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 <__cstddef/size_t.h>
14#include <__fwd/istream.h>
15#include <__fwd/ostream.h>
16#include <__random/is_seed_sequence.h>
17#include <__random/log2.h>
18#include <__type_traits/conditional.h>
19#include <__type_traits/enable_if.h>
20#include <__type_traits/is_convertible.h>
21#include <__utility/move.h>
22#include <limits>
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_LIBCPP_BEGIN_NAMESPACE_STD
32
33template <class _Engine, size_t __w, class _UIntType>
34class independent_bits_engine {
35 template <class _UInt, _UInt _R0, size_t _Wp, size_t _Mp>
36 class __get_n {
37 static _LIBCPP_CONSTEXPR const size_t _Dt = numeric_limits<_UInt>::digits;
38 static _LIBCPP_CONSTEXPR const size_t _Np = _Wp / _Mp + (_Wp % _Mp != 0);
39 static _LIBCPP_CONSTEXPR const size_t _W0 = _Wp / _Np;
40 static _LIBCPP_CONSTEXPR const _UInt _Y0 = _W0 >= _Dt ? 0 : (_R0 >> _W0) << _W0;
41
42 public:
43 static _LIBCPP_CONSTEXPR const size_t value = _R0 - _Y0 > _Y0 / _Np ? _Np + 1 : _Np;
44 };
45
46public:
47 // types
48 typedef _UIntType result_type;
49
50private:
51 _Engine __e_;
52
53 static _LIBCPP_CONSTEXPR const result_type _Dt = numeric_limits<result_type>::digits;
54 static_assert(0 < __w, "independent_bits_engine invalid parameters");
55 static_assert(__w <= _Dt, "independent_bits_engine invalid parameters");
56
57 typedef typename _Engine::result_type _Engine_result_type;
58 typedef __conditional_t<sizeof(_Engine_result_type) <= sizeof(result_type), result_type, _Engine_result_type>
59 _Working_result_type;
60#ifdef _LIBCPP_CXX03_LANG
61 static const _Working_result_type _Rp = _Engine::_Max - _Engine::_Min + _Working_result_type(1);
62#else
63 static _LIBCPP_CONSTEXPR const _Working_result_type _Rp = _Engine::max() - _Engine::min() + _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 __n = __get_n<_Working_result_type, _Rp, __w, __m>::value;
67 static _LIBCPP_CONSTEXPR const size_t __w0 = __w / __n;
68 static _LIBCPP_CONSTEXPR const size_t __n0 = __n - __w % __n;
69 static _LIBCPP_CONSTEXPR const size_t _WDt = numeric_limits<_Working_result_type>::digits;
70 static _LIBCPP_CONSTEXPR const size_t _EDt = numeric_limits<_Engine_result_type>::digits;
71 static _LIBCPP_CONSTEXPR const _Working_result_type __y0 = __w0 >= _WDt ? 0 : (_Rp >> __w0) << __w0;
72 static _LIBCPP_CONSTEXPR const _Working_result_type __y1 = __w0 >= _WDt - 1 ? 0 : (_Rp >> (__w0 + 1)) << (__w0 + 1);
73 static _LIBCPP_CONSTEXPR const
74 _Engine_result_type __mask0 = __w0 > 0 ? _Engine_result_type(~0) >> (_EDt - __w0) : _Engine_result_type(0);
75 static _LIBCPP_CONSTEXPR const _Engine_result_type __mask1 =
76 __w0 < _EDt - 1 ? _Engine_result_type(~0) >> (_EDt - (__w0 + 1)) : _Engine_result_type(~0);
77
78public:
79 static _LIBCPP_CONSTEXPR const result_type _Min = 0;
80 static _LIBCPP_CONSTEXPR const result_type _Max =
81 __w == _Dt ? result_type(~0) : (result_type(1) << __w) - result_type(1);
82 static_assert(_Min < _Max, "independent_bits_engine invalid parameters");
83
84 // engine characteristics
85 _LIBCPP_HIDE_FROM_ABI static _LIBCPP_CONSTEXPR result_type min() { return _Min; }
86 _LIBCPP_HIDE_FROM_ABI static _LIBCPP_CONSTEXPR result_type max() { return _Max; }
87
88 // constructors and seeding functions
89 _LIBCPP_HIDE_FROM_ABI independent_bits_engine() {}
90 _LIBCPP_HIDE_FROM_ABI explicit independent_bits_engine(const _Engine& __e) : __e_(__e) {}
91#ifndef _LIBCPP_CXX03_LANG
92 _LIBCPP_HIDE_FROM_ABI explicit independent_bits_engine(_Engine&& __e) : __e_(std::move(__e)) {}
93#endif // _LIBCPP_CXX03_LANG
94 _LIBCPP_HIDE_FROM_ABI explicit independent_bits_engine(result_type __sd) : __e_(__sd) {}
95 template <
96 class _Sseq,
97 __enable_if_t<__is_seed_sequence<_Sseq, independent_bits_engine>::value && !is_convertible<_Sseq, _Engine>::value,
98 int> = 0>
99 _LIBCPP_HIDE_FROM_ABI explicit independent_bits_engine(_Sseq& __q) : __e_(__q) {}
100 _LIBCPP_HIDE_FROM_ABI void seed() { __e_.seed(); }
101 _LIBCPP_HIDE_FROM_ABI void seed(result_type __sd) { __e_.seed(__sd); }
102 template <class _Sseq, __enable_if_t<__is_seed_sequence<_Sseq, independent_bits_engine>::value, int> = 0>
103 _LIBCPP_HIDE_FROM_ABI void seed(_Sseq& __q) {
104 __e_.seed(__q);
105 }
106
107 // generating functions
108 _LIBCPP_HIDE_FROM_ABI result_type operator()() { return __eval(integral_constant<bool, _Rp != 0>()); }
109 _LIBCPP_HIDE_FROM_ABI void discard(unsigned long long __z) {
110 for (; __z; --__z)
111 operator()();
112 }
113
114 // property functions
115 _LIBCPP_HIDE_FROM_ABI const _Engine& base() const _NOEXCEPT { return __e_; }
116
117 template <class _Eng, size_t _Wp, class _UInt>
118 friend bool operator==(const independent_bits_engine<_Eng, _Wp, _UInt>& __x,
119 const independent_bits_engine<_Eng, _Wp, _UInt>& __y);
120
121 template <class _Eng, size_t _Wp, class _UInt>
122 friend bool operator!=(const independent_bits_engine<_Eng, _Wp, _UInt>& __x,
123 const independent_bits_engine<_Eng, _Wp, _UInt>& __y);
124
125 template <class _CharT, class _Traits, class _Eng, size_t _Wp, class _UInt>
126 friend basic_ostream<_CharT, _Traits>&
127 operator<<(basic_ostream<_CharT, _Traits>& __os, const independent_bits_engine<_Eng, _Wp, _UInt>& __x);
128
129 template <class _CharT, class _Traits, class _Eng, size_t _Wp, class _UInt>
130 friend basic_istream<_CharT, _Traits>&
131 operator>>(basic_istream<_CharT, _Traits>& __is, independent_bits_engine<_Eng, _Wp, _UInt>& __x);
132
133private:
134 _LIBCPP_HIDE_FROM_ABI result_type __eval(false_type);
135 _LIBCPP_HIDE_FROM_ABI result_type __eval(true_type);
136
137 template <size_t __count,
138 __enable_if_t<__count< _Dt, int> = 0> _LIBCPP_HIDE_FROM_ABI static result_type __lshift(result_type __x) {
139 return __x << __count;
140 }
141
142 template <size_t __count, __enable_if_t<(__count >= _Dt), int> = 0>
143 _LIBCPP_HIDE_FROM_ABI static result_type __lshift(result_type) {
144 return result_type(0);
145 }
146};
147
148template <class _Engine, size_t __w, class _UIntType>
149inline _UIntType independent_bits_engine<_Engine, __w, _UIntType>::__eval(false_type) {
150 return static_cast<result_type>(__e_() & __mask0);
151}
152
153template <class _Engine, size_t __w, class _UIntType>
154_UIntType independent_bits_engine<_Engine, __w, _UIntType>::__eval(true_type) {
155 result_type __sp = 0;
156 for (size_t __k = 0; __k < __n0; ++__k) {
157 _Engine_result_type __u;
158 do {
159 __u = __e_() - _Engine::min();
160 } while (__u >= __y0);
161 __sp = static_cast<result_type>(__lshift<__w0>(__sp) + (__u & __mask0));
162 }
163 for (size_t __k = __n0; __k < __n; ++__k) {
164 _Engine_result_type __u;
165 do {
166 __u = __e_() - _Engine::min();
167 } while (__u >= __y1);
168 __sp = static_cast<result_type>(__lshift<__w0 + 1>(__sp) + (__u & __mask1));
169 }
170 return __sp;
171}
172
173template <class _Eng, size_t _Wp, class _UInt>
174inline _LIBCPP_HIDE_FROM_ABI bool
175operator==(const independent_bits_engine<_Eng, _Wp, _UInt>& __x, const independent_bits_engine<_Eng, _Wp, _UInt>& __y) {
176 return __x.base() == __y.base();
177}
178
179template <class _Eng, size_t _Wp, class _UInt>
180inline _LIBCPP_HIDE_FROM_ABI bool
181operator!=(const independent_bits_engine<_Eng, _Wp, _UInt>& __x, const independent_bits_engine<_Eng, _Wp, _UInt>& __y) {
182 return !(__x == __y);
183}
184
185template <class _CharT, class _Traits, class _Eng, size_t _Wp, class _UInt>
186_LIBCPP_HIDE_FROM_ABI basic_ostream<_CharT, _Traits>&
187operator<<(basic_ostream<_CharT, _Traits>& __os, const independent_bits_engine<_Eng, _Wp, _UInt>& __x) {
188 return __os << __x.base();
189}
190
191template <class _CharT, class _Traits, class _Eng, size_t _Wp, class _UInt>
192_LIBCPP_HIDE_FROM_ABI basic_istream<_CharT, _Traits>&
193operator>>(basic_istream<_CharT, _Traits>& __is, independent_bits_engine<_Eng, _Wp, _UInt>& __x) {
194 _Eng __e;
195 __is >> __e;
196 if (!__is.fail())
197 __x.__e_ = __e;
198 return __is;
199}
200
201_LIBCPP_END_NAMESPACE_STD
202
203_LIBCPP_POP_MACROS
204
205#endif // _LIBCPP___RANDOM_INDEPENDENT_BITS_ENGINE_H
206