[cairo] [cairo-commit] 3 commits - src/cairo-array.c src/cairoint.h src/cairo-types-private.h

[Behdad Esfahbod]

On 11/24/10 08:47, Andrea Canciani wrote:
> +const void *
> +_cairo_array_index_const (const cairo_array_t *array, unsigned int index)
> +{
> +    /* We allow an index of 0 for the no-elements case.
> +     * This makes for cleaner calling code which will often look like:
> +     *
> +     *    elements = _cairo_array_index_const (array, num_elements);
> +     *	  for (i=0; i < num_elements; i++) {
> +     *        ... read elements[i] here ...
> +     *    }
> +     *
> +     * which in the num_elements==0 case gets the NULL pointer here,
> +     * but never dereferences it.
> +     */
> +    if (index == 0 && array->num_elements == 0)
> +	return NULL;
> +
> +    assert (index < array->num_elements);
> +
> +    return array->elements + index * array->element_size;
> +}

Actually the C standard allows for getting the address of the element right
after the end of an array.  That's a very legitimate use, for example to
compute an "end" pointer to which you'll compare your iterator in a loop.  The
element 0 of an empty array is just a special case of that.  May want to allow
it here as well.

Cheers,
behdad