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_INDEPENDENT_BITS_ENGINE_H
10 #define _LIBCPP___RANDOM_INDEPENDENT_BITS_ENGINE_H
11 
12 #include <__config>
13 #include <__random/is_seed_sequence.h>
14 #include <__random/log2.h>
15 #include <__utility/move.h>
16 #include <iosfwd>
17 #include <limits>
18 #include <type_traits>
19 
20 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
21 #  pragma GCC system_header
22 #endif
23 
24 _LIBCPP_PUSH_MACROS
25 #include <__undef_macros>
26 
27 _LIBCPP_BEGIN_NAMESPACE_STD
28 
29 template<class _Engine, size_t __w, class _UIntType>
30 class _LIBCPP_TEMPLATE_VIS independent_bits_engine
31 {
32     template <class _UInt, _UInt _R0, size_t _Wp, size_t _Mp>
33     class __get_n
34     {
35         static _LIBCPP_CONSTEXPR const size_t _Dt = numeric_limits<_UInt>::digits;
36         static _LIBCPP_CONSTEXPR const size_t _Np = _Wp / _Mp + (_Wp % _Mp != 0);
37         static _LIBCPP_CONSTEXPR const size_t _W0 = _Wp / _Np;
38         static _LIBCPP_CONSTEXPR const _UInt _Y0 = _W0 >= _Dt ? 0 : (_R0 >> _W0) << _W0;
39     public:
40         static _LIBCPP_CONSTEXPR const size_t value = _R0 - _Y0 > _Y0 / _Np ? _Np + 1 : _Np;
41     };
42 public:
43     // types
44     typedef _UIntType result_type;
45 
46 private:
47     _Engine __e_;
48 
49     static _LIBCPP_CONSTEXPR const result_type _Dt = numeric_limits<result_type>::digits;
50     static_assert(  0 <  __w, "independent_bits_engine invalid parameters");
51     static_assert(__w <= _Dt, "independent_bits_engine invalid parameters");
52 
53     typedef typename _Engine::result_type _Engine_result_type;
54     typedef typename conditional
55         <
56             sizeof(_Engine_result_type) <= sizeof(result_type),
57                 result_type,
58                 _Engine_result_type
59         >::type _Working_result_type;
60 #ifdef _LIBCPP_CXX03_LANG
61     static const _Working_result_type _Rp = _Engine::_Max - _Engine::_Min
62                                           + _Working_result_type(1);
63 #else
64     static _LIBCPP_CONSTEXPR const _Working_result_type _Rp = _Engine::max() - _Engine::min()
65                                                             + _Working_result_type(1);
66 #endif
67     static _LIBCPP_CONSTEXPR const size_t __m = __log2<_Working_result_type, _Rp>::value;
68     static _LIBCPP_CONSTEXPR const size_t __n = __get_n<_Working_result_type, _Rp, __w, __m>::value;
69     static _LIBCPP_CONSTEXPR const size_t __w0 = __w / __n;
70     static _LIBCPP_CONSTEXPR const size_t __n0 = __n - __w % __n;
71     static _LIBCPP_CONSTEXPR const size_t _WDt = numeric_limits<_Working_result_type>::digits;
72     static _LIBCPP_CONSTEXPR const size_t _EDt = numeric_limits<_Engine_result_type>::digits;
73     static _LIBCPP_CONSTEXPR const _Working_result_type __y0 = __w0 >= _WDt ? 0 :
74                                                                (_Rp >> __w0) << __w0;
75     static _LIBCPP_CONSTEXPR const _Working_result_type __y1 = __w0 >= _WDt - 1 ? 0 :
76                                                                (_Rp >> (__w0+1)) << (__w0+1);
77     static _LIBCPP_CONSTEXPR const _Engine_result_type __mask0 = __w0 > 0 ?
78                                 _Engine_result_type(~0) >> (_EDt - __w0) :
79                                 _Engine_result_type(0);
80     static _LIBCPP_CONSTEXPR const _Engine_result_type __mask1 = __w0 < _EDt - 1 ?
81                                 _Engine_result_type(~0) >> (_EDt - (__w0 + 1)) :
82                                 _Engine_result_type(~0);
83 public:
84     static _LIBCPP_CONSTEXPR const result_type _Min = 0;
85     static _LIBCPP_CONSTEXPR const result_type _Max = __w == _Dt ? result_type(~0) :
86                                                       (result_type(1) << __w) - result_type(1);
87     static_assert(_Min < _Max, "independent_bits_engine invalid parameters");
88 
89     // engine characteristics
90     _LIBCPP_INLINE_VISIBILITY
min()91     static _LIBCPP_CONSTEXPR result_type min() { return _Min; }
92     _LIBCPP_INLINE_VISIBILITY
max()93     static _LIBCPP_CONSTEXPR result_type max() { return _Max; }
94 
95     // constructors and seeding functions
96     _LIBCPP_INLINE_VISIBILITY
independent_bits_engine()97     independent_bits_engine() {}
98     _LIBCPP_INLINE_VISIBILITY
independent_bits_engine(const _Engine & __e)99     explicit independent_bits_engine(const _Engine& __e)
100         : __e_(__e) {}
101 #ifndef _LIBCPP_CXX03_LANG
102     _LIBCPP_INLINE_VISIBILITY
independent_bits_engine(_Engine && __e)103     explicit independent_bits_engine(_Engine&& __e)
104         : __e_(_VSTD::move(__e)) {}
105 #endif // _LIBCPP_CXX03_LANG
106     _LIBCPP_INLINE_VISIBILITY
independent_bits_engine(result_type __sd)107     explicit independent_bits_engine(result_type __sd) : __e_(__sd) {}
108     template<class _Sseq>
109         _LIBCPP_INLINE_VISIBILITY
110         explicit independent_bits_engine(_Sseq& __q,
111         typename enable_if<__is_seed_sequence<_Sseq, independent_bits_engine>::value &&
112                            !is_convertible<_Sseq, _Engine>::value>::type* = 0)
__e_(__q)113          : __e_(__q) {}
114     _LIBCPP_INLINE_VISIBILITY
seed()115     void seed() {__e_.seed();}
116     _LIBCPP_INLINE_VISIBILITY
seed(result_type __sd)117     void seed(result_type __sd) {__e_.seed(__sd);}
118     template<class _Sseq>
119         _LIBCPP_INLINE_VISIBILITY
120         typename enable_if
121         <
122             __is_seed_sequence<_Sseq, independent_bits_engine>::value,
123             void
124         >::type
seed(_Sseq & __q)125         seed(_Sseq& __q) {__e_.seed(__q);}
126 
127     // generating functions
128     _LIBCPP_INLINE_VISIBILITY
operator()129     result_type operator()() {return __eval(integral_constant<bool, _Rp != 0>());}
130     _LIBCPP_INLINE_VISIBILITY
discard(unsigned long long __z)131     void discard(unsigned long long __z) {for (; __z; --__z) operator()();}
132 
133     // property functions
134     _LIBCPP_INLINE_VISIBILITY
base()135     const _Engine& base() const _NOEXCEPT {return __e_;}
136 
137     template<class _Eng, size_t _Wp, class _UInt>
138     friend
139     bool
140     operator==(
141         const independent_bits_engine<_Eng, _Wp, _UInt>& __x,
142         const independent_bits_engine<_Eng, _Wp, _UInt>& __y);
143 
144     template<class _Eng, size_t _Wp, class _UInt>
145     friend
146     bool
147     operator!=(
148         const independent_bits_engine<_Eng, _Wp, _UInt>& __x,
149         const independent_bits_engine<_Eng, _Wp, _UInt>& __y);
150 
151     template <class _CharT, class _Traits,
152               class _Eng, size_t _Wp, class _UInt>
153     friend
154     basic_ostream<_CharT, _Traits>&
155     operator<<(basic_ostream<_CharT, _Traits>& __os,
156                const independent_bits_engine<_Eng, _Wp, _UInt>& __x);
157 
158     template <class _CharT, class _Traits,
159               class _Eng, size_t _Wp, class _UInt>
160     friend
161     basic_istream<_CharT, _Traits>&
162     operator>>(basic_istream<_CharT, _Traits>& __is,
163                independent_bits_engine<_Eng, _Wp, _UInt>& __x);
164 
165 private:
166     _LIBCPP_INLINE_VISIBILITY
167     result_type __eval(false_type);
168     result_type __eval(true_type);
169 
170     template <size_t __count>
171         _LIBCPP_INLINE_VISIBILITY
172         static
173         typename enable_if
174         <
175             __count < _Dt,
176             result_type
177         >::type
178         __lshift(result_type __x) {return __x << __count;}
179 
180     template <size_t __count>
181         _LIBCPP_INLINE_VISIBILITY
182         static
183         typename enable_if
184         <
185             (__count >= _Dt),
186             result_type
187         >::type
__lshift(result_type)188         __lshift(result_type) {return result_type(0);}
189 };
190 
191 template<class _Engine, size_t __w, class _UIntType>
192 inline
193 _UIntType
__eval(false_type)194 independent_bits_engine<_Engine, __w, _UIntType>::__eval(false_type)
195 {
196     return static_cast<result_type>(__e_() & __mask0);
197 }
198 
199 template<class _Engine, size_t __w, class _UIntType>
200 _UIntType
__eval(true_type)201 independent_bits_engine<_Engine, __w, _UIntType>::__eval(true_type)
202 {
203     result_type _Sp = 0;
204     for (size_t __k = 0; __k < __n0; ++__k)
205     {
206         _Engine_result_type __u;
207         do
208         {
209             __u = __e_() - _Engine::min();
210         } while (__u >= __y0);
211         _Sp = static_cast<result_type>(__lshift<__w0>(_Sp) + (__u & __mask0));
212     }
213     for (size_t __k = __n0; __k < __n; ++__k)
214     {
215         _Engine_result_type __u;
216         do
217         {
218             __u = __e_() - _Engine::min();
219         } while (__u >= __y1);
220         _Sp = static_cast<result_type>(__lshift<__w0+1>(_Sp) + (__u & __mask1));
221     }
222     return _Sp;
223 }
224 
225 template<class _Eng, size_t _Wp, class _UInt>
226 inline _LIBCPP_INLINE_VISIBILITY
227 bool
228 operator==(
229     const independent_bits_engine<_Eng, _Wp, _UInt>& __x,
230     const independent_bits_engine<_Eng, _Wp, _UInt>& __y)
231 {
232     return __x.base() == __y.base();
233 }
234 
235 template<class _Eng, size_t _Wp, class _UInt>
236 inline _LIBCPP_INLINE_VISIBILITY
237 bool
238 operator!=(
239     const independent_bits_engine<_Eng, _Wp, _UInt>& __x,
240     const independent_bits_engine<_Eng, _Wp, _UInt>& __y)
241 {
242     return !(__x == __y);
243 }
244 
245 template <class _CharT, class _Traits,
246           class _Eng, size_t _Wp, class _UInt>
247 basic_ostream<_CharT, _Traits>&
248 operator<<(basic_ostream<_CharT, _Traits>& __os,
249            const independent_bits_engine<_Eng, _Wp, _UInt>& __x)
250 {
251     return __os << __x.base();
252 }
253 
254 template <class _CharT, class _Traits,
255           class _Eng, size_t _Wp, class _UInt>
256 basic_istream<_CharT, _Traits>&
257 operator>>(basic_istream<_CharT, _Traits>& __is,
258            independent_bits_engine<_Eng, _Wp, _UInt>& __x)
259 {
260     _Eng __e;
261     __is >> __e;
262     if (!__is.fail())
263         __x.__e_ = __e;
264     return __is;
265 }
266 
267 _LIBCPP_END_NAMESPACE_STD
268 
269 _LIBCPP_POP_MACROS
270 
271 #endif // _LIBCPP___RANDOM_INDEPENDENT_BITS_ENGINE_H
272