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 <__cstddef/size_t.h>
  14 #include <__random/is_seed_sequence.h>
  15 #include <__type_traits/enable_if.h>
  16 #include <__type_traits/is_convertible.h>
  17 #include <__utility/move.h>
  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   _Engine __e_;
  33   int __n_;
  34
  35   static_assert(0 < __r, "discard_block_engine invalid parameters");
  36   static_assert(__r <= __p, "discard_block_engine invalid parameters");
  37 #ifndef _LIBCPP_CXX03_LANG // numeric_limits::max() is not constexpr in C++03
  38   static_assert(__r <= numeric_limits<int>::max(), "discard_block_engine invalid parameters");
  39 #endif
  40
  41 public:
  42   // types
  43   typedef typename _Engine::result_type result_type;
  44
  45   // engine characteristics
  46   static inline _LIBCPP_CONSTEXPR const size_t block_size = __p;
  47   static inline _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 constexpr result_type _Min = _Engine::min();
  54   static constexpr result_type _Max = _Engine::max();
  55 #endif
  56
  57   _LIBCPP_HIDE_FROM_ABI static _LIBCPP_CONSTEXPR result_type min() { return _Engine::min(); }
  58   _LIBCPP_HIDE_FROM_ABI static _LIBCPP_CONSTEXPR result_type max() { return _Engine::max(); }
  59
  60   // constructors and seeding functions
  61   _LIBCPP_HIDE_FROM_ABI discard_block_engine() : __n_(0) {}
  62   _LIBCPP_HIDE_FROM_ABI explicit discard_block_engine(const _Engine& __e) : __e_(__e), __n_(0) {}
  63 #ifndef _LIBCPP_CXX03_LANG
  64   _LIBCPP_HIDE_FROM_ABI explicit discard_block_engine(_Engine&& __e) : __e_(std::move(__e)), __n_(0) {}
  65 #endif // _LIBCPP_CXX03_LANG
  66   _LIBCPP_HIDE_FROM_ABI explicit discard_block_engine(result_type __sd) : __e_(__sd), __n_(0) {}
  67   template <
  68       class _Sseq,
  69       __enable_if_t<__is_seed_sequence<_Sseq, discard_block_engine>::value && !is_convertible<_Sseq, _Engine>::value,
  70                     int> = 0>
  71   _LIBCPP_HIDE_FROM_ABI explicit discard_block_engine(_Sseq& __q) : __e_(__q), __n_(0) {}
  72   _LIBCPP_HIDE_FROM_ABI void seed() {
  73     __e_.seed();
  74     __n_ = 0;
  75   }
  76   _LIBCPP_HIDE_FROM_ABI void seed(result_type __sd) {
  77     __e_.seed(__sd);
  78     __n_ = 0;
  79   }
  80   template <class _Sseq, __enable_if_t<__is_seed_sequence<_Sseq, discard_block_engine>::value, int> = 0>
  81   _LIBCPP_HIDE_FROM_ABI void seed(_Sseq& __q) {
  82     __e_.seed(__q);
  83     __n_ = 0;
  84   }
  85
  86   // generating functions
  87   _LIBCPP_HIDE_FROM_ABI result_type operator()();
  88   _LIBCPP_HIDE_FROM_ABI void discard(unsigned long long __z) {
  89     for (; __z; --__z)
  90       operator()();
  91   }
  92
  93   // property functions
  94   _LIBCPP_HIDE_FROM_ABI const _Engine& base() const _NOEXCEPT { return __e_; }
  95
  96   template <class _Eng, size_t _Pp, size_t _Rp>
  97   friend bool
  98   operator==(const discard_block_engine<_Eng, _Pp, _Rp>& __x, const discard_block_engine<_Eng, _Pp, _Rp>& __y);
  99
 100   template <class _Eng, size_t _Pp, size_t _Rp>
 101   friend bool
 102   operator!=(const discard_block_engine<_Eng, _Pp, _Rp>& __x, const discard_block_engine<_Eng, _Pp, _Rp>& __y);
 103
 104   template <class _CharT, class _Traits, class _Eng, size_t _Pp, size_t _Rp>
 105   friend basic_ostream<_CharT, _Traits>&
 106   operator<<(basic_ostream<_CharT, _Traits>& __os, const discard_block_engine<_Eng, _Pp, _Rp>& __x);
 107
 108   template <class _CharT, class _Traits, class _Eng, size_t _Pp, size_t _Rp>
 109   friend basic_istream<_CharT, _Traits>&
 110   operator>>(basic_istream<_CharT, _Traits>& __is, discard_block_engine<_Eng, _Pp, _Rp>& __x);
 111 };
 112
 113 template <class _Engine, size_t __p, size_t __r>
 114 typename discard_block_engine<_Engine, __p, __r>::result_type discard_block_engine<_Engine, __p, __r>::operator()() {
 115   if (__n_ >= static_cast<int>(__r)) {
 116     __e_.discard(__p - __r);
 117     __n_ = 0;
 118   }
 119   ++__n_;
 120   return __e_();
 121 }
 122
 123 template <class _Eng, size_t _Pp, size_t _Rp>
 124 inline _LIBCPP_HIDE_FROM_ABI bool
 125 operator==(const discard_block_engine<_Eng, _Pp, _Rp>& __x, const discard_block_engine<_Eng, _Pp, _Rp>& __y) {
 126   return __x.__n_ == __y.__n_ && __x.__e_ == __y.__e_;
 127 }
 128
 129 template <class _Eng, size_t _Pp, size_t _Rp>
 130 inline _LIBCPP_HIDE_FROM_ABI bool
 131 operator!=(const discard_block_engine<_Eng, _Pp, _Rp>& __x, const discard_block_engine<_Eng, _Pp, _Rp>& __y) {
 132   return !(__x == __y);
 133 }
 134
 135 template <class _CharT, class _Traits, class _Eng, size_t _Pp, size_t _Rp>
 136 _LIBCPP_HIDE_FROM_ABI basic_ostream<_CharT, _Traits>&
 137 operator<<(basic_ostream<_CharT, _Traits>& __os, const discard_block_engine<_Eng, _Pp, _Rp>& __x) {
 138   __save_flags<_CharT, _Traits> __lx(__os);
 139   typedef basic_ostream<_CharT, _Traits> _Ostream;
 140   __os.flags(_Ostream::dec | _Ostream::left);
 141   _CharT __sp = __os.widen(' ');
 142   __os.fill(__sp);
 143   return __os << __x.__e_ << __sp << __x.__n_;
 144 }
 145
 146 template <class _CharT, class _Traits, class _Eng, size_t _Pp, size_t _Rp>
 147 _LIBCPP_HIDE_FROM_ABI basic_istream<_CharT, _Traits>&
 148 operator>>(basic_istream<_CharT, _Traits>& __is, discard_block_engine<_Eng, _Pp, _Rp>& __x) {
 149   __save_flags<_CharT, _Traits> __lx(__is);
 150   typedef basic_istream<_CharT, _Traits> _Istream;
 151   __is.flags(_Istream::dec | _Istream::skipws);
 152   _Eng __e;
 153   int __n;
 154   __is >> __e >> __n;
 155   if (!__is.fail()) {
 156     __x.__e_ = __e;
 157     __x.__n_ = __n;
 158   }
 159   return __is;
 160 }
 161
 162 _LIBCPP_END_NAMESPACE_STD
 163
 164 _LIBCPP_POP_MACROS
 165
 166 #endif // _LIBCPP___RANDOM_DISCARD_BLOCK_ENGINE_H