#include <assert.h>
#include <stdlib.h>
#include <stdint.h>

#include "array.h"

void *
array_new(size_t item_size)
{
    array_header_t *h = malloc((item_size * ARRAY_INITIAL_CAPACITY) + sizeof(array_header_t));
    if (h == NULL) {
        return NULL;
    }
    h->length = 0;
    h->item_size = item_size;
    h->capacity = ARRAY_INITIAL_CAPACITY;
    return h + sizeof(array_header_t);
}

array_header_t *
array_get_header(void *arr)
{
    return (array_header_t *) arr - sizeof(array_header_t);
}

void *
array_grow(void *arr)
{
	array_header_t *h = array_get_header(arr);
	h->capacity *= 2;
	h = realloc(h, sizeof(array_header_t) + (h->capacity * h->item_size));
	return h + sizeof(array_header_t);
}

size_t
array_length(void *arr)
{
    assert(arr);
    array_header_t *header = array_get_header(arr);
    return header->length;
}