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      1 /*
      2  *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
      3  *
      4  *  Use of this source code is governed by a BSD-style license
      5  *  that can be found in the LICENSE file in the root of the source
      6  *  tree. An additional intellectual property rights grant can be found
      7  *  in the file PATENTS.  All contributing project authors may
      8  *  be found in the AUTHORS file in the root of the source tree.
      9  */
     10 
     11 #ifndef WEBRTC_BASE_TASKRUNNER_H__
     12 #define WEBRTC_BASE_TASKRUNNER_H__
     13 
     14 #include <vector>
     15 
     16 #include "webrtc/base/basictypes.h"
     17 #include "webrtc/base/sigslot.h"
     18 #include "webrtc/base/taskparent.h"
     19 
     20 namespace rtc {
     21 class Task;
     22 
     23 const int64_t kSecToMsec = 1000;
     24 const int64_t kMsecTo100ns = 10000;
     25 const int64_t kSecTo100ns = kSecToMsec * kMsecTo100ns;
     26 
     27 class TaskRunner : public TaskParent, public sigslot::has_slots<> {
     28  public:
     29   TaskRunner();
     30   ~TaskRunner() override;
     31 
     32   virtual void WakeTasks() = 0;
     33 
     34   // Returns the current time in 100ns units.  It is used for
     35   // determining timeouts.  The origin is not important, only
     36   // the units and that rollover while the computer is running.
     37   //
     38   // On Windows, GetSystemTimeAsFileTime is the typical implementation.
     39   virtual int64_t CurrentTime() = 0;
     40 
     41   void StartTask(Task *task);
     42   void RunTasks();
     43   void PollTasks();
     44 
     45   void UpdateTaskTimeout(Task* task, int64_t previous_task_timeout_time);
     46 
     47 #if !defined(NDEBUG)
     48   bool is_ok_to_delete(Task* task) {
     49     return task == deleting_task_;
     50   }
     51 
     52   void IncrementAbortCount() {
     53     ++abort_count_;
     54   }
     55 
     56   void DecrementAbortCount() {
     57     --abort_count_;
     58   }
     59 #endif
     60 
     61   // Returns the next absolute time when a task times out
     62   // OR "0" if there is no next timeout.
     63   int64_t next_task_timeout() const;
     64 
     65  protected:
     66   // The primary usage of this method is to know if
     67   // a callback timer needs to be set-up or adjusted.
     68   // This method will be called
     69   //  * when the next_task_timeout() becomes a smaller value OR
     70   //  * when next_task_timeout() has changed values and the previous
     71   //    value is in the past.
     72   //
     73   // If the next_task_timeout moves to the future, this method will *not*
     74   // get called (because it subclass should check next_task_timeout()
     75   // when its timer goes off up to see if it needs to set-up a new timer).
     76   //
     77   // Note that this maybe called conservatively.  In that it may be
     78   // called when no time change has happened.
     79   virtual void OnTimeoutChange() {
     80     // by default, do nothing.
     81   }
     82 
     83  private:
     84   void InternalRunTasks(bool in_destructor);
     85   void CheckForTimeoutChange(int64_t previous_timeout_time);
     86 
     87   std::vector<Task *> tasks_;
     88   Task *next_timeout_task_;
     89   bool tasks_running_;
     90 #if !defined(NDEBUG)
     91   int abort_count_;
     92   Task* deleting_task_;
     93 #endif
     94 
     95   void RecalcNextTimeout(Task *exclude_task);
     96 };
     97 
     98 } // namespace rtc
     99 
    100 #endif  // TASK_BASE_TASKRUNNER_H__
    101