v1/__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___RANDOM_SEED_SEQ_H
0010 #define _LIBCPP___RANDOM_SEED_SEQ_H
0011
0012 #include <__algorithm/copy.h>
0013 #include <__algorithm/fill.h>
0014 #include <__algorithm/max.h>
0015 #include <__config>
0016 #include <__iterator/iterator_traits.h>
0017 #include <__type_traits/enable_if.h>
0018 #include <__type_traits/is_integral.h>
0019 #include <__type_traits/is_unsigned.h>
0020 #include <__vector/vector.h>
0021 #include <cstdint>
0022 #include <initializer_list>
0023
0024 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
0025 #  pragma GCC system_header
0026 #endif
0027
0028 _LIBCPP_PUSH_MACROS
0029 #include <__undef_macros>
0030
0031 _LIBCPP_BEGIN_NAMESPACE_STD
0032
0033 class _LIBCPP_TEMPLATE_VIS seed_seq {
0034 public:
0035   // types
0036   typedef uint32_t result_type;
0037
0038   // constructors
0039   _LIBCPP_HIDE_FROM_ABI seed_seq() _NOEXCEPT {}
0040 #ifndef _LIBCPP_CXX03_LANG
0041   template <class _Tp, __enable_if_t<is_integral<_Tp>::value, int> = 0>
0042   _LIBCPP_HIDE_FROM_ABI seed_seq(initializer_list<_Tp> __il) {
0043     __init(__il.begin(), __il.end());
0044   }
0045 #endif // _LIBCPP_CXX03_LANG
0046
0047   template <class _InputIterator>
0048   _LIBCPP_HIDE_FROM_ABI seed_seq(_InputIterator __first, _InputIterator __last) {
0049     static_assert(is_integral<typename iterator_traits<_InputIterator>::value_type>::value,
0050                   "Mandates: iterator_traits<InputIterator>::value_type is an integer type");
0051     __init(__first, __last);
0052   }
0053
0054   // generating functions
0055   template <class _RandomAccessIterator>
0056   _LIBCPP_HIDE_FROM_ABI void generate(_RandomAccessIterator __first, _RandomAccessIterator __last);
0057
0058   // property functions
0059   _LIBCPP_HIDE_FROM_ABI size_t size() const _NOEXCEPT { return __v_.size(); }
0060   template <class _OutputIterator>
0061   _LIBCPP_HIDE_FROM_ABI void param(_OutputIterator __dest) const {
0062     std::copy(__v_.begin(), __v_.end(), __dest);
0063   }
0064
0065   seed_seq(const seed_seq&)       = delete;
0066   void operator=(const seed_seq&) = delete;
0067
0068   _LIBCPP_HIDE_FROM_ABI static result_type _Tp(result_type __x) { return __x ^ (__x >> 27); }
0069
0070 private:
0071   template <class _InputIterator>
0072   _LIBCPP_HIDE_FROM_ABI void __init(_InputIterator __first, _InputIterator __last);
0073
0074   vector<result_type> __v_;
0075 };
0076
0077 template <class _InputIterator>
0078 void seed_seq::__init(_InputIterator __first, _InputIterator __last) {
0079   for (_InputIterator __s = __first; __s != __last; ++__s)
0080     __v_.push_back(*__s & 0xFFFFFFFF);
0081 }
0082
0083 template <class _RandomAccessIterator>
0084 void seed_seq::generate(_RandomAccessIterator __first, _RandomAccessIterator __last) {
0085   using _ValueType = typename iterator_traits<_RandomAccessIterator>::value_type;
0086   static_assert(is_unsigned<_ValueType>::value && sizeof(_ValueType) >= sizeof(uint32_t),
0087                 "[rand.util.seedseq]/7 requires the value_type of the iterator to be an unsigned "
0088                 "integer capable of accommodating 32-bit quantities.");
0089
0090   if (__first != __last) {
0091     std::fill(__first, __last, 0x8b8b8b8b);
0092     const size_t __n = static_cast<size_t>(__last - __first);
0093     const size_t __s = __v_.size();
0094     const size_t __t = (__n >= 623) ? 11 : (__n >= 68) ? 7 : (__n >= 39) ? 5 : (__n >= 7) ? 3 : (__n - 1) / 2;
0095     const size_t __p = (__n - __t) / 2;
0096     const size_t __q = __p + __t;
0097     const size_t __m = std::max(__s + 1, __n);
0098     // __k = 0;
0099     {
0100       result_type __r = 1664525 * _Tp(__first[0] ^ __first[__p] ^ __first[__n - 1]);
0101       __first[__p] += __r;
0102       __r += __s;
0103       __first[__q] += __r;
0104       __first[0] = __r;
0105     }
0106     // Initialize indexing terms used with if statements as an optimization to
0107     // avoid calculating modulo n on every loop iteration for each term.
0108     size_t __kmodn  = 0;         // __k % __n
0109     size_t __k1modn = __n - 1;   // (__k - 1) % __n
0110     size_t __kpmodn = __p % __n; // (__k + __p) % __n
0111     size_t __kqmodn = __q % __n; // (__k + __q) % __n
0112
0113     for (size_t __k = 1; __k <= __s; ++__k) {
0114       if (++__kmodn == __n)
0115         __kmodn = 0;
0116       if (++__k1modn == __n)
0117         __k1modn = 0;
0118       if (++__kpmodn == __n)
0119         __kpmodn = 0;
0120       if (++__kqmodn == __n)
0121         __kqmodn = 0;
0122
0123       result_type __r = 1664525 * _Tp(__first[__kmodn] ^ __first[__kpmodn] ^ __first[__k1modn]);
0124       __first[__kpmodn] += __r;
0125       __r += __kmodn + __v_[__k - 1];
0126       __first[__kqmodn] += __r;
0127       __first[__kmodn] = __r;
0128     }
0129     for (size_t __k = __s + 1; __k < __m; ++__k) {
0130       if (++__kmodn == __n)
0131         __kmodn = 0;
0132       if (++__k1modn == __n)
0133         __k1modn = 0;
0134       if (++__kpmodn == __n)
0135         __kpmodn = 0;
0136       if (++__kqmodn == __n)
0137         __kqmodn = 0;
0138
0139       result_type __r = 1664525 * _Tp(__first[__kmodn] ^ __first[__kpmodn] ^ __first[__k1modn]);
0140       __first[__kpmodn] += __r;
0141       __r += __kmodn;
0142       __first[__kqmodn] += __r;
0143       __first[__kmodn] = __r;
0144     }
0145     for (size_t __k = __m; __k < __m + __n; ++__k) {
0146       if (++__kmodn == __n)
0147         __kmodn = 0;
0148       if (++__k1modn == __n)
0149         __k1modn = 0;
0150       if (++__kpmodn == __n)
0151         __kpmodn = 0;
0152       if (++__kqmodn == __n)
0153         __kqmodn = 0;
0154
0155       result_type __r = 1566083941 * _Tp(__first[__kmodn] + __first[__kpmodn] + __first[__k1modn]);
0156       __first[__kpmodn] ^= __r;
0157       __r -= __kmodn;
0158       __first[__kqmodn] ^= __r;
0159       __first[__kmodn] = __r;
0160     }
0161   }
0162 }
0163
0164 _LIBCPP_END_NAMESPACE_STD
0165
0166 _LIBCPP_POP_MACROS
0167
0168 #endif // _LIBCPP___RANDOM_SEED_SEQ_H