thread
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// <thread> -*- C++ -*-
// Copyright (C) 2008-2023 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library. This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 3, or (at your option)
// any later version.
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.
// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
// <http://www.gnu.org/licenses/>.
/** @file include/thread
* This is a Standard C++ Library header.
*/
#ifndef _GLIBCXX_THREAD
#define _GLIBCXX_THREAD 1
#pragma GCC system_header
#include <bits/requires_hosted.h> // concurrency
#if __cplusplus < 201103L
# include <bits/c++0x_warning.h>
#else
#if __cplusplus > 201703L
# include <compare> // std::strong_ordering
# include <stop_token> // std::stop_source, std::stop_token, std::nostopstate
#endif
#include <bits/std_thread.h> // std::thread, get_id, yield
#include <bits/this_thread_sleep.h> // std::this_thread::sleep_for, sleep_until
namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION
/**
* @defgroup threads Threads
* @ingroup concurrency
* @since C++11
*
* Classes for thread support.
* @{
*/
// std::thread is defined in <bits/std_thread.h>
/// @relates std::thread::id @{
#if __cpp_lib_three_way_comparison
inline strong_ordering
operator<=>(thread::id __x, thread::id __y) noexcept
{ return __x._M_thread <=> __y._M_thread; }
#else
inline bool
operator!=(thread::id __x, thread::id __y) noexcept
{ return !(__x == __y); }
inline bool
operator<(thread::id __x, thread::id __y) noexcept
{
// Pthreads doesn't define any way to do this, so we just have to
// assume native_handle_type is LessThanComparable.
return __x._M_thread < __y._M_thread;
}
inline bool
operator<=(thread::id __x, thread::id __y) noexcept
{ return !(__y < __x); }
inline bool
operator>(thread::id __x, thread::id __y) noexcept
{ return __y < __x; }
inline bool
operator>=(thread::id __x, thread::id __y) noexcept
{ return !(__x < __y); }
#endif // __cpp_lib_three_way_comparison
template<class _CharT, class _Traits>
inline basic_ostream<_CharT, _Traits>&
operator<<(basic_ostream<_CharT, _Traits>& __out, thread::id __id)
{
if (__id == thread::id())
return __out << "thread::id of a non-executing thread";
else
return __out << __id._M_thread;
}
/// @}
#ifdef __cpp_lib_jthread
/// @cond undocumented
#ifndef __STRICT_ANSI__
template<typename _Callable, typename... _Args>
constexpr bool __pmf_expects_stop_token = false;
template<typename _Callable, typename _Obj, typename... _Args>
constexpr bool __pmf_expects_stop_token<_Callable, _Obj, _Args...>
= __and_<is_member_function_pointer<remove_reference_t<_Callable>>,
is_invocable<_Callable, _Obj, stop_token, _Args...>>::value;
#endif
/// @endcond
/** A thread with cancellation and automatic joining.
*
* Unlike `std::thread`, destroying a joinable `std::jthread` will not
* terminate the process. Instead, it will try to request its thread to
* stop, then will join it.
*
* A `std::jthread` has a `std::stop_source` member which will be passed
* as the first argument to the callable that runs in the new thread
* (as long as the callable will accept that argument). That can then
* be used to send a stop request that the new thread can test for.
*
* @headerfile thread
* @since C++20
*/
class jthread
{
public:
using id = thread::id;
using native_handle_type = thread::native_handle_type;
jthread() noexcept
: _M_stop_source{nostopstate}
{ }
template<typename _Callable, typename... _Args,
typename = enable_if_t<!is_same_v<remove_cvref_t<_Callable>,
jthread>>>
explicit
jthread(_Callable&& __f, _Args&&... __args)
: _M_thread{_S_create(_M_stop_source, std::forward<_Callable>(__f),
std::forward<_Args>(__args)...)}
{ }
jthread(const jthread&) = delete;
jthread(jthread&&) noexcept = default;
~jthread()
{
if (joinable())
{
request_stop();
join();
}
}
jthread&
operator=(const jthread&) = delete;
jthread&
operator=(jthread&& __other) noexcept
{
std::jthread(std::move(__other)).swap(*this);
return *this;
}
void
swap(jthread& __other) noexcept
{
std::swap(_M_stop_source, __other._M_stop_source);
std::swap(_M_thread, __other._M_thread);
}
[[nodiscard]] bool
joinable() const noexcept
{
return _M_thread.joinable();
}
void
join()
{
_M_thread.join();
}
void
detach()
{
_M_thread.detach();
}
[[nodiscard]] id
get_id() const noexcept
{
return _M_thread.get_id();
}
[[nodiscard]] native_handle_type
native_handle()
{
return _M_thread.native_handle();
}
[[nodiscard]] static unsigned
hardware_concurrency() noexcept
{
return thread::hardware_concurrency();
}
[[nodiscard]] stop_source
get_stop_source() noexcept
{
return _M_stop_source;
}
[[nodiscard]] stop_token
get_stop_token() const noexcept
{
return _M_stop_source.get_token();
}
bool request_stop() noexcept
{
return _M_stop_source.request_stop();
}
friend void swap(jthread& __lhs, jthread& __rhs) noexcept
{
__lhs.swap(__rhs);
}
private:
template<typename _Callable, typename... _Args>
static thread
_S_create(stop_source& __ssrc, _Callable&& __f, _Args&&... __args)
{
#ifndef __STRICT_ANSI__
if constexpr (__pmf_expects_stop_token<_Callable, _Args...>)
return _S_create_pmf(__ssrc, __f, std::forward<_Args>(__args)...);
else
#endif
if constexpr(is_invocable_v<decay_t<_Callable>, stop_token,
decay_t<_Args>...>)
return thread{std::forward<_Callable>(__f), __ssrc.get_token(),
std::forward<_Args>(__args)...};
else
{
static_assert(is_invocable_v<decay_t<_Callable>,
decay_t<_Args>...>,
"std::jthread arguments must be invocable after"
" conversion to rvalues");
return thread{std::forward<_Callable>(__f),
std::forward<_Args>(__args)...};
}
}
#ifndef __STRICT_ANSI__
template<typename _Callable, typename _Obj, typename... _Args>
static thread
_S_create_pmf(stop_source& __ssrc, _Callable __f, _Obj&& __obj,
_Args&&... __args)
{
return thread{__f, std::forward<_Obj>(__obj), __ssrc.get_token(),
std::forward<_Args>(__args)...};
}
#endif
stop_source _M_stop_source;
thread _M_thread;
};
#endif // __cpp_lib_jthread
/// @} group threads
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace
#endif // C++11
#endif // _GLIBCXX_THREAD