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