__cxx03/__random/seed_seq.h

0001 //===----------------------------------------------------------------------===//
0002 //
0003 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
0004 // See https://llvm.org/LICENSE.txt for license information.
0005 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
0006 //
0007 //===----------------------------------------------------------------------===//
0008
0009 #ifndef _LIBCPP___CXX03___RANDOM_SEED_SEQ_H
0010 #define _LIBCPP___CXX03___RANDOM_SEED_SEQ_H
0011
0012 #include <__cxx03/__algorithm/copy.h>
0013 #include <__cxx03/__algorithm/fill.h>
0014 #include <__cxx03/__algorithm/max.h>
0015 #include <__cxx03/__config>
0016 #include <__cxx03/__iterator/iterator_traits.h>
0017 #include <__cxx03/__type_traits/is_unsigned.h>
0018 #include <__cxx03/cstdint>
0019 #include <__cxx03/initializer_list>
0020 #include <__cxx03/vector>
0021
0022 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
0023 #  pragma GCC system_header
0024 #endif
0025
0026 _LIBCPP_PUSH_MACROS
0027 #include <__cxx03/__undef_macros>
0028
0029 _LIBCPP_BEGIN_NAMESPACE_STD
0030
0031 class _LIBCPP_TEMPLATE_VIS seed_seq {
0032 public:
0033   // types
0034   typedef uint32_t result_type;
0035
0036   // constructors
0037   _LIBCPP_HIDE_FROM_ABI seed_seq() _NOEXCEPT {}
0038 #ifndef _LIBCPP_CXX03_LANG
0039   template <class _Tp, __enable_if_t<is_integral<_Tp>::value, int> = 0>
0040   _LIBCPP_HIDE_FROM_ABI seed_seq(initializer_list<_Tp> __il) {
0041     __init(__il.begin(), __il.end());
0042   }
0043 #endif // _LIBCPP_CXX03_LANG
0044
0045   template <class _InputIterator>
0046   _LIBCPP_HIDE_FROM_ABI seed_seq(_InputIterator __first, _InputIterator __last) {
0047     static_assert(is_integral<typename iterator_traits<_InputIterator>::value_type>::value,
0048                   "Mandates: iterator_traits<InputIterator>::value_type is an integer type");
0049     __init(__first, __last);
0050   }
0051
0052   // generating functions
0053   template <class _RandomAccessIterator>
0054   _LIBCPP_HIDE_FROM_ABI void generate(_RandomAccessIterator __first, _RandomAccessIterator __last);
0055
0056   // property functions
0057   _LIBCPP_HIDE_FROM_ABI size_t size() const _NOEXCEPT { return __v_.size(); }
0058   template <class _OutputIterator>
0059   _LIBCPP_HIDE_FROM_ABI void param(_OutputIterator __dest) const {
0060     std::copy(__v_.begin(), __v_.end(), __dest);
0061   }
0062
0063   seed_seq(const seed_seq&)       = delete;
0064   void operator=(const seed_seq&) = delete;
0065
0066   _LIBCPP_HIDE_FROM_ABI static result_type _Tp(result_type __x) { return __x ^ (__x >> 27); }
0067
0068 private:
0069   template <class _InputIterator>
0070   _LIBCPP_HIDE_FROM_ABI void __init(_InputIterator __first, _InputIterator __last);
0071
0072   vector<result_type> __v_;
0073 };
0074
0075 template <class _InputIterator>
0076 void seed_seq::__init(_InputIterator __first, _InputIterator __last) {
0077   for (_InputIterator __s = __first; __s != __last; ++__s)
0078     __v_.push_back(*__s & 0xFFFFFFFF);
0079 }
0080
0081 template <class _RandomAccessIterator>
0082 void seed_seq::generate(_RandomAccessIterator __first, _RandomAccessIterator __last) {
0083   using _ValueType = typename iterator_traits<_RandomAccessIterator>::value_type;
0084   static_assert(is_unsigned<_ValueType>::value && sizeof(_ValueType) >= sizeof(uint32_t),
0085                 "[rand.util.seedseq]/7 requires the value_type of the iterator to be an unsigned "
0086                 "integer capable of accommodating 32-bit quantities.");
0087
0088   if (__first != __last) {
0089     std::fill(__first, __last, 0x8b8b8b8b);
0090     const size_t __n = static_cast<size_t>(__last - __first);
0091     const size_t __s = __v_.size();
0092     const size_t __t = (__n >= 623) ? 11 : (__n >= 68) ? 7 : (__n >= 39) ? 5 : (__n >= 7) ? 3 : (__n - 1) / 2;
0093     const size_t __p = (__n - __t) / 2;
0094     const size_t __q = __p + __t;
0095     const size_t __m = std::max(__s + 1, __n);
0096     // __k = 0;
0097     {
0098       result_type __r = 1664525 * _Tp(__first[0] ^ __first[__p] ^ __first[__n - 1]);
0099       __first[__p] += __r;
0100       __r += __s;
0101       __first[__q] += __r;
0102       __first[0] = __r;
0103     }
0104     // Initialize indexing terms used with if statements as an optimization to
0105     // avoid calculating modulo n on every loop iteration for each term.
0106     size_t __kmodn  = 0;         // __k % __n
0107     size_t __k1modn = __n - 1;   // (__k - 1) % __n
0108     size_t __kpmodn = __p % __n; // (__k + __p) % __n
0109     size_t __kqmodn = __q % __n; // (__k + __q) % __n
0110
0111     for (size_t __k = 1; __k <= __s; ++__k) {
0112       if (++__kmodn == __n)
0113         __kmodn = 0;
0114       if (++__k1modn == __n)
0115         __k1modn = 0;
0116       if (++__kpmodn == __n)
0117         __kpmodn = 0;
0118       if (++__kqmodn == __n)
0119         __kqmodn = 0;
0120
0121       result_type __r = 1664525 * _Tp(__first[__kmodn] ^ __first[__kpmodn] ^ __first[__k1modn]);
0122       __first[__kpmodn] += __r;
0123       __r += __kmodn + __v_[__k - 1];
0124       __first[__kqmodn] += __r;
0125       __first[__kmodn] = __r;
0126     }
0127     for (size_t __k = __s + 1; __k < __m; ++__k) {
0128       if (++__kmodn == __n)
0129         __kmodn = 0;
0130       if (++__k1modn == __n)
0131         __k1modn = 0;
0132       if (++__kpmodn == __n)
0133         __kpmodn = 0;
0134       if (++__kqmodn == __n)
0135         __kqmodn = 0;
0136
0137       result_type __r = 1664525 * _Tp(__first[__kmodn] ^ __first[__kpmodn] ^ __first[__k1modn]);
0138       __first[__kpmodn] += __r;
0139       __r += __kmodn;
0140       __first[__kqmodn] += __r;
0141       __first[__kmodn] = __r;
0142     }
0143     for (size_t __k = __m; __k < __m + __n; ++__k) {
0144       if (++__kmodn == __n)
0145         __kmodn = 0;
0146       if (++__k1modn == __n)
0147         __k1modn = 0;
0148       if (++__kpmodn == __n)
0149         __kpmodn = 0;
0150       if (++__kqmodn == __n)
0151         __kqmodn = 0;
0152
0153       result_type __r = 1566083941 * _Tp(__first[__kmodn] + __first[__kpmodn] + __first[__k1modn]);
0154       __first[__kpmodn] ^= __r;
0155       __r -= __kmodn;
0156       __first[__kqmodn] ^= __r;
0157       __first[__kmodn] = __r;
0158     }
0159   }
0160 }
0161
0162 _LIBCPP_END_NAMESPACE_STD
0163
0164 _LIBCPP_POP_MACROS
0165
0166 #endif // _LIBCPP___CXX03___RANDOM_SEED_SEQ_H