libcxx/include/__mutex/once_flag.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___MUTEX_ONCE_FLAG_H
  10 #define _LIBCPP___MUTEX_ONCE_FLAG_H
  11
  12 #include <__config>
  13 #include <__functional/invoke.h>
  14 #include <__memory/shared_count.h> // __libcpp_acquire_load
  15 #include <__tuple/tuple_indices.h>
  16 #include <__tuple/tuple_size.h>
  17 #include <__utility/forward.h>
  18 #include <__utility/move.h>
  19 #include <cstdint>
  20 #ifndef _LIBCPP_CXX03_LANG
  21 #  include <tuple>
  22 #endif
  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 struct _LIBCPP_TEMPLATE_VIS once_flag;
  34
  35 #ifndef _LIBCPP_CXX03_LANG
  36
  37 template <class _Callable, class... _Args>
  38 _LIBCPP_HIDE_FROM_ABI void call_once(once_flag&, _Callable&&, _Args&&...);
  39
  40 #else // _LIBCPP_CXX03_LANG
  41
  42 template <class _Callable>
  43 _LIBCPP_HIDE_FROM_ABI void call_once(once_flag&, _Callable&);
  44
  45 template <class _Callable>
  46 _LIBCPP_HIDE_FROM_ABI void call_once(once_flag&, const _Callable&);
  47
  48 #endif // _LIBCPP_CXX03_LANG
  49
  50 struct _LIBCPP_TEMPLATE_VIS once_flag {
  51   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR once_flag() _NOEXCEPT : __state_(_Unset) {}
  52   once_flag(const once_flag&)            = delete;
  53   once_flag& operator=(const once_flag&) = delete;
  54
  55 #if defined(_LIBCPP_ABI_MICROSOFT)
  56   typedef uintptr_t _State_type;
  57 #else
  58   typedef unsigned long _State_type;
  59 #endif
  60
  61   static const _State_type _Unset    = 0;
  62   static const _State_type _Pending  = 1;
  63   static const _State_type _Complete = ~_State_type(0);
  64
  65 private:
  66   _State_type __state_;
  67
  68 #ifndef _LIBCPP_CXX03_LANG
  69   template <class _Callable, class... _Args>
  70   friend void call_once(once_flag&, _Callable&&, _Args&&...);
  71 #else  // _LIBCPP_CXX03_LANG
  72   template <class _Callable>
  73   friend void call_once(once_flag&, _Callable&);
  74
  75   template <class _Callable>
  76   friend void call_once(once_flag&, const _Callable&);
  77 #endif // _LIBCPP_CXX03_LANG
  78 };
  79
  80 #ifndef _LIBCPP_CXX03_LANG
  81
  82 template <class _Fp>
  83 class __call_once_param {
  84   _Fp& __f_;
  85
  86 public:
  87   _LIBCPP_HIDE_FROM_ABI explicit __call_once_param(_Fp& __f) : __f_(__f) {}
  88
  89   _LIBCPP_HIDE_FROM_ABI void operator()() {
  90     typedef typename __make_tuple_indices<tuple_size<_Fp>::value, 1>::type _Index;
  91     __execute(_Index());
  92   }
  93
  94 private:
  95   template <size_t... _Indices>
  96   _LIBCPP_HIDE_FROM_ABI void __execute(__tuple_indices<_Indices...>) {
  97     std::__invoke(std::get<0>(std::move(__f_)), std::get<_Indices>(std::move(__f_))...);
  98   }
  99 };
 100
 101 #else
 102
 103 template <class _Fp>
 104 class __call_once_param {
 105   _Fp& __f_;
 106
 107 public:
 108   _LIBCPP_HIDE_FROM_ABI explicit __call_once_param(_Fp& __f) : __f_(__f) {}
 109
 110   _LIBCPP_HIDE_FROM_ABI void operator()() { __f_(); }
 111 };
 112
 113 #endif
 114
 115 template <class _Fp>
 116 void _LIBCPP_HIDE_FROM_ABI __call_once_proxy(void* __vp) {
 117   __call_once_param<_Fp>* __p = static_cast<__call_once_param<_Fp>*>(__vp);
 118   (*__p)();
 119 }
 120
 121 _LIBCPP_EXPORTED_FROM_ABI void __call_once(volatile once_flag::_State_type&, void*, void (*)(void*));
 122
 123 #ifndef _LIBCPP_CXX03_LANG
 124
 125 template <class _Callable, class... _Args>
 126 inline _LIBCPP_HIDE_FROM_ABI void call_once(once_flag& __flag, _Callable&& __func, _Args&&... __args) {
 127   if (__libcpp_acquire_load(&__flag.__state_) != once_flag::_Complete) {
 128     typedef tuple<_Callable&&, _Args&&...> _Gp;
 129     _Gp __f(std::forward<_Callable>(__func), std::forward<_Args>(__args)...);
 130     __call_once_param<_Gp> __p(__f);
 131     std::__call_once(__flag.__state_, &__p, &__call_once_proxy<_Gp>);
 132   }
 133 }
 134
 135 #else // _LIBCPP_CXX03_LANG
 136
 137 template <class _Callable>
 138 inline _LIBCPP_HIDE_FROM_ABI void call_once(once_flag& __flag, _Callable& __func) {
 139   if (__libcpp_acquire_load(&__flag.__state_) != once_flag::_Complete) {
 140     __call_once_param<_Callable> __p(__func);
 141     std::__call_once(__flag.__state_, &__p, &__call_once_proxy<_Callable>);
 142   }
 143 }
 144
 145 template <class _Callable>
 146 inline _LIBCPP_HIDE_FROM_ABI void call_once(once_flag& __flag, const _Callable& __func) {
 147   if (__libcpp_acquire_load(&__flag.__state_) != once_flag::_Complete) {
 148     __call_once_param<const _Callable> __p(__func);
 149     std::__call_once(__flag.__state_, &__p, &__call_once_proxy<const _Callable>);
 150   }
 151 }
 152
 153 #endif // _LIBCPP_CXX03_LANG
 154
 155 _LIBCPP_END_NAMESPACE_STD
 156
 157 _LIBCPP_POP_MACROS
 158
 159 #endif // _LIBCPP___MUTEX_ONCE_FLAG_H