chromium/third_party/libc++/src/include/__mutex/once_flag.h

//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

#ifndef _LIBCPP___MUTEX_ONCE_FLAG_H
#define _LIBCPP___MUTEX_ONCE_FLAG_H

#include <__config>
#include <__functional/invoke.h>
#include <__memory/shared_ptr.h> // __libcpp_acquire_load
#include <__tuple/tuple_indices.h>
#include <__tuple/tuple_size.h>
#include <__utility/forward.h>
#include <__utility/move.h>
#include <cstdint>
#ifndef _LIBCPP_CXX03_LANG
#  include <tuple>
#endif

#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
#  pragma GCC system_header
#endif

_LIBCPP_PUSH_MACROS
#include <__undef_macros>

_LIBCPP_BEGIN_NAMESPACE_STD

struct _LIBCPP_TEMPLATE_VIS once_flag;

#ifndef _LIBCPP_CXX03_LANG

template <class _Callable, class... _Args>
_LIBCPP_HIDE_FROM_ABI void call_once(once_flag&, _Callable&&, _Args&&...);

#else // _LIBCPP_CXX03_LANG

template <class _Callable>
_LIBCPP_HIDE_FROM_ABI void call_once(once_flag&, _Callable&);

template <class _Callable>
_LIBCPP_HIDE_FROM_ABI void call_once(once_flag&, const _Callable&);

#endif // _LIBCPP_CXX03_LANG

struct _LIBCPP_TEMPLATE_VIS once_flag { … };

#ifndef _LIBCPP_CXX03_LANG

template <class _Fp>
class __call_once_param { … };

#else

template <class _Fp>
class __call_once_param {
  _Fp& __f_;

public:
  _LIBCPP_HIDE_FROM_ABI explicit __call_once_param(_Fp& __f) : __f_(__f) {}

  _LIBCPP_HIDE_FROM_ABI void operator()() { __f_(); }
};

#endif

template <class _Fp>
void _LIBCPP_HIDE_FROM_ABI __call_once_proxy(void* __vp) { … }

_LIBCPP_EXPORTED_FROM_ABI void __call_once(volatile once_flag::_State_type&, void*, void (*)(void*));

#ifndef _LIBCPP_CXX03_LANG

template <class _Callable, class... _Args>
inline _LIBCPP_HIDE_FROM_ABI void call_once(once_flag& __flag, _Callable&& __func, _Args&&... __args) { … }

#else // _LIBCPP_CXX03_LANG

template <class _Callable>
inline _LIBCPP_HIDE_FROM_ABI void call_once(once_flag& __flag, _Callable& __func) {
  if (__libcpp_acquire_load(&__flag.__state_) != once_flag::_Complete) {
    __call_once_param<_Callable> __p(__func);
    std::__call_once(__flag.__state_, &__p, &__call_once_proxy<_Callable>);
  }
}

template <class _Callable>
inline _LIBCPP_HIDE_FROM_ABI void call_once(once_flag& __flag, const _Callable& __func) {
  if (__libcpp_acquire_load(&__flag.__state_) != once_flag::_Complete) {
    __call_once_param<const _Callable> __p(__func);
    std::__call_once(__flag.__state_, &__p, &__call_once_proxy<const _Callable>);
  }
}

#endif // _LIBCPP_CXX03_LANG

_LIBCPP_END_NAMESPACE_STD

_LIBCPP_POP_MACROS

#endif // _LIBCPP___MUTEX_ONCE_FLAG_H