libcxx/include/__random/discard_block_engine.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_DISCARD_BLOCK_ENGINE_H
  10 #define _LIBCPP___RANDOM_DISCARD_BLOCK_ENGINE_H
  11
  12 #include <__config>
  13 #include <__random/is_seed_sequence.h>
  14 #include <__type_traits/enable_if.h>
  15 #include <__type_traits/is_convertible.h>
  16 #include <__utility/move.h>
  17 #include <cstddef>
  18 #include <iosfwd>
  19 #include <limits>
  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 template<class _Engine, size_t __p, size_t __r>
  31 class _LIBCPP_TEMPLATE_VIS discard_block_engine
  32 {
  33     _Engine __e_;
  34     int     __n_;
  35
  36     static_assert(  0 <  __r, "discard_block_engine invalid parameters");
  37     static_assert(__r <= __p, "discard_block_engine invalid parameters");
  38 #ifndef _LIBCPP_CXX03_LANG // numeric_limits::max() is not constexpr in C++03
  39     static_assert(__r <= numeric_limits<int>::max(), "discard_block_engine invalid parameters");
  40 #endif
  41 public:
  42     // types
  43     typedef typename _Engine::result_type result_type;
  44
  45     // engine characteristics
  46     static _LIBCPP_CONSTEXPR const size_t block_size = __p;
  47     static _LIBCPP_CONSTEXPR const size_t used_block = __r;
  48
  49 #ifdef _LIBCPP_CXX03_LANG
  50     static const result_type _Min = _Engine::_Min;
  51     static const result_type _Max = _Engine::_Max;
  52 #else
  53     static _LIBCPP_CONSTEXPR const result_type _Min = _Engine::min();
  54     static _LIBCPP_CONSTEXPR const result_type _Max = _Engine::max();
  55 #endif
  56
  57     _LIBCPP_INLINE_VISIBILITY
  58     static _LIBCPP_CONSTEXPR result_type min() { return _Engine::min(); }
  59     _LIBCPP_INLINE_VISIBILITY
  60     static _LIBCPP_CONSTEXPR result_type max() { return _Engine::max(); }
  61
  62     // constructors and seeding functions
  63     _LIBCPP_INLINE_VISIBILITY
  64     discard_block_engine() : __n_(0) {}
  65     _LIBCPP_INLINE_VISIBILITY
  66     explicit discard_block_engine(const _Engine& __e)
  67         : __e_(__e), __n_(0) {}
  68 #ifndef _LIBCPP_CXX03_LANG
  69     _LIBCPP_INLINE_VISIBILITY
  70     explicit discard_block_engine(_Engine&& __e)
  71         : __e_(_VSTD::move(__e)), __n_(0) {}
  72 #endif // _LIBCPP_CXX03_LANG
  73     _LIBCPP_INLINE_VISIBILITY
  74     explicit discard_block_engine(result_type __sd) : __e_(__sd), __n_(0) {}
  75     template<class _Sseq, __enable_if_t<__is_seed_sequence<_Sseq, discard_block_engine>::value &&
  76                                         !is_convertible<_Sseq, _Engine>::value, int> = 0>
  77         _LIBCPP_INLINE_VISIBILITY
  78         explicit discard_block_engine(_Sseq& __q)
  79         : __e_(__q), __n_(0) {}
  80     _LIBCPP_INLINE_VISIBILITY
  81     void seed() {__e_.seed(); __n_ = 0;}
  82     _LIBCPP_INLINE_VISIBILITY
  83     void seed(result_type __sd) {__e_.seed(__sd); __n_ = 0;}
  84     template<class _Sseq, __enable_if_t<__is_seed_sequence<_Sseq, discard_block_engine>::value, int> = 0>
  85         _LIBCPP_INLINE_VISIBILITY
  86         void
  87         seed(_Sseq& __q) {__e_.seed(__q); __n_ = 0;}
  88
  89     // generating functions
  90     _LIBCPP_HIDE_FROM_ABI result_type operator()();
  91     _LIBCPP_INLINE_VISIBILITY
  92     void discard(unsigned long long __z) {for (; __z; --__z) operator()();}
  93
  94     // property functions
  95     _LIBCPP_INLINE_VISIBILITY
  96     const _Engine& base() const _NOEXCEPT {return __e_;}
  97
  98     template<class _Eng, size_t _Pp, size_t _Rp>
  99     friend
 100     bool
 101     operator==(
 102         const discard_block_engine<_Eng, _Pp, _Rp>& __x,
 103         const discard_block_engine<_Eng, _Pp, _Rp>& __y);
 104
 105     template<class _Eng, size_t _Pp, size_t _Rp>
 106     friend
 107     bool
 108     operator!=(
 109         const discard_block_engine<_Eng, _Pp, _Rp>& __x,
 110         const discard_block_engine<_Eng, _Pp, _Rp>& __y);
 111
 112     template <class _CharT, class _Traits,
 113               class _Eng, size_t _Pp, size_t _Rp>
 114     friend
 115     basic_ostream<_CharT, _Traits>&
 116     operator<<(basic_ostream<_CharT, _Traits>& __os,
 117                const discard_block_engine<_Eng, _Pp, _Rp>& __x);
 118
 119     template <class _CharT, class _Traits,
 120               class _Eng, size_t _Pp, size_t _Rp>
 121     friend
 122     basic_istream<_CharT, _Traits>&
 123     operator>>(basic_istream<_CharT, _Traits>& __is,
 124                discard_block_engine<_Eng, _Pp, _Rp>& __x);
 125 };
 126
 127 template<class _Engine, size_t __p, size_t __r>
 128     _LIBCPP_CONSTEXPR const size_t discard_block_engine<_Engine, __p, __r>::block_size;
 129
 130 template<class _Engine, size_t __p, size_t __r>
 131     _LIBCPP_CONSTEXPR const size_t discard_block_engine<_Engine, __p, __r>::used_block;
 132
 133 template<class _Engine, size_t __p, size_t __r>
 134 typename discard_block_engine<_Engine, __p, __r>::result_type
 135 discard_block_engine<_Engine, __p, __r>::operator()()
 136 {
 137     if (__n_ >= static_cast<int>(__r))
 138     {
 139         __e_.discard(__p - __r);
 140         __n_ = 0;
 141     }
 142     ++__n_;
 143     return __e_();
 144 }
 145
 146 template<class _Eng, size_t _Pp, size_t _Rp>
 147 inline _LIBCPP_INLINE_VISIBILITY
 148 bool
 149 operator==(const discard_block_engine<_Eng, _Pp, _Rp>& __x,
 150            const discard_block_engine<_Eng, _Pp, _Rp>& __y)
 151 {
 152     return __x.__n_ == __y.__n_ && __x.__e_ == __y.__e_;
 153 }
 154
 155 template<class _Eng, size_t _Pp, size_t _Rp>
 156 inline _LIBCPP_INLINE_VISIBILITY
 157 bool
 158 operator!=(const discard_block_engine<_Eng, _Pp, _Rp>& __x,
 159            const discard_block_engine<_Eng, _Pp, _Rp>& __y)
 160 {
 161     return !(__x == __y);
 162 }
 163
 164 template <class _CharT, class _Traits,
 165           class _Eng, size_t _Pp, size_t _Rp>
 166 _LIBCPP_HIDE_FROM_ABI basic_ostream<_CharT, _Traits>&
 167 operator<<(basic_ostream<_CharT, _Traits>& __os,
 168            const discard_block_engine<_Eng, _Pp, _Rp>& __x)
 169 {
 170     __save_flags<_CharT, _Traits> __lx(__os);
 171     typedef basic_ostream<_CharT, _Traits> _Ostream;
 172     __os.flags(_Ostream::dec | _Ostream::left);
 173     _CharT __sp = __os.widen(' ');
 174     __os.fill(__sp);
 175     return __os << __x.__e_ << __sp << __x.__n_;
 176 }
 177
 178 template <class _CharT, class _Traits,
 179           class _Eng, size_t _Pp, size_t _Rp>
 180 _LIBCPP_HIDE_FROM_ABI basic_istream<_CharT, _Traits>&
 181 operator>>(basic_istream<_CharT, _Traits>& __is,
 182            discard_block_engine<_Eng, _Pp, _Rp>& __x)
 183 {
 184     __save_flags<_CharT, _Traits> __lx(__is);
 185     typedef basic_istream<_CharT, _Traits> _Istream;
 186     __is.flags(_Istream::dec | _Istream::skipws);
 187     _Eng __e;
 188     int __n;
 189     __is >> __e >> __n;
 190     if (!__is.fail())
 191     {
 192         __x.__e_ = __e;
 193         __x.__n_ = __n;
 194     }
 195     return __is;
 196 }
 197
 198 _LIBCPP_END_NAMESPACE_STD
 199
 200 _LIBCPP_POP_MACROS
 201
 202 #endif // _LIBCPP___RANDOM_DISCARD_BLOCK_ENGINE_H