net/proxy/load_state_change_coalescer.h

   1 // Copyright 2015 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 NET_PROXY_LOAD_STATE_CHANGE_COALESCER_H_
   6 #define NET_PROXY_LOAD_STATE_CHANGE_COALESCER_H_
   7
   8 #include "base/cancelable_callback.h"
   9 #include "base/time/time.h"
  10 #include "base/timer/timer.h"
  11 #include "net/base/load_states.h"
  12
  13 namespace net {
  14
  15 // A class that coalesces LoadState changes. When a new LoadState is reported,
  16 // it becomes the pending LoadState and is queued for |timeout|. If the timeout
  17 // elapses without another new LoadState, the pending LoadState becomes the
  18 // committed LoadState and the callback is called with that LoadState. If a new
  19 // LoadState is reported before the timeout has elapsed, the pending LoadState
  20 // is discarded and the new LoadState becomes the new pending LoadState, unless
  21 // it's the same as the committed LoadState, in which case no pending LoadState
  22 // is queued.
  23 class LoadStateChangeCoalescer {
  24  public:
  25   LoadStateChangeCoalescer(const base::Callback<void(LoadState)>& callback,
  26                            const base::TimeDelta& timeout,
  27                            LoadState initial_load_state);
  28   ~LoadStateChangeCoalescer();
  29
  30   // Adds a LoadState change to the pipeline. If it isn't coalesced, |callback_|
  31   // will be called with |load_state| after |timeout_|.
  32   void LoadStateChanged(LoadState load_state);
  33
  34  private:
  35   void SendLoadStateChanged();
  36
  37   // The callback to call to report a LoadState change.
  38   const base::Callback<void(LoadState)> callback_;
  39
  40   // The amount of time for which a LoadState change can be coalesced.
  41   const base::TimeDelta timeout_;
  42
  43   base::OneShotTimer<LoadStateChangeCoalescer> timer_;
  44   LoadState committed_load_state_;
  45   LoadState pending_load_state_;
  46
  47   DISALLOW_COPY_AND_ASSIGN(LoadStateChangeCoalescer);
  48 };
  49
  50 }  // namespace net
  51
  52 #endif  // NET_PROXY_LOAD_STATE_CHANGE_COALESCER_H_