rusefi-1/firmware/util/cyclic_buffer.cpp

/**
 * @file	cyclic_buffer.c
 * @brief	A cyclic buffer is a data structure that uses a single, fixed-size buffer as if it were connected end-to-end.
 *
 * http://en.wikipedia.org/wiki/Circular_buffer
 *
 * @date Dec 8, 2013
 * @author Andrey Belomutskiy, Daniel Hill (c) 2012-2014
 * @author Daniel Hill - Modified to use C++ - Mar 2, 2014
 */


#include "cyclic_buffer.h"
#include <string.h>

//ctor
cyclic_buffer::cyclic_buffer()
{
  memset((void*)elements, 0, sizeof(elements)); // I would usually use static_cast, but due to the elements being volatile we cannot.
  currentIndex = 0;
  count = 0;
}

//cpctor
cyclic_buffer::cyclic_buffer(const cyclic_buffer& cb)
{
  //Deep copy the data
  currentIndex = cb.currentIndex;
  count = cb.count;
  for(int i = 0; i < CB_MAX_SIZE; ++i)
  {
    elements[i] = cb.elements[i];
  }
}

//dtor
cyclic_buffer::~cyclic_buffer()
{
  //No dynamic allocation - safe to leave
}

//overloaded =operator
cyclic_buffer& cyclic_buffer::operator=(const cyclic_buffer& rhCb)
{
  //Deep copy
  currentIndex = rhCb.currentIndex;
  count = rhCb.count;
  for(int i = 0; i < CB_MAX_SIZE; ++i)
  {
    elements[i] = rhCb.elements[i];
  }
  return *this;
}

void cyclic_buffer::add(int value)
{
  ++currentIndex;
  if(currentIndex == CB_MAX_SIZE)
  {
    currentIndex = 0;
  }
  elements[currentIndex] = value;

  ++count;
}

void cyclic_buffer::clear() {
	count = 0;
}

int cyclic_buffer::sum(int length)
{
  if(length > count)
  {
    length = count;
  }

  int ci = currentIndex; // local copy to increase thread-safety
  int result = 0;

  for(int i = 0; i < length; ++i)
  {
    int index = ci - i;
		while (index < 0)
		{
      index += CB_MAX_SIZE;
		}

    result += elements[index];
  }

  return result;
}