libcxx/include/__cxx03/__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___CXX03___RANDOM_SEED_SEQ_H
  10 #define _LIBCPP___CXX03___RANDOM_SEED_SEQ_H
  11
  12 #include <__cxx03/__algorithm/copy.h>
  13 #include <__cxx03/__algorithm/fill.h>
  14 #include <__cxx03/__algorithm/max.h>
  15 #include <__cxx03/__config>
  16 #include <__cxx03/__iterator/iterator_traits.h>
  17 #include <__cxx03/__type_traits/is_unsigned.h>
  18 #include <__cxx03/cstdint>
  19 #include <__cxx03/initializer_list>
  20 #include <__cxx03/vector>
  21
  22 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  23 #  pragma GCC system_header
  24 #endif
  25
  26 _LIBCPP_PUSH_MACROS
  27 #include <__cxx03/__undef_macros>
  28
  29 _LIBCPP_BEGIN_NAMESPACE_STD
  30
  31 class _LIBCPP_TEMPLATE_VIS seed_seq {
  32 public:
  33   // types
  34   typedef uint32_t result_type;
  35
  36   // constructors
  37   _LIBCPP_HIDE_FROM_ABI seed_seq() _NOEXCEPT {}
  38 #ifndef _LIBCPP_CXX03_LANG
  39   template <class _Tp, __enable_if_t<is_integral<_Tp>::value, int> = 0>
  40   _LIBCPP_HIDE_FROM_ABI seed_seq(initializer_list<_Tp> __il) {
  41     __init(__il.begin(), __il.end());
  42   }
  43 #endif // _LIBCPP_CXX03_LANG
  44
  45   template <class _InputIterator>
  46   _LIBCPP_HIDE_FROM_ABI seed_seq(_InputIterator __first, _InputIterator __last) {
  47     static_assert(is_integral<typename iterator_traits<_InputIterator>::value_type>::value,
  48                   "Mandates: iterator_traits<InputIterator>::value_type is an integer type");
  49     __init(__first, __last);
  50   }
  51
  52   // generating functions
  53   template <class _RandomAccessIterator>
  54   _LIBCPP_HIDE_FROM_ABI void generate(_RandomAccessIterator __first, _RandomAccessIterator __last);
  55
  56   // property functions
  57   _LIBCPP_HIDE_FROM_ABI size_t size() const _NOEXCEPT { return __v_.size(); }
  58   template <class _OutputIterator>
  59   _LIBCPP_HIDE_FROM_ABI void param(_OutputIterator __dest) const {
  60     std::copy(__v_.begin(), __v_.end(), __dest);
  61   }
  62
  63   seed_seq(const seed_seq&)       = delete;
  64   void operator=(const seed_seq&) = delete;
  65
  66   _LIBCPP_HIDE_FROM_ABI static result_type _Tp(result_type __x) { return __x ^ (__x >> 27); }
  67
  68 private:
  69   template <class _InputIterator>
  70   _LIBCPP_HIDE_FROM_ABI void __init(_InputIterator __first, _InputIterator __last);
  71
  72   vector<result_type> __v_;
  73 };
  74
  75 template <class _InputIterator>
  76 void seed_seq::__init(_InputIterator __first, _InputIterator __last) {
  77   for (_InputIterator __s = __first; __s != __last; ++__s)
  78     __v_.push_back(*__s & 0xFFFFFFFF);
  79 }
  80
  81 template <class _RandomAccessIterator>
  82 void seed_seq::generate(_RandomAccessIterator __first, _RandomAccessIterator __last) {
  83   using _ValueType = typename iterator_traits<_RandomAccessIterator>::value_type;
  84   static_assert(is_unsigned<_ValueType>::value && sizeof(_ValueType) >= sizeof(uint32_t),
  85                 "[rand.util.seedseq]/7 requires the value_type of the iterator to be an unsigned "
  86                 "integer capable of accommodating 32-bit quantities.");
  87
  88   if (__first != __last) {
  89     std::fill(__first, __last, 0x8b8b8b8b);
  90     const size_t __n = static_cast<size_t>(__last - __first);
  91     const size_t __s = __v_.size();
  92     const size_t __t = (__n >= 623) ? 11 : (__n >= 68) ? 7 : (__n >= 39) ? 5 : (__n >= 7) ? 3 : (__n - 1) / 2;
  93     const size_t __p = (__n - __t) / 2;
  94     const size_t __q = __p + __t;
  95     const size_t __m = std::max(__s + 1, __n);
  96     // __k = 0;
  97     {
  98       result_type __r = 1664525 * _Tp(__first[0] ^ __first[__p] ^ __first[__n - 1]);
  99       __first[__p] += __r;
 100       __r += __s;
 101       __first[__q] += __r;
 102       __first[0] = __r;
 103     }
 104     // Initialize indexing terms used with if statements as an optimization to
 105     // avoid calculating modulo n on every loop iteration for each term.
 106     size_t __kmodn  = 0;         // __k % __n
 107     size_t __k1modn = __n - 1;   // (__k - 1) % __n
 108     size_t __kpmodn = __p % __n; // (__k + __p) % __n
 109     size_t __kqmodn = __q % __n; // (__k + __q) % __n
 110
 111     for (size_t __k = 1; __k <= __s; ++__k) {
 112       if (++__kmodn == __n)
 113         __kmodn = 0;
 114       if (++__k1modn == __n)
 115         __k1modn = 0;
 116       if (++__kpmodn == __n)
 117         __kpmodn = 0;
 118       if (++__kqmodn == __n)
 119         __kqmodn = 0;
 120
 121       result_type __r = 1664525 * _Tp(__first[__kmodn] ^ __first[__kpmodn] ^ __first[__k1modn]);
 122       __first[__kpmodn] += __r;
 123       __r += __kmodn + __v_[__k - 1];
 124       __first[__kqmodn] += __r;
 125       __first[__kmodn] = __r;
 126     }
 127     for (size_t __k = __s + 1; __k < __m; ++__k) {
 128       if (++__kmodn == __n)
 129         __kmodn = 0;
 130       if (++__k1modn == __n)
 131         __k1modn = 0;
 132       if (++__kpmodn == __n)
 133         __kpmodn = 0;
 134       if (++__kqmodn == __n)
 135         __kqmodn = 0;
 136
 137       result_type __r = 1664525 * _Tp(__first[__kmodn] ^ __first[__kpmodn] ^ __first[__k1modn]);
 138       __first[__kpmodn] += __r;
 139       __r += __kmodn;
 140       __first[__kqmodn] += __r;
 141       __first[__kmodn] = __r;
 142     }
 143     for (size_t __k = __m; __k < __m + __n; ++__k) {
 144       if (++__kmodn == __n)
 145         __kmodn = 0;
 146       if (++__k1modn == __n)
 147         __k1modn = 0;
 148       if (++__kpmodn == __n)
 149         __kpmodn = 0;
 150       if (++__kqmodn == __n)
 151         __kqmodn = 0;
 152
 153       result_type __r = 1566083941 * _Tp(__first[__kmodn] + __first[__kpmodn] + __first[__k1modn]);
 154       __first[__kpmodn] ^= __r;
 155       __r -= __kmodn;
 156       __first[__kqmodn] ^= __r;
 157       __first[__kmodn] = __r;
 158     }
 159   }
 160 }
 161
 162 _LIBCPP_END_NAMESPACE_STD
 163
 164 _LIBCPP_POP_MACROS
 165
 166 #endif // _LIBCPP___CXX03___RANDOM_SEED_SEQ_H