text: //
  // system_context.hpp
  // ~~~~~~~~~~~~~~~~~~
  //
  // 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_SYSTEM_CONTEXT_HPP
  #define ASIO_SYSTEM_CONTEXT_HPP
  
  #if defined(_MSC_VER) && (_MSC_VER >= 1200)
  # pragma once
  #endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
  
  #include "asio/detail/config.hpp"
  #include "asio/detail/scheduler.hpp"
  #include "asio/detail/thread_group.hpp"
  #include "asio/execution.hpp"
  #include "asio/execution_context.hpp"
  
  #include "asio/detail/push_options.hpp"
  
  namespace asio {
  
  template <typename Blocking, typename Relationship, typename Allocator>
  class basic_system_executor;
  
  /// The executor context for the system executor.
  class system_context : public execution_context
  {
  public:
    /// The executor type associated with the context.
    typedef basic_system_executor<
        execution::blocking_t::possibly_t,
        execution::relationship_t::fork_t,
        std::allocator<void>
      > executor_type;
  
    /// Destructor shuts down all threads in the system thread pool.
    ASIO_DECL ~system_context();
  
    /// Obtain an executor for the context.
    executor_type get_executor() ASIO_NOEXCEPT;
  
    /// Signal all threads in the system thread pool to stop.
    ASIO_DECL void stop();
  
    /// Determine whether the system thread pool has been stopped.
    ASIO_DECL bool stopped() const ASIO_NOEXCEPT;
  
    /// Join all threads in the system thread pool.
    ASIO_DECL void join();
  
  #if defined(GENERATING_DOCUMENTATION)
  private:
  #endif // defined(GENERATING_DOCUMENTATION)
    // Constructor creates all threads in the system thread pool.
    ASIO_DECL system_context();
  
  private:
    template <typename, typename, typename> friend class basic_system_executor;
  
    struct thread_function;
  
    // Helper function to create the underlying scheduler.
    ASIO_DECL detail::scheduler& add_scheduler(detail::scheduler* s);
  
    // The underlying scheduler.
    detail::scheduler& scheduler_;
  
    // The threads in the system thread pool.
    detail::thread_group threads_;
  
    // The number of threads in the pool.
    std::size_t num_threads_;
  };
  
  } // namespace asio
  
  #include "asio/detail/pop_options.hpp"
  
  #include "asio/impl/system_context.hpp"
  #if defined(ASIO_HEADER_ONLY)
  # include "asio/impl/system_context.ipp"
  #endif // defined(ASIO_HEADER_ONLY)
  
  #endif // ASIO_SYSTEM_CONTEXT_HPP
  