Class thread_executor

example/cpp11/executors/pipeline.cpp:27–92

An executor that launches a new thread for each function submitted to it. This class satisfies the executor requirements.

// An executor that launches a new thread for each function submitted to it.
// This class satisfies the executor requirements.
class thread_executor
{
private:
  // Service to track all threads started through a thread_executor.
  class thread_bag : public execution_context::service
  {
  public:
    typedef thread_bag key_type;

    explicit thread_bag(execution_context& ctx)
      : execution_context::service(ctx)
    {
    }

    void add_thread(std::thread&& t)
    {
      std::unique_lock<std::mutex> lock(mutex_);
      threads_.push_back(std::move(t));
    }

  private:
    virtual void shutdown()
    {
      for (auto& t : threads_)
        t.join();
    }

    std::mutex mutex_;
    std::vector<std::thread> threads_;
  };

public:
  execution_context& query(execution::context_t) const
  {
    return boost::asio::query(system_executor(), execution::context);
  }

  execution::blocking_t query(execution::blocking_t) const
  {
    return execution::blocking.never;
  }

  thread_executor require(execution::blocking_t::never_t) const
  {
    return *this;
  }

  template <class Func>
  void execute(Func f) const
  {
    thread_bag& bag = use_service<thread_bag>(query(execution::context));
    bag.add_thread(std::thread(std::move(f)));
  }

  friend bool operator==(const thread_executor&,
      const thread_executor&) noexcept
  {
    return true;