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+//
+// detail/scheduler.hpp
+// ~~~~~~~~~~~~~~~~~~~~
+//
+// Copyright (c) 2003-2018 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_SCHEDULER_HPP
+#define ASIO_DETAIL_SCHEDULER_HPP
+
+#if defined(_MSC_VER) && (_MSC_VER >= 1200)
+# pragma once
+#endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
+
+#include "asio/detail/config.hpp"
+
+#include "asio/error_code.hpp"
+#include "asio/execution_context.hpp"
+#include "asio/detail/atomic_count.hpp"
+#include "asio/detail/conditionally_enabled_event.hpp"
+#include "asio/detail/conditionally_enabled_mutex.hpp"
+#include "asio/detail/op_queue.hpp"
+#include "asio/detail/reactor_fwd.hpp"
+#include "asio/detail/scheduler_operation.hpp"
+#include "asio/detail/thread_context.hpp"
+
+#include "asio/detail/push_options.hpp"
+
+namespace asio {
+namespace detail {
+
+struct scheduler_thread_info;
+
+class scheduler
+ : public execution_context_service_base<scheduler>,
+ public thread_context
+{
+public:
+ typedef scheduler_operation operation;
+
+ // Constructor. Specifies the number of concurrent threads that are likely to
+ // run the scheduler. If set to 1 certain optimisation are performed.
+ ASIO_DECL scheduler(asio::execution_context& ctx,
+ int concurrency_hint = 0);
+
+ // Destroy all user-defined handler objects owned by the service.
+ ASIO_DECL void shutdown();
+
+ // Initialise the task, if required.
+ ASIO_DECL void init_task();
+
+ // Run the event loop until interrupted or no more work.
+ ASIO_DECL std::size_t run(asio::error_code& ec);
+
+ // Run until interrupted or one operation is performed.
+ ASIO_DECL std::size_t run_one(asio::error_code& ec);
+
+ // Run until timeout, interrupted, or one operation is performed.
+ ASIO_DECL std::size_t wait_one(
+ long usec, asio::error_code& ec);
+
+ // Poll for operations without blocking.
+ ASIO_DECL std::size_t poll(asio::error_code& ec);
+
+ // Poll for one operation without blocking.
+ ASIO_DECL std::size_t poll_one(asio::error_code& ec);
+
+ // Interrupt the event processing loop.
+ ASIO_DECL void stop();
+
+ // Determine whether the scheduler is stopped.
+ ASIO_DECL bool stopped() const;
+
+ // Restart in preparation for a subsequent run invocation.
+ ASIO_DECL void restart();
+
+ // Notify that some work has started.
+ void work_started()
+ {
+ ++outstanding_work_;
+ }
+
+ // Used to compensate for a forthcoming work_finished call. Must be called
+ // from within a scheduler-owned thread.
+ ASIO_DECL void compensating_work_started();
+
+ // Notify that some work has finished.
+ void work_finished()
+ {
+ if (--outstanding_work_ == 0)
+ stop();
+ }
+
+ // Return whether a handler can be dispatched immediately.
+ bool can_dispatch()
+ {
+ return thread_call_stack::contains(this) != 0;
+ }
+
+ // Request invocation of the given operation and return immediately. Assumes
+ // that work_started() has not yet been called for the operation.
+ ASIO_DECL void post_immediate_completion(
+ operation* op, bool is_continuation);
+
+ // 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(operation* op);
+
+ // Request invocation of the given operations and return immediately. Assumes
+ // that work_started() was previously called for each operation.
+ ASIO_DECL void post_deferred_completions(op_queue<operation>& ops);
+
+ // Enqueue the given operation following a failed attempt to dispatch the
+ // operation for immediate invocation.
+ ASIO_DECL void do_dispatch(operation* op);
+
+ // Process unfinished operations as part of a shutdownoperation. Assumes that
+ // work_started() was previously called for the operations.
+ ASIO_DECL void abandon_operations(op_queue<operation>& ops);
+
+ // Get the concurrency hint that was used to initialise the scheduler.
+ int concurrency_hint() const
+ {
+ return concurrency_hint_;
+ }
+
+private:
+ // The mutex type used by this scheduler.
+ typedef conditionally_enabled_mutex mutex;
+
+ // The event type used by this scheduler.
+ typedef conditionally_enabled_event event;
+
+ // Structure containing thread-specific data.
+ typedef scheduler_thread_info thread_info;
+
+ // Run at most one operation. May block.
+ ASIO_DECL std::size_t do_run_one(mutex::scoped_lock& lock,
+ thread_info& this_thread, const asio::error_code& ec);
+
+ // Run at most one operation with a timeout. May block.
+ ASIO_DECL std::size_t do_wait_one(mutex::scoped_lock& lock,
+ thread_info& this_thread, long usec, const asio::error_code& ec);
+
+ // Poll for at most one operation.
+ ASIO_DECL std::size_t do_poll_one(mutex::scoped_lock& lock,
+ thread_info& this_thread, const asio::error_code& ec);
+
+ // Stop the task and all idle threads.
+ ASIO_DECL void stop_all_threads(mutex::scoped_lock& lock);
+
+ // Wake a single idle thread, or the task, and always unlock the mutex.
+ ASIO_DECL void wake_one_thread_and_unlock(
+ mutex::scoped_lock& lock);
+
+ // Helper class to perform task-related operations on block exit.
+ struct task_cleanup;
+ friend struct task_cleanup;
+
+ // Helper class to call work-related operations on block exit.
+ struct work_cleanup;
+ friend struct work_cleanup;
+
+ // Whether to optimise for single-threaded use cases.
+ const bool one_thread_;
+
+ // Mutex to protect access to internal data.
+ mutable mutex mutex_;
+
+ // Event to wake up blocked threads.
+ event wakeup_event_;
+
+ // The task to be run by this service.
+ reactor* task_;
+
+ // Operation object to represent the position of the task in the queue.
+ struct task_operation : operation
+ {
+ task_operation() : operation(0) {}
+ } task_operation_;
+
+ // Whether the task has been interrupted.
+ bool task_interrupted_;
+
+ // The count of unfinished work.
+ atomic_count outstanding_work_;
+
+ // The queue of handlers that are ready to be delivered.
+ op_queue<operation> op_queue_;
+
+ // Flag to indicate that the dispatcher has been stopped.
+ bool stopped_;
+
+ // Flag to indicate that the dispatcher has been shut down.
+ bool shutdown_;
+
+ // The concurrency hint used to initialise the scheduler.
+ const int concurrency_hint_;
+};
+
+} // namespace detail
+} // namespace asio
+
+#include "asio/detail/pop_options.hpp"
+
+#if defined(ASIO_HEADER_ONLY)
+# include "asio/detail/impl/scheduler.ipp"
+#endif // defined(ASIO_HEADER_ONLY)
+
+#endif // ASIO_DETAIL_SCHEDULER_HPP