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+//
+// detail/win_iocp_io_context.hpp
+// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+//
+// Copyright (c) 2003-2024 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_DETAIL_WIN_IOCP_IO_CONTEXT_HPP
+#define ASIO_DETAIL_WIN_IOCP_IO_CONTEXT_HPP
+
+#if defined(_MSC_VER) && (_MSC_VER >= 1200)
+# pragma once
+#endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
+
+#include "asio/detail/config.hpp"
+
+#if defined(ASIO_HAS_IOCP)
+
+#include "asio/detail/limits.hpp"
+#include "asio/detail/mutex.hpp"
+#include "asio/detail/op_queue.hpp"
+#include "asio/detail/scoped_ptr.hpp"
+#include "asio/detail/socket_types.hpp"
+#include "asio/detail/thread.hpp"
+#include "asio/detail/thread_context.hpp"
+#include "asio/detail/timer_queue_base.hpp"
+#include "asio/detail/timer_queue_set.hpp"
+#include "asio/detail/wait_op.hpp"
+#include "asio/detail/win_iocp_operation.hpp"
+#include "asio/detail/win_iocp_thread_info.hpp"
+#include "asio/execution_context.hpp"
+
+#include "asio/detail/push_options.hpp"
+
+namespace asio {
+namespace detail {
+
+class wait_op;
+
+class win_iocp_io_context
+ : public execution_context_service_base<win_iocp_io_context>,
+ public thread_context
+{
+public:
+ // Constructor. Specifies a concurrency hint that is passed through to the
+ // underlying I/O completion port.
+ ASIO_DECL win_iocp_io_context(asio::execution_context& ctx,
+ int concurrency_hint = -1, bool own_thread = true);
+
+ // Destructor.
+ ASIO_DECL ~win_iocp_io_context();
+
+ // Destroy all user-defined handler objects owned by the service.
+ ASIO_DECL void shutdown();
+
+ // Initialise the task. Nothing to do here.
+ void init_task()
+ {
+ }
+
+ // Register a handle with the IO completion port.
+ ASIO_DECL asio::error_code register_handle(
+ HANDLE handle, asio::error_code& ec);
+
+ // Run the event loop until stopped or no more work.
+ ASIO_DECL size_t run(asio::error_code& ec);
+
+ // Run until stopped or one operation is performed.
+ ASIO_DECL size_t run_one(asio::error_code& ec);
+
+ // Run until timeout, interrupted, or one operation is performed.
+ ASIO_DECL size_t wait_one(long usec, asio::error_code& ec);
+
+ // Poll for operations without blocking.
+ ASIO_DECL size_t poll(asio::error_code& ec);
+
+ // Poll for one operation without blocking.
+ ASIO_DECL size_t poll_one(asio::error_code& ec);
+
+ // Stop the event processing loop.
+ ASIO_DECL void stop();
+
+ // Determine whether the io_context is stopped.
+ bool stopped() const
+ {
+ return ::InterlockedExchangeAdd(&stopped_, 0) != 0;
+ }
+
+ // Restart in preparation for a subsequent run invocation.
+ void restart()
+ {
+ ::InterlockedExchange(&stopped_, 0);
+ }
+
+ // Notify that some work has started.
+ void work_started()
+ {
+ ::InterlockedIncrement(&outstanding_work_);
+ }
+
+ // Notify that some work has finished.
+ void work_finished()
+ {
+ if (::InterlockedDecrement(&outstanding_work_) == 0)
+ stop();
+ }
+
+ // Return whether a handler can be dispatched immediately.
+ ASIO_DECL bool can_dispatch();
+
+ /// Capture the current exception so it can be rethrown from a run function.
+ ASIO_DECL void capture_current_exception();
+
+ // Request invocation of the given operation and return immediately. Assumes
+ // that work_started() has not yet been called for the operation.
+ void post_immediate_completion(win_iocp_operation* op, bool)
+ {
+ work_started();
+ post_deferred_completion(op);
+ }
+
+ // Request invocation of the given operation and return immediately. Assumes
+ // that work_started() was previously called for the operation.
+ ASIO_DECL void post_deferred_completion(win_iocp_operation* op);
+
+ // Request invocation of the given operation and return immediately. Assumes
+ // that work_started() was previously called for the operations.
+ ASIO_DECL void post_deferred_completions(
+ op_queue<win_iocp_operation>& ops);
+
+ // Request invocation of the given operation using the thread-private queue
+ // and return immediately. Assumes that work_started() has not yet been
+ // called for the operation.
+ void post_private_immediate_completion(win_iocp_operation* op)
+ {
+ post_immediate_completion(op, false);
+ }
+
+ // Request invocation of the given operation using the thread-private queue
+ // and return immediately. Assumes that work_started() was previously called
+ // for the operation.
+ void post_private_deferred_completion(win_iocp_operation* op)
+ {
+ post_deferred_completion(op);
+ }
+
+ // Enqueue the given operation following a failed attempt to dispatch the
+ // operation for immediate invocation.
+ void do_dispatch(operation* op)
+ {
+ post_immediate_completion(op, false);
+ }
+
+ // Process unfinished operations as part of a shutdown operation. Assumes
+ // that work_started() was previously called for the operations.
+ ASIO_DECL void abandon_operations(op_queue<operation>& ops);
+
+ // Called after starting an overlapped I/O operation that did not complete
+ // immediately. The caller must have already called work_started() prior to
+ // starting the operation.
+ ASIO_DECL void on_pending(win_iocp_operation* op);
+
+ // Called after starting an overlapped I/O operation that completed
+ // immediately. The caller must have already called work_started() prior to
+ // starting the operation.
+ ASIO_DECL void on_completion(win_iocp_operation* op,
+ DWORD last_error = 0, DWORD bytes_transferred = 0);
+
+ // Called after starting an overlapped I/O operation that completed
+ // immediately. The caller must have already called work_started() prior to
+ // starting the operation.
+ ASIO_DECL void on_completion(win_iocp_operation* op,
+ const asio::error_code& ec, DWORD bytes_transferred = 0);
+
+ // Add a new timer queue to the service.
+ template <typename Time_Traits>
+ void add_timer_queue(timer_queue<Time_Traits>& timer_queue);
+
+ // Remove a timer queue from the service.
+ template <typename Time_Traits>
+ void remove_timer_queue(timer_queue<Time_Traits>& timer_queue);
+
+ // Schedule a new operation in the given timer queue to expire at the
+ // specified absolute time.
+ template <typename Time_Traits>
+ void schedule_timer(timer_queue<Time_Traits>& queue,
+ const typename Time_Traits::time_type& time,
+ typename timer_queue<Time_Traits>::per_timer_data& timer, wait_op* op);
+
+ // Cancel the timer associated with the given token. Returns the number of
+ // handlers that have been posted or dispatched.
+ template <typename Time_Traits>
+ std::size_t cancel_timer(timer_queue<Time_Traits>& queue,
+ typename timer_queue<Time_Traits>::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 Time_Traits>
+ void cancel_timer_by_key(timer_queue<Time_Traits>& queue,
+ typename timer_queue<Time_Traits>::per_timer_data* timer,
+ void* cancellation_key);
+
+ // Move the timer operations associated with the given timer.
+ template <typename Time_Traits>
+ void move_timer(timer_queue<Time_Traits>& queue,
+ typename timer_queue<Time_Traits>::per_timer_data& to,
+ typename timer_queue<Time_Traits>::per_timer_data& from);
+
+ // Get the concurrency hint that was used to initialise the io_context.
+ int concurrency_hint() const
+ {
+ return concurrency_hint_;
+ }
+
+private:
+#if defined(WINVER) && (WINVER < 0x0500)
+ typedef DWORD dword_ptr_t;
+ typedef ULONG ulong_ptr_t;
+#else // defined(WINVER) && (WINVER < 0x0500)
+ typedef DWORD_PTR dword_ptr_t;
+ typedef ULONG_PTR ulong_ptr_t;
+#endif // defined(WINVER) && (WINVER < 0x0500)
+
+ // Dequeues at most one operation from the I/O completion port, and then
+ // executes it. Returns the number of operations that were dequeued (i.e.
+ // either 0 or 1).
+ ASIO_DECL size_t do_one(DWORD msec,
+ win_iocp_thread_info& this_thread, asio::error_code& ec);
+
+ // Helper to calculate the GetQueuedCompletionStatus timeout.
+ ASIO_DECL static DWORD get_gqcs_timeout();
+
+ // Helper function to add a new timer queue.
+ ASIO_DECL void do_add_timer_queue(timer_queue_base& queue);
+
+ // Helper function to remove a timer queue.
+ ASIO_DECL void do_remove_timer_queue(timer_queue_base& queue);
+
+ // Called to recalculate and update the timeout.
+ ASIO_DECL void update_timeout();
+
+ // Helper class to call work_finished() on block exit.
+ struct work_finished_on_block_exit;
+
+ // Helper class for managing a HANDLE.
+ struct auto_handle
+ {
+ HANDLE handle;
+ auto_handle() : handle(0) {}
+ ~auto_handle() { if (handle) ::CloseHandle(handle); }
+ };
+
+ // The IO completion port used for queueing operations.
+ auto_handle iocp_;
+
+ // The count of unfinished work.
+ long outstanding_work_;
+
+ // Flag to indicate whether the event loop has been stopped.
+ mutable long stopped_;
+
+ // Flag to indicate whether there is an in-flight stop event. Every event
+ // posted using PostQueuedCompletionStatus consumes non-paged pool, so to
+ // avoid exhausting this resouce we limit the number of outstanding events.
+ long stop_event_posted_;
+
+ // Flag to indicate whether the service has been shut down.
+ long shutdown_;
+
+ enum
+ {
+#if !defined(_WIN32_WINNT) || (_WIN32_WINNT < 0x0600)
+ // Timeout to use with GetQueuedCompletionStatus on older versions of
+ // Windows. Some versions of windows have a "bug" where a call to
+ // GetQueuedCompletionStatus can appear stuck even though there are events
+ // waiting on the queue. Using a timeout helps to work around the issue.
+ default_gqcs_timeout = 500,
+#endif // !defined(_WIN32_WINNT) || (_WIN32_WINNT < 0x0600)
+
+ // Maximum waitable timer timeout, in milliseconds.
+ max_timeout_msec = 5 * 60 * 1000,
+
+ // Maximum waitable timer timeout, in microseconds.
+ max_timeout_usec = max_timeout_msec * 1000,
+
+ // Completion key value used to wake up a thread to dispatch timers or
+ // completed operations.
+ wake_for_dispatch = 1,
+
+ // Completion key value to indicate that an operation has posted with the
+ // original last_error and bytes_transferred values stored in the fields of
+ // the OVERLAPPED structure.
+ overlapped_contains_result = 2
+ };
+
+ // Timeout to use with GetQueuedCompletionStatus.
+ const DWORD gqcs_timeout_;
+
+ // Helper class to run the scheduler in its own thread.
+ struct thread_function;
+ friend struct thread_function;
+
+ // Function object for processing timeouts in a background thread.
+ struct timer_thread_function;
+ friend struct timer_thread_function;
+
+ // Background thread used for processing timeouts.
+ scoped_ptr<thread> timer_thread_;
+
+ // A waitable timer object used for waiting for timeouts.
+ auto_handle waitable_timer_;
+
+ // Non-zero if timers or completed operations need to be dispatched.
+ long dispatch_required_;
+
+ // Mutex for protecting access to the timer queues and completed operations.
+ mutex dispatch_mutex_;
+
+ // The timer queues.
+ timer_queue_set timer_queues_;
+
+ // The operations that are ready to dispatch.
+ op_queue<win_iocp_operation> completed_ops_;
+
+ // The concurrency hint used to initialise the io_context.
+ const int concurrency_hint_;
+
+ // The thread that is running the io_context.
+ scoped_ptr<thread> thread_;
+};
+
+} // namespace detail
+} // namespace asio
+
+#include "asio/detail/pop_options.hpp"
+
+#include "asio/detail/impl/win_iocp_io_context.hpp"
+#if defined(ASIO_HEADER_ONLY)
+# include "asio/detail/impl/win_iocp_io_context.ipp"
+#endif // defined(ASIO_HEADER_ONLY)
+
+#endif // defined(ASIO_HAS_IOCP)
+
+#endif // ASIO_DETAIL_WIN_IOCP_IO_CONTEXT_HPP