native_client_sdk/src/examples/demo/flock/frame_counter.h

   1 // Copyright 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 FRAME_COUNTER_H_
   6 #define FRAME_COUNTER_H_
   7
   8 class FrameCounter {
   9  public:
  10   FrameCounter()
  11       : frame_duration_accumulator_(0),
  12         frame_count_(0),
  13         frames_per_second_(0) {}
  14   ~FrameCounter() {}
  15
  16   // Record the current time, which is used to compute the frame duration
  17   // when EndFrame() is called.
  18   void BeginFrame();
  19
  20   // Compute the delta since the last call to BeginFrame() and increment the
  21   // frame count.  Update the frame rate whenever the prescribed number of
  22   // frames have been counted, or at least one second of simulator time has
  23   // passed, whichever is less.
  24   void EndFrame();
  25
  26   // Reset the frame counters back to 0.
  27   void Reset();
  28
  29   // The current frame rate.  Note that this is 0 for the first second in
  30   // the accumulator, and is updated every 100 frames (and at least once
  31   // every second of simulation time or so).
  32   double frames_per_second() const {
  33     return frames_per_second_;
  34   }
  35
  36  private:
  37   static const double kMicroSecondsPerSecond = 1000000.0;
  38   static const int32_t kFrameRateRefreshCount = 100;
  39
  40   double frame_duration_accumulator_;  // Measured in microseconds.
  41   int32_t frame_count_;
  42   double frame_start_;
  43   double frames_per_second_;
  44 };
  45
  46 #endif  // FRAME_COUNTER_H_