset.insert(5);
/// bitset.insert(6);
///
/// // Now the bitset is not empty.
/// assert_eq!(bitset.len(), 3);
/// assert!(!bitset.is_empty());
/// assert!(bitset.contains(4));
/// assert!(bitset.contains(5));
/// assert!(bitset.contains(6));
///
/// // Remove an element from the bitset.
/// let was_present = bitset.remove(6);
/// assert!(was_present);
/// assert!(!bitset.contains(6));
/// assert_eq!(bitset.len(), 2);
///
/// // Can iterate over the elements in the set.
/// let elems: Vec<_> = bitset.iter().collect();
/// assert_eq!(elems, [4, 5]);
/// ```
#[derive(Clone, Copy, PartialEq, Eq)]
#[cfg_attr(
    feature = "enable-serde",
    derive(serde_derive::Serialize, serde_derive::Deserialize)
)]
pub struct ScalarBitSet<T>(pub T);

impl<T> core::fmt::Debug for ScalarBitSet<T>
where
    T: ScalarBitSetStorage,
{
    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
        let mut s = f.debug_struct(core::any::type_name::<Self>());
        for i in 0..Self::capacity() {
            use alloc::string::ToString;
            let i = u8::try_from(i).unwrap();
            s.field(&i.to_string(), &self.contains(i));
        }
        s.finish()
    }
}

impl<T> Default for ScalarBitSet<T>
where
    T: ScalarBitSetStorage,
{
    #[inline]
    fn default() -> Self {
        Self::new()
    }
}

impl<T> ScalarBitSet<T>
where
    T: ScalarBitSetStorage,
{
    /// Create a new, empty bitset.
    ///
    /// # Example
    ///
    /// ```
    /// use cranelift_bitset::ScalarBitSet;
    ///
    /// let bitset = ScalarBitSet::<u64>::new();
    ///
    /// assert!(bitset.is_empty());
    /// ```
    #[inline]
    pub fn new() -> Self {
        Self(T::from(0))
    }

    /// Construct a bitset with the half-open range `[lo, hi)` inserted.
    ///
    /// # Example
    ///
    /// ```
    /// use cranelift_bitset::ScalarBitSet;
    ///
    /// let bitset = ScalarBitSet::<u64>::from_range(3, 6);
    ///
    /// assert_eq!(bitset.len(), 3);
    ///
    /// assert!(bitset.contains(3));
    /// assert!(bitset.contains(4));
    /// assert!(bitset.contains(5));
    /// ```
    ///
    /// # Panics
    ///
    /// Panics if `lo > hi` or if `hi > Self::capacity()`.
    ///
    /// ```should_panic
    /// use cranelift_bitset::ScalarBitSet;
    ///
    /// // The lower bound may not be larger than the upper bound.
    /// let bitset = ScalarBitSet::<u64>::from_range(6, 3);
    /// ```
    ///
    /// ```should_panic
    /// use cranelift_bitset::ScalarBitSet;
    ///
    /// // The bounds must fit within the backing scalar type.
    /// let bitset = ScalarBitSet::<u64>::from_range(3, 69);
    /// ```
    #[inline]
    pub fn from_range(lo: u8, hi: u8) -> Self {
        assert!(lo <= hi);
        assert!(hi <= Self::capacity());

        let one = T::from(1);

        // We can't just do (one << hi) - one here as the shift may overflow
        let hi_rng = if hi >= 1 {
            (one << (hi - 1)) + ((one << (hi - 1)) - one)
        } else {
            T::from(0)
        };

        let lo_rng = (one << lo) - one;

        Self(hi_rng - lo_rng)
    }

    /// The maximum number of bits that can be stored in this bitset.
    ///
    /// If you need more bits than this, use a
    /// [`CompoundBitSet`][crate::CompoundBitSet] instead of a `ScalarBitSet`.
    ///
    /// # Example
    ///
    /// ```
    /// use cranelift_bitset::ScalarBitSet;
    ///
    /// assert_eq!(ScalarBitSet::<u8>::capacity(), 8);
    /// assert_eq!(ScalarBitSet::<u64>::capacity(), 64);
    /// ```
    #[inline]
    pub fn capacity() -> u8 {
        u8::try_from(size_of::<T>()).unwrap() * 8
    }

    /// Get the number of elements in this set.
    ///
    /// # Example
    ///
    /// ```
    /// use cranelift_bitset::ScalarBitSet;
    ///
    /// let mut bitset = ScalarBitSet::<u64>::new();
    ///
    /// assert_eq!(bitset.len(), 0);
    ///
    /// bitset.insert(24);
    /// bitset.insert(13);
    /// bitset.insert(36);
    ///
    /// assert_eq!(bitset.len(), 3);
    /// ```
    #[inline]
    pub fn len(&self) -> u8 {
        self.0.count_ones()
    }

    /// Is this bitset empty?
    ///
    /// # Example
    ///
    /// ```
    /// use cranelift_bitset::ScalarBitSet;
    ///
    /// let mut bitset = ScalarBitSet::<u16>::new();
    ///
    /// assert!(bitset.is_empty());
    ///
    /// bitset.insert(10);
    ///
    /// assert!(!bitset.is_empty());
    /// ```
    #[inline]
    pub fn is_empty(&self) -> bool {
        self.0 == T::from(0)
    }

    /// Check whether this bitset contains `i`.
    ///
    /// # Example
    ///
    /// ```
    /// use cranelift_bitset::ScalarBitSet;
    ///
    /// let mut bitset = ScalarBitSet::<u8>::new();
    ///
    /// assert!(!bitset.contains(7));
    ///
    /// bitset.insert(7);
    ///
    /// assert!(bitset.contains(7));
    /// ```
    ///
    /// # Panics
    ///
    /// Panics if `i` is greater than or equal to [`Self::capacity()`][Self::capacity].
    ///
    /// ```should_panic
    /// use cranelift_bitset::ScalarBitSet;
    ///
    /// let mut bitset = ScalarBitSet::<u8>::new();
    ///
    /// // A `ScalarBitSet<u8>` can only hold the elements `0..=7`, so `8` is
    /// // out of bounds and will trigger a panic.
    /// bitset.contains(8);
    /// ```
    #[inline]
    pub fn contains(&self, i: u8) -> bool {
        assert!(i < Self::capacity());
        self.0 & (T::from(1) << i) != T::from(0)
    }

    /// Insert `i` into this bitset.
    ///
    /// Returns whether the value was newly inserted. That is:
    ///
    /// * If the set did not previously contain `i` then `true` is returned.
    ///
    /// * If the set already contained `i` then `false` is returned.
    ///
    /// # Example
    ///
    /// ```
    /// use cranelift_bitset::ScalarBitSet;
    ///
    /// let mut bitset = ScalarBitSet::<u8>::new();
    ///
    /// // When an element is inserted that was not already present in the set,
    /// // then `true` is returned.
    /// let is_new = bitset.insert(7);
    /// assert!(is_new);
    ///
    /// // The element is now present in the set.
    /// assert!(bitset.contains(7));
    ///
    /// // And when the element is already in the set, `false` is returned from
    /// // `insert`.
    /// let is_new = bitset.insert(7);
    /// assert!(!is_new);
    /// ```
    ///
    /// # Panics
    ///
    /// Panics if `i` is greater than or equal to [`Self::capacity()`][Self::capacity].
    ///
    /// ```should_panic
    /// use cranelift_bitset::ScalarBitSet;
    ///
    /// let mut bitset = ScalarBitSet::<u32>::new();
    ///
    /// // A `ScalarBitSet<u32>` can only hold the elements `0..=31`, so `42` is
    /// // out of bounds and will trigger a panic.
    /// bitset.insert(42);
    /// ```
    #[inline]
    pub fn insert(&mut self, i: u8) -> bool {
        let is_new = !self.contains(i);
        self.0 = self.0 | (T::from(1) << i);
        is_new
    }

    /// Remove `i` from this bitset.
    ///
    /// Returns whether `i` was previously in this set or not.
    ///
    /// # Example
    ///
    /// ```
    /// use cranelift_bitset::ScalarBitSet;
    ///
    /// let mut bitset = ScalarBitSet::<u128>::new();
    ///
    /// // Removing an element that was not present in the set returns `false`.
    /// let was_present = bitset.remove(100);
    /// assert!(!was_present);
    ///
    /// // And when the element was in the set, `true` is returned.
    /// bitset.insert(100);
    /// let was_present = bitset.remove(100);
    /// assert!(was_present);
    /// ```
    ///
    /// # Panics
    ///
    /// Panics if `i` is greater than or equal to [`Self::capacity()`][Self::capacity].
    ///
    /// ```should_panic
    /// use cranelift_bitset::ScalarBitSet;
    ///
    /// let mut bitset = ScalarBitSet::<u16>::new();
    ///
    /// // A `ScalarBitSet<u16>` can only hold the elements `0..=15`, so `20` is
    /// // out of bounds and will trigger a panic.
    /// bitset.remove(20);
    /// ```
    #[inline]
    pub fn remove(&mut self, i: u8) -> bool {
        let was_present = self.contains(i);
        self.0 = self.0 & !(T::from(1) << i);
        was_present
    }

    /// Remove all entries from this bitset.
    ///
    /// # Example
    ///
    /// ```
    /// use cranelift_bitset::ScalarBitSet;
    ///
    /// let mut bitset = ScalarBitSet::<u32>::new();
    ///
    /// bitset.insert(10);
    /// bitset.insert(20);
    /// bitset.insert(30);
    ///
    /// bitset.clear();
    ///
    /// assert!(bitset.is_empty());
    /// ```
    #[inline]
    pub fn clear(&mut self) {
        self.0 = T::from(0);
    }

    /// Remove and return the smallest value in the bitset.
    ///
    /// # Example
    ///
    /// ```
    /// use cranelift_bitset::ScalarBitSet;
    ///
    /// let mut bitset = ScalarBitSet::<u64>::new();
    ///
    /// bitset.insert(0);
    /// bitset.insert(24);
    /// bitset.insert(13);
    /// bitset.insert(36);
    ///
    /// assert_eq!(bitset.pop_min(), Some(0));
    /// assert_eq!(bitset.pop_min(), Some(13));
    /// assert_eq!(bitset.pop_min(), Some(24));
    /// assert_eq!(bitset.pop_min(), Some(36));
    /// assert_eq!(bitset.pop_min(), None);
    /// ```
    #[inline]
    pub fn pop_min(&mut self) -> Option<u8> {
        let min = self.min()?;
        self.remove(min);
        Some(min)
    }

    /// Remove and return the largest value in the bitset.
    ///
    /// # Example
    ///
    /// ```
    /// use cranelift_bitset::ScalarBitSet;
    ///
    /// let mut bitset = ScalarBitSet::<u64>::new();
    ///
    /// bitset.insert(0);
    /// bitset.insert(24);
    /// bitset.insert(13);
    /// bitset.insert(36);
    ///
    /// assert_eq!(bitset.pop_max(), Some(36));
    /// assert_eq!(bitset.pop_max(), Some(24));
    /// assert_eq!(bitset.pop_max(), Some(13));
    /// assert_eq!(bitset.pop_max(), Some(0));
    /// assert_eq!(bitset.pop_max(), None);
    /// ```
    #[inline]
    pub fn pop_max(&mut self) -> Option<u8> {
        let max = self.max()?;
        self.remove(max);
        Some(max)
    }

    /// Return the smallest number contained in this bitset or `None` if this
    /// bitset is empty.
    ///
    /// # Example
    ///
    /// ```
    /// use cranelift_bitset::ScalarBitSet;
    ///
    /// let mut bitset = ScalarBitSet::<u64>::new();
    ///
    /// // When the bitset is empty, `min` returns `None`.
    /// assert_eq!(bitset.min(), None);
    ///
    /// bitset.insert(28);
    /// bitset.insert(1);
    /// bitset.insert(63);
    ///
    /// // When the bitset is not empty, it returns the smallest element.
    /// assert_eq!(bitset.min(), Some(1));
    /// ```
    #[inline]
    pub fn min(&self) -> Option<u8> {
        if self.0 == T::from(0) {
            None
        } else {
            Some(self.0.trailing_zeros())
        }
    }

    /// Return the largest number contained in the bitset or None if this bitset
    /// is empty
    ///
    /// # Example
    ///
    /// ```
    /// use cranelift_bitset::ScalarBitSet;
    ///
    /// let mut bitset = ScalarBitSet::<u64>::new();
    ///
    /// // When the bitset is empty, `max` returns `None`.
    /// assert_eq!(bitset.max(), None);
    ///
    /// bitset.insert(0);
    /// bitset.insert(36);
    /// bitset.insert(49);
    ///
    /// // When the bitset is not empty, it returns the smallest element.
    /// assert_eq!(bitset.max(), Some(49));
    /// ```
    #[inline]
    pub fn max(&self) -> Option<u8> {
        if self.0 == T::from(0) {
            None
        } else {
            let leading_zeroes = self.0.leading_zeros();
            Some(Self::capacity() - leading_zeroes - 1)
        }
    }

    /// Iterate over the items in this set.
    ///
    /// Items are always yielded in sorted order.
    ///
    /// # Example
    ///
    /// ```
    /// use cranelift_bitset::ScalarBitSet;
    ///
    /// let mut bitset = ScalarBitSet::<u64>::new();
    ///
    /// bitset.insert(19);
    /// bitset.insert(3);
    /// bitset.insert(63);
    /// bitset.insert(0);
    ///
    /// assert_eq!(
    ///     bitset.iter().collect::<Vec<_>>(),
    ///     [0, 3, 19, 63],
    /// );
    /// ```
    #[inline]
    pub fn iter(self) -> Iter<T> {
        Iter { bitset: self }
    }
}

impl<T> IntoIterator for ScalarBitSet<T>
where
    T: ScalarBitSetStorage,
{
    type Item = u8;

    type IntoIter = Iter<T>;

    #[inline]
    fn into_iter(self) -> Self::IntoIter {
        self.iter()
    }
}

impl<'a, T> IntoIterator for &'a ScalarBitSet<T>
where
    T: ScalarBitSetStorage,
{
    type Item = u8;

    type IntoIter = Iter<T>;

    #[inline]
    fn into_iter(self) -> Self::IntoIter {
        self.iter()
    }
}

impl<T: ScalarBitSetStorage> From<T> for ScalarBitSet<T> {
    fn from(bits: T) -> Self {
        Self(bits)
    }
}

/// A trait implemented by all integers that can be used as the backing storage
/// for a [`ScalarBitSet`].
///
/// You shouldn't have to implement this yourself, it is already implemented for
/// `u{8,16,32,64,128}` and if you need more bits than that, then use
/// [`CompoundBitSet`][crate::CompoundBitSet] instead.
pub trait ScalarBitSetStorage:
    Default
    + From<u8>
    + Shl<u8, Output = Self>
    + Shr<u8, Output = Self>
    + BitAnd<Output = Self>
    + BitOr<Output = Self>
    + Not<Output = Self>
    + Sub<Output = Self>
    + Add<Output = Self>
    + PartialEq
    + Copy
{
    /// Count the number of leading zeros.
    fn leading_zeros(self) -> u8;

    /// Count the number of trailing zeros.
    fn trailing_zeros(self) -> u8;

    /// Count the number of bits set in this integer.
    fn count_ones(self) -> u8;
}

macro_rules! impl_storage {
    ( $int:ty ) => {
        impl ScalarBitSetStorage for $int {
            fn leading_zeros(self) -> u8 {
                u8::try_from(self.leading_zeros()).unwrap()
            }

            fn trailing_zeros(self) -> u8 {
                u8::try_from(self.trailing_zeros()).unwrap()
            }

            fn count_ones(self) -> u8 {
                u8::try_from(self.count_ones()).unwrap()
            }
        }
    };
}

impl_storage!(u8);
impl_storage!(u16);
impl_storage!(u32);
impl_storage!(u64);
impl_storage!(u128);
impl_storage!(usize);

/// An iterator over the elements in a [`ScalarBitSet`].
pub struct Iter<T> {
    bitset: ScalarBitSet<T>,
}

impl<T> Iterator for Iter<T>
where
    T: ScalarBitSetStorage,
{
    type Item = u8;

    #[inline]
    fn next(&mut self) -> Option<u8> {
        self.bitset.pop_min()
    }
}

impl<T> DoubleEndedIterator for Iter<T>
where
    T: ScalarBitSetStorage,
{
    #[inline]
    fn next_back(&mut self) -> Option<Self::Item> {
        self.bitset.pop_max()
    }
}

impl<T> ExactSizeIterator for Iter<T>
where
    T: ScalarBitSetStorage,
{
    #[inline]
    fn len(&self) -> usize {
        usize::from(self.bitset.len())
    }
}

#[cfg(feature = "arbitrary")]
impl<'a, T> arbitrary::Arbitrary<'a> for ScalarBitSet<T>
where
    T: ScalarBitSetStorage + arbitrary::Arbitrary<'a>,
{
    fn arbitrary(u: &mut arbitrary::Unstructured<'a>) -> arbitrary::Result<Self> {
        T::arbitrary(u).map(Self)
    }
}