libcxx/include/__random/uniform_int_distribution.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_UNIFORM_INT_DISTRIBUTION_H
  10 #define _LIBCPP___RANDOM_UNIFORM_INT_DISTRIBUTION_H
  11
  12 #include <__bit/countl.h>
  13 #include <__config>
  14 #include <__random/is_valid.h>
  15 #include <__random/log2.h>
  16 #include <__type_traits/conditional.h>
  17 #include <__type_traits/make_unsigned.h>
  18 #include <cstddef>
  19 #include <cstdint>
  20 #include <iosfwd>
  21 #include <limits>
  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 __conditional_t<sizeof(_Engine_result_type) <= sizeof(result_type), result_type, _Engine_result_type>
  42         _Working_result_type;
  43
  44     _Engine& __e_;
  45     size_t __w_;
  46     size_t __w0_;
  47     size_t __n_;
  48     size_t __n0_;
  49     _Working_result_type __y0_;
  50     _Working_result_type __y1_;
  51     _Engine_result_type __mask0_;
  52     _Engine_result_type __mask1_;
  53
  54 #ifdef _LIBCPP_CXX03_LANG
  55     static const _Working_result_type _Rp = _Engine::_Max - _Engine::_Min
  56                                           + _Working_result_type(1);
  57 #else
  58     static _LIBCPP_CONSTEXPR const _Working_result_type _Rp = _Engine::max() - _Engine::min()
  59                                                       + _Working_result_type(1);
  60 #endif
  61     static _LIBCPP_CONSTEXPR const size_t __m = __log2<_Working_result_type, _Rp>::value;
  62     static _LIBCPP_CONSTEXPR const size_t _WDt = numeric_limits<_Working_result_type>::digits;
  63     static _LIBCPP_CONSTEXPR const size_t _EDt = numeric_limits<_Engine_result_type>::digits;
  64
  65 public:
  66     // constructors and seeding functions
  67     _LIBCPP_HIDE_FROM_ABI __independent_bits_engine(_Engine& __e, size_t __w);
  68
  69     // generating functions
  70     _LIBCPP_HIDE_FROM_ABI result_type operator()() {return __eval(integral_constant<bool, _Rp != 0>());}
  71
  72 private:
  73     _LIBCPP_HIDE_FROM_ABI result_type __eval(false_type);
  74     _LIBCPP_HIDE_FROM_ABI result_type __eval(true_type);
  75 };
  76
  77 template<class _Engine, class _UIntType>
  78 __independent_bits_engine<_Engine, _UIntType>
  79     ::__independent_bits_engine(_Engine& __e, size_t __w)
  80         : __e_(__e),
  81           __w_(__w)
  82 {
  83     __n_ = __w_ / __m + (__w_ % __m != 0);
  84     __w0_ = __w_ / __n_;
  85     if (_Rp == 0)
  86         __y0_ = _Rp;
  87     else if (__w0_ < _WDt)
  88         __y0_ = (_Rp >> __w0_) << __w0_;
  89     else
  90         __y0_ = 0;
  91     if (_Rp - __y0_ > __y0_ / __n_)
  92     {
  93         ++__n_;
  94         __w0_ = __w_ / __n_;
  95         if (__w0_ < _WDt)
  96             __y0_ = (_Rp >> __w0_) << __w0_;
  97         else
  98             __y0_ = 0;
  99     }
 100     __n0_ = __n_ - __w_ % __n_;
 101     if (__w0_ < _WDt - 1)
 102         __y1_ = (_Rp >> (__w0_ + 1)) << (__w0_ + 1);
 103     else
 104         __y1_ = 0;
 105     __mask0_ = __w0_ > 0 ? _Engine_result_type(~0) >> (_EDt - __w0_) :
 106                           _Engine_result_type(0);
 107     __mask1_ = __w0_ < _EDt - 1 ?
 108                                _Engine_result_type(~0) >> (_EDt - (__w0_ + 1)) :
 109                                _Engine_result_type(~0);
 110 }
 111
 112 template<class _Engine, class _UIntType>
 113 inline
 114 _UIntType
 115 __independent_bits_engine<_Engine, _UIntType>::__eval(false_type)
 116 {
 117     return static_cast<result_type>(__e_() & __mask0_);
 118 }
 119
 120 template<class _Engine, class _UIntType>
 121 _UIntType
 122 __independent_bits_engine<_Engine, _UIntType>::__eval(true_type)
 123 {
 124     const size_t __w_rt = numeric_limits<result_type>::digits;
 125     result_type __sp = 0;
 126     for (size_t __k = 0; __k < __n0_; ++__k)
 127     {
 128         _Engine_result_type __u;
 129         do
 130         {
 131             __u = __e_() - _Engine::min();
 132         } while (__u >= __y0_);
 133         if (__w0_ < __w_rt)
 134             __sp <<= __w0_;
 135         else
 136             __sp = 0;
 137         __sp += __u & __mask0_;
 138     }
 139     for (size_t __k = __n0_; __k < __n_; ++__k)
 140     {
 141         _Engine_result_type __u;
 142         do
 143         {
 144             __u = __e_() - _Engine::min();
 145         } while (__u >= __y1_);
 146         if (__w0_ < __w_rt - 1)
 147             __sp <<= __w0_ + 1;
 148         else
 149             __sp = 0;
 150         __sp += __u & __mask1_;
 151     }
 152     return __sp;
 153 }
 154
 155 template<class _IntType = int>
 156 class uniform_int_distribution
 157 {
 158     static_assert(__libcpp_random_is_valid_inttype<_IntType>::value, "IntType must be a supported integer type");
 159 public:
 160     // types
 161     typedef _IntType result_type;
 162
 163     class param_type
 164     {
 165         result_type __a_;
 166         result_type __b_;
 167     public:
 168         typedef uniform_int_distribution distribution_type;
 169
 170         _LIBCPP_HIDE_FROM_ABI explicit param_type(result_type __a = 0,
 171                             result_type __b = numeric_limits<result_type>::max())
 172             : __a_(__a), __b_(__b) {}
 173
 174         _LIBCPP_HIDE_FROM_ABI result_type a() const {return __a_;}
 175         _LIBCPP_HIDE_FROM_ABI result_type b() const {return __b_;}
 176
 177         _LIBCPP_HIDE_FROM_ABI
 178         friend bool operator==(const param_type& __x, const param_type& __y)
 179             {return __x.__a_ == __y.__a_ && __x.__b_ == __y.__b_;}
 180         _LIBCPP_HIDE_FROM_ABI
 181         friend bool operator!=(const param_type& __x, const param_type& __y)
 182             {return !(__x == __y);}
 183     };
 184
 185 private:
 186     param_type __p_;
 187
 188 public:
 189     // constructors and reset functions
 190 #ifndef _LIBCPP_CXX03_LANG
 191     _LIBCPP_HIDE_FROM_ABI uniform_int_distribution() : uniform_int_distribution(0) {}
 192     _LIBCPP_HIDE_FROM_ABI explicit uniform_int_distribution(
 193         result_type __a, result_type __b = numeric_limits<result_type>::max())
 194         : __p_(param_type(__a, __b)) {}
 195 #else
 196     explicit uniform_int_distribution(
 197         result_type __a = 0,
 198         result_type __b = numeric_limits<result_type>::max())
 199         : __p_(param_type(__a, __b)) {}
 200 #endif
 201     _LIBCPP_HIDE_FROM_ABI explicit uniform_int_distribution(const param_type& __p) : __p_(__p) {}
 202     _LIBCPP_HIDE_FROM_ABI void reset() {}
 203
 204     // generating functions
 205     template<class _URNG>
 206     _LIBCPP_HIDE_FROM_ABI result_type operator()(_URNG& __g)
 207         {return (*this)(__g, __p_);}
 208     template<class _URNG>
 209     _LIBCPP_HIDE_FROM_ABI result_type operator()(_URNG& __g, const param_type& __p);
 210
 211     // property functions
 212     _LIBCPP_HIDE_FROM_ABI result_type a() const {return __p_.a();}
 213     _LIBCPP_HIDE_FROM_ABI result_type b() const {return __p_.b();}
 214
 215     _LIBCPP_HIDE_FROM_ABI param_type param() const {return __p_;}
 216     _LIBCPP_HIDE_FROM_ABI void param(const param_type& __p) {__p_ = __p;}
 217
 218     _LIBCPP_HIDE_FROM_ABI result_type min() const {return a();}
 219     _LIBCPP_HIDE_FROM_ABI result_type max() const {return b();}
 220
 221     _LIBCPP_HIDE_FROM_ABI
 222     friend bool operator==(const uniform_int_distribution& __x,
 223                            const uniform_int_distribution& __y)
 224         {return __x.__p_ == __y.__p_;}
 225     _LIBCPP_HIDE_FROM_ABI
 226     friend bool operator!=(const uniform_int_distribution& __x,
 227                            const uniform_int_distribution& __y)
 228             {return !(__x == __y);}
 229 };
 230
 231 template<class _IntType>
 232 template<class _URNG>
 233 typename uniform_int_distribution<_IntType>::result_type
 234 uniform_int_distribution<_IntType>::operator()(_URNG& __g, const param_type& __p)
 235 _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK
 236 {
 237     static_assert(__libcpp_random_is_valid_urng<_URNG>::value, "");
 238     typedef __conditional_t<sizeof(result_type) <= sizeof(uint32_t), uint32_t, __make_unsigned_t<result_type> >
 239         _UIntType;
 240     const _UIntType __rp = _UIntType(__p.b()) - _UIntType(__p.a()) + _UIntType(1);
 241     if (__rp == 1)
 242         return __p.a();
 243     const size_t __dt = numeric_limits<_UIntType>::digits;
 244     typedef __independent_bits_engine<_URNG, _UIntType> _Eng;
 245     if (__rp == 0)
 246         return static_cast<result_type>(_Eng(__g, __dt)());
 247     size_t __w = __dt - std::__countl_zero(__rp) - 1;
 248     if ((__rp & (numeric_limits<_UIntType>::max() >> (__dt - __w))) != 0)
 249         ++__w;
 250     _Eng __e(__g, __w);
 251     _UIntType __u;
 252     do
 253     {
 254         __u = __e();
 255     } while (__u >= __rp);
 256     return static_cast<result_type>(__u + __p.a());
 257 }
 258
 259 template <class _CharT, class _Traits, class _IT>
 260 _LIBCPP_HIDE_FROM_ABI basic_ostream<_CharT, _Traits>&
 261 operator<<(basic_ostream<_CharT, _Traits>& __os,
 262            const uniform_int_distribution<_IT>& __x)
 263 {
 264     __save_flags<_CharT, _Traits> __lx(__os);
 265     typedef basic_ostream<_CharT, _Traits> _Ostream;
 266     __os.flags(_Ostream::dec | _Ostream::left);
 267     _CharT __sp = __os.widen(' ');
 268     __os.fill(__sp);
 269     return __os << __x.a() << __sp << __x.b();
 270 }
 271
 272 template <class _CharT, class _Traits, class _IT>
 273 _LIBCPP_HIDE_FROM_ABI basic_istream<_CharT, _Traits>&
 274 operator>>(basic_istream<_CharT, _Traits>& __is,
 275            uniform_int_distribution<_IT>& __x)
 276 {
 277     typedef uniform_int_distribution<_IT> _Eng;
 278     typedef typename _Eng::result_type result_type;
 279     typedef typename _Eng::param_type param_type;
 280     __save_flags<_CharT, _Traits> __lx(__is);
 281     typedef basic_istream<_CharT, _Traits> _Istream;
 282     __is.flags(_Istream::dec | _Istream::skipws);
 283     result_type __a;
 284     result_type __b;
 285     __is >> __a >> __b;
 286     if (!__is.fail())
 287         __x.param(param_type(__a, __b));
 288     return __is;
 289 }
 290
 291 _LIBCPP_END_NAMESPACE_STD
 292
 293 _LIBCPP_POP_MACROS
 294
 295 #endif // _LIBCPP___RANDOM_UNIFORM_INT_DISTRIBUTION_H