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 //
 // detail/epoll_reactor.hpp
 // ~~~~~~~~~~~~~~~~~~~~~~~~
 //
 // Copyright (c) 2003-2025 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_EPOLL_REACTOR_HPP
 #define BOOST_ASIO_DETAIL_EPOLL_REACTOR_HPP
 
 #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_HAS_EPOLL)
 
 #include <boost/asio/detail/atomic_count.hpp>
 #include <boost/asio/detail/conditionally_enabled_mutex.hpp>
 #include <boost/asio/detail/limits.hpp>
 #include <boost/asio/detail/object_pool.hpp>
 #include <boost/asio/detail/op_queue.hpp>
 #include <boost/asio/detail/reactor_op.hpp>
 #include <boost/asio/detail/scheduler_task.hpp>
 #include <boost/asio/detail/select_interrupter.hpp>
 #include <boost/asio/detail/socket_types.hpp>
 #include <boost/asio/detail/timer_queue_base.hpp>
 #include <boost/asio/detail/timer_queue_set.hpp>
 #include <boost/asio/detail/wait_op.hpp>
 #include <boost/asio/execution_context.hpp>
 
 #if defined(BOOST_ASIO_HAS_TIMERFD)
 # include <sys/timerfd.h>
 #endif // defined(BOOST_ASIO_HAS_TIMERFD)
 
 #include <boost/asio/detail/push_options.hpp>
 
 namespace boost {
 namespace asio {
 namespace detail {
 
 class epoll_reactor
   : public execution_context_service_base<epoll_reactor>,
     public scheduler_task
 {
 private:
   // The mutex type used by this reactor.
   typedef conditionally_enabled_mutex mutex;
 
 public:
   enum op_types { read_op = 0, write_op = 1,
     connect_op = 1, except_op = 2, max_ops = 3 };
 
   // Per-descriptor queues.
   struct descriptor_state : operation
   {
     descriptor_state* next_;
     descriptor_state* prev_;
 
     mutex mutex_;
     epoll_reactor* reactor_;
     int descriptor_;
     uint32_t registered_events_;
     op_queue<reactor_op> op_queue_[max_ops];
     bool try_speculative_[max_ops];
     bool shutdown_;
 
     BOOST_ASIO_DECL descriptor_state(bool locking, int spin_count);
     void set_ready_events(uint32_t events) { task_result_ = events; }
     void add_ready_events(uint32_t events) { task_result_ |= events; }
     BOOST_ASIO_DECL operation* perform_io(uint32_t events);
     BOOST_ASIO_DECL static void do_complete(
         void* owner, operation* base,
         const boost::system::error_code& ec, std::size_t bytes_transferred);
   };
 
   // Per-descriptor data.
   typedef descriptor_state* per_descriptor_data;
 
   // Constructor.
   BOOST_ASIO_DECL epoll_reactor(boost::asio::execution_context& ctx);
 
   // Destructor.
   BOOST_ASIO_DECL ~epoll_reactor();
 
   // Destroy all user-defined handler objects owned by the service.
   BOOST_ASIO_DECL void shutdown();
 
   // Recreate internal descriptors following a fork.
   BOOST_ASIO_DECL void notify_fork(
       boost::asio::execution_context::fork_event fork_ev);
 
   // Initialise the task.
   BOOST_ASIO_DECL void init_task();
 
   // Register a socket with the reactor. Returns 0 on success, system error
   // code on failure.
   BOOST_ASIO_DECL int register_descriptor(socket_type descriptor,
       per_descriptor_data& descriptor_data);
 
   // Register a descriptor with an associated single operation. Returns 0 on
   // success, system error code on failure.
   BOOST_ASIO_DECL int register_internal_descriptor(
       int op_type, socket_type descriptor,
       per_descriptor_data& descriptor_data, reactor_op* op);
 
   // Move descriptor registration from one descriptor_data object to another.
   BOOST_ASIO_DECL void move_descriptor(socket_type descriptor,
       per_descriptor_data& target_descriptor_data,
       per_descriptor_data& source_descriptor_data);
 
   // Post a reactor operation for immediate completion.
   void post_immediate_completion(operation* op, bool is_continuation) const;
 
   // Post a reactor operation for immediate completion.
   BOOST_ASIO_DECL static void call_post_immediate_completion(
       operation* op, bool is_continuation, const void* self);
 
   // Start a new operation. The reactor operation will be performed when the
   // given descriptor is flagged as ready, or an error has occurred.
   BOOST_ASIO_DECL void start_op(int op_type, socket_type descriptor,
       per_descriptor_data& descriptor_data, reactor_op* op,
       bool is_continuation, bool allow_speculative,
       void (*on_immediate)(operation*, bool, const void*),
       const void* immediate_arg);
 
   // Start a new operation. The reactor operation will be performed when the
   // given descriptor is flagged as ready, or an error has occurred.
   void start_op(int op_type, socket_type descriptor,
       per_descriptor_data& descriptor_data, reactor_op* op,
       bool is_continuation, bool allow_speculative)
   {
     start_op(op_type, descriptor, descriptor_data,
         op, is_continuation, allow_speculative,
         &epoll_reactor::call_post_immediate_completion, this);
   }
 
   // Cancel all operations associated with the given descriptor. The
   // handlers associated with the descriptor will be invoked with the
   // operation_aborted error.
   BOOST_ASIO_DECL void cancel_ops(socket_type descriptor,
       per_descriptor_data& descriptor_data);
 
   // Cancel all operations associated with the given descriptor and key. The
   // handlers associated with the descriptor will be invoked with the
   // operation_aborted error.
   BOOST_ASIO_DECL void cancel_ops_by_key(socket_type descriptor,
       per_descriptor_data& descriptor_data,
       int op_type, void* cancellation_key);
 
   // Cancel any operations that are running against the descriptor and remove
   // its registration from the reactor. The reactor resources associated with
   // the descriptor must be released by calling cleanup_descriptor_data.
   BOOST_ASIO_DECL void deregister_descriptor(socket_type descriptor,
       per_descriptor_data& descriptor_data, bool closing);
 
   // Remove the descriptor's registration from the reactor. The reactor
   // resources associated with the descriptor must be released by calling
   // cleanup_descriptor_data.
   BOOST_ASIO_DECL void deregister_internal_descriptor(
       socket_type descriptor, per_descriptor_data& descriptor_data);
 
   // Perform any post-deregistration cleanup tasks associated with the
   // descriptor data.
   BOOST_ASIO_DECL void cleanup_descriptor_data(
       per_descriptor_data& descriptor_data);
 
   // Add a new timer queue to the reactor.
   template <typename TimeTraits, typename Allocator>
   void add_timer_queue(timer_queue<TimeTraits, Allocator>& timer_queue);
 
   // Remove a timer queue from the reactor.
   template <typename TimeTraits, typename Allocator>
   void remove_timer_queue(timer_queue<TimeTraits, Allocator>& timer_queue);
 
   // Schedule a new operation in the given timer queue to expire at the
   // specified absolute time.
   template <typename TimeTraits, typename Allocator>
   void schedule_timer(timer_queue<TimeTraits, Allocator>& queue,
       const typename TimeTraits::time_type& time,
       typename timer_queue<TimeTraits, Allocator>::per_timer_data& timer,
       wait_op* op);
 
   // Cancel the timer operations associated with the given token. Returns the
   // number of operations that have been posted or dispatched.
   template <typename TimeTraits, typename Allocator>
   std::size_t cancel_timer(timer_queue<TimeTraits, Allocator>& queue,
       typename timer_queue<TimeTraits, Allocator>::per_timer_data& timer,
       std::size_t max_cancelled = (std::numeric_limits<std::size_t>::max)());
 
   // Cancel the timer operations associated with the given key.
   template <typename TimeTraits, typename Allocator>
   void cancel_timer_by_key(timer_queue<TimeTraits, Allocator>& queue,
       typename timer_queue<TimeTraits, Allocator>::per_timer_data* timer,
       void* cancellation_key);
 
   // Move the timer operations associated with the given timer.
   template <typename TimeTraits, typename Allocator>
   void move_timer(timer_queue<TimeTraits, Allocator>& queue,
       typename timer_queue<TimeTraits, Allocator>::per_timer_data& target,
       typename timer_queue<TimeTraits, Allocator>::per_timer_data& source);
 
   // Run epoll once until interrupted or events are ready to be dispatched.
   BOOST_ASIO_DECL void run(long usec, op_queue<operation>& ops);
 
   // Interrupt the select loop.
   BOOST_ASIO_DECL void interrupt();
 
 private:
   // The hint to pass to epoll_create to size its data structures.
   enum { epoll_size = 20000 };
 
   // Create the epoll file descriptor. Throws an exception if the descriptor
   // cannot be created.
   BOOST_ASIO_DECL static int do_epoll_create();
 
   // Create the timerfd file descriptor. Does not throw.
   BOOST_ASIO_DECL static int do_timerfd_create();
 
   // Allocate a new descriptor state object.
   BOOST_ASIO_DECL descriptor_state* allocate_descriptor_state();
 
   // Free an existing descriptor state object.
   BOOST_ASIO_DECL void free_descriptor_state(descriptor_state* s);
 
   // Helper function to add a new timer queue.
   BOOST_ASIO_DECL void do_add_timer_queue(timer_queue_base& queue);
 
   // Helper function to remove a timer queue.
   BOOST_ASIO_DECL void do_remove_timer_queue(timer_queue_base& queue);
 
   // Called to recalculate and update the timeout.
   BOOST_ASIO_DECL void update_timeout();
 
   // Get the timeout value for the epoll_wait call. The timeout value is
   // returned as a number of milliseconds. A return value of -1 indicates
   // that epoll_wait should block indefinitely.
   BOOST_ASIO_DECL int get_timeout(int msec);
 
 #if defined(BOOST_ASIO_HAS_TIMERFD)
   // Get the timeout value for the timer descriptor. The return value is the
   // flag argument to be used when calling timerfd_settime.
   BOOST_ASIO_DECL int get_timeout(itimerspec& ts);
 #endif // defined(BOOST_ASIO_HAS_TIMERFD)
 
   // The scheduler implementation used to post completions.
   scheduler& scheduler_;
 
   // Mutex to protect access to internal data.
   mutex mutex_;
 
   // The interrupter is used to break a blocking epoll_wait call.
   select_interrupter interrupter_;
 
   // The epoll file descriptor.
   int epoll_fd_;
 
   // The timer file descriptor.
   int timer_fd_;
 
   // The timer queues.
   timer_queue_set timer_queues_;
 
   // Whether the service has been shut down.
   bool shutdown_;
 
   // Whether I/O locking is enabled.
   const bool io_locking_;
 
   // How any times to spin waiting for the I/O mutex.
   const int io_locking_spin_count_;
 
   // Mutex to protect access to the registered descriptors.
   mutex registered_descriptors_mutex_;
 
   // Keep track of all registered descriptors.
   object_pool<descriptor_state, execution_context::allocator<void>>
     registered_descriptors_;
 
   // Helper class to do post-perform_io cleanup.
   struct perform_io_cleanup_on_block_exit;
   friend struct perform_io_cleanup_on_block_exit;
 };
 
 } // namespace detail
 } // namespace asio
 } // namespace boost
 
 #include <boost/asio/detail/pop_options.hpp>
 
 #include <boost/asio/detail/impl/epoll_reactor.hpp>
 #if defined(BOOST_ASIO_HEADER_ONLY)
 # include <boost/asio/detail/impl/epoll_reactor.ipp>
 #endif // defined(BOOST_ASIO_HEADER_ONLY)
 
 #endif // defined(BOOST_ASIO_HAS_EPOLL)
 
 #endif // BOOST_ASIO_DETAIL_EPOLL_REACTOR_HPP

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