dynamic_arrays.c

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

typedef struct array {
	void *array;
	size_t used;
	size_t size;
} array_t;

// initializes an array. 
// param type data type (int, char, void*, etc...)
// param arr array_t*
// param s initialize array size
#define A_INIT(type, arr, s) arr = malloc(sizeof(array_t)); \
	arr->array = (type *) malloc(s * sizeof(type)); \
	arr->used = 0; \
	arr->size = s;

// add element to array
// param type data type (int, char, ...)
// param arr array_t* to add the element to
// param e element to add
#define A_ADD(type, arr, e) if(arr->used == arr->size) { \
		arr->size += 64; \
		printf("Resizing... to %i\n", arr->size); \
		arr->array = (type *)realloc(arr->array, arr->size * sizeof(type)); \
	} \
	((type *)arr->array)[arr->used++] = e;

// get element from array
// param type data type (int, char, ...)
// param arr array_t* to get the element from
// param index index to return
#define A_GET(type, arr, index) ((type *)arr->array)[index]

// iterate array_t*
// param type data type (int, char, ...)
// param arr array_t* to get the element from
// param e element to use inside the iteration
// param i counter
#define A_EACH(type, arr, e, i) for(i = 0; i < arr->used; i++) { \
			type e = A_GET(type, arr, i);
#define A_END }

int main() {
	array_t *a;
	A_INIT(int, a, 10);
	for(int i = 0; i < 2048; i++) {
		A_ADD(int, a, i * 2);
	}
	for(int i = 0; i < a->used; i++) {
		printf("%i\n", A_GET(int, a, i));
	}
	
	// array_t of array_t's
	array_t *b;
	A_INIT(array_t*, b, 0);
	A_ADD(array_t*, b, a);
	array_t *c = A_GET(array_t*, b, 0);
	printf("%i!\n", A_GET(int, c, 5));

	// each element
	int counter;
	A_EACH(int, c, elem, counter) {
		printf("Elem %i: %i\n", counter, elem);	
	} A_END

	return 0;
}