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

   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 #include <time.h>
   6 #include <limits>
   7
   8 #include "nacl_app/flock.h"
   9
  10 void FrameCounter::BeginFrame() {
  11   struct timeval start_time;
  12   gettimeofday(&start_time, NULL);
  13   frame_start_ = start_time.tv_sec * kMicroSecondsPerSecond +
  14                  start_time.tv_usec;
  15 }
  16
  17 void FrameCounter::EndFrame() {
  18   struct timeval end_time;
  19   gettimeofday(&end_time, NULL);
  20   double frame_end = end_time.tv_sec * kMicroSecondsPerSecond +
  21                      end_time.tv_usec;
  22   double dt = frame_end - frame_start_;
  23   if (dt < 0)
  24     return;
  25   frame_duration_accumulator_ += dt;
  26   frame_count_++;
  27   if (frame_count_ > kFrameRateRefreshCount ||
  28       frame_duration_accumulator_ >= kMicroSecondsPerSecond) {
  29     double elapsed_time = frame_duration_accumulator_ /
  30                           kMicroSecondsPerSecond;
  31     if (fabs(elapsed_time) > std::numeric_limits<double>::epsilon()) {
  32       frames_per_second_ = frame_count_ / elapsed_time;
  33     }
  34     frame_duration_accumulator_ = 0;
  35     frame_count_ = 0;
  36   }
  37 }
  38
  39 void FrameCounter::Reset() {
  40   frames_per_second_ = 0;
  41   frame_duration_accumulator_ = 0;
  42   frame_count_ = 0;
  43 }