rolling_averager.cpp

namespace rollingaveragernamespace {
RollingAverager::RollingAverager() {
  this.buffer_index_ = 0;
  this.buffer_ = {0};
  this.sum = 0;
}

long RollingAverager::Roll(long next_input) {
  ++this.buffer_index_;
  this.buffer_index_ &= (kBufferSize - 1);
  this.sum += next_input;
  this.sum -= this.buffer_[this.buffer_index_];
  this.buffer_[this.buffer_index_] = next_input;
  return this.sum / kBufferSize;
}
}

rolling_averager.h

#ifndef PROJECT_PATH_ROLLING_AVERAGER_H_
#define PROJECT_PATH_ROLLING_AVERAGER_H_
namespace rollingaveragernamespace {
class RollingAverager {
private:
  const char kBufferSize = 8;
  char buffer_index_;
  long buffer_[kBufferSize];
  long sum;
public:
  RollingAverager();
  long Roll(long next_input);
};
} // namespace rollingaveragernamespace
#endif // PROJECT_PATH_ROLLING_AVERAGER_H_