text: //
  // impl/thread_pool.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 ASIO_IMPL_THREAD_POOL_IPP
  #define ASIO_IMPL_THREAD_POOL_IPP
  
  #if defined(_MSC_VER) && (_MSC_VER >= 1200)
  # pragma once
  #endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
  
  #include "asio/detail/config.hpp"
  #include <stdexcept>
  #include "asio/thread_pool.hpp"
  #include "asio/detail/throw_exception.hpp"
  
  #include "asio/detail/push_options.hpp"
  
  namespace asio {
  
  struct thread_pool::thread_function
  {
    detail::scheduler* scheduler_;
  
    void operator()()
    {
  #if !defined(ASIO_NO_EXCEPTIONS)
      try
      {
  #endif// !defined(ASIO_NO_EXCEPTIONS)
        asio::error_code ec;
        scheduler_->run(ec);
  #if !defined(ASIO_NO_EXCEPTIONS)
      }
      catch (...)
      {
        std::terminate();
      }
  #endif// !defined(ASIO_NO_EXCEPTIONS)
    }
  };
  
  #if !defined(ASIO_NO_TS_EXECUTORS)
  namespace detail {
  
  inline long default_thread_pool_size()
  {
    std::size_t num_threads = thread::hardware_concurrency() * 2;
    num_threads = num_threads == 0 ? 2 : num_threads;
    return static_cast<long>(num_threads);
  }
  
  } // namespace detail
  
  thread_pool::thread_pool()
    : scheduler_(add_scheduler(new detail::scheduler(*this, 0, false))),
      num_threads_(detail::default_thread_pool_size())
  {
    scheduler_.work_started();
  
    thread_function f = { &scheduler_ };
    threads_.create_threads(f, static_cast<std::size_t>(num_threads_));
  }
  #endif // !defined(ASIO_NO_TS_EXECUTORS)
  
  namespace detail {
  
  inline long clamp_thread_pool_size(std::size_t n)
  {
    if (n > 0x7FFFFFFF)
    {
      std::out_of_range ex("thread pool size");
      asio::detail::throw_exception(ex);
    }
    return static_cast<long>(n & 0x7FFFFFFF);
  }
  
  } // namespace detail
  
  thread_pool::thread_pool(std::size_t num_threads)
    : scheduler_(add_scheduler(new detail::scheduler(
            *this, num_threads == 1 ? 1 : 0, false))),
      num_threads_(detail::clamp_thread_pool_size(num_threads))
  {
    scheduler_.work_started();
  
    thread_function f = { &scheduler_ };
    threads_.create_threads(f, static_cast<std::size_t>(num_threads_));
  }
  
  thread_pool::~thread_pool()
  {
    stop();
    join();
  }
  
  void thread_pool::stop()
  {
    scheduler_.stop();
  }
  
  void thread_pool::attach()
  {
    ++num_threads_;
    thread_function f = { &scheduler_ };
    f();
  }
  
  void thread_pool::join()
  {
    if (!threads_.empty())
    {
      scheduler_.work_finished();
      threads_.join();
    }
  }
  
  detail::scheduler& thread_pool::add_scheduler(detail::scheduler* s)
  {
    detail::scoped_ptr<detail::scheduler> scoped_impl(s);
    asio::add_service<detail::scheduler>(*this, scoped_impl.get());
    return *scoped_impl.release();
  }
  
  void thread_pool::wait()
  {
    scheduler_.work_finished();
    threads_.join();
  }
  
  } // namespace asio
  
  #include "asio/detail/pop_options.hpp"
  
  #endif // ASIO_IMPL_THREAD_POOL_IPP
  