libstdc++-v3/include/experimental/timer

// <experimental/timer> -*- C++ -*-

// Copyright (C) 2015-2025 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 experimental/timer
 *  This is a TS C++ Library header.
 *  @ingroup networking-ts
 */

#ifndef _GLIBCXX_EXPERIMENTAL_TIMER
#define _GLIBCXX_EXPERIMENTAL_TIMER 1

#ifdef _GLIBCXX_SYSHDR
#pragma GCC system_header
#endif

#include <bits/requires_hosted.h> // experimental is currently omitted

#if __cplusplus >= 201402L

#include <bits/chrono.h>
#include <system_error>
#include <thread>
#include <experimental/netfwd>
#include <experimental/io_context>
#include <experimental/bits/net.h>

namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION
namespace experimental
{
namespace net
{
inline namespace v1
{

  /** @addtogroup networking-ts
   *  @{
   */

  template<typename _Clock>
    struct wait_traits
    {
      static typename _Clock::duration
      to_wait_duration(const typename _Clock::duration& __d)
      { return __d; }

      static typename _Clock::duration
      to_wait_duration(const typename _Clock::time_point& __t)
      {
	auto __now = _Clock::now();
	auto __diff = __t - __now;
	if (__diff > _Clock::duration::max())
	  return _Clock::duration::max();
	if (__diff < _Clock::duration::min())
	  return _Clock::duration::min();
	return __diff;
      }
    };

  template<typename _Clock, typename _WaitTraits>
    class basic_waitable_timer
    {
    public:
      // types:

      using executor_type = io_context::executor_type;
      using clock_type = _Clock;
      using duration = typename clock_type::duration;
      using time_point = typename clock_type::time_point;
      using traits_type = _WaitTraits;

      // construct / copy / destroy:

      explicit
      basic_waitable_timer(io_context& __ctx)
      : _M_ex(__ctx.get_executor()), _M_expiry()
      { }

      basic_waitable_timer(io_context& __ctx, const time_point& __t)
      : _M_ex(__ctx.get_executor()), _M_expiry(__t)
      { }

      basic_waitable_timer(io_context& __ctx, const duration& __d)
      : _M_ex(__ctx.get_executor()), _M_expiry(_Clock::now() + __d)
      { }

      basic_waitable_timer(const basic_waitable_timer&) = delete;

      basic_waitable_timer(basic_waitable_timer&& __rhs)
      : _M_ex(std::move(__rhs._M_ex)), _M_expiry(__rhs._M_expiry)
      {
	_M_key.swap(__rhs._M_key);
	__rhs._M_expiry = time_point{};
      }

      ~basic_waitable_timer() { cancel(); }

      basic_waitable_timer& operator=(const basic_waitable_timer&) = delete;

      basic_waitable_timer&
      operator=(basic_waitable_timer&& __rhs)
      {
	if (this == std::addressof(__rhs))
	  return *this;
	cancel();
	_M_ex = std::move(__rhs._M_ex);
	_M_expiry = __rhs._M_expiry;
	__rhs._M_expiry = time_point{};
	_M_key.swap(__rhs._M_key);
	return *this;
      }

      // basic_waitable_timer operations:

      executor_type get_executor() noexcept { return _M_ex; }

      size_t cancel() { return _M_ex.context().cancel(*this); }
      size_t cancel_one() { return _M_ex.context().cancel_one(*this); }

      time_point expiry() const { return _M_expiry; }

      size_t expires_at(const time_point& __t)
      {
	size_t __cancelled = cancel();
	_M_expiry = __t;
	return __cancelled;
      }

      size_t expires_after(const duration& __d)
      { return expires_at(_Clock::now() + __d); }

      void wait();
      void wait(error_code& __ec);

      template<typename _CompletionToken>
	__deduced_t<_CompletionToken, void(error_code)>
	async_wait(_CompletionToken&& __token)
	{
	  async_completion<_CompletionToken, void(error_code)> __init(__token);
	  _M_ex.context().async_wait(*this,
				     std::move(__init.completion_handler));
	  return __init.result.get();
	}

    private:
      executor_type _M_ex;
      time_point _M_expiry;

      struct _Key { };  // TODO move _M_expiry into here?
      unique_ptr<_Key> _M_key{new _Key};

      friend class io_context;
    };

  using system_timer = basic_waitable_timer<chrono::system_clock>;
  using steady_timer = basic_waitable_timer<chrono::steady_clock>;
  using high_resolution_timer
    = basic_waitable_timer<chrono::high_resolution_clock>;

  template<typename _Clock, typename _WaitTraits>
    void
    basic_waitable_timer<_Clock, _WaitTraits>::wait()
    {
      _M_ex.dispatch([this] {
	  while (clock_type::now() < _M_expiry)
	    this_thread::sleep_for(traits_type::to_wait_duration(_M_expiry));
      }, allocator<void>{});
    }

  template<typename _Clock, typename _WaitTraits>
    void
    basic_waitable_timer<_Clock, _WaitTraits>::wait(error_code&)
    {
      _M_ex.dispatch([this] {
	  while (clock_type::now() < _M_expiry)
	    this_thread::sleep_for(traits_type::to_wait_duration(_M_expiry));
      }, allocator<void>{});
    }

  /// @}

} // namespace v1
} // namespace net
} // namespace experimental
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace std

#endif // C++14

#endif // _GLIBCXX_EXPERIMENTAL_TIMER