text: //
  // detail/impl/win_thread.ipp
  // ~~~~~~~~~~~~~~~~~~~~~~~~~~
  //
  // Copyright (c) 2003-2020 Christopher M. Kohlhoff (chris at kohlhoff dot com)
  //
  // Distributed under the Boost Software License, Version 1.0. (See accompanying
  // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  //
  
  #ifndef BOOST_ASIO_DETAIL_IMPL_WIN_THREAD_IPP
  #define BOOST_ASIO_DETAIL_IMPL_WIN_THREAD_IPP
  
  #if defined(_MSC_VER) && (_MSC_VER >= 1200)
  # pragma once
  #endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
  
  #include <boost/asio/detail/config.hpp>
  
  #if defined(BOOST_ASIO_WINDOWS) \
    && !defined(BOOST_ASIO_WINDOWS_APP) \
    && !defined(UNDER_CE)
  
  #include <process.h>
  #include <boost/asio/detail/throw_error.hpp>
  #include <boost/asio/detail/win_thread.hpp>
  #include <boost/asio/error.hpp>
  
  #include <boost/asio/detail/push_options.hpp>
  
  namespace boost {
  namespace asio {
  namespace detail {
  
  win_thread::~win_thread()
  {
    ::CloseHandle(thread_);
  
    // The exit_event_ handle is deliberately allowed to leak here since it
    // is an error for the owner of an internal thread not to join() it.
  }
  
  void win_thread::join()
  {
    HANDLE handles[2] = { exit_event_, thread_ };
    ::WaitForMultipleObjects(2, handles, FALSE, INFINITE);
    ::CloseHandle(exit_event_);
    if (terminate_threads())
    {
      ::TerminateThread(thread_, 0);
    }
    else
    {
      ::QueueUserAPC(apc_function, thread_, 0);
      ::WaitForSingleObject(thread_, INFINITE);
    }
  }
  
  std::size_t win_thread::hardware_concurrency()
  {
    SYSTEM_INFO system_info;
    ::GetSystemInfo(&system_info);
    return system_info.dwNumberOfProcessors;
  }
  
  void win_thread::start_thread(func_base* arg, unsigned int stack_size)
  {
    ::HANDLE entry_event = 0;
    arg->entry_event_ = entry_event = ::CreateEventW(0, true, false, 0);
    if (!entry_event)
    {
      DWORD last_error = ::GetLastError();
      delete arg;
      boost::system::error_code ec(last_error,
          boost::asio::error::get_system_category());
      boost::asio::detail::throw_error(ec, "thread.entry_event");
    }
  
    arg->exit_event_ = exit_event_ = ::CreateEventW(0, true, false, 0);
    if (!exit_event_)
    {
      DWORD last_error = ::GetLastError();
      delete arg;
      boost::system::error_code ec(last_error,
          boost::asio::error::get_system_category());
      boost::asio::detail::throw_error(ec, "thread.exit_event");
    }
  
    unsigned int thread_id = 0;
    thread_ = reinterpret_cast<HANDLE>(::_beginthreadex(0,
          stack_size, win_thread_function, arg, 0, &thread_id));
    if (!thread_)
    {
      DWORD last_error = ::GetLastError();
      delete arg;
      if (entry_event)
        ::CloseHandle(entry_event);
      if (exit_event_)
        ::CloseHandle(exit_event_);
      boost::system::error_code ec(last_error,
          boost::asio::error::get_system_category());
      boost::asio::detail::throw_error(ec, "thread");
    }
  
    if (entry_event)
    {
      ::WaitForSingleObject(entry_event, INFINITE);
      ::CloseHandle(entry_event);
    }
  }
  
  unsigned int __stdcall win_thread_function(void* arg)
  {
    win_thread::auto_func_base_ptr func = {
        static_cast<win_thread::func_base*>(arg) };
  
    ::SetEvent(func.ptr->entry_event_);
  
    func.ptr->run();
  
    // Signal that the thread has finished its work, but rather than returning go
    // to sleep to put the thread into a well known state. If the thread is being
    // joined during global object destruction then it may be killed using
    // TerminateThread (to avoid a deadlock in DllMain). Otherwise, the SleepEx
    // call will be interrupted using QueueUserAPC and the thread will shut down
    // cleanly.
    HANDLE exit_event = func.ptr->exit_event_;
    delete func.ptr;
    func.ptr = 0;
    ::SetEvent(exit_event);
    ::SleepEx(INFINITE, TRUE);
  
    return 0;
  }
  
  #if defined(WINVER) && (WINVER < 0x0500)
  void __stdcall apc_function(ULONG) {}
  #else
  void __stdcall apc_function(ULONG_PTR) {}
  #endif
  
  } // namespace detail
  } // namespace asio
  } // namespace boost
  
  #include <boost/asio/detail/pop_options.hpp>
  
  #endif // defined(BOOST_ASIO_WINDOWS)
         // && !defined(BOOST_ASIO_WINDOWS_APP)
         // && !defined(UNDER_CE)
  
  #endif // BOOST_ASIO_DETAIL_IMPL_WIN_THREAD_IPP
  