libcxx/include/__random/seed_seq.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_SEED_SEQ_H
  10 #define _LIBCPP___RANDOM_SEED_SEQ_H
  11
  12 #include <__algorithm/copy.h>
  13 #include <__algorithm/fill.h>
  14 #include <__algorithm/max.h>
  15 #include <__config>
  16 #include <__iterator/iterator_traits.h>
  17 #include <cstdint>
  18 #include <initializer_list>
  19 #include <vector>
  20
  21 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  22 #  pragma GCC system_header
  23 #endif
  24
  25 _LIBCPP_PUSH_MACROS
  26 #include <__undef_macros>
  27
  28 _LIBCPP_BEGIN_NAMESPACE_STD
  29
  30 class _LIBCPP_TEMPLATE_VIS seed_seq
  31 {
  32 public:
  33     // types
  34     typedef uint32_t result_type;
  35
  36     // constructors
  37     _LIBCPP_INLINE_VISIBILITY
  38     seed_seq() _NOEXCEPT {}
  39 #ifndef _LIBCPP_CXX03_LANG
  40     template<class _Tp, __enable_if_t<is_integral<_Tp>::value>* = nullptr>
  41     _LIBCPP_INLINE_VISIBILITY
  42     seed_seq(initializer_list<_Tp> __il) {
  43         __init(__il.begin(), __il.end());
  44     }
  45 #endif // _LIBCPP_CXX03_LANG
  46
  47     template<class _InputIterator>
  48     _LIBCPP_INLINE_VISIBILITY
  49     seed_seq(_InputIterator __first, _InputIterator __last) {
  50         static_assert(is_integral<typename iterator_traits<_InputIterator>::value_type>::value,
  51             "Mandates: iterator_traits<InputIterator>::value_type is an integer type");
  52         __init(__first, __last);
  53     }
  54
  55     // generating functions
  56     template<class _RandomAccessIterator>
  57     _LIBCPP_HIDE_FROM_ABI void generate(_RandomAccessIterator __first, _RandomAccessIterator __last);
  58
  59     // property functions
  60     _LIBCPP_INLINE_VISIBILITY
  61     size_t size() const _NOEXCEPT {return __v_.size();}
  62     template<class _OutputIterator>
  63         _LIBCPP_INLINE_VISIBILITY
  64         void param(_OutputIterator __dest) const
  65             {_VSTD::copy(__v_.begin(), __v_.end(), __dest);}
  66
  67     seed_seq(const seed_seq&) = delete;
  68     void operator=(const seed_seq&) = delete;
  69
  70     _LIBCPP_INLINE_VISIBILITY
  71     static result_type _Tp(result_type __x) {return __x ^ (__x >> 27);}
  72
  73 private:
  74     template<class _InputIterator>
  75     _LIBCPP_HIDE_FROM_ABI void __init(_InputIterator __first, _InputIterator __last);
  76
  77     vector<result_type> __v_;
  78 };
  79
  80 template<class _InputIterator>
  81 void
  82 seed_seq::__init(_InputIterator __first, _InputIterator __last)
  83 {
  84     for (_InputIterator __s = __first; __s != __last; ++__s)
  85         __v_.push_back(*__s & 0xFFFFFFFF);
  86 }
  87
  88 template<class _RandomAccessIterator>
  89 void
  90 seed_seq::generate(_RandomAccessIterator __first, _RandomAccessIterator __last)
  91 {
  92     if (__first != __last)
  93     {
  94         _VSTD::fill(__first, __last, 0x8b8b8b8b);
  95         const size_t __n = static_cast<size_t>(__last - __first);
  96         const size_t __s = __v_.size();
  97         const size_t __t = (__n >= 623) ? 11
  98                          : (__n >= 68) ? 7
  99                          : (__n >= 39) ? 5
 100                          : (__n >= 7)  ? 3
 101                          : (__n - 1) / 2;
 102         const size_t __p = (__n - __t) / 2;
 103         const size_t __q = __p + __t;
 104         const size_t __m = _VSTD::max(__s + 1, __n);
 105         // __k = 0;
 106         {
 107             result_type __r = 1664525 * _Tp(__first[0] ^ __first[__p]
 108                                                       ^  __first[__n - 1]);
 109             __first[__p] += __r;
 110             __r += __s;
 111             __first[__q] += __r;
 112             __first[0] = __r;
 113         }
 114         // Initialize indexing terms used with if statements as an optimization to
 115         // avoid calculating modulo n on every loop iteration for each term.
 116         size_t __kmodn = 0;          // __k % __n
 117         size_t __k1modn = __n - 1;   // (__k - 1) % __n
 118         size_t __kpmodn = __p % __n; // (__k + __p) % __n
 119         size_t __kqmodn = __q % __n; // (__k + __q) % __n
 120
 121         for (size_t __k = 1; __k <= __s; ++__k)
 122         {
 123           if (++__kmodn == __n)
 124             __kmodn = 0;
 125           if (++__k1modn == __n)
 126             __k1modn = 0;
 127           if (++__kpmodn == __n)
 128             __kpmodn = 0;
 129           if (++__kqmodn == __n)
 130             __kqmodn = 0;
 131
 132           result_type __r = 1664525 * _Tp(__first[__kmodn] ^ __first[__kpmodn] ^ __first[__k1modn]);
 133           __first[__kpmodn] += __r;
 134           __r += __kmodn + __v_[__k - 1];
 135           __first[__kqmodn] += __r;
 136           __first[__kmodn] = __r;
 137         }
 138         for (size_t __k = __s + 1; __k < __m; ++__k)
 139         {
 140           if (++__kmodn == __n)
 141             __kmodn = 0;
 142           if (++__k1modn == __n)
 143             __k1modn = 0;
 144           if (++__kpmodn == __n)
 145             __kpmodn = 0;
 146           if (++__kqmodn == __n)
 147             __kqmodn = 0;
 148
 149           result_type __r = 1664525 * _Tp(__first[__kmodn] ^ __first[__kpmodn] ^ __first[__k1modn]);
 150           __first[__kpmodn] += __r;
 151           __r += __kmodn;
 152           __first[__kqmodn] += __r;
 153           __first[__kmodn] = __r;
 154         }
 155         for (size_t __k = __m; __k < __m + __n; ++__k)
 156         {
 157           if (++__kmodn == __n)
 158             __kmodn = 0;
 159           if (++__k1modn == __n)
 160             __k1modn = 0;
 161           if (++__kpmodn == __n)
 162             __kpmodn = 0;
 163           if (++__kqmodn == __n)
 164             __kqmodn = 0;
 165
 166           result_type __r = 1566083941 * _Tp(__first[__kmodn] + __first[__kpmodn] + __first[__k1modn]);
 167           __first[__kpmodn] ^= __r;
 168           __r -= __kmodn;
 169           __first[__kqmodn] ^= __r;
 170           __first[__kmodn] = __r;
 171         }
 172     }
 173 }
 174
 175 _LIBCPP_END_NAMESPACE_STD
 176
 177 _LIBCPP_POP_MACROS
 178
 179 #endif // _LIBCPP___RANDOM_SEED_SEQ_H