| // Copyright 2015 The Chromium OS Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #ifndef LIBBRILLO_BRILLO_MESSAGE_LOOPS_MESSAGE_LOOP_H_ |
| #define LIBBRILLO_BRILLO_MESSAGE_LOOPS_MESSAGE_LOOP_H_ |
| |
| #include <string> |
| #include <utility> |
| |
| #include <base/callback.h> |
| #include <base/location.h> |
| #include <base/time/time.h> |
| #include <brillo/brillo_export.h> |
| |
| namespace brillo { |
| |
| class BRILLO_EXPORT MessageLoop { |
| public: |
| virtual ~MessageLoop(); |
| |
| // A unique task identifier used to refer to scheduled callbacks. |
| using TaskId = uint64_t; |
| |
| // The kNullEventId is reserved for an invalid task and will never be used |
| // to refer to a real task. |
| static const TaskId kTaskIdNull; |
| |
| // Return the MessageLoop for the current thread. It is a fatal error to |
| // request the current MessageLoop if SetAsCurrent() was not called on the |
| // current thread. If you really need to, use ThreadHasCurrent() to check if |
| // there is a current thread. |
| static MessageLoop* current(); |
| |
| // Return whether there is a MessageLoop in the current thread. |
| static bool ThreadHasCurrent(); |
| |
| // Set this message loop as the current thread main loop. Only one message |
| // loop can be set at a time. Use ReleaseFromCurrent() to release it. |
| void SetAsCurrent(); |
| |
| // Release this instance from the current thread. This instance must have |
| // been previously set with SetAsCurrent(). |
| void ReleaseFromCurrent(); |
| |
| // Schedule a Closure |task| to be executed after a |delay|. Returns a task |
| // identifier for the scheduled task that can be used to cancel the task |
| // before it is fired by passing it to CancelTask(). |
| // In case of an error scheduling the task, the kTaskIdNull is returned. |
| // Note that once the call is executed or canceled, the TaskId could be reused |
| // at a later point. |
| // This method can only be called from the same thread running the main loop. |
| virtual TaskId PostDelayedTask(const base::Location& from_here, |
| base::OnceClosure task, |
| base::TimeDelta delay) = 0; |
| // Variant without the Location for easier usage. |
| TaskId PostDelayedTask(base::OnceClosure task, base::TimeDelta delay) { |
| return PostDelayedTask(base::Location(), std::move(task), delay); |
| } |
| |
| // A convenience method to schedule a call with no delay. |
| // This method can only be called from the same thread running the main loop. |
| TaskId PostTask(base::OnceClosure task) { |
| return PostDelayedTask(std::move(task), base::TimeDelta()); |
| } |
| TaskId PostTask(const base::Location& from_here, base::OnceClosure task) { |
| return PostDelayedTask(from_here, std::move(task), base::TimeDelta()); |
| } |
| |
| // Cancel a scheduled task. Returns whether the task was canceled. For |
| // example, if the callback was already executed (or is being executed) or was |
| // already canceled this method will fail. Note that the TaskId can be reused |
| // after it was executed or cancelled. |
| virtual bool CancelTask(TaskId task_id) = 0; |
| |
| // --------------------------------------------------------------------------- |
| // Methods used to run and stop the message loop. |
| |
| // Run one iteration of the message loop, dispatching up to one task. The |
| // |may_block| tells whether this method is allowed to block waiting for a |
| // task to be ready to run. Returns whether it ran a task. Note that even |
| // if |may_block| is true, this method can return false immediately if there |
| // are no more tasks registered. |
| virtual bool RunOnce(bool may_block) = 0; |
| |
| // Run the main loop until there are no more registered tasks. |
| virtual void Run(); |
| |
| // Quit the running main loop immediately. This method will make the current |
| // running Run() method to return right after the current task returns back |
| // to the message loop without processing any other task. |
| virtual void BreakLoop(); |
| |
| protected: |
| MessageLoop() = default; |
| MessageLoop(const MessageLoop&) = delete; |
| MessageLoop& operator=(const MessageLoop&) = delete; |
| |
| private: |
| // Tells whether Run() should quit the message loop in the default |
| // implementation. |
| bool should_exit_ = false; |
| }; |
| |
| } // namespace brillo |
| |
| #endif // LIBBRILLO_BRILLO_MESSAGE_LOOPS_MESSAGE_LOOP_H_ |