libcxx/include/__random/independent_bits_engine.h

   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
  33 template <class _Engine, size_t __w, class _UIntType>
  34 class _LIBCPP_TEMPLATE_VIS 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
  46 public:
  47   // types
  48   typedef _UIntType result_type;
  49
  50 private:
  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
  78 public:
  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
 133 private:
 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
 148 template <class _Engine, size_t __w, class _UIntType>
 149 inline _UIntType independent_bits_engine<_Engine, __w, _UIntType>::__eval(false_type) {
 150   return static_cast<result_type>(__e_() & __mask0);
 151 }
 152
 153 template <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
 173 template <class _Eng, size_t _Wp, class _UInt>
 174 inline _LIBCPP_HIDE_FROM_ABI bool
 175 operator==(const independent_bits_engine<_Eng, _Wp, _UInt>& __x, const independent_bits_engine<_Eng, _Wp, _UInt>& __y) {
 176   return __x.base() == __y.base();
 177 }
 178
 179 template <class _Eng, size_t _Wp, class _UInt>
 180 inline _LIBCPP_HIDE_FROM_ABI bool
 181 operator!=(const independent_bits_engine<_Eng, _Wp, _UInt>& __x, const independent_bits_engine<_Eng, _Wp, _UInt>& __y) {
 182   return !(__x == __y);
 183 }
 184
 185 template <class _CharT, class _Traits, class _Eng, size_t _Wp, class _UInt>
 186 _LIBCPP_HIDE_FROM_ABI basic_ostream<_CharT, _Traits>&
 187 operator<<(basic_ostream<_CharT, _Traits>& __os, const independent_bits_engine<_Eng, _Wp, _UInt>& __x) {
 188   return __os << __x.base();
 189 }
 190
 191 template <class _CharT, class _Traits, class _Eng, size_t _Wp, class _UInt>
 192 _LIBCPP_HIDE_FROM_ABI basic_istream<_CharT, _Traits>&
 193 operator>>(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