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      1 // Copyright 2014 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #ifndef CHROME_BROWSER_SAFE_BROWSING_INCIDENT_REPORTING_DELAYED_CALLBACK_RUNNER_H_
      6 #define CHROME_BROWSER_SAFE_BROWSING_INCIDENT_REPORTING_DELAYED_CALLBACK_RUNNER_H_
      7 
      8 #include <list>
      9 
     10 #include "base/callback_forward.h"
     11 #include "base/macros.h"
     12 #include "base/memory/ref_counted.h"
     13 #include "base/task_runner.h"
     14 #include "base/threading/thread_checker.h"
     15 #include "base/time/time.h"
     16 #include "base/timer/timer.h"
     17 
     18 namespace safe_browsing {
     19 
     20 // Runs callbacks on a given task runner, waiting a certain amount of time
     21 // between each. The delay also applies to running the first callback (i.e.,
     22 // the first callback will be run some time after Start() is invoked). Callbacks
     23 // are deleted after they are run. Start() is idempotent: calling it while the
     24 // runner is doing its job has no effect.
     25 class DelayedCallbackRunner {
     26  public:
     27   // Constructs an instance that runs tasks on |callback_runner|, waiting for
     28   // |delay| time to pass before and between each callback.
     29   DelayedCallbackRunner(base::TimeDelta delay,
     30                         const scoped_refptr<base::TaskRunner>& task_runner);
     31   ~DelayedCallbackRunner();
     32 
     33   // Registers |callback| with the runner. A copy of |callback| is held until it
     34   // is run.
     35   void RegisterCallback(const base::Closure& callback);
     36 
     37   // Starts running the callbacks after the delay.
     38   void Start();
     39 
     40  private:
     41   typedef std::list<base::Closure> CallbackList;
     42 
     43   // A callback invoked by the timer to run the next callback. The timer is
     44   // restarted to process the next callback if there is one.
     45   void OnTimer();
     46 
     47   base::ThreadChecker thread_checker_;
     48 
     49   // The runner on which callbacks are to be run.
     50   scoped_refptr<base::TaskRunner> task_runner_;
     51 
     52   // The list of callbacks to run. Callbacks are removed when run.
     53   CallbackList callbacks_;
     54 
     55   // callbacks_.end() when no work is being done. Any other value otherwise.
     56   CallbackList::iterator next_callback_;
     57 
     58   // A timer upon the firing of which the next callback will be run.
     59   base::DelayTimer<DelayedCallbackRunner> timer_;
     60 
     61   DISALLOW_COPY_AND_ASSIGN(DelayedCallbackRunner);
     62 };
     63 
     64 }  // namespace safe_browsing
     65 
     66 #endif  // CHROME_BROWSER_SAFE_BROWSING_INCIDENT_REPORTING_DELAYED_CALLBACK_RUNNER_H_
     67