Function bitmap_clear_range

kernel/generic/src/adt/bitmap.c:166–213

Clear range of bits. * * @param bitmap Bitmap structure. * @param start Starting bit. * @param count Number of bits to clear. * */

 *
 */
void bitmap_clear_range(bitmap_t *bitmap, size_t start, size_t count)
{
	assert(start + count <= bitmap->elements);

	if (count == 0)
		return;

	size_t start_byte = start / BITMAP_ELEMENT;
	size_t aligned_start = ALIGN_UP(start, BITMAP_ELEMENT);

	/* Leading unaligned bits */
	size_t lub = min(aligned_start - start, count);

	/* Aligned middle bits */
	size_t amb = (count > lub) ? (count - lub) : 0;

	/* Trailing aligned bits */
	size_t tab = amb % BITMAP_ELEMENT;

	if (start + count < aligned_start) {
		/* Set bits in the middle of byte */
		bitmap->bits[start_byte] &=
		    ~(((1 << lub) - 1) << (start & BITMAP_REMAINER));
		return;
	}

	if (lub) {
		/* Make sure to clear any leading unaligned bits. */
		bitmap->bits[start_byte] &=
		    (1 << (BITMAP_ELEMENT - lub)) - 1;
	}

	size_t i;

	for (i = 0; i < amb / BITMAP_ELEMENT; i++) {
		/* The middle bits can be cleared byte by byte. */
		bitmap->bits[aligned_start / BITMAP_ELEMENT + i] =
		    ALL_ZEROES;
	}

	if (tab) {
		/* Make sure to clear any trailing aligned bits. */
		bitmap->bits[aligned_start / BITMAP_ELEMENT + i] &=
		    ~((1 << tab) - 1);
	}

	bitmap->next_fit = start_byte;
}

/** Copy portion of one bitmap into another bitmap.
 *