Function elem_start_pt

dpdk/lib/eal/common/malloc_elem.c:218–273

* calculate the starting point of where data of the requested size * and alignment would fit in the current element. If the data doesn't * fit, return NULL. */

 * fit, return NULL.
 */
static void *
elem_start_pt(struct malloc_elem *elem, size_t size, unsigned align,
		size_t bound, bool contig)
{
	size_t elem_size = elem->size;

	/*
	 * we're allocating from the end, so adjust the size of element by
	 * alignment size.
	 */
	while (elem_size >= size) {
		const size_t bmask = ~(bound - 1);
		uintptr_t end_pt = (uintptr_t)elem +
				elem_size - MALLOC_ELEM_TRAILER_LEN;
		uintptr_t new_data_start = RTE_ALIGN_FLOOR((end_pt - size),
				align);
		uintptr_t new_elem_start;

		/* check boundary */
		if ((new_data_start & bmask) != ((end_pt - 1) & bmask)) {
			end_pt = RTE_ALIGN_FLOOR(end_pt, bound);
			new_data_start = RTE_ALIGN_FLOOR((end_pt - size),
					align);
			end_pt = new_data_start + size;

			if (((end_pt - 1) & bmask) != (new_data_start & bmask))
				return NULL;
		}

		new_elem_start = new_data_start - MALLOC_ELEM_HEADER_LEN;

		/* if the new start point is before the exist start,
		 * it won't fit
		 */
		if (new_elem_start < (uintptr_t)elem)
			return NULL;

		if (contig) {
			size_t new_data_size = end_pt - new_data_start;

			/*
			 * if physical contiguousness was requested and we
			 * couldn't fit all data into one physically contiguous
			 * block, try again with lower addresses.
			 */
			if (!elem_check_phys_contig(elem->msl,
					(void *)new_data_start,
					new_data_size)) {
				elem_size -= align;
				continue;
			}
		}
		return (void *)new_elem_start;
	}
	return NULL;
}

/*