1 //===----------------------------------------------------------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
9 #ifndef _LIBCPP___RANDOM_UNIFORM_INT_DISTRIBUTION_H
10 #define _LIBCPP___RANDOM_UNIFORM_INT_DISTRIBUTION_H
11 
12 #include <__bit/countl.h>
13 #include <__config>
14 #include <__random/is_valid.h>
15 #include <__random/log2.h>
16 #include <__type_traits/conditional.h>
17 #include <__type_traits/make_unsigned.h>
18 #include <cstddef>
19 #include <cstdint>
20 #include <iosfwd>
21 #include <limits>
22 
23 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
24 #  pragma GCC system_header
25 #endif
26 
27 _LIBCPP_PUSH_MACROS
28 #include <__undef_macros>
29 
30 _LIBCPP_BEGIN_NAMESPACE_STD
31 
32 template<class _Engine, class _UIntType>
33 class __independent_bits_engine
34 {
35 public:
36     // types
37     typedef _UIntType result_type;
38 
39 private:
40     typedef typename _Engine::result_type _Engine_result_type;
41     typedef __conditional_t<sizeof(_Engine_result_type) <= sizeof(result_type), result_type, _Engine_result_type>
42         _Working_result_type;
43 
44     _Engine& __e_;
45     size_t __w_;
46     size_t __w0_;
47     size_t __n_;
48     size_t __n0_;
49     _Working_result_type __y0_;
50     _Working_result_type __y1_;
51     _Engine_result_type __mask0_;
52     _Engine_result_type __mask1_;
53 
54 #ifdef _LIBCPP_CXX03_LANG
55     static const _Working_result_type _Rp = _Engine::_Max - _Engine::_Min
56                                           + _Working_result_type(1);
57 #else
58     static _LIBCPP_CONSTEXPR const _Working_result_type _Rp = _Engine::max() - _Engine::min()
59                                                       + _Working_result_type(1);
60 #endif
61     static _LIBCPP_CONSTEXPR const size_t __m = __log2<_Working_result_type, _Rp>::value;
62     static _LIBCPP_CONSTEXPR const size_t _WDt = numeric_limits<_Working_result_type>::digits;
63     static _LIBCPP_CONSTEXPR const size_t _EDt = numeric_limits<_Engine_result_type>::digits;
64 
65 public:
66     // constructors and seeding functions
67     _LIBCPP_HIDE_FROM_ABI __independent_bits_engine(_Engine& __e, size_t __w);
68 
69     // generating functions
70     _LIBCPP_HIDE_FROM_ABI result_type operator()() {return __eval(integral_constant<bool, _Rp != 0>());}
71 
72 private:
73     _LIBCPP_HIDE_FROM_ABI result_type __eval(false_type);
74     _LIBCPP_HIDE_FROM_ABI result_type __eval(true_type);
75 };
76 
77 template<class _Engine, class _UIntType>
78 __independent_bits_engine<_Engine, _UIntType>
79     ::__independent_bits_engine(_Engine& __e, size_t __w)
80         : __e_(__e),
81           __w_(__w)
82 {
83     __n_ = __w_ / __m + (__w_ % __m != 0);
84     __w0_ = __w_ / __n_;
85     if (_Rp == 0)
86         __y0_ = _Rp;
87     else if (__w0_ < _WDt)
88         __y0_ = (_Rp >> __w0_) << __w0_;
89     else
90         __y0_ = 0;
91     if (_Rp - __y0_ > __y0_ / __n_)
92     {
93         ++__n_;
94         __w0_ = __w_ / __n_;
95         if (__w0_ < _WDt)
96             __y0_ = (_Rp >> __w0_) << __w0_;
97         else
98             __y0_ = 0;
99     }
100     __n0_ = __n_ - __w_ % __n_;
101     if (__w0_ < _WDt - 1)
102         __y1_ = (_Rp >> (__w0_ + 1)) << (__w0_ + 1);
103     else
104         __y1_ = 0;
105     __mask0_ = __w0_ > 0 ? _Engine_result_type(~0) >> (_EDt - __w0_) :
106                           _Engine_result_type(0);
107     __mask1_ = __w0_ < _EDt - 1 ?
108                                _Engine_result_type(~0) >> (_EDt - (__w0_ + 1)) :
109                                _Engine_result_type(~0);
110 }
111 
112 template<class _Engine, class _UIntType>
113 inline
114 _UIntType
115 __independent_bits_engine<_Engine, _UIntType>::__eval(false_type)
116 {
117     return static_cast<result_type>(__e_() & __mask0_);
118 }
119 
120 template<class _Engine, class _UIntType>
121 _UIntType
122 __independent_bits_engine<_Engine, _UIntType>::__eval(true_type)
123 {
124     const size_t __w_rt = numeric_limits<result_type>::digits;
125     result_type __sp = 0;
126     for (size_t __k = 0; __k < __n0_; ++__k)
127     {
128         _Engine_result_type __u;
129         do
130         {
131             __u = __e_() - _Engine::min();
132         } while (__u >= __y0_);
133         if (__w0_ < __w_rt)
134             __sp <<= __w0_;
135         else
136             __sp = 0;
137         __sp += __u & __mask0_;
138     }
139     for (size_t __k = __n0_; __k < __n_; ++__k)
140     {
141         _Engine_result_type __u;
142         do
143         {
144             __u = __e_() - _Engine::min();
145         } while (__u >= __y1_);
146         if (__w0_ < __w_rt - 1)
147             __sp <<= __w0_ + 1;
148         else
149             __sp = 0;
150         __sp += __u & __mask1_;
151     }
152     return __sp;
153 }
154 
155 template<class _IntType = int>
156 class uniform_int_distribution
157 {
158     static_assert(__libcpp_random_is_valid_inttype<_IntType>::value, "IntType must be a supported integer type");
159 public:
160     // types
161     typedef _IntType result_type;
162 
163     class param_type
164     {
165         result_type __a_;
166         result_type __b_;
167     public:
168         typedef uniform_int_distribution distribution_type;
169 
170         _LIBCPP_HIDE_FROM_ABI explicit param_type(result_type __a = 0,
171                             result_type __b = numeric_limits<result_type>::max())
172             : __a_(__a), __b_(__b) {}
173 
174         _LIBCPP_HIDE_FROM_ABI result_type a() const {return __a_;}
175         _LIBCPP_HIDE_FROM_ABI result_type b() const {return __b_;}
176 
177         _LIBCPP_HIDE_FROM_ABI
178         friend bool operator==(const param_type& __x, const param_type& __y)
179             {return __x.__a_ == __y.__a_ && __x.__b_ == __y.__b_;}
180         _LIBCPP_HIDE_FROM_ABI
181         friend bool operator!=(const param_type& __x, const param_type& __y)
182             {return !(__x == __y);}
183     };
184 
185 private:
186     param_type __p_;
187 
188 public:
189     // constructors and reset functions
190 #ifndef _LIBCPP_CXX03_LANG
191     _LIBCPP_HIDE_FROM_ABI uniform_int_distribution() : uniform_int_distribution(0) {}
192     _LIBCPP_HIDE_FROM_ABI explicit uniform_int_distribution(
193         result_type __a, result_type __b = numeric_limits<result_type>::max())
194         : __p_(param_type(__a, __b)) {}
195 #else
196     explicit uniform_int_distribution(
197         result_type __a = 0,
198         result_type __b = numeric_limits<result_type>::max())
199         : __p_(param_type(__a, __b)) {}
200 #endif
201     _LIBCPP_HIDE_FROM_ABI explicit uniform_int_distribution(const param_type& __p) : __p_(__p) {}
202     _LIBCPP_HIDE_FROM_ABI void reset() {}
203 
204     // generating functions
205     template<class _URNG>
206     _LIBCPP_HIDE_FROM_ABI result_type operator()(_URNG& __g)
207         {return (*this)(__g, __p_);}
208     template<class _URNG>
209     _LIBCPP_HIDE_FROM_ABI result_type operator()(_URNG& __g, const param_type& __p);
210 
211     // property functions
212     _LIBCPP_HIDE_FROM_ABI result_type a() const {return __p_.a();}
213     _LIBCPP_HIDE_FROM_ABI result_type b() const {return __p_.b();}
214 
215     _LIBCPP_HIDE_FROM_ABI param_type param() const {return __p_;}
216     _LIBCPP_HIDE_FROM_ABI void param(const param_type& __p) {__p_ = __p;}
217 
218     _LIBCPP_HIDE_FROM_ABI result_type min() const {return a();}
219     _LIBCPP_HIDE_FROM_ABI result_type max() const {return b();}
220 
221     _LIBCPP_HIDE_FROM_ABI
222     friend bool operator==(const uniform_int_distribution& __x,
223                            const uniform_int_distribution& __y)
224         {return __x.__p_ == __y.__p_;}
225     _LIBCPP_HIDE_FROM_ABI
226     friend bool operator!=(const uniform_int_distribution& __x,
227                            const uniform_int_distribution& __y)
228             {return !(__x == __y);}
229 };
230 
231 template<class _IntType>
232 template<class _URNG>
233 typename uniform_int_distribution<_IntType>::result_type
234 uniform_int_distribution<_IntType>::operator()(_URNG& __g, const param_type& __p)
235 _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK
236 {
237     static_assert(__libcpp_random_is_valid_urng<_URNG>::value, "");
238     typedef __conditional_t<sizeof(result_type) <= sizeof(uint32_t), uint32_t, __make_unsigned_t<result_type> >
239         _UIntType;
240     const _UIntType __rp = _UIntType(__p.b()) - _UIntType(__p.a()) + _UIntType(1);
241     if (__rp == 1)
242         return __p.a();
243     const size_t __dt = numeric_limits<_UIntType>::digits;
244     typedef __independent_bits_engine<_URNG, _UIntType> _Eng;
245     if (__rp == 0)
246         return static_cast<result_type>(_Eng(__g, __dt)());
247     size_t __w = __dt - std::__countl_zero(__rp) - 1;
248     if ((__rp & (numeric_limits<_UIntType>::max() >> (__dt - __w))) != 0)
249         ++__w;
250     _Eng __e(__g, __w);
251     _UIntType __u;
252     do
253     {
254         __u = __e();
255     } while (__u >= __rp);
256     return static_cast<result_type>(__u + __p.a());
257 }
258 
259 template <class _CharT, class _Traits, class _IT>
260 _LIBCPP_HIDE_FROM_ABI basic_ostream<_CharT, _Traits>&
261 operator<<(basic_ostream<_CharT, _Traits>& __os,
262            const uniform_int_distribution<_IT>& __x)
263 {
264     __save_flags<_CharT, _Traits> __lx(__os);
265     typedef basic_ostream<_CharT, _Traits> _Ostream;
266     __os.flags(_Ostream::dec | _Ostream::left);
267     _CharT __sp = __os.widen(' ');
268     __os.fill(__sp);
269     return __os << __x.a() << __sp << __x.b();
270 }
271 
272 template <class _CharT, class _Traits, class _IT>
273 _LIBCPP_HIDE_FROM_ABI basic_istream<_CharT, _Traits>&
274 operator>>(basic_istream<_CharT, _Traits>& __is,
275            uniform_int_distribution<_IT>& __x)
276 {
277     typedef uniform_int_distribution<_IT> _Eng;
278     typedef typename _Eng::result_type result_type;
279     typedef typename _Eng::param_type param_type;
280     __save_flags<_CharT, _Traits> __lx(__is);
281     typedef basic_istream<_CharT, _Traits> _Istream;
282     __is.flags(_Istream::dec | _Istream::skipws);
283     result_type __a;
284     result_type __b;
285     __is >> __a >> __b;
286     if (!__is.fail())
287         __x.param(param_type(__a, __b));
288     return __is;
289 }
290 
291 _LIBCPP_END_NAMESPACE_STD
292 
293 _LIBCPP_POP_MACROS
294 
295 #endif // _LIBCPP___RANDOM_UNIFORM_INT_DISTRIBUTION_H
296