123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194195196197198199200201202 |
- //
- // prioritised_handlers.cpp
- // ~~~~~~~~~~~~~~~~~~~~~~~~
- //
- // Copyright (c) 2003-2019 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)
- //
- #include <boost/asio.hpp>
- #include <iostream>
- #include <memory>
- #include <queue>
- using boost::asio::ip::tcp;
- class handler_priority_queue : public boost::asio::execution_context
- {
- public:
- template <typename Function>
- void add(int priority, Function function)
- {
- std::unique_ptr<queued_handler_base> handler(
- new queued_handler<Function>(
- priority, std::move(function)));
- handlers_.push(std::move(handler));
- }
- void execute_all()
- {
- while (!handlers_.empty())
- {
- handlers_.top()->execute();
- handlers_.pop();
- }
- }
- class executor
- {
- public:
- executor(handler_priority_queue& q, int p)
- : context_(q), priority_(p)
- {
- }
- handler_priority_queue& context() const noexcept
- {
- return context_;
- }
- template <typename Function, typename Allocator>
- void dispatch(Function f, const Allocator&) const
- {
- context_.add(priority_, std::move(f));
- }
- template <typename Function, typename Allocator>
- void post(Function f, const Allocator&) const
- {
- context_.add(priority_, std::move(f));
- }
- template <typename Function, typename Allocator>
- void defer(Function f, const Allocator&) const
- {
- context_.add(priority_, std::move(f));
- }
- void on_work_started() const noexcept {}
- void on_work_finished() const noexcept {}
- bool operator==(const executor& other) const noexcept
- {
- return &context_ == &other.context_ && priority_ == other.priority_;
- }
- bool operator!=(const executor& other) const noexcept
- {
- return !operator==(other);
- }
- private:
- handler_priority_queue& context_;
- int priority_;
- };
- template <typename Handler>
- boost::asio::executor_binder<Handler, executor>
- wrap(int priority, Handler handler)
- {
- return boost::asio::bind_executor(
- executor(*this, priority), std::move(handler));
- }
- private:
- class queued_handler_base
- {
- public:
- queued_handler_base(int p)
- : priority_(p)
- {
- }
- virtual ~queued_handler_base()
- {
- }
- virtual void execute() = 0;
- friend bool operator<(const std::unique_ptr<queued_handler_base>& a,
- const std::unique_ptr<queued_handler_base>& b) noexcept
- {
- return a->priority_ < b->priority_;
- }
- private:
- int priority_;
- };
- template <typename Function>
- class queued_handler : public queued_handler_base
- {
- public:
- queued_handler(int p, Function f)
- : queued_handler_base(p), function_(std::move(f))
- {
- }
- void execute() override
- {
- function_();
- }
- private:
- Function function_;
- };
- std::priority_queue<std::unique_ptr<queued_handler_base>> handlers_;
- };
- //----------------------------------------------------------------------
- void high_priority_handler(const boost::system::error_code& /*ec*/,
- tcp::socket /*socket*/)
- {
- std::cout << "High priority handler\n";
- }
- void middle_priority_handler(const boost::system::error_code& /*ec*/)
- {
- std::cout << "Middle priority handler\n";
- }
- struct low_priority_handler
- {
- // Make the handler a move-only type.
- low_priority_handler() = default;
- low_priority_handler(const low_priority_handler&) = delete;
- low_priority_handler(low_priority_handler&&) = default;
- void operator()()
- {
- std::cout << "Low priority handler\n";
- }
- };
- int main()
- {
- boost::asio::io_context io_context;
- handler_priority_queue pri_queue;
- // Post a completion handler to be run immediately.
- boost::asio::post(io_context, pri_queue.wrap(0, low_priority_handler()));
- // Start an asynchronous accept that will complete immediately.
- tcp::endpoint endpoint(boost::asio::ip::address_v4::loopback(), 0);
- tcp::acceptor acceptor(io_context, endpoint);
- tcp::socket server_socket(io_context);
- acceptor.async_accept(pri_queue.wrap(100, high_priority_handler));
- tcp::socket client_socket(io_context);
- client_socket.connect(acceptor.local_endpoint());
- // Set a deadline timer to expire immediately.
- boost::asio::steady_timer timer(io_context);
- timer.expires_at(boost::asio::steady_timer::clock_type::time_point::min());
- timer.async_wait(pri_queue.wrap(42, middle_priority_handler));
- while (io_context.run_one())
- {
- // The custom invocation hook adds the handlers to the priority queue
- // rather than executing them from within the poll_one() call.
- while (io_context.poll_one())
- ;
- pri_queue.execute_all();
- }
- return 0;
- }
|