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 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
operator()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>
__independent_bits_engine(_Engine & __e,size_t __w)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>
__eval(false_type)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>
__eval(true_type)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())
__a_(__a)152         : __a_(__a), __b_(__b) {}
153 
a()154     _LIBCPP_HIDE_FROM_ABI result_type a() const { return __a_; }
b()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
uniform_int_distribution()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())
__p_(param_type (__a,__b))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
uniform_int_distribution(const param_type & __p)177   _LIBCPP_HIDE_FROM_ABI explicit uniform_int_distribution(const param_type& __p) : __p_(__p) {}
reset()178   _LIBCPP_HIDE_FROM_ABI void reset() {}
179 
180   // generating functions
181   template <class _URNG>
operator()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
a()189   _LIBCPP_HIDE_FROM_ABI result_type a() const { return __p_.a(); }
b()190   _LIBCPP_HIDE_FROM_ABI result_type b() const { return __p_.b(); }
191 
param()192   _LIBCPP_HIDE_FROM_ABI param_type param() const { return __p_; }
param(const param_type & __p)193   _LIBCPP_HIDE_FROM_ABI void param(const param_type& __p) { __p_ = __p; }
194 
min()195   _LIBCPP_HIDE_FROM_ABI result_type min() const { return a(); }
max()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>
operator()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
265