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 <__cstddef/size_t.h>
  15 #include <__random/is_valid.h>
  16 #include <__random/log2.h>
  17 #include <__type_traits/conditional.h>
  18 #include <__type_traits/make_unsigned.h>
  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 public:
  35   // types
  36   typedef _UIntType result_type;
  37
  38 private:
  39   typedef typename _Engine::result_type _Engine_result_type;
  40   typedef __conditional_t<sizeof(_Engine_result_type) <= sizeof(result_type), result_type, _Engine_result_type>
  41       _Working_result_type;
  42
  43   _Engine& __e_;
  44   size_t __w_;
  45   size_t __w0_;
  46   size_t __n_;
  47   size_t __n0_;
  48   _Working_result_type __y0_;
  49   _Working_result_type __y1_;
  50   _Engine_result_type __mask0_;
  51   _Engine_result_type __mask1_;
  52
  53 #ifdef _LIBCPP_CXX03_LANG
  54   static const _Working_result_type _Rp = _Engine::_Max - _Engine::_Min + _Working_result_type(1);
  55 #else
  56   static _LIBCPP_CONSTEXPR const _Working_result_type _Rp = _Engine::max() - _Engine::min() + _Working_result_type(1);
  57 #endif
  58   static _LIBCPP_CONSTEXPR const size_t __m  = __log2<_Working_result_type, _Rp>::value;
  59   static _LIBCPP_CONSTEXPR const size_t _WDt = numeric_limits<_Working_result_type>::digits;
  60   static _LIBCPP_CONSTEXPR const size_t _EDt = numeric_limits<_Engine_result_type>::digits;
  61
  62 public:
  63   // constructors and seeding functions
  64   _LIBCPP_HIDE_FROM_ABI __independent_bits_engine(_Engine& __e, size_t __w);
  65
  66   // generating functions
  67   _LIBCPP_HIDE_FROM_ABI result_type operator()() { return __eval(integral_constant<bool, _Rp != 0>()); }
  68
  69 private:
  70   _LIBCPP_HIDE_FROM_ABI result_type __eval(false_type);
  71   _LIBCPP_HIDE_FROM_ABI result_type __eval(true_type);
  72 };
  73
  74 template <class _Engine, class _UIntType>
  75 __independent_bits_engine<_Engine, _UIntType>::__independent_bits_engine(_Engine& __e, size_t __w)
  76     : __e_(__e), __w_(__w) {
  77   __n_  = __w_ / __m + (__w_ % __m != 0);
  78   __w0_ = __w_ / __n_;
  79   if (_Rp == 0)
  80     __y0_ = _Rp;
  81   else if (__w0_ < _WDt)
  82     __y0_ = (_Rp >> __w0_) << __w0_;
  83   else
  84     __y0_ = 0;
  85   if (_Rp - __y0_ > __y0_ / __n_) {
  86     ++__n_;
  87     __w0_ = __w_ / __n_;
  88     if (__w0_ < _WDt)
  89       __y0_ = (_Rp >> __w0_) << __w0_;
  90     else
  91       __y0_ = 0;
  92   }
  93   __n0_ = __n_ - __w_ % __n_;
  94   if (__w0_ < _WDt - 1)
  95     __y1_ = (_Rp >> (__w0_ + 1)) << (__w0_ + 1);
  96   else
  97     __y1_ = 0;
  98   __mask0_ = __w0_ > 0 ? _Engine_result_type(~0) >> (_EDt - __w0_) : _Engine_result_type(0);
  99   __mask1_ = __w0_ < _EDt - 1 ? _Engine_result_type(~0) >> (_EDt - (__w0_ + 1)) : _Engine_result_type(~0);
 100 }
 101
 102 template <class _Engine, class _UIntType>
 103 inline _UIntType __independent_bits_engine<_Engine, _UIntType>::__eval(false_type) {
 104   return static_cast<result_type>(__e_() & __mask0_);
 105 }
 106
 107 template <class _Engine, class _UIntType>
 108 _UIntType __independent_bits_engine<_Engine, _UIntType>::__eval(true_type) {
 109   const size_t __w_rt = numeric_limits<result_type>::digits;
 110   result_type __sp    = 0;
 111   for (size_t __k = 0; __k < __n0_; ++__k) {
 112     _Engine_result_type __u;
 113     do {
 114       __u = __e_() - _Engine::min();
 115     } while (__u >= __y0_);
 116     if (__w0_ < __w_rt)
 117       __sp <<= __w0_;
 118     else
 119       __sp = 0;
 120     __sp += __u & __mask0_;
 121   }
 122   for (size_t __k = __n0_; __k < __n_; ++__k) {
 123     _Engine_result_type __u;
 124     do {
 125       __u = __e_() - _Engine::min();
 126     } while (__u >= __y1_);
 127     if (__w0_ < __w_rt - 1)
 128       __sp <<= __w0_ + 1;
 129     else
 130       __sp = 0;
 131     __sp += __u & __mask1_;
 132   }
 133   return __sp;
 134 }
 135
 136 template <class _IntType = int>
 137 class uniform_int_distribution {
 138   static_assert(__libcpp_random_is_valid_inttype<_IntType>::value, "IntType must be a supported integer type");
 139
 140 public:
 141   // types
 142   typedef _IntType result_type;
 143
 144   class param_type {
 145     result_type __a_;
 146     result_type __b_;
 147
 148   public:
 149     typedef uniform_int_distribution distribution_type;
 150
 151     _LIBCPP_HIDE_FROM_ABI explicit param_type(result_type __a = 0, result_type __b = numeric_limits<result_type>::max())
 152         : __a_(__a), __b_(__b) {}
 153
 154     _LIBCPP_HIDE_FROM_ABI result_type a() const { return __a_; }
 155     _LIBCPP_HIDE_FROM_ABI result_type b() const { return __b_; }
 156
 157     _LIBCPP_HIDE_FROM_ABI friend bool operator==(const param_type& __x, const param_type& __y) {
 158       return __x.__a_ == __y.__a_ && __x.__b_ == __y.__b_;
 159     }
 160     _LIBCPP_HIDE_FROM_ABI friend bool operator!=(const param_type& __x, const param_type& __y) { return !(__x == __y); }
 161   };
 162
 163 private:
 164   param_type __p_;
 165
 166 public:
 167   // constructors and reset functions
 168 #ifndef _LIBCPP_CXX03_LANG
 169   _LIBCPP_HIDE_FROM_ABI uniform_int_distribution() : uniform_int_distribution(0) {}
 170   _LIBCPP_HIDE_FROM_ABI explicit uniform_int_distribution(
 171       result_type __a, result_type __b = numeric_limits<result_type>::max())
 172       : __p_(param_type(__a, __b)) {}
 173 #else
 174   explicit uniform_int_distribution(result_type __a = 0, result_type __b = numeric_limits<result_type>::max())
 175       : __p_(param_type(__a, __b)) {}
 176 #endif
 177   _LIBCPP_HIDE_FROM_ABI explicit uniform_int_distribution(const param_type& __p) : __p_(__p) {}
 178   _LIBCPP_HIDE_FROM_ABI void reset() {}
 179
 180   // generating functions
 181   template <class _URNG>
 182   _LIBCPP_HIDE_FROM_ABI result_type operator()(_URNG& __g) {
 183     return (*this)(__g, __p_);
 184   }
 185   template <class _URNG>
 186   _LIBCPP_HIDE_FROM_ABI result_type operator()(_URNG& __g, const param_type& __p);
 187
 188   // property functions
 189   _LIBCPP_HIDE_FROM_ABI result_type a() const { return __p_.a(); }
 190   _LIBCPP_HIDE_FROM_ABI result_type b() const { return __p_.b(); }
 191
 192   _LIBCPP_HIDE_FROM_ABI param_type param() const { return __p_; }
 193   _LIBCPP_HIDE_FROM_ABI void param(const param_type& __p) { __p_ = __p; }
 194
 195   _LIBCPP_HIDE_FROM_ABI result_type min() const { return a(); }
 196   _LIBCPP_HIDE_FROM_ABI result_type max() const { return b(); }
 197
 198   _LIBCPP_HIDE_FROM_ABI friend bool
 199   operator==(const uniform_int_distribution& __x, const uniform_int_distribution& __y) {
 200     return __x.__p_ == __y.__p_;
 201   }
 202   _LIBCPP_HIDE_FROM_ABI friend bool
 203   operator!=(const uniform_int_distribution& __x, const uniform_int_distribution& __y) {
 204     return !(__x == __y);
 205   }
 206 };
 207
 208 template <class _IntType>
 209 template <class _URNG>
 210 typename uniform_int_distribution<_IntType>::result_type uniform_int_distribution<_IntType>::operator()(
 211     _URNG& __g, const param_type& __p) _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK {
 212   static_assert(__libcpp_random_is_valid_urng<_URNG>::value, "");
 213   typedef __conditional_t<sizeof(result_type) <= sizeof(uint32_t), uint32_t, __make_unsigned_t<result_type> > _UIntType;
 214   const _UIntType __rp = _UIntType(__p.b()) - _UIntType(__p.a()) + _UIntType(1);
 215   if (__rp == 1)
 216     return __p.a();
 217   const size_t __dt = numeric_limits<_UIntType>::digits;
 218   typedef __independent_bits_engine<_URNG, _UIntType> _Eng;
 219   if (__rp == 0)
 220     return static_cast<result_type>(_Eng(__g, __dt)());
 221   size_t __w = __dt - std::__countl_zero(__rp) - 1;
 222   if ((__rp & (numeric_limits<_UIntType>::max() >> (__dt - __w))) != 0)
 223     ++__w;
 224   _Eng __e(__g, __w);
 225   _UIntType __u;
 226   do {
 227     __u = __e();
 228   } while (__u >= __rp);
 229   return static_cast<result_type>(__u + __p.a());
 230 }
 231
 232 template <class _CharT, class _Traits, class _IT>
 233 _LIBCPP_HIDE_FROM_ABI basic_ostream<_CharT, _Traits>&
 234 operator<<(basic_ostream<_CharT, _Traits>& __os, const uniform_int_distribution<_IT>& __x) {
 235   __save_flags<_CharT, _Traits> __lx(__os);
 236   typedef basic_ostream<_CharT, _Traits> _Ostream;
 237   __os.flags(_Ostream::dec | _Ostream::left);
 238   _CharT __sp = __os.widen(' ');
 239   __os.fill(__sp);
 240   return __os << __x.a() << __sp << __x.b();
 241 }
 242
 243 template <class _CharT, class _Traits, class _IT>
 244 _LIBCPP_HIDE_FROM_ABI basic_istream<_CharT, _Traits>&
 245 operator>>(basic_istream<_CharT, _Traits>& __is, uniform_int_distribution<_IT>& __x) {
 246   typedef uniform_int_distribution<_IT> _Eng;
 247   typedef typename _Eng::result_type result_type;
 248   typedef typename _Eng::param_type param_type;
 249   __save_flags<_CharT, _Traits> __lx(__is);
 250   typedef basic_istream<_CharT, _Traits> _Istream;
 251   __is.flags(_Istream::dec | _Istream::skipws);
 252   result_type __a;
 253   result_type __b;
 254   __is >> __a >> __b;
 255   if (!__is.fail())
 256     __x.param(param_type(__a, __b));
 257   return __is;
 258 }
 259
 260 _LIBCPP_END_NAMESPACE_STD
 261
 262 _LIBCPP_POP_MACROS
 263
 264 #endif // _LIBCPP___RANDOM_UNIFORM_INT_DISTRIBUTION_H