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 <__fwd/istream.h>
  14 #include <__fwd/ostream.h>
  15 #include <__random/is_seed_sequence.h>
  16 #include <__random/log2.h>
  17 #include <__type_traits/conditional.h>
  18 #include <__type_traits/enable_if.h>
  19 #include <__type_traits/is_convertible.h>
  20 #include <__utility/move.h>
  21 #include <cstddef>
  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 {
  36     template <class _UInt, _UInt _R0, size_t _Wp, size_t _Mp>
  37     class __get_n
  38     {
  39         static _LIBCPP_CONSTEXPR const size_t _Dt = numeric_limits<_UInt>::digits;
  40         static _LIBCPP_CONSTEXPR const size_t _Np = _Wp / _Mp + (_Wp % _Mp != 0);
  41         static _LIBCPP_CONSTEXPR const size_t _W0 = _Wp / _Np;
  42         static _LIBCPP_CONSTEXPR const _UInt _Y0 = _W0 >= _Dt ? 0 : (_R0 >> _W0) << _W0;
  43     public:
  44         static _LIBCPP_CONSTEXPR const size_t value = _R0 - _Y0 > _Y0 / _Np ? _Np + 1 : _Np;
  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
  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
  91     static _LIBCPP_CONSTEXPR result_type min() { return _Min; }
  92     _LIBCPP_INLINE_VISIBILITY
  93     static _LIBCPP_CONSTEXPR result_type max() { return _Max; }
  94
  95     // constructors and seeding functions
  96     _LIBCPP_INLINE_VISIBILITY
  97     independent_bits_engine() {}
  98     _LIBCPP_INLINE_VISIBILITY
  99     explicit independent_bits_engine(const _Engine& __e)
 100         : __e_(__e) {}
 101 #ifndef _LIBCPP_CXX03_LANG
 102     _LIBCPP_INLINE_VISIBILITY
 103     explicit independent_bits_engine(_Engine&& __e)
 104         : __e_(_VSTD::move(__e)) {}
 105 #endif // _LIBCPP_CXX03_LANG
 106     _LIBCPP_INLINE_VISIBILITY
 107     explicit independent_bits_engine(result_type __sd) : __e_(__sd) {}
 108     template<class _Sseq, __enable_if_t<__is_seed_sequence<_Sseq, independent_bits_engine>::value &&
 109                                         !is_convertible<_Sseq, _Engine>::value, int> = 0>
 110         _LIBCPP_INLINE_VISIBILITY
 111         explicit independent_bits_engine(_Sseq& __q)
 112          : __e_(__q) {}
 113     _LIBCPP_INLINE_VISIBILITY
 114     void seed() {__e_.seed();}
 115     _LIBCPP_INLINE_VISIBILITY
 116     void seed(result_type __sd) {__e_.seed(__sd);}
 117     template<class _Sseq, __enable_if_t<__is_seed_sequence<_Sseq, independent_bits_engine>::value, int> = 0>
 118         _LIBCPP_INLINE_VISIBILITY
 119         void
 120         seed(_Sseq& __q) {__e_.seed(__q);}
 121
 122     // generating functions
 123     _LIBCPP_INLINE_VISIBILITY
 124     result_type operator()() {return __eval(integral_constant<bool, _Rp != 0>());}
 125     _LIBCPP_INLINE_VISIBILITY
 126     void discard(unsigned long long __z) {for (; __z; --__z) operator()();}
 127
 128     // property functions
 129     _LIBCPP_INLINE_VISIBILITY
 130     const _Engine& base() const _NOEXCEPT {return __e_;}
 131
 132     template<class _Eng, size_t _Wp, class _UInt>
 133     friend
 134     bool
 135     operator==(
 136         const independent_bits_engine<_Eng, _Wp, _UInt>& __x,
 137         const independent_bits_engine<_Eng, _Wp, _UInt>& __y);
 138
 139     template<class _Eng, size_t _Wp, class _UInt>
 140     friend
 141     bool
 142     operator!=(
 143         const independent_bits_engine<_Eng, _Wp, _UInt>& __x,
 144         const independent_bits_engine<_Eng, _Wp, _UInt>& __y);
 145
 146     template <class _CharT, class _Traits,
 147               class _Eng, size_t _Wp, class _UInt>
 148     friend
 149     basic_ostream<_CharT, _Traits>&
 150     operator<<(basic_ostream<_CharT, _Traits>& __os,
 151                const independent_bits_engine<_Eng, _Wp, _UInt>& __x);
 152
 153     template <class _CharT, class _Traits,
 154               class _Eng, size_t _Wp, class _UInt>
 155     friend
 156     basic_istream<_CharT, _Traits>&
 157     operator>>(basic_istream<_CharT, _Traits>& __is,
 158                independent_bits_engine<_Eng, _Wp, _UInt>& __x);
 159
 160 private:
 161     _LIBCPP_INLINE_VISIBILITY
 162     result_type __eval(false_type);
 163     _LIBCPP_HIDE_FROM_ABI result_type __eval(true_type);
 164
 165     template <size_t __count, __enable_if_t<__count < _Dt, int> = 0>
 166         _LIBCPP_INLINE_VISIBILITY
 167         static
 168         result_type
 169         __lshift(result_type __x) {return __x << __count;}
 170
 171     template <size_t __count, __enable_if_t<(__count >= _Dt), int> = 0>
 172         _LIBCPP_INLINE_VISIBILITY
 173         static
 174         result_type
 175         __lshift(result_type) {return result_type(0);}
 176 };
 177
 178 template<class _Engine, size_t __w, class _UIntType>
 179 inline
 180 _UIntType
 181 independent_bits_engine<_Engine, __w, _UIntType>::__eval(false_type)
 182 {
 183     return static_cast<result_type>(__e_() & __mask0);
 184 }
 185
 186 template<class _Engine, size_t __w, class _UIntType>
 187 _UIntType
 188 independent_bits_engine<_Engine, __w, _UIntType>::__eval(true_type)
 189 {
 190     result_type __sp = 0;
 191     for (size_t __k = 0; __k < __n0; ++__k)
 192     {
 193         _Engine_result_type __u;
 194         do
 195         {
 196             __u = __e_() - _Engine::min();
 197         } while (__u >= __y0);
 198         __sp = static_cast<result_type>(__lshift<__w0>(__sp) + (__u & __mask0));
 199     }
 200     for (size_t __k = __n0; __k < __n; ++__k)
 201     {
 202         _Engine_result_type __u;
 203         do
 204         {
 205             __u = __e_() - _Engine::min();
 206         } while (__u >= __y1);
 207         __sp = static_cast<result_type>(__lshift<__w0+1>(__sp) + (__u & __mask1));
 208     }
 209     return __sp;
 210 }
 211
 212 template<class _Eng, size_t _Wp, class _UInt>
 213 inline _LIBCPP_INLINE_VISIBILITY
 214 bool
 215 operator==(
 216     const independent_bits_engine<_Eng, _Wp, _UInt>& __x,
 217     const independent_bits_engine<_Eng, _Wp, _UInt>& __y)
 218 {
 219     return __x.base() == __y.base();
 220 }
 221
 222 template<class _Eng, size_t _Wp, class _UInt>
 223 inline _LIBCPP_INLINE_VISIBILITY
 224 bool
 225 operator!=(
 226     const independent_bits_engine<_Eng, _Wp, _UInt>& __x,
 227     const independent_bits_engine<_Eng, _Wp, _UInt>& __y)
 228 {
 229     return !(__x == __y);
 230 }
 231
 232 template <class _CharT, class _Traits,
 233           class _Eng, size_t _Wp, class _UInt>
 234 _LIBCPP_HIDE_FROM_ABI basic_ostream<_CharT, _Traits>&
 235 operator<<(basic_ostream<_CharT, _Traits>& __os,
 236            const independent_bits_engine<_Eng, _Wp, _UInt>& __x)
 237 {
 238     return __os << __x.base();
 239 }
 240
 241 template <class _CharT, class _Traits,
 242           class _Eng, size_t _Wp, class _UInt>
 243 _LIBCPP_HIDE_FROM_ABI basic_istream<_CharT, _Traits>&
 244 operator>>(basic_istream<_CharT, _Traits>& __is,
 245            independent_bits_engine<_Eng, _Wp, _UInt>& __x)
 246 {
 247     _Eng __e;
 248     __is >> __e;
 249     if (!__is.fail())
 250         __x.__e_ = __e;
 251     return __is;
 252 }
 253
 254 _LIBCPP_END_NAMESPACE_STD
 255
 256 _LIBCPP_POP_MACROS
 257
 258 #endif // _LIBCPP___RANDOM_INDEPENDENT_BITS_ENGINE_H