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