1// -*- C++ -*-
2//===----------------------------------------------------------------------===//
3//
4// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
5// See https://llvm.org/LICENSE.txt for license information.
6// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7//
8//===----------------------------------------------------------------------===//
9
10#ifndef _LIBCPP___BIT_REFERENCE
11#define _LIBCPP___BIT_REFERENCE
12
13#include <__algorithm/copy_n.h>
14#include <__algorithm/fill_n.h>
15#include <__algorithm/min.h>
16#include <__bits>
17#include <__config>
18#include <__iterator/iterator_traits.h>
19#include <__memory/construct_at.h>
20#include <__memory/pointer_traits.h>
21#include <cstring>
22#include <type_traits>
23
24#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
25#  pragma GCC system_header
26#endif
27
28_LIBCPP_PUSH_MACROS
29#include <__undef_macros>
30
31
32_LIBCPP_BEGIN_NAMESPACE_STD
33
34template <class _Cp, bool _IsConst, typename _Cp::__storage_type = 0> class __bit_iterator;
35template <class _Cp> class __bit_const_reference;
36
37template <class _Tp>
38struct __has_storage_type
39{
40    static const bool value = false;
41};
42
43template <class _Cp, bool = __has_storage_type<_Cp>::value>
44class __bit_reference
45{
46    typedef typename _Cp::__storage_type    __storage_type;
47    typedef typename _Cp::__storage_pointer __storage_pointer;
48
49    __storage_pointer __seg_;
50    __storage_type    __mask_;
51
52    friend typename _Cp::__self;
53
54    friend class __bit_const_reference<_Cp>;
55    friend class __bit_iterator<_Cp, false>;
56public:
57    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
58    __bit_reference(const __bit_reference&) = default;
59
60    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 operator bool() const _NOEXCEPT
61        {return static_cast<bool>(*__seg_ & __mask_);}
62    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 bool operator ~() const _NOEXCEPT
63        {return !static_cast<bool>(*this);}
64
65    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
66    __bit_reference& operator=(bool __x) _NOEXCEPT
67    {
68        if (__x)
69            *__seg_ |= __mask_;
70        else
71            *__seg_ &= ~__mask_;
72        return *this;
73    }
74
75#if _LIBCPP_STD_VER > 20
76    _LIBCPP_HIDE_FROM_ABI constexpr const __bit_reference& operator=(bool __x) const noexcept {
77        if (__x)
78            *__seg_ |= __mask_;
79        else
80            *__seg_ &= ~__mask_;
81        return *this;
82    }
83#endif
84
85    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
86    __bit_reference& operator=(const __bit_reference& __x) _NOEXCEPT
87        {return operator=(static_cast<bool>(__x));}
88
89    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 void flip() _NOEXCEPT {*__seg_ ^= __mask_;}
90    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 __bit_iterator<_Cp, false> operator&() const _NOEXCEPT
91        {return __bit_iterator<_Cp, false>(__seg_, static_cast<unsigned>(__libcpp_ctz(__mask_)));}
92private:
93    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
94    explicit __bit_reference(__storage_pointer __s, __storage_type __m) _NOEXCEPT
95        : __seg_(__s), __mask_(__m) {}
96};
97
98template <class _Cp>
99class __bit_reference<_Cp, false>
100{
101};
102
103template <class _Cp>
104inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
105void
106swap(__bit_reference<_Cp> __x, __bit_reference<_Cp> __y) _NOEXCEPT
107{
108    bool __t = __x;
109    __x = __y;
110    __y = __t;
111}
112
113template <class _Cp, class _Dp>
114inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
115void
116swap(__bit_reference<_Cp> __x, __bit_reference<_Dp> __y) _NOEXCEPT
117{
118    bool __t = __x;
119    __x = __y;
120    __y = __t;
121}
122
123template <class _Cp>
124inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
125void
126swap(__bit_reference<_Cp> __x, bool& __y) _NOEXCEPT
127{
128    bool __t = __x;
129    __x = __y;
130    __y = __t;
131}
132
133template <class _Cp>
134inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
135void
136swap(bool& __x, __bit_reference<_Cp> __y) _NOEXCEPT
137{
138    bool __t = __x;
139    __x = __y;
140    __y = __t;
141}
142
143template <class _Cp>
144class __bit_const_reference
145{
146    typedef typename _Cp::__storage_type          __storage_type;
147    typedef typename _Cp::__const_storage_pointer __storage_pointer;
148
149    __storage_pointer        __seg_;
150    __storage_type __mask_;
151
152    friend typename _Cp::__self;
153    friend class __bit_iterator<_Cp, true>;
154public:
155    _LIBCPP_INLINE_VISIBILITY
156    __bit_const_reference(const __bit_const_reference&) = default;
157
158    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
159    __bit_const_reference(const __bit_reference<_Cp>& __x) _NOEXCEPT
160        : __seg_(__x.__seg_), __mask_(__x.__mask_) {}
161
162    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR operator bool() const _NOEXCEPT
163        {return static_cast<bool>(*__seg_ & __mask_);}
164
165    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 __bit_iterator<_Cp, true> operator&() const _NOEXCEPT
166        {return __bit_iterator<_Cp, true>(__seg_, static_cast<unsigned>(__libcpp_ctz(__mask_)));}
167private:
168    _LIBCPP_INLINE_VISIBILITY
169    _LIBCPP_CONSTEXPR
170    explicit __bit_const_reference(__storage_pointer __s, __storage_type __m) _NOEXCEPT
171        : __seg_(__s), __mask_(__m) {}
172
173    __bit_const_reference& operator=(const __bit_const_reference&) = delete;
174};
175
176// find
177
178template <class _Cp, bool _IsConst>
179_LIBCPP_CONSTEXPR_AFTER_CXX17 __bit_iterator<_Cp, _IsConst>
180__find_bool_true(__bit_iterator<_Cp, _IsConst> __first, typename _Cp::size_type __n)
181{
182    typedef __bit_iterator<_Cp, _IsConst> _It;
183    typedef typename _It::__storage_type __storage_type;
184    const int __bits_per_word = _It::__bits_per_word;
185    // do first partial word
186    if (__first.__ctz_ != 0)
187    {
188        __storage_type __clz_f = static_cast<__storage_type>(__bits_per_word - __first.__ctz_);
189        __storage_type __dn = _VSTD::min(__clz_f, __n);
190        __storage_type __m = (~__storage_type(0) << __first.__ctz_) & (~__storage_type(0) >> (__clz_f - __dn));
191        __storage_type __b = *__first.__seg_ & __m;
192        if (__b)
193            return _It(__first.__seg_, static_cast<unsigned>(_VSTD::__libcpp_ctz(__b)));
194        if (__n == __dn)
195            return __first + __n;
196        __n -= __dn;
197        ++__first.__seg_;
198    }
199    // do middle whole words
200    for (; __n >= __bits_per_word; ++__first.__seg_, __n -= __bits_per_word)
201        if (*__first.__seg_)
202            return _It(__first.__seg_, static_cast<unsigned>(_VSTD::__libcpp_ctz(*__first.__seg_)));
203    // do last partial word
204    if (__n > 0)
205    {
206        __storage_type __m = ~__storage_type(0) >> (__bits_per_word - __n);
207        __storage_type __b = *__first.__seg_ & __m;
208        if (__b)
209            return _It(__first.__seg_, static_cast<unsigned>(_VSTD::__libcpp_ctz(__b)));
210    }
211    return _It(__first.__seg_, static_cast<unsigned>(__n));
212}
213
214template <class _Cp, bool _IsConst>
215_LIBCPP_CONSTEXPR_AFTER_CXX17 __bit_iterator<_Cp, _IsConst>
216__find_bool_false(__bit_iterator<_Cp, _IsConst> __first, typename _Cp::size_type __n)
217{
218    typedef __bit_iterator<_Cp, _IsConst> _It;
219    typedef typename _It::__storage_type __storage_type;
220    const int __bits_per_word = _It::__bits_per_word;
221    // do first partial word
222    if (__first.__ctz_ != 0)
223    {
224        __storage_type __clz_f = static_cast<__storage_type>(__bits_per_word - __first.__ctz_);
225        __storage_type __dn = _VSTD::min(__clz_f, __n);
226        __storage_type __m = (~__storage_type(0) << __first.__ctz_) & (~__storage_type(0) >> (__clz_f - __dn));
227        __storage_type __b = ~*__first.__seg_ & __m;
228        if (__b)
229            return _It(__first.__seg_, static_cast<unsigned>(_VSTD::__libcpp_ctz(__b)));
230        if (__n == __dn)
231            return __first + __n;
232        __n -= __dn;
233        ++__first.__seg_;
234    }
235    // do middle whole words
236    for (; __n >= __bits_per_word; ++__first.__seg_, __n -= __bits_per_word)
237    {
238        __storage_type __b = ~*__first.__seg_;
239        if (__b)
240            return _It(__first.__seg_, static_cast<unsigned>(_VSTD::__libcpp_ctz(__b)));
241    }
242    // do last partial word
243    if (__n > 0)
244    {
245        __storage_type __m = ~__storage_type(0) >> (__bits_per_word - __n);
246        __storage_type __b = ~*__first.__seg_ & __m;
247        if (__b)
248            return _It(__first.__seg_, static_cast<unsigned>(_VSTD::__libcpp_ctz(__b)));
249    }
250    return _It(__first.__seg_, static_cast<unsigned>(__n));
251}
252
253template <class _Cp, bool _IsConst, class _Tp>
254inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
255__bit_iterator<_Cp, _IsConst>
256find(__bit_iterator<_Cp, _IsConst> __first, __bit_iterator<_Cp, _IsConst> __last, const _Tp& __value)
257{
258    if (static_cast<bool>(__value))
259        return _VSTD::__find_bool_true(__first, static_cast<typename _Cp::size_type>(__last - __first));
260    return _VSTD::__find_bool_false(__first, static_cast<typename _Cp::size_type>(__last - __first));
261}
262
263// count
264
265template <class _Cp, bool _IsConst>
266typename __bit_iterator<_Cp, _IsConst>::difference_type
267__count_bool_true(__bit_iterator<_Cp, _IsConst> __first, typename _Cp::size_type __n)
268{
269    typedef __bit_iterator<_Cp, _IsConst> _It;
270    typedef typename _It::__storage_type __storage_type;
271    typedef typename _It::difference_type difference_type;
272    const int __bits_per_word = _It::__bits_per_word;
273    difference_type __r = 0;
274    // do first partial word
275    if (__first.__ctz_ != 0)
276    {
277        __storage_type __clz_f = static_cast<__storage_type>(__bits_per_word - __first.__ctz_);
278        __storage_type __dn = _VSTD::min(__clz_f, __n);
279        __storage_type __m = (~__storage_type(0) << __first.__ctz_) & (~__storage_type(0) >> (__clz_f - __dn));
280        __r = _VSTD::__libcpp_popcount(*__first.__seg_ & __m);
281        __n -= __dn;
282        ++__first.__seg_;
283    }
284    // do middle whole words
285    for (; __n >= __bits_per_word; ++__first.__seg_, __n -= __bits_per_word)
286        __r += _VSTD::__libcpp_popcount(*__first.__seg_);
287    // do last partial word
288    if (__n > 0)
289    {
290        __storage_type __m = ~__storage_type(0) >> (__bits_per_word - __n);
291        __r += _VSTD::__libcpp_popcount(*__first.__seg_ & __m);
292    }
293    return __r;
294}
295
296template <class _Cp, bool _IsConst>
297typename __bit_iterator<_Cp, _IsConst>::difference_type
298__count_bool_false(__bit_iterator<_Cp, _IsConst> __first, typename _Cp::size_type __n)
299{
300    typedef __bit_iterator<_Cp, _IsConst> _It;
301    typedef typename _It::__storage_type __storage_type;
302    typedef typename _It::difference_type difference_type;
303    const int __bits_per_word = _It::__bits_per_word;
304    difference_type __r = 0;
305    // do first partial word
306    if (__first.__ctz_ != 0)
307    {
308        __storage_type __clz_f = static_cast<__storage_type>(__bits_per_word - __first.__ctz_);
309        __storage_type __dn = _VSTD::min(__clz_f, __n);
310        __storage_type __m = (~__storage_type(0) << __first.__ctz_) & (~__storage_type(0) >> (__clz_f - __dn));
311        __r = _VSTD::__libcpp_popcount(~*__first.__seg_ & __m);
312        __n -= __dn;
313        ++__first.__seg_;
314    }
315    // do middle whole words
316    for (; __n >= __bits_per_word; ++__first.__seg_, __n -= __bits_per_word)
317        __r += _VSTD::__libcpp_popcount(~*__first.__seg_);
318    // do last partial word
319    if (__n > 0)
320    {
321        __storage_type __m = ~__storage_type(0) >> (__bits_per_word - __n);
322        __r += _VSTD::__libcpp_popcount(~*__first.__seg_ & __m);
323    }
324    return __r;
325}
326
327template <class _Cp, bool _IsConst, class _Tp>
328inline _LIBCPP_INLINE_VISIBILITY
329typename __bit_iterator<_Cp, _IsConst>::difference_type
330count(__bit_iterator<_Cp, _IsConst> __first, __bit_iterator<_Cp, _IsConst> __last, const _Tp& __value)
331{
332    if (static_cast<bool>(__value))
333        return _VSTD::__count_bool_true(__first, static_cast<typename _Cp::size_type>(__last - __first));
334    return _VSTD::__count_bool_false(__first, static_cast<typename _Cp::size_type>(__last - __first));
335}
336
337// fill_n
338
339template <class _Cp>
340_LIBCPP_CONSTEXPR_AFTER_CXX17 void
341__fill_n_false(__bit_iterator<_Cp, false> __first, typename _Cp::size_type __n)
342{
343    typedef __bit_iterator<_Cp, false> _It;
344    typedef typename _It::__storage_type __storage_type;
345    const int __bits_per_word = _It::__bits_per_word;
346    // do first partial word
347    if (__first.__ctz_ != 0)
348    {
349        __storage_type __clz_f = static_cast<__storage_type>(__bits_per_word - __first.__ctz_);
350        __storage_type __dn = _VSTD::min(__clz_f, __n);
351        __storage_type __m = (~__storage_type(0) << __first.__ctz_) & (~__storage_type(0) >> (__clz_f - __dn));
352        *__first.__seg_ &= ~__m;
353        __n -= __dn;
354        ++__first.__seg_;
355    }
356    // do middle whole words
357    __storage_type __nw = __n / __bits_per_word;
358    std::fill_n(std::__to_address(__first.__seg_), __nw, 0);
359    __n -= __nw * __bits_per_word;
360    // do last partial word
361    if (__n > 0)
362    {
363        __first.__seg_ += __nw;
364        __storage_type __m = ~__storage_type(0) >> (__bits_per_word - __n);
365        *__first.__seg_ &= ~__m;
366    }
367}
368
369template <class _Cp>
370_LIBCPP_CONSTEXPR_AFTER_CXX17 void
371__fill_n_true(__bit_iterator<_Cp, false> __first, typename _Cp::size_type __n)
372{
373    typedef __bit_iterator<_Cp, false> _It;
374    typedef typename _It::__storage_type __storage_type;
375    const int __bits_per_word = _It::__bits_per_word;
376    // do first partial word
377    if (__first.__ctz_ != 0)
378    {
379        __storage_type __clz_f = static_cast<__storage_type>(__bits_per_word - __first.__ctz_);
380        __storage_type __dn = _VSTD::min(__clz_f, __n);
381        __storage_type __m = (~__storage_type(0) << __first.__ctz_) & (~__storage_type(0) >> (__clz_f - __dn));
382        *__first.__seg_ |= __m;
383        __n -= __dn;
384        ++__first.__seg_;
385    }
386    // do middle whole words
387    __storage_type __nw = __n / __bits_per_word;
388    // __storage_type is always an unsigned type, so -1 sets all bits
389    std::fill_n(std::__to_address(__first.__seg_), __nw, static_cast<__storage_type>(-1));
390    __n -= __nw * __bits_per_word;
391    // do last partial word
392    if (__n > 0)
393    {
394        __first.__seg_ += __nw;
395        __storage_type __m = ~__storage_type(0) >> (__bits_per_word - __n);
396        *__first.__seg_ |= __m;
397    }
398}
399
400template <class _Cp>
401inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
402void
403fill_n(__bit_iterator<_Cp, false> __first, typename _Cp::size_type __n, bool __value)
404{
405    if (__n > 0)
406    {
407        if (__value)
408            _VSTD::__fill_n_true(__first, __n);
409        else
410            _VSTD::__fill_n_false(__first, __n);
411    }
412}
413
414// fill
415
416template <class _Cp>
417inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
418void
419fill(__bit_iterator<_Cp, false> __first, __bit_iterator<_Cp, false> __last, bool __value)
420{
421    _VSTD::fill_n(__first, static_cast<typename _Cp::size_type>(__last - __first), __value);
422}
423
424// copy
425
426template <class _Cp, bool _IsConst>
427_LIBCPP_CONSTEXPR_AFTER_CXX17
428__bit_iterator<_Cp, false>
429__copy_aligned(__bit_iterator<_Cp, _IsConst> __first, __bit_iterator<_Cp, _IsConst> __last,
430                                                     __bit_iterator<_Cp, false> __result)
431{
432    typedef __bit_iterator<_Cp, _IsConst> _In;
433    typedef  typename _In::difference_type difference_type;
434    typedef typename _In::__storage_type __storage_type;
435    const int __bits_per_word = _In::__bits_per_word;
436    difference_type __n = __last - __first;
437    if (__n > 0)
438    {
439        // do first word
440        if (__first.__ctz_ != 0)
441        {
442            unsigned __clz = __bits_per_word - __first.__ctz_;
443            difference_type __dn = _VSTD::min(static_cast<difference_type>(__clz), __n);
444            __n -= __dn;
445            __storage_type __m = (~__storage_type(0) << __first.__ctz_) & (~__storage_type(0) >> (__clz - __dn));
446            __storage_type __b = *__first.__seg_ & __m;
447            *__result.__seg_ &= ~__m;
448            *__result.__seg_ |= __b;
449            __result.__seg_ += (__dn + __result.__ctz_) / __bits_per_word;
450            __result.__ctz_ = static_cast<unsigned>((__dn + __result.__ctz_)  % __bits_per_word);
451            ++__first.__seg_;
452            // __first.__ctz_ = 0;
453        }
454        // __first.__ctz_ == 0;
455        // do middle words
456        __storage_type __nw = __n / __bits_per_word;
457        std::copy_n(std::__to_address(__first.__seg_), __nw, std::__to_address(__result.__seg_));
458        __n -= __nw * __bits_per_word;
459        __result.__seg_ += __nw;
460        // do last word
461        if (__n > 0)
462        {
463            __first.__seg_ += __nw;
464            __storage_type __m = ~__storage_type(0) >> (__bits_per_word - __n);
465            __storage_type __b = *__first.__seg_ & __m;
466            *__result.__seg_ &= ~__m;
467            *__result.__seg_ |= __b;
468            __result.__ctz_ = static_cast<unsigned>(__n);
469        }
470    }
471    return __result;
472}
473
474template <class _Cp, bool _IsConst>
475_LIBCPP_CONSTEXPR_AFTER_CXX17
476__bit_iterator<_Cp, false>
477__copy_unaligned(__bit_iterator<_Cp, _IsConst> __first, __bit_iterator<_Cp, _IsConst> __last,
478                                                       __bit_iterator<_Cp, false> __result)
479{
480    typedef __bit_iterator<_Cp, _IsConst> _In;
481    typedef  typename _In::difference_type difference_type;
482    typedef typename _In::__storage_type __storage_type;
483    const int __bits_per_word = _In::__bits_per_word;
484    difference_type __n = __last - __first;
485    if (__n > 0)
486    {
487        // do first word
488        if (__first.__ctz_ != 0)
489        {
490            unsigned __clz_f = __bits_per_word - __first.__ctz_;
491            difference_type __dn = _VSTD::min(static_cast<difference_type>(__clz_f), __n);
492            __n -= __dn;
493            __storage_type __m = (~__storage_type(0) << __first.__ctz_) & (~__storage_type(0) >> (__clz_f - __dn));
494            __storage_type __b = *__first.__seg_ & __m;
495            unsigned __clz_r = __bits_per_word - __result.__ctz_;
496            __storage_type __ddn = _VSTD::min<__storage_type>(__dn, __clz_r);
497            __m = (~__storage_type(0) << __result.__ctz_) & (~__storage_type(0) >> (__clz_r - __ddn));
498            *__result.__seg_ &= ~__m;
499            if (__result.__ctz_ > __first.__ctz_)
500                *__result.__seg_ |= __b << (__result.__ctz_ - __first.__ctz_);
501            else
502                *__result.__seg_ |= __b >> (__first.__ctz_ - __result.__ctz_);
503            __result.__seg_ += (__ddn + __result.__ctz_) / __bits_per_word;
504            __result.__ctz_ = static_cast<unsigned>((__ddn + __result.__ctz_)  % __bits_per_word);
505            __dn -= __ddn;
506            if (__dn > 0)
507            {
508                __m = ~__storage_type(0) >> (__bits_per_word - __dn);
509                *__result.__seg_ &= ~__m;
510                *__result.__seg_ |= __b >> (__first.__ctz_ + __ddn);
511                __result.__ctz_ = static_cast<unsigned>(__dn);
512            }
513            ++__first.__seg_;
514            // __first.__ctz_ = 0;
515        }
516        // __first.__ctz_ == 0;
517        // do middle words
518        unsigned __clz_r = __bits_per_word - __result.__ctz_;
519        __storage_type __m = ~__storage_type(0) << __result.__ctz_;
520        for (; __n >= __bits_per_word; __n -= __bits_per_word, ++__first.__seg_)
521        {
522            __storage_type __b = *__first.__seg_;
523            *__result.__seg_ &= ~__m;
524            *__result.__seg_ |= __b << __result.__ctz_;
525            ++__result.__seg_;
526            *__result.__seg_ &= __m;
527            *__result.__seg_ |= __b >> __clz_r;
528        }
529        // do last word
530        if (__n > 0)
531        {
532            __m = ~__storage_type(0) >> (__bits_per_word - __n);
533            __storage_type __b = *__first.__seg_ & __m;
534            __storage_type __dn = _VSTD::min(__n, static_cast<difference_type>(__clz_r));
535            __m = (~__storage_type(0) << __result.__ctz_) & (~__storage_type(0) >> (__clz_r - __dn));
536            *__result.__seg_ &= ~__m;
537            *__result.__seg_ |= __b << __result.__ctz_;
538            __result.__seg_ += (__dn + __result.__ctz_) / __bits_per_word;
539            __result.__ctz_ = static_cast<unsigned>((__dn + __result.__ctz_)  % __bits_per_word);
540            __n -= __dn;
541            if (__n > 0)
542            {
543                __m = ~__storage_type(0) >> (__bits_per_word - __n);
544                *__result.__seg_ &= ~__m;
545                *__result.__seg_ |= __b >> __dn;
546                __result.__ctz_ = static_cast<unsigned>(__n);
547            }
548        }
549    }
550    return __result;
551}
552
553template <class _Cp, bool _IsConst>
554inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
555__bit_iterator<_Cp, false>
556copy(__bit_iterator<_Cp, _IsConst> __first, __bit_iterator<_Cp, _IsConst> __last, __bit_iterator<_Cp, false> __result)
557{
558    if (__first.__ctz_ == __result.__ctz_)
559        return _VSTD::__copy_aligned(__first, __last, __result);
560    return _VSTD::__copy_unaligned(__first, __last, __result);
561}
562
563// copy_backward
564
565template <class _Cp, bool _IsConst>
566_LIBCPP_CONSTEXPR_AFTER_CXX17 __bit_iterator<_Cp, false>
567__copy_backward_aligned(__bit_iterator<_Cp, _IsConst> __first, __bit_iterator<_Cp, _IsConst> __last,
568                                                     __bit_iterator<_Cp, false> __result)
569{
570    typedef __bit_iterator<_Cp, _IsConst> _In;
571    typedef  typename _In::difference_type difference_type;
572    typedef typename _In::__storage_type __storage_type;
573    const int __bits_per_word = _In::__bits_per_word;
574    difference_type __n = __last - __first;
575    if (__n > 0)
576    {
577        // do first word
578        if (__last.__ctz_ != 0)
579        {
580            difference_type __dn = _VSTD::min(static_cast<difference_type>(__last.__ctz_), __n);
581            __n -= __dn;
582            unsigned __clz = __bits_per_word - __last.__ctz_;
583            __storage_type __m = (~__storage_type(0) << (__last.__ctz_ - __dn)) & (~__storage_type(0) >> __clz);
584            __storage_type __b = *__last.__seg_ & __m;
585            *__result.__seg_ &= ~__m;
586            *__result.__seg_ |= __b;
587            __result.__ctz_ = static_cast<unsigned>(((-__dn & (__bits_per_word - 1)) +
588                                                       __result.__ctz_)  % __bits_per_word);
589            // __last.__ctz_ = 0
590         }
591        // __last.__ctz_ == 0 || __n == 0
592        // __result.__ctz_ == 0 || __n == 0
593        // do middle words
594        __storage_type __nw = __n / __bits_per_word;
595        __result.__seg_ -= __nw;
596        __last.__seg_ -= __nw;
597        std::copy_n(std::__to_address(__last.__seg_), __nw, std::__to_address(__result.__seg_));
598        __n -= __nw * __bits_per_word;
599        // do last word
600        if (__n > 0)
601        {
602            __storage_type __m = ~__storage_type(0) << (__bits_per_word - __n);
603            __storage_type __b = *--__last.__seg_ & __m;
604            *--__result.__seg_ &= ~__m;
605            *__result.__seg_ |= __b;
606            __result.__ctz_ = static_cast<unsigned>(-__n & (__bits_per_word - 1));
607        }
608    }
609    return __result;
610}
611
612template <class _Cp, bool _IsConst>
613_LIBCPP_CONSTEXPR_AFTER_CXX17 __bit_iterator<_Cp, false>
614__copy_backward_unaligned(__bit_iterator<_Cp, _IsConst> __first, __bit_iterator<_Cp, _IsConst> __last,
615                                                       __bit_iterator<_Cp, false> __result)
616{
617    typedef __bit_iterator<_Cp, _IsConst> _In;
618    typedef  typename _In::difference_type difference_type;
619    typedef typename _In::__storage_type __storage_type;
620    const int __bits_per_word = _In::__bits_per_word;
621    difference_type __n = __last - __first;
622    if (__n > 0)
623    {
624        // do first word
625        if (__last.__ctz_ != 0)
626        {
627            difference_type __dn = _VSTD::min(static_cast<difference_type>(__last.__ctz_), __n);
628            __n -= __dn;
629            unsigned __clz_l = __bits_per_word - __last.__ctz_;
630            __storage_type __m = (~__storage_type(0) << (__last.__ctz_ - __dn)) & (~__storage_type(0) >> __clz_l);
631            __storage_type __b = *__last.__seg_ & __m;
632            unsigned __clz_r = __bits_per_word - __result.__ctz_;
633            __storage_type __ddn = _VSTD::min(__dn, static_cast<difference_type>(__result.__ctz_));
634            if (__ddn > 0)
635            {
636                __m = (~__storage_type(0) << (__result.__ctz_ - __ddn)) & (~__storage_type(0) >> __clz_r);
637                *__result.__seg_ &= ~__m;
638                if (__result.__ctz_ > __last.__ctz_)
639                    *__result.__seg_ |= __b << (__result.__ctz_ - __last.__ctz_);
640                else
641                    *__result.__seg_ |= __b >> (__last.__ctz_ - __result.__ctz_);
642                __result.__ctz_ = static_cast<unsigned>(((-__ddn & (__bits_per_word - 1)) +
643                                                         __result.__ctz_)  % __bits_per_word);
644                __dn -= __ddn;
645            }
646            if (__dn > 0)
647            {
648                // __result.__ctz_ == 0
649                --__result.__seg_;
650                __result.__ctz_ = static_cast<unsigned>(-__dn & (__bits_per_word - 1));
651                __m = ~__storage_type(0) << __result.__ctz_;
652                *__result.__seg_ &= ~__m;
653                __last.__ctz_ -= __dn + __ddn;
654                *__result.__seg_ |= __b << (__result.__ctz_ - __last.__ctz_);
655            }
656            // __last.__ctz_ = 0
657         }
658        // __last.__ctz_ == 0 || __n == 0
659        // __result.__ctz_ != 0 || __n == 0
660        // do middle words
661        unsigned __clz_r = __bits_per_word - __result.__ctz_;
662        __storage_type __m = ~__storage_type(0) >> __clz_r;
663        for (; __n >= __bits_per_word; __n -= __bits_per_word)
664        {
665            __storage_type __b = *--__last.__seg_;
666            *__result.__seg_ &= ~__m;
667            *__result.__seg_ |= __b >> __clz_r;
668            *--__result.__seg_ &= __m;
669            *__result.__seg_ |= __b << __result.__ctz_;
670        }
671        // do last word
672        if (__n > 0)
673        {
674            __m = ~__storage_type(0) << (__bits_per_word - __n);
675            __storage_type __b = *--__last.__seg_ & __m;
676            __clz_r = __bits_per_word - __result.__ctz_;
677            __storage_type __dn = _VSTD::min(__n, static_cast<difference_type>(__result.__ctz_));
678            __m = (~__storage_type(0) << (__result.__ctz_ - __dn)) & (~__storage_type(0) >> __clz_r);
679            *__result.__seg_ &= ~__m;
680            *__result.__seg_ |= __b >> (__bits_per_word - __result.__ctz_);
681            __result.__ctz_ = static_cast<unsigned>(((-__dn & (__bits_per_word - 1)) +
682                                                     __result.__ctz_)  % __bits_per_word);
683            __n -= __dn;
684            if (__n > 0)
685            {
686                // __result.__ctz_ == 0
687                --__result.__seg_;
688                __result.__ctz_ = static_cast<unsigned>(-__n & (__bits_per_word - 1));
689                __m = ~__storage_type(0) << __result.__ctz_;
690                *__result.__seg_ &= ~__m;
691                *__result.__seg_ |= __b << (__result.__ctz_ - (__bits_per_word - __n - __dn));
692            }
693        }
694    }
695    return __result;
696}
697
698template <class _Cp, bool _IsConst>
699inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
700__bit_iterator<_Cp, false>
701copy_backward(__bit_iterator<_Cp, _IsConst> __first, __bit_iterator<_Cp, _IsConst> __last, __bit_iterator<_Cp, false> __result)
702{
703    if (__last.__ctz_ == __result.__ctz_)
704        return _VSTD::__copy_backward_aligned(__first, __last, __result);
705    return _VSTD::__copy_backward_unaligned(__first, __last, __result);
706}
707
708// move
709
710template <class _Cp, bool _IsConst>
711inline _LIBCPP_INLINE_VISIBILITY
712__bit_iterator<_Cp, false>
713move(__bit_iterator<_Cp, _IsConst> __first, __bit_iterator<_Cp, _IsConst> __last, __bit_iterator<_Cp, false> __result)
714{
715    return _VSTD::copy(__first, __last, __result);
716}
717
718// move_backward
719
720template <class _Cp, bool _IsConst>
721inline _LIBCPP_INLINE_VISIBILITY
722__bit_iterator<_Cp, false>
723move_backward(__bit_iterator<_Cp, _IsConst> __first, __bit_iterator<_Cp, _IsConst> __last, __bit_iterator<_Cp, false> __result)
724{
725    return _VSTD::copy_backward(__first, __last, __result);
726}
727
728// swap_ranges
729
730template <class __C1, class __C2>
731__bit_iterator<__C2, false>
732__swap_ranges_aligned(__bit_iterator<__C1, false> __first, __bit_iterator<__C1, false> __last,
733                      __bit_iterator<__C2, false> __result)
734{
735    typedef __bit_iterator<__C1, false> _I1;
736    typedef  typename _I1::difference_type difference_type;
737    typedef typename _I1::__storage_type __storage_type;
738    const int __bits_per_word = _I1::__bits_per_word;
739    difference_type __n = __last - __first;
740    if (__n > 0)
741    {
742        // do first word
743        if (__first.__ctz_ != 0)
744        {
745            unsigned __clz = __bits_per_word - __first.__ctz_;
746            difference_type __dn = _VSTD::min(static_cast<difference_type>(__clz), __n);
747            __n -= __dn;
748            __storage_type __m = (~__storage_type(0) << __first.__ctz_) & (~__storage_type(0) >> (__clz - __dn));
749            __storage_type __b1 = *__first.__seg_ & __m;
750            *__first.__seg_ &= ~__m;
751            __storage_type __b2 = *__result.__seg_ & __m;
752            *__result.__seg_ &= ~__m;
753            *__result.__seg_ |= __b1;
754            *__first.__seg_  |= __b2;
755            __result.__seg_ += (__dn + __result.__ctz_) / __bits_per_word;
756            __result.__ctz_ = static_cast<unsigned>((__dn + __result.__ctz_)  % __bits_per_word);
757            ++__first.__seg_;
758            // __first.__ctz_ = 0;
759        }
760        // __first.__ctz_ == 0;
761        // do middle words
762        for (; __n >= __bits_per_word; __n -= __bits_per_word, ++__first.__seg_, ++__result.__seg_)
763            swap(*__first.__seg_, *__result.__seg_);
764        // do last word
765        if (__n > 0)
766        {
767            __storage_type __m = ~__storage_type(0) >> (__bits_per_word - __n);
768            __storage_type __b1 = *__first.__seg_ & __m;
769            *__first.__seg_ &= ~__m;
770            __storage_type __b2 = *__result.__seg_ & __m;
771            *__result.__seg_ &= ~__m;
772            *__result.__seg_ |= __b1;
773            *__first.__seg_  |= __b2;
774            __result.__ctz_ = static_cast<unsigned>(__n);
775        }
776    }
777    return __result;
778}
779
780template <class __C1, class __C2>
781__bit_iterator<__C2, false>
782__swap_ranges_unaligned(__bit_iterator<__C1, false> __first, __bit_iterator<__C1, false> __last,
783                        __bit_iterator<__C2, false> __result)
784{
785    typedef __bit_iterator<__C1, false> _I1;
786    typedef  typename _I1::difference_type difference_type;
787    typedef typename _I1::__storage_type __storage_type;
788    const int __bits_per_word = _I1::__bits_per_word;
789    difference_type __n = __last - __first;
790    if (__n > 0)
791    {
792        // do first word
793        if (__first.__ctz_ != 0)
794        {
795            unsigned __clz_f = __bits_per_word - __first.__ctz_;
796            difference_type __dn = _VSTD::min(static_cast<difference_type>(__clz_f), __n);
797            __n -= __dn;
798            __storage_type __m = (~__storage_type(0) << __first.__ctz_) & (~__storage_type(0) >> (__clz_f - __dn));
799            __storage_type __b1 = *__first.__seg_ & __m;
800            *__first.__seg_ &= ~__m;
801            unsigned __clz_r = __bits_per_word - __result.__ctz_;
802            __storage_type __ddn = _VSTD::min<__storage_type>(__dn, __clz_r);
803            __m = (~__storage_type(0) << __result.__ctz_) & (~__storage_type(0) >> (__clz_r - __ddn));
804            __storage_type __b2 = *__result.__seg_ & __m;
805            *__result.__seg_ &= ~__m;
806            if (__result.__ctz_ > __first.__ctz_)
807            {
808                unsigned __s = __result.__ctz_ - __first.__ctz_;
809                *__result.__seg_ |= __b1 << __s;
810                *__first.__seg_  |= __b2 >> __s;
811            }
812            else
813            {
814                unsigned __s = __first.__ctz_ - __result.__ctz_;
815                *__result.__seg_ |= __b1 >> __s;
816                *__first.__seg_  |= __b2 << __s;
817            }
818            __result.__seg_ += (__ddn + __result.__ctz_) / __bits_per_word;
819            __result.__ctz_ = static_cast<unsigned>((__ddn + __result.__ctz_)  % __bits_per_word);
820            __dn -= __ddn;
821            if (__dn > 0)
822            {
823                __m = ~__storage_type(0) >> (__bits_per_word - __dn);
824                __b2 = *__result.__seg_ & __m;
825                *__result.__seg_ &= ~__m;
826                unsigned __s = __first.__ctz_ + __ddn;
827                *__result.__seg_ |= __b1 >> __s;
828                *__first.__seg_  |= __b2 << __s;
829                __result.__ctz_ = static_cast<unsigned>(__dn);
830            }
831            ++__first.__seg_;
832            // __first.__ctz_ = 0;
833        }
834        // __first.__ctz_ == 0;
835        // do middle words
836        __storage_type __m = ~__storage_type(0) << __result.__ctz_;
837        unsigned __clz_r = __bits_per_word - __result.__ctz_;
838        for (; __n >= __bits_per_word; __n -= __bits_per_word, ++__first.__seg_)
839        {
840            __storage_type __b1 = *__first.__seg_;
841            __storage_type __b2 = *__result.__seg_ & __m;
842            *__result.__seg_ &= ~__m;
843            *__result.__seg_ |= __b1 << __result.__ctz_;
844            *__first.__seg_  = __b2 >> __result.__ctz_;
845            ++__result.__seg_;
846            __b2 = *__result.__seg_ & ~__m;
847            *__result.__seg_ &= __m;
848            *__result.__seg_ |= __b1 >> __clz_r;
849            *__first.__seg_  |= __b2 << __clz_r;
850        }
851        // do last word
852        if (__n > 0)
853        {
854            __m = ~__storage_type(0) >> (__bits_per_word - __n);
855            __storage_type __b1 = *__first.__seg_ & __m;
856            *__first.__seg_ &= ~__m;
857            __storage_type __dn = _VSTD::min<__storage_type>(__n, __clz_r);
858            __m = (~__storage_type(0) << __result.__ctz_) & (~__storage_type(0) >> (__clz_r - __dn));
859            __storage_type __b2 = *__result.__seg_ & __m;
860            *__result.__seg_ &= ~__m;
861            *__result.__seg_ |= __b1 << __result.__ctz_;
862            *__first.__seg_  |= __b2 >> __result.__ctz_;
863            __result.__seg_ += (__dn + __result.__ctz_) / __bits_per_word;
864            __result.__ctz_ = static_cast<unsigned>((__dn + __result.__ctz_)  % __bits_per_word);
865            __n -= __dn;
866            if (__n > 0)
867            {
868                __m = ~__storage_type(0) >> (__bits_per_word - __n);
869                __b2 = *__result.__seg_ & __m;
870                *__result.__seg_ &= ~__m;
871                *__result.__seg_ |= __b1 >> __dn;
872                *__first.__seg_  |= __b2 << __dn;
873                __result.__ctz_ = static_cast<unsigned>(__n);
874            }
875        }
876    }
877    return __result;
878}
879
880template <class __C1, class __C2>
881inline _LIBCPP_INLINE_VISIBILITY
882__bit_iterator<__C2, false>
883swap_ranges(__bit_iterator<__C1, false> __first1, __bit_iterator<__C1, false> __last1,
884            __bit_iterator<__C2, false> __first2)
885{
886    if (__first1.__ctz_ == __first2.__ctz_)
887        return _VSTD::__swap_ranges_aligned(__first1, __last1, __first2);
888    return _VSTD::__swap_ranges_unaligned(__first1, __last1, __first2);
889}
890
891// rotate
892
893template <class _Cp>
894struct __bit_array
895{
896    typedef typename _Cp::difference_type difference_type;
897    typedef typename _Cp::__storage_type  __storage_type;
898    typedef typename _Cp::__storage_pointer __storage_pointer;
899    typedef typename _Cp::iterator        iterator;
900    static const unsigned __bits_per_word = _Cp::__bits_per_word;
901    static const unsigned _Np = 4;
902
903    difference_type __size_;
904    __storage_type __word_[_Np];
905
906    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 static difference_type capacity()
907        {return static_cast<difference_type>(_Np * __bits_per_word);}
908    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 explicit __bit_array(difference_type __s) : __size_(__s) {
909        if (__libcpp_is_constant_evaluated()) {
910            for (size_t __i = 0; __i != __bit_array<_Cp>::_Np; ++__i)
911                std::__construct_at(__word_ + __i, 0);
912        }
913    }
914    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 iterator begin()
915    {
916        return iterator(pointer_traits<__storage_pointer>::pointer_to(__word_[0]), 0);
917    }
918    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 iterator end()
919    {
920        return iterator(pointer_traits<__storage_pointer>::pointer_to(__word_[0]) + __size_ / __bits_per_word,
921                                                  static_cast<unsigned>(__size_ % __bits_per_word));
922    }
923};
924
925template <class _Cp>
926_LIBCPP_CONSTEXPR_AFTER_CXX17 __bit_iterator<_Cp, false>
927rotate(__bit_iterator<_Cp, false> __first, __bit_iterator<_Cp, false> __middle, __bit_iterator<_Cp, false> __last)
928{
929    typedef __bit_iterator<_Cp, false> _I1;
930    typedef  typename _I1::difference_type difference_type;
931    difference_type __d1 = __middle - __first;
932    difference_type __d2 = __last - __middle;
933    _I1 __r = __first + __d2;
934    while (__d1 != 0 && __d2 != 0)
935    {
936        if (__d1 <= __d2)
937        {
938            if (__d1 <= __bit_array<_Cp>::capacity())
939            {
940                __bit_array<_Cp> __b(__d1);
941                _VSTD::copy(__first, __middle, __b.begin());
942                _VSTD::copy(__b.begin(), __b.end(), _VSTD::copy(__middle, __last, __first));
943                break;
944            }
945            else
946            {
947                __bit_iterator<_Cp, false> __mp = _VSTD::swap_ranges(__first, __middle, __middle);
948                __first = __middle;
949                __middle = __mp;
950                __d2 -= __d1;
951            }
952        }
953        else
954        {
955            if (__d2 <= __bit_array<_Cp>::capacity())
956            {
957                __bit_array<_Cp> __b(__d2);
958                _VSTD::copy(__middle, __last, __b.begin());
959                _VSTD::copy_backward(__b.begin(), __b.end(), _VSTD::copy_backward(__first, __middle, __last));
960                break;
961            }
962            else
963            {
964                __bit_iterator<_Cp, false> __mp = __first + __d2;
965                _VSTD::swap_ranges(__first, __mp, __middle);
966                __first = __mp;
967                __d1 -= __d2;
968            }
969        }
970    }
971    return __r;
972}
973
974// equal
975
976template <class _Cp, bool _IC1, bool _IC2>
977_LIBCPP_CONSTEXPR_AFTER_CXX17 bool
978__equal_unaligned(__bit_iterator<_Cp, _IC1> __first1, __bit_iterator<_Cp, _IC1> __last1,
979                  __bit_iterator<_Cp, _IC2> __first2)
980{
981    typedef __bit_iterator<_Cp, _IC1> _It;
982    typedef  typename _It::difference_type difference_type;
983    typedef typename _It::__storage_type __storage_type;
984    const int __bits_per_word = _It::__bits_per_word;
985    difference_type __n = __last1 - __first1;
986    if (__n > 0)
987    {
988        // do first word
989        if (__first1.__ctz_ != 0)
990        {
991            unsigned __clz_f = __bits_per_word - __first1.__ctz_;
992            difference_type __dn = _VSTD::min(static_cast<difference_type>(__clz_f), __n);
993            __n -= __dn;
994            __storage_type __m = (~__storage_type(0) << __first1.__ctz_) & (~__storage_type(0) >> (__clz_f - __dn));
995            __storage_type __b = *__first1.__seg_ & __m;
996            unsigned __clz_r = __bits_per_word - __first2.__ctz_;
997            __storage_type __ddn = _VSTD::min<__storage_type>(__dn, __clz_r);
998            __m = (~__storage_type(0) << __first2.__ctz_) & (~__storage_type(0) >> (__clz_r - __ddn));
999            if (__first2.__ctz_ > __first1.__ctz_)
1000            {
1001                if ((*__first2.__seg_ & __m) != (__b << (__first2.__ctz_ - __first1.__ctz_)))
1002                    return false;
1003            }
1004            else
1005            {
1006                if ((*__first2.__seg_ & __m) != (__b >> (__first1.__ctz_ - __first2.__ctz_)))
1007                    return false;
1008            }
1009            __first2.__seg_ += (__ddn + __first2.__ctz_) / __bits_per_word;
1010            __first2.__ctz_ = static_cast<unsigned>((__ddn + __first2.__ctz_)  % __bits_per_word);
1011            __dn -= __ddn;
1012            if (__dn > 0)
1013            {
1014                __m = ~__storage_type(0) >> (__bits_per_word - __dn);
1015                if ((*__first2.__seg_ & __m) != (__b >> (__first1.__ctz_ + __ddn)))
1016                    return false;
1017                __first2.__ctz_ = static_cast<unsigned>(__dn);
1018            }
1019            ++__first1.__seg_;
1020            // __first1.__ctz_ = 0;
1021        }
1022        // __first1.__ctz_ == 0;
1023        // do middle words
1024        unsigned __clz_r = __bits_per_word - __first2.__ctz_;
1025        __storage_type __m = ~__storage_type(0) << __first2.__ctz_;
1026        for (; __n >= __bits_per_word; __n -= __bits_per_word, ++__first1.__seg_)
1027        {
1028            __storage_type __b = *__first1.__seg_;
1029            if ((*__first2.__seg_ & __m) != (__b << __first2.__ctz_))
1030                return false;
1031            ++__first2.__seg_;
1032            if ((*__first2.__seg_ & ~__m) != (__b >> __clz_r))
1033                return false;
1034        }
1035        // do last word
1036        if (__n > 0)
1037        {
1038            __m = ~__storage_type(0) >> (__bits_per_word - __n);
1039            __storage_type __b = *__first1.__seg_ & __m;
1040            __storage_type __dn = _VSTD::min(__n, static_cast<difference_type>(__clz_r));
1041            __m = (~__storage_type(0) << __first2.__ctz_) & (~__storage_type(0) >> (__clz_r - __dn));
1042            if ((*__first2.__seg_ & __m) != (__b << __first2.__ctz_))
1043                return false;
1044            __first2.__seg_ += (__dn + __first2.__ctz_) / __bits_per_word;
1045            __first2.__ctz_ = static_cast<unsigned>((__dn + __first2.__ctz_)  % __bits_per_word);
1046            __n -= __dn;
1047            if (__n > 0)
1048            {
1049                __m = ~__storage_type(0) >> (__bits_per_word - __n);
1050                if ((*__first2.__seg_ & __m) != (__b >> __dn))
1051                    return false;
1052            }
1053        }
1054    }
1055    return true;
1056}
1057
1058template <class _Cp, bool _IC1, bool _IC2>
1059_LIBCPP_CONSTEXPR_AFTER_CXX17 bool
1060__equal_aligned(__bit_iterator<_Cp, _IC1> __first1, __bit_iterator<_Cp, _IC1> __last1,
1061                __bit_iterator<_Cp, _IC2> __first2)
1062{
1063    typedef __bit_iterator<_Cp, _IC1> _It;
1064    typedef  typename _It::difference_type difference_type;
1065    typedef typename _It::__storage_type __storage_type;
1066    const int __bits_per_word = _It::__bits_per_word;
1067    difference_type __n = __last1 - __first1;
1068    if (__n > 0)
1069    {
1070        // do first word
1071        if (__first1.__ctz_ != 0)
1072        {
1073            unsigned __clz = __bits_per_word - __first1.__ctz_;
1074            difference_type __dn = _VSTD::min(static_cast<difference_type>(__clz), __n);
1075            __n -= __dn;
1076            __storage_type __m = (~__storage_type(0) << __first1.__ctz_) & (~__storage_type(0) >> (__clz - __dn));
1077            if ((*__first2.__seg_ & __m) != (*__first1.__seg_ & __m))
1078                return false;
1079            ++__first2.__seg_;
1080            ++__first1.__seg_;
1081            // __first1.__ctz_ = 0;
1082            // __first2.__ctz_ = 0;
1083        }
1084        // __first1.__ctz_ == 0;
1085        // __first2.__ctz_ == 0;
1086        // do middle words
1087        for (; __n >= __bits_per_word; __n -= __bits_per_word, ++__first1.__seg_, ++__first2.__seg_)
1088            if (*__first2.__seg_ != *__first1.__seg_)
1089                return false;
1090        // do last word
1091        if (__n > 0)
1092        {
1093            __storage_type __m = ~__storage_type(0) >> (__bits_per_word - __n);
1094            if ((*__first2.__seg_ & __m) != (*__first1.__seg_ & __m))
1095                return false;
1096        }
1097    }
1098    return true;
1099}
1100
1101template <class _Cp, bool _IC1, bool _IC2>
1102inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1103bool
1104equal(__bit_iterator<_Cp, _IC1> __first1, __bit_iterator<_Cp, _IC1> __last1, __bit_iterator<_Cp, _IC2> __first2)
1105{
1106    if (__first1.__ctz_ == __first2.__ctz_)
1107        return _VSTD::__equal_aligned(__first1, __last1, __first2);
1108    return _VSTD::__equal_unaligned(__first1, __last1, __first2);
1109}
1110
1111template <class _Cp, bool _IsConst,
1112          typename _Cp::__storage_type>
1113class __bit_iterator
1114{
1115public:
1116    typedef typename _Cp::difference_type                                                          difference_type;
1117    typedef bool                                                                                  value_type;
1118    typedef __bit_iterator                                                                        pointer;
1119#ifndef _LIBCPP_ABI_BITSET_VECTOR_BOOL_CONST_SUBSCRIPT_RETURN_BOOL
1120    typedef typename conditional<_IsConst, __bit_const_reference<_Cp>, __bit_reference<_Cp> >::type reference;
1121#else
1122    using reference = typename conditional<_IsConst, bool, __bit_reference<_Cp> >::type;
1123#endif
1124    typedef random_access_iterator_tag                                                            iterator_category;
1125
1126private:
1127    typedef typename _Cp::__storage_type                                           __storage_type;
1128    typedef typename conditional<_IsConst, typename _Cp::__const_storage_pointer,
1129                                           typename _Cp::__storage_pointer>::type  __storage_pointer;
1130    static const unsigned __bits_per_word = _Cp::__bits_per_word;
1131
1132    __storage_pointer __seg_;
1133    unsigned          __ctz_;
1134
1135public:
1136    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 __bit_iterator() _NOEXCEPT
1137#if _LIBCPP_STD_VER > 11
1138    : __seg_(nullptr), __ctz_(0)
1139#endif
1140    {}
1141
1142    // When _IsConst=false, this is the copy constructor.
1143    // It is non-trivial. Making it trivial would break ABI.
1144    // When _IsConst=true, this is a converting constructor;
1145    // the copy and move constructors are implicitly generated
1146    // and trivial.
1147    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1148    __bit_iterator(const __bit_iterator<_Cp, false>& __it) _NOEXCEPT
1149        : __seg_(__it.__seg_), __ctz_(__it.__ctz_) {}
1150
1151    // When _IsConst=false, we have a user-provided copy constructor,
1152    // so we must also provide a copy assignment operator because
1153    // the implicit generation of a defaulted one is deprecated.
1154    // When _IsConst=true, the assignment operators are
1155    // implicitly generated and trivial.
1156    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1157    __bit_iterator& operator=(const _If<_IsConst, struct __private_nat, __bit_iterator>& __it) {
1158        __seg_ = __it.__seg_;
1159        __ctz_ = __it.__ctz_;
1160        return *this;
1161    }
1162
1163    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 reference operator*() const _NOEXCEPT {
1164        return typename conditional<_IsConst, __bit_const_reference<_Cp>, __bit_reference<_Cp> >
1165                ::type(__seg_, __storage_type(1) << __ctz_);
1166    }
1167
1168    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 __bit_iterator& operator++()
1169    {
1170        if (__ctz_ != __bits_per_word-1)
1171            ++__ctz_;
1172        else
1173        {
1174            __ctz_ = 0;
1175            ++__seg_;
1176        }
1177        return *this;
1178    }
1179
1180    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 __bit_iterator operator++(int)
1181    {
1182        __bit_iterator __tmp = *this;
1183        ++(*this);
1184        return __tmp;
1185    }
1186
1187    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 __bit_iterator& operator--()
1188    {
1189        if (__ctz_ != 0)
1190            --__ctz_;
1191        else
1192        {
1193            __ctz_ = __bits_per_word - 1;
1194            --__seg_;
1195        }
1196        return *this;
1197    }
1198
1199    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 __bit_iterator operator--(int)
1200    {
1201        __bit_iterator __tmp = *this;
1202        --(*this);
1203        return __tmp;
1204    }
1205
1206    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 __bit_iterator& operator+=(difference_type __n)
1207    {
1208        if (__n >= 0)
1209            __seg_ += (__n + __ctz_) / __bits_per_word;
1210        else
1211            __seg_ += static_cast<difference_type>(__n - __bits_per_word + __ctz_ + 1)
1212                    / static_cast<difference_type>(__bits_per_word);
1213        __n &= (__bits_per_word - 1);
1214        __ctz_ = static_cast<unsigned>((__n + __ctz_)  % __bits_per_word);
1215        return *this;
1216    }
1217
1218    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 __bit_iterator& operator-=(difference_type __n)
1219    {
1220        return *this += -__n;
1221    }
1222
1223    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 __bit_iterator operator+(difference_type __n) const
1224    {
1225        __bit_iterator __t(*this);
1226        __t += __n;
1227        return __t;
1228    }
1229
1230    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 __bit_iterator operator-(difference_type __n) const
1231    {
1232        __bit_iterator __t(*this);
1233        __t -= __n;
1234        return __t;
1235    }
1236
1237    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1238    friend __bit_iterator operator+(difference_type __n, const __bit_iterator& __it) {return __it + __n;}
1239
1240    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1241    friend difference_type operator-(const __bit_iterator& __x, const __bit_iterator& __y)
1242        {return (__x.__seg_ - __y.__seg_) * __bits_per_word + __x.__ctz_ - __y.__ctz_;}
1243
1244    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 reference operator[](difference_type __n) const {return *(*this + __n);}
1245
1246    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 friend bool operator==(const __bit_iterator& __x, const __bit_iterator& __y)
1247        {return __x.__seg_ == __y.__seg_ && __x.__ctz_ == __y.__ctz_;}
1248
1249    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 friend bool operator!=(const __bit_iterator& __x, const __bit_iterator& __y)
1250        {return !(__x == __y);}
1251
1252    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 friend bool operator<(const __bit_iterator& __x, const __bit_iterator& __y)
1253        {return __x.__seg_ < __y.__seg_ || (__x.__seg_ == __y.__seg_ && __x.__ctz_ < __y.__ctz_);}
1254
1255    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 friend bool operator>(const __bit_iterator& __x, const __bit_iterator& __y)
1256        {return __y < __x;}
1257
1258    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 friend bool operator<=(const __bit_iterator& __x, const __bit_iterator& __y)
1259        {return !(__y < __x);}
1260
1261    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 friend bool operator>=(const __bit_iterator& __x, const __bit_iterator& __y)
1262        {return !(__x < __y);}
1263
1264private:
1265    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
1266    explicit __bit_iterator(__storage_pointer __s, unsigned __ctz) _NOEXCEPT
1267        : __seg_(__s), __ctz_(__ctz) {}
1268
1269    friend typename _Cp::__self;
1270
1271    friend class __bit_reference<_Cp>;
1272    friend class __bit_const_reference<_Cp>;
1273    friend class __bit_iterator<_Cp, true>;
1274    template <class _Dp> friend struct __bit_array;
1275    template <class _Dp>
1276    _LIBCPP_CONSTEXPR_AFTER_CXX17
1277    friend void __fill_n_false(__bit_iterator<_Dp, false> __first, typename _Dp::size_type __n);
1278
1279    template <class _Dp>
1280    _LIBCPP_CONSTEXPR_AFTER_CXX17
1281    friend void __fill_n_true(__bit_iterator<_Dp, false> __first, typename _Dp::size_type __n);
1282
1283    template <class _Dp, bool _IC>
1284    _LIBCPP_CONSTEXPR_AFTER_CXX17
1285    friend __bit_iterator<_Dp, false> __copy_aligned(__bit_iterator<_Dp, _IC> __first,
1286                                                     __bit_iterator<_Dp, _IC> __last,
1287                                                     __bit_iterator<_Dp, false> __result);
1288    template <class _Dp, bool _IC>
1289    _LIBCPP_CONSTEXPR_AFTER_CXX17
1290    friend __bit_iterator<_Dp, false> __copy_unaligned(__bit_iterator<_Dp, _IC> __first,
1291                                                       __bit_iterator<_Dp, _IC> __last,
1292                                                       __bit_iterator<_Dp, false> __result);
1293    template <class _Dp, bool _IC>
1294    _LIBCPP_CONSTEXPR_AFTER_CXX17
1295    friend __bit_iterator<_Dp, false> copy(__bit_iterator<_Dp, _IC> __first,
1296                                           __bit_iterator<_Dp, _IC> __last,
1297                                           __bit_iterator<_Dp, false> __result);
1298    template <class _Dp, bool _IC>
1299    _LIBCPP_CONSTEXPR_AFTER_CXX17
1300    friend __bit_iterator<_Dp, false> __copy_backward_aligned(__bit_iterator<_Dp, _IC> __first,
1301                                                              __bit_iterator<_Dp, _IC> __last,
1302                                                              __bit_iterator<_Dp, false> __result);
1303    template <class _Dp, bool _IC>
1304    _LIBCPP_CONSTEXPR_AFTER_CXX17
1305    friend __bit_iterator<_Dp, false> __copy_backward_unaligned(__bit_iterator<_Dp, _IC> __first,
1306                                                                __bit_iterator<_Dp, _IC> __last,
1307                                                                __bit_iterator<_Dp, false> __result);
1308    template <class _Dp, bool _IC>
1309    _LIBCPP_CONSTEXPR_AFTER_CXX17
1310    friend __bit_iterator<_Dp, false> copy_backward(__bit_iterator<_Dp, _IC> __first,
1311                                                    __bit_iterator<_Dp, _IC> __last,
1312                                                    __bit_iterator<_Dp, false> __result);
1313    template <class __C1, class __C2>friend __bit_iterator<__C2, false> __swap_ranges_aligned(__bit_iterator<__C1, false>,
1314                                                                                           __bit_iterator<__C1, false>,
1315                                                                                           __bit_iterator<__C2, false>);
1316    template <class __C1, class __C2>friend __bit_iterator<__C2, false> __swap_ranges_unaligned(__bit_iterator<__C1, false>,
1317                                                                                             __bit_iterator<__C1, false>,
1318                                                                                             __bit_iterator<__C2, false>);
1319    template <class __C1, class __C2>friend __bit_iterator<__C2, false> swap_ranges(__bit_iterator<__C1, false>,
1320                                                                                 __bit_iterator<__C1, false>,
1321                                                                                 __bit_iterator<__C2, false>);
1322    template <class _Dp>
1323    _LIBCPP_CONSTEXPR_AFTER_CXX17
1324    friend __bit_iterator<_Dp, false> rotate(__bit_iterator<_Dp, false>,
1325                                             __bit_iterator<_Dp, false>,
1326                                             __bit_iterator<_Dp, false>);
1327    template <class _Dp, bool _IC1, bool _IC2>
1328    _LIBCPP_CONSTEXPR_AFTER_CXX17
1329    friend bool __equal_aligned(__bit_iterator<_Dp, _IC1>,
1330                                __bit_iterator<_Dp, _IC1>,
1331                                __bit_iterator<_Dp, _IC2>);
1332    template <class _Dp, bool _IC1, bool _IC2>
1333    _LIBCPP_CONSTEXPR_AFTER_CXX17
1334    friend bool __equal_unaligned(__bit_iterator<_Dp, _IC1>,
1335                                  __bit_iterator<_Dp, _IC1>,
1336                                  __bit_iterator<_Dp, _IC2>);
1337    template <class _Dp, bool _IC1, bool _IC2>
1338    _LIBCPP_CONSTEXPR_AFTER_CXX17
1339    friend bool equal(__bit_iterator<_Dp, _IC1>,
1340                      __bit_iterator<_Dp, _IC1>,
1341                      __bit_iterator<_Dp, _IC2>);
1342    template <class _Dp, bool _IC>
1343    _LIBCPP_CONSTEXPR_AFTER_CXX17
1344    friend __bit_iterator<_Dp, _IC> __find_bool_true(__bit_iterator<_Dp, _IC>, typename _Dp::size_type);
1345    template <class _Dp, bool _IC>
1346    _LIBCPP_CONSTEXPR_AFTER_CXX17
1347    friend __bit_iterator<_Dp, _IC> __find_bool_false(__bit_iterator<_Dp, _IC>, typename _Dp::size_type);
1348    template <class _Dp, bool _IC> friend typename __bit_iterator<_Dp, _IC>::difference_type
1349                   __count_bool_true(__bit_iterator<_Dp, _IC>, typename _Dp::size_type);
1350    template <class _Dp, bool _IC> friend typename __bit_iterator<_Dp, _IC>::difference_type
1351                   __count_bool_false(__bit_iterator<_Dp, _IC>, typename _Dp::size_type);
1352};
1353
1354_LIBCPP_END_NAMESPACE_STD
1355
1356_LIBCPP_POP_MACROS
1357
1358#endif // _LIBCPP___BIT_REFERENCE
1359