moving_avg.c

#include <stdio.h>
#include <stdlib.h>

typedef struct {
  int *pArrNumbers;
  long pSum;
  int pos;
  int len;
  int (*funcMovingAvg)(void *self, int nextNum);
} MovingAvg;

int getMovingAvg(void *self, int nextNum)
{
  MovingAvg *ma = self;
  // printf("pSum: %lu\n", ma->pSum);
  // printf("nextNum: %d\n", nextNum);
  // printf("ma->pos: %d\n", ma->pos);
  // printf("ma->pArrNumbers[ma->pos]: %d\n", (ma->pArrNumbers)[(ma->pos)]);
  ma->pSum = ma->pSum - ma->pArrNumbers[ma->pos] + nextNum;
  ma->pArrNumbers[ma->pos] = nextNum;
  ma->pos++;
  if (ma->pos >= ma->len){
    ma->pos = 0;
  }

  return ma->pSum / ma->len;
}

MovingAvg *MovingAvg_new(int arrSize)
{
  MovingAvg *movingAvg = malloc(sizeof(MovingAvg));
  int *arrNumbers = calloc(arrSize, sizeof(int));
  movingAvg->pArrNumbers = arrNumbers;
  movingAvg->pSum = 0;
  movingAvg->pos = 0;
  movingAvg->len = arrSize;
  movingAvg->funcMovingAvg = getMovingAvg;

  return movingAvg;
}

void MovingAvg_destroy(void *self)
{
  MovingAvg *ma = self;

  if(ma) {
    if(ma->pArrNumbers) free(ma->pArrNumbers);
    free(ma);
  }
}

int main(int argc, char *argv[])
{
  // a sample array of numbers. The represent "readings" from a sensor over time
  int sample[] = {50, 10, 20, 18, 20, 100, 18, 10, 13, 500, 50, 40, 10};
  // the size of this array represents how many numbers will be used
  // to calculate the average
  int count = sizeof(sample) / sizeof(int);
  int newAvg = 0;

  MovingAvg *movingAvg = MovingAvg_new(10);

  for(int i = 0; i < count; i++){
    newAvg = movingAvg->funcMovingAvg(movingAvg, sample[i]);
    printf("The new average is %d\n", newAvg);
  }

  return 0;
}