c array helpers

array.c

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

#define ARRAY_CAPACITY_INDEX 0
#define ARRAY_LENGTH_INDEX 1
#define ARRAY_DATA_START_INDEX 2

#define capacity(array) array[ARRAY_CAPACITY_INDEX]
#define length(array) array[ARRAY_LENGTH_INDEX]
#define get(array, index) array[ARRAY_DATA_START_INDEX + index]
#define set(array, index, value) get(array, index) = value

static int *array_grow(int *array, int size)
{
  int desired_capacity = length(array) + size + 2;
  if (desired_capacity > capacity(array)) {
    int new_capacity = capacity(array);
    while (desired_capacity > new_capacity) {
      new_capacity = new_capacity * 2;
    }
    capacity(array) = new_capacity;
    array = realloc(array, new_capacity * sizeof(int));
  }
  return array;
}

void array_print(int *array)
{
  printf("length = %d, capacity = %d\n", length(array), capacity(array));
  printf("[");
  for (int i = 0; i < length(array); i++) {
    if (i == length(array) - 1) {
      printf("%d", get(array, i));
    } else {
      printf("%d, ", get(array, i));
    }
  }
  printf("]\n");
}

int *array_new(int cap)
{
  if (cap < 2) {
    cap = 2;
  }
  int *array = malloc(cap * sizeof(int));
  length(array) = 0;
  capacity(array) = cap;
  return array;
}

int *array_push(int *array, int value)
{
  int len = length(array);
  array = array_grow(array, len + 1);
  set(array, len, value);
  length(array) = len + 1;
  return array;
}