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
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
//-
// Copyright 2017, 2018 The proptest developers
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

//! Strategies for working with bit sets.
//!
//! Besides `BitSet` itself, this also defines strategies for all the primitive
//! integer types. These strategies are appropriate for integers which are used
//! as bit flags, etc; e.g., where the most reasonable simplification of `64`
//! is `0` (clearing one bit) and not `63` (clearing one bit but setting 6
//! others). For integers treated as numeric values, see the corresponding
//! modules of the `num` module instead.

use crate::std_facade::{fmt, Vec};
use core::marker::PhantomData;
use core::mem;

#[cfg(feature = "bit-set")]
use bit_set::BitSet;
#[cfg(feature = "bit-set")]
use bit_vec::BitVec;
use rand::{self, seq::IteratorRandom, Rng};

use crate::collection::SizeRange;
use crate::num::sample_uniform_incl;
use crate::strategy::*;
use crate::test_runner::*;

/// Trait for types which can be handled with `BitSetStrategy`.
#[cfg_attr(clippy, allow(len_without_is_empty))]
pub trait BitSetLike: Clone + fmt::Debug {
    /// Create a new value of `Self` with space for up to `max` bits, all
    /// initialised to zero.
    fn new_bitset(max: usize) -> Self;
    /// Return an upper bound on the greatest bit set _plus one_.
    fn len(&self) -> usize;
    /// Test whether the given bit is set.
    fn test(&self, ix: usize) -> bool;
    /// Set the given bit.
    fn set(&mut self, ix: usize);
    /// Clear the given bit.
    fn clear(&mut self, ix: usize);
    /// Return the number of bits set.
    ///
    /// This has a default for backwards compatibility, which simply does a
    /// linear scan through the bits. Implementations are strongly encouraged
    /// to override this.
    fn count(&self) -> usize {
        let mut n = 0;
        for i in 0..self.len() {
            if self.test(i) {
                n += 1;
            }
        }
        n
    }
}

macro_rules! int_bitset {
    ($typ:ty) => {
        impl BitSetLike for $typ {
            fn new_bitset(_: usize) -> Self {
                0
            }
            fn len(&self) -> usize {
                mem::size_of::<$typ>() * 8
            }
            fn test(&self, ix: usize) -> bool {
                0 != (*self & ((1 as $typ) << ix))
            }
            fn set(&mut self, ix: usize) {
                *self |= (1 as $typ) << ix;
            }
            fn clear(&mut self, ix: usize) {
                *self &= !((1 as $typ) << ix);
            }
            fn count(&self) -> usize {
                self.count_ones() as usize
            }
        }
    };
}
int_bitset!(u8);
int_bitset!(u16);
int_bitset!(u32);
int_bitset!(u64);
int_bitset!(usize);
int_bitset!(i8);
int_bitset!(i16);
int_bitset!(i32);
int_bitset!(i64);
int_bitset!(isize);

#[cfg(feature = "bit-set")]
#[cfg_attr(docsrs, doc(cfg(feature = "bit-set")))]
impl BitSetLike for BitSet {
    fn new_bitset(max: usize) -> Self {
        BitSet::with_capacity(max)
    }

    fn len(&self) -> usize {
        self.capacity()
    }

    fn test(&self, bit: usize) -> bool {
        self.contains(bit)
    }

    fn set(&mut self, bit: usize) {
        self.insert(bit);
    }

    fn clear(&mut self, bit: usize) {
        self.remove(bit);
    }

    fn count(&self) -> usize {
        self.len()
    }
}

impl BitSetLike for Vec<bool> {
    fn new_bitset(max: usize) -> Self {
        vec![false; max]
    }

    fn len(&self) -> usize {
        self.len()
    }

    fn test(&self, bit: usize) -> bool {
        if bit >= self.len() {
            false
        } else {
            self[bit]
        }
    }

    fn set(&mut self, bit: usize) {
        if bit >= self.len() {
            self.resize(bit + 1, false);
        }

        self[bit] = true;
    }

    fn clear(&mut self, bit: usize) {
        if bit < self.len() {
            self[bit] = false;
        }
    }

    fn count(&self) -> usize {
        self.iter().filter(|&&b| b).count()
    }
}

/// Generates values as a set of bits between the two bounds.
///
/// Values are generated by uniformly setting individual bits to 0
/// or 1 between the bounds. Shrinking iteratively clears bits.
#[must_use = "strategies do nothing unless used"]
#[derive(Clone, Copy, Debug)]
pub struct BitSetStrategy<T: BitSetLike> {
    min: usize,
    max: usize,
    mask: Option<T>,
}

impl<T: BitSetLike> BitSetStrategy<T> {
    /// Create a strategy which generates values where bits between `min`
    /// (inclusive) and `max` (exclusive) may be set.
    ///
    /// Due to the generics, the functions in the typed submodules are usually
    /// preferable to calling this directly.
    pub fn new(min: usize, max: usize) -> Self {
        BitSetStrategy {
            min,
            max,
            mask: None,
        }
    }

    /// Create a strategy which generates values where any bits set (and only
    /// those bits) in `mask` may be set.
    pub fn masked(mask: T) -> Self {
        BitSetStrategy {
            min: 0,
            max: mask.len(),
            mask: Some(mask),
        }
    }
}

impl<T: BitSetLike> Strategy for BitSetStrategy<T> {
    type Tree = BitSetValueTree<T>;
    type Value = T;

    fn new_tree(&self, runner: &mut TestRunner) -> NewTree<Self> {
        let mut inner = T::new_bitset(self.max);
        for bit in self.min..self.max {
            if self.mask.as_ref().map_or(true, |mask| mask.test(bit))
                && runner.rng().gen()
            {
                inner.set(bit);
            }
        }

        Ok(BitSetValueTree {
            inner,
            shrink: self.min,
            prev_shrink: None,
            min_count: 0,
        })
    }
}

/// Generates bit sets with a particular number of bits set.
///
/// Specifically, this strategy is given both a size range and a bit range. To
/// produce a new value, it selects a size, then uniformly selects that many
/// bits from within the bit range.
///
/// Shrinking happens as with [`BitSetStrategy`](struct.BitSetStrategy.html).
#[derive(Clone, Debug)]
#[must_use = "strategies do nothing unless used"]
pub struct SampledBitSetStrategy<T: BitSetLike> {
    size: SizeRange,
    bits: SizeRange,
    _marker: PhantomData<T>,
}

impl<T: BitSetLike> SampledBitSetStrategy<T> {
    /// Create a strategy which generates values where bits within the bounds
    /// given by `bits` may be set. The number of bits that are set is chosen
    /// to be in the range given by `size`.
    ///
    /// Due to the generics, the functions in the typed submodules are usually
    /// preferable to calling this directly.
    ///
    /// ## Panics
    ///
    /// Panics if `size` includes a value that is greater than the number of
    /// bits in `bits`.
    pub fn new(size: impl Into<SizeRange>, bits: impl Into<SizeRange>) -> Self {
        let size = size.into();
        let bits = bits.into();
        size.assert_nonempty();

        let available_bits = bits.end_excl() - bits.start();
        assert!(
            size.end_excl() <= available_bits + 1,
            "Illegal SampledBitSetStrategy: have {} bits available, \
             but requested size is {}..{}",
            available_bits,
            size.start(),
            size.end_excl()
        );
        SampledBitSetStrategy {
            size,
            bits,
            _marker: PhantomData,
        }
    }
}

impl<T: BitSetLike> Strategy for SampledBitSetStrategy<T> {
    type Tree = BitSetValueTree<T>;
    type Value = T;

    fn new_tree(&self, runner: &mut TestRunner) -> NewTree<Self> {
        let mut bits = T::new_bitset(self.bits.end_excl());
        let count = sample_uniform_incl(
            runner,
            self.size.start(),
            self.size.end_incl(),
        );
        if bits.len() < count {
            panic!("not enough bits to sample");
        }

        for bit in self.bits.iter().choose_multiple(runner.rng(), count) {
            bits.set(bit);
        }

        Ok(BitSetValueTree {
            inner: bits,
            shrink: self.bits.start(),
            prev_shrink: None,
            min_count: self.size.start(),
        })
    }
}

/// Value tree produced by `BitSetStrategy` and `SampledBitSetStrategy`.
#[derive(Clone, Copy, Debug)]
pub struct BitSetValueTree<T: BitSetLike> {
    inner: T,
    shrink: usize,
    prev_shrink: Option<usize>,
    min_count: usize,
}

impl<T: BitSetLike> ValueTree for BitSetValueTree<T> {
    type Value = T;

    fn current(&self) -> T {
        self.inner.clone()
    }

    fn simplify(&mut self) -> bool {
        if self.inner.count() <= self.min_count {
            return false;
        }

        while self.shrink < self.inner.len() && !self.inner.test(self.shrink) {
            self.shrink += 1;
        }

        if self.shrink >= self.inner.len() {
            self.prev_shrink = None;
            false
        } else {
            self.prev_shrink = Some(self.shrink);
            self.inner.clear(self.shrink);
            self.shrink += 1;
            true
        }
    }

    fn complicate(&mut self) -> bool {
        if let Some(bit) = self.prev_shrink.take() {
            self.inner.set(bit);
            true
        } else {
            false
        }
    }
}

macro_rules! int_api {
    ($typ:ident, $max:expr) => {
        #[allow(missing_docs)]
        pub mod $typ {
            use super::*;

            /// Generates integers where all bits may be set.
            pub const ANY: BitSetStrategy<$typ> = BitSetStrategy {
                min: 0,
                max: $max,
                mask: None,
            };

            /// Generates values where bits between the given bounds may be
            /// set.
            pub fn between(min: usize, max: usize) -> BitSetStrategy<$typ> {
                BitSetStrategy::new(min, max)
            }

            /// Generates values where any bits set in `mask` (and no others)
            /// may be set.
            pub fn masked(mask: $typ) -> BitSetStrategy<$typ> {
                BitSetStrategy::masked(mask)
            }

            /// Create a strategy which generates values where bits within the
            /// bounds given by `bits` may be set. The number of bits that are
            /// set is chosen to be in the range given by `size`.
            ///
            /// ## Panics
            ///
            /// Panics if `size` includes a value that is greater than the
            /// number of bits in `bits`.
            pub fn sampled(
                size: impl Into<SizeRange>,
                bits: impl Into<SizeRange>,
            ) -> SampledBitSetStrategy<$typ> {
                SampledBitSetStrategy::new(size, bits)
            }
        }
    };
}

int_api!(u8, 8);
int_api!(u16, 16);
int_api!(u32, 32);
int_api!(u64, 64);
int_api!(i8, 8);
int_api!(i16, 16);
int_api!(i32, 32);
int_api!(i64, 64);

macro_rules! minimal_api {
    ($md:ident, $typ:ty) => {
        #[allow(missing_docs)]
        pub mod $md {
            use super::*;

            /// Generates values where bits between the given bounds may be
            /// set.
            pub fn between(min: usize, max: usize) -> BitSetStrategy<$typ> {
                BitSetStrategy::new(min, max)
            }

            /// Generates values where any bits set in `mask` (and no others)
            /// may be set.
            pub fn masked(mask: $typ) -> BitSetStrategy<$typ> {
                BitSetStrategy::masked(mask)
            }

            /// Create a strategy which generates values where bits within the
            /// bounds given by `bits` may be set. The number of bits that are
            /// set is chosen to be in the range given by `size`.
            ///
            /// ## Panics
            ///
            /// Panics if `size` includes a value that is greater than the
            /// number of bits in `bits`.
            pub fn sampled(
                size: impl Into<SizeRange>,
                bits: impl Into<SizeRange>,
            ) -> SampledBitSetStrategy<$typ> {
                SampledBitSetStrategy::new(size, bits)
            }
        }
    };
}
minimal_api!(usize, usize);
minimal_api!(isize, isize);
#[cfg(feature = "bit-set")]
#[cfg_attr(docsrs, doc(cfg(feature = "bit-set")))]
minimal_api!(bitset, BitSet);
minimal_api!(bool_vec, Vec<bool>);

pub(crate) mod varsize {
    use super::*;
    use core::iter::FromIterator;

    #[cfg(feature = "bit-set")]
    type Inner = BitSet;
    #[cfg(not(feature = "bit-set"))]
    type Inner = Vec<bool>;

    /// A bit set is a set of bit flags.
    #[derive(Debug, Clone)]
    pub struct VarBitSet(Inner);

    impl VarBitSet {
        /// Create a bit set of `len` set values.
        #[cfg(not(feature = "bit-set"))]
        pub fn saturated(len: usize) -> Self {
            Self(vec![true; len])
        }

        /// Create a bit set of `len` set values.
        #[cfg(feature = "bit-set")]
        pub fn saturated(len: usize) -> Self {
            Self(BitSet::from_bit_vec(BitVec::from_elem(len, true)))
        }

        #[cfg(not(feature = "bit-set"))]
        pub(crate) fn iter<'a>(&'a self) -> impl Iterator<Item = usize> + 'a {
            (0..self.len()).into_iter().filter(move |&ix| self.test(ix))
        }

        #[cfg(feature = "bit-set")]
        pub(crate) fn iter<'a>(&'a self) -> impl Iterator<Item = usize> + 'a {
            self.0.iter()
        }
    }

    impl BitSetLike for VarBitSet {
        fn new_bitset(max: usize) -> Self {
            VarBitSet(Inner::new_bitset(max))
        }

        fn len(&self) -> usize {
            BitSetLike::len(&self.0)
        }

        fn test(&self, bit: usize) -> bool {
            BitSetLike::test(&self.0, bit)
        }

        fn set(&mut self, bit: usize) {
            BitSetLike::set(&mut self.0, bit);
        }

        fn clear(&mut self, bit: usize) {
            BitSetLike::clear(&mut self.0, bit);
        }

        fn count(&self) -> usize {
            BitSetLike::count(&self.0)
        }
    }

    impl FromIterator<usize> for VarBitSet {
        fn from_iter<T: IntoIterator<Item = usize>>(into_iter: T) -> Self {
            let iter = into_iter.into_iter();
            let lower_bound = iter.size_hint().0;
            let mut bits = VarBitSet::new_bitset(lower_bound);
            for bit in iter {
                bits.set(bit);
            }
            bits
        }
    }

    /*
    pub(crate) fn between(min: usize, max: usize) -> BitSetStrategy<VarBitSet> {
        BitSetStrategy::new(min, max)
    }

    pub(crate) fn masked(mask: VarBitSet) -> BitSetStrategy<VarBitSet> {
        BitSetStrategy::masked(mask)
    }
    */

    pub(crate) fn sampled(
        size: impl Into<SizeRange>,
        bits: impl Into<SizeRange>,
    ) -> SampledBitSetStrategy<VarBitSet> {
        SampledBitSetStrategy::new(size, bits)
    }
}

pub use self::varsize::VarBitSet;

#[cfg(test)]
mod test {
    use super::*;

    #[test]
    fn generates_values_in_range() {
        let input = u32::between(4, 8);

        let mut runner = TestRunner::default();
        for _ in 0..256 {
            let value = input.new_tree(&mut runner).unwrap().current();
            assert!(0 == value & !0xF0u32, "Generate value {}", value);
        }
    }

    #[test]
    fn generates_values_in_mask() {
        let mut accum = 0;

        let mut runner = TestRunner::deterministic();
        let input = u32::masked(0xdeadbeef);
        for _ in 0..1024 {
            accum |= input.new_tree(&mut runner).unwrap().current();
        }

        assert_eq!(0xdeadbeef, accum);
    }

    #[cfg(feature = "bit-set")]
    #[test]
    fn mask_bounds_for_bitset_correct() {
        let mut seen_0 = false;
        let mut seen_2 = false;

        let mut mask = BitSet::new();
        mask.insert(0);
        mask.insert(2);

        let mut runner = TestRunner::deterministic();
        let input = bitset::masked(mask);
        for _ in 0..32 {
            let v = input.new_tree(&mut runner).unwrap().current();
            seen_0 |= v.contains(0);
            seen_2 |= v.contains(2);
        }

        assert!(seen_0);
        assert!(seen_2);
    }

    #[test]
    fn mask_bounds_for_vecbool_correct() {
        let mut seen_0 = false;
        let mut seen_2 = false;

        let mask = vec![true, false, true, false];

        let mut runner = TestRunner::deterministic();
        let input = bool_vec::masked(mask);
        for _ in 0..32 {
            let v = input.new_tree(&mut runner).unwrap().current();
            assert_eq!(4, v.len());
            seen_0 |= v[0];
            seen_2 |= v[2];
        }

        assert!(seen_0);
        assert!(seen_2);
    }

    #[test]
    fn shrinks_to_zero() {
        let input = u32::between(4, 24);

        let mut runner = TestRunner::default();
        for _ in 0..256 {
            let mut value = input.new_tree(&mut runner).unwrap();
            let mut prev = value.current();
            while value.simplify() {
                let v = value.current();
                assert!(
                    1 == (prev & !v).count_ones(),
                    "Shrank from {} to {}",
                    prev,
                    v
                );
                prev = v;
            }

            assert_eq!(0, value.current());
        }
    }

    #[test]
    fn complicates_to_previous() {
        let input = u32::between(4, 24);

        let mut runner = TestRunner::default();
        for _ in 0..256 {
            let mut value = input.new_tree(&mut runner).unwrap();
            let orig = value.current();
            if value.simplify() {
                assert!(value.complicate());
                assert_eq!(orig, value.current());
            }
        }
    }

    #[test]
    fn sampled_selects_correct_sizes_and_bits() {
        let input = u32::sampled(4..8, 10..20);
        let mut seen_counts = [0; 32];
        let mut seen_bits = [0; 32];

        let mut runner = TestRunner::deterministic();
        for _ in 0..2048 {
            let value = input.new_tree(&mut runner).unwrap().current();
            let count = value.count_ones() as usize;
            assert!(count >= 4 && count < 8);
            seen_counts[count] += 1;

            for bit in 0..32 {
                if 0 != value & (1 << bit) {
                    assert!(bit >= 10 && bit < 20);
                    seen_bits[bit] += value;
                }
            }
        }

        for i in 4..8 {
            assert!(seen_counts[i] >= 256 && seen_counts[i] < 1024);
        }

        let least_seen_bit_count =
            seen_bits[10..20].iter().cloned().min().unwrap();
        let most_seen_bit_count =
            seen_bits[10..20].iter().cloned().max().unwrap();
        assert_eq!(1, most_seen_bit_count / least_seen_bit_count);
    }

    #[test]
    fn sampled_doesnt_shrink_below_min_size() {
        let input = u32::sampled(4..8, 10..20);

        let mut runner = TestRunner::default();
        for _ in 0..256 {
            let mut value = input.new_tree(&mut runner).unwrap();
            while value.simplify() {}

            assert_eq!(4, value.current().count_ones());
        }
    }

    #[test]
    fn test_sanity() {
        check_strategy_sanity(u32::masked(0xdeadbeef), None);
    }
}