1// Copyright (c) 2013 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 COMPONENTS_POLICY_CORE_COMMON_CLOUD_RATE_LIMITER_H_
6#define COMPONENTS_POLICY_CORE_COMMON_CLOUD_RATE_LIMITER_H_
7
8#include <queue>
9
10#include "base/basictypes.h"
11#include "base/callback.h"
12#include "base/cancelable_callback.h"
13#include "base/memory/ref_counted.h"
14#include "base/memory/scoped_ptr.h"
15#include "base/threading/non_thread_safe.h"
16#include "base/time/time.h"
17#include "components/policy/policy_export.h"
18
19namespace base {
20class SequencedTaskRunner;
21class TickClock;
22}
23
24namespace policy {
25
26// A simple class to limit the rate at which a callback is invoked.
27class POLICY_EXPORT RateLimiter : public base::NonThreadSafe {
28 public:
29  // Will limit invocations of |callback| to |max_requests| per |duration|.
30  // |task_runner| is used to post delayed tasks, and |clock| is used to
31  // measure elapsed time.
32  RateLimiter(size_t max_requests,
33              const base::TimeDelta& duration,
34              const base::Closure& callback,
35              scoped_refptr<base::SequencedTaskRunner> task_runner,
36              scoped_ptr<base::TickClock> clock);
37  ~RateLimiter();
38
39  // Posts a request to invoke |callback_|. It is invoked immediately if the
40  // rate in the preceding |duration_| period is within the limit, otherwise
41  // the callback will be invoked later, ensuring the allowed rate is not
42  // exceeded.
43  void PostRequest();
44
45 private:
46  const size_t max_requests_;
47  const base::TimeDelta duration_;
48  base::Closure callback_;
49  scoped_refptr<base::SequencedTaskRunner> task_runner_;
50  scoped_ptr<base::TickClock> clock_;
51
52  std::queue<base::TimeTicks> invocation_times_;
53  base::CancelableClosure delayed_callback_;
54
55  DISALLOW_COPY_AND_ASSIGN(RateLimiter);
56};
57
58}  // namespace policy
59
60#endif  // COMPONENTS_POLICY_CORE_COMMON_CLOUD_RATE_LIMITER_H_
61