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_ptr.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_BEGIN_NAMESPACE_STD
  29
  30 struct _LIBCPP_TEMPLATE_VIS once_flag;
  31
  32 #ifndef _LIBCPP_CXX03_LANG
  33
  34 template <class _Callable, class... _Args>
  35 _LIBCPP_HIDE_FROM_ABI void call_once(once_flag&, _Callable&&, _Args&&...);
  36
  37 #else // _LIBCPP_CXX03_LANG
  38
  39 template <class _Callable>
  40 _LIBCPP_HIDE_FROM_ABI void call_once(once_flag&, _Callable&);
  41
  42 template <class _Callable>
  43 _LIBCPP_HIDE_FROM_ABI void call_once(once_flag&, const _Callable&);
  44
  45 #endif // _LIBCPP_CXX03_LANG
  46
  47 struct _LIBCPP_TEMPLATE_VIS once_flag {
  48   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR once_flag() _NOEXCEPT : __state_(_Unset) {}
  49   once_flag(const once_flag&)            = delete;
  50   once_flag& operator=(const once_flag&) = delete;
  51
  52 #if defined(_LIBCPP_ABI_MICROSOFT)
  53   typedef uintptr_t _State_type;
  54 #else
  55   typedef unsigned long _State_type;
  56 #endif
  57
  58   static const _State_type _Unset    = 0;
  59   static const _State_type _Pending  = 1;
  60   static const _State_type _Complete = ~_State_type(0);
  61
  62 private:
  63   _State_type __state_;
  64
  65 #ifndef _LIBCPP_CXX03_LANG
  66   template <class _Callable, class... _Args>
  67   friend void call_once(once_flag&, _Callable&&, _Args&&...);
  68 #else  // _LIBCPP_CXX03_LANG
  69   template <class _Callable>
  70   friend void call_once(once_flag&, _Callable&);
  71
  72   template <class _Callable>
  73   friend void call_once(once_flag&, const _Callable&);
  74 #endif // _LIBCPP_CXX03_LANG
  75 };
  76
  77 #ifndef _LIBCPP_CXX03_LANG
  78
  79 template <class _Fp>
  80 class __call_once_param {
  81   _Fp& __f_;
  82
  83 public:
  84   _LIBCPP_HIDE_FROM_ABI explicit __call_once_param(_Fp& __f) : __f_(__f) {}
  85
  86   _LIBCPP_HIDE_FROM_ABI void operator()() {
  87     typedef typename __make_tuple_indices<tuple_size<_Fp>::value, 1>::type _Index;
  88     __execute(_Index());
  89   }
  90
  91 private:
  92   template <size_t... _Indices>
  93   _LIBCPP_HIDE_FROM_ABI void __execute(__tuple_indices<_Indices...>) {
  94     _VSTD::__invoke(_VSTD::get<0>(_VSTD::move(__f_)), _VSTD::get<_Indices>(_VSTD::move(__f_))...);
  95   }
  96 };
  97
  98 #else
  99
 100 template <class _Fp>
 101 class __call_once_param {
 102   _Fp& __f_;
 103
 104 public:
 105   _LIBCPP_HIDE_FROM_ABI explicit __call_once_param(_Fp& __f) : __f_(__f) {}
 106
 107   _LIBCPP_HIDE_FROM_ABI void operator()() { __f_(); }
 108 };
 109
 110 #endif
 111
 112 template <class _Fp>
 113 void _LIBCPP_HIDE_FROM_ABI __call_once_proxy(void* __vp) {
 114   __call_once_param<_Fp>* __p = static_cast<__call_once_param<_Fp>*>(__vp);
 115   (*__p)();
 116 }
 117
 118 _LIBCPP_EXPORTED_FROM_ABI void __call_once(volatile once_flag::_State_type&, void*, void (*)(void*));
 119
 120 #ifndef _LIBCPP_CXX03_LANG
 121
 122 template <class _Callable, class... _Args>
 123 inline _LIBCPP_HIDE_FROM_ABI void call_once(once_flag& __flag, _Callable&& __func, _Args&&... __args) {
 124   if (__libcpp_acquire_load(&__flag.__state_) != once_flag::_Complete) {
 125     typedef tuple<_Callable&&, _Args&&...> _Gp;
 126     _Gp __f(_VSTD::forward<_Callable>(__func), _VSTD::forward<_Args>(__args)...);
 127     __call_once_param<_Gp> __p(__f);
 128     std::__call_once(__flag.__state_, &__p, &__call_once_proxy<_Gp>);
 129   }
 130 }
 131
 132 #else // _LIBCPP_CXX03_LANG
 133
 134 template <class _Callable>
 135 inline _LIBCPP_HIDE_FROM_ABI void call_once(once_flag& __flag, _Callable& __func) {
 136   if (__libcpp_acquire_load(&__flag.__state_) != once_flag::_Complete) {
 137     __call_once_param<_Callable> __p(__func);
 138     std::__call_once(__flag.__state_, &__p, &__call_once_proxy<_Callable>);
 139   }
 140 }
 141
 142 template <class _Callable>
 143 inline _LIBCPP_HIDE_FROM_ABI void call_once(once_flag& __flag, const _Callable& __func) {
 144   if (__libcpp_acquire_load(&__flag.__state_) != once_flag::_Complete) {
 145     __call_once_param<const _Callable> __p(__func);
 146     std::__call_once(__flag.__state_, &__p, &__call_once_proxy<const _Callable>);
 147   }
 148 }
 149
 150 #endif // _LIBCPP_CXX03_LANG
 151
 152 _LIBCPP_END_NAMESPACE_STD
 153
 154 #endif // _LIBCPP___MUTEX_ONCE_FLAG_H