@@ -65,6 +65,17 @@ struct HBitmapIter {
HBitmap *hbitmap_alloc(uint64_t size, int granularity);
/**
+ * hbitmap_merge:
+ * @a: The bitmap to store the result in.
+ * @b: The bitmap to merge into @a.
+ *
+ * Merge two bitmaps together.
+ * A := A (BITOR) B.
+ * B is left unmodified.
+ */
+bool hbitmap_merge(HBitmap *a, const HBitmap *b);
+
+/**
* hbitmap_empty:
* @hb: HBitmap to operate on.
*
@@ -395,3 +395,35 @@ HBitmap *hbitmap_alloc(uint64_t size, int granularity)
hb->levels[0][0] |= 1UL << (BITS_PER_LONG - 1);
return hb;
}
+
+/**
+ * Given HBitmaps A and B, let A := A (BITOR) B.
+ * Bitmap B will not be modified.
+ */
+bool hbitmap_merge(HBitmap *a, const HBitmap *b)
+{
+ int i, j;
+ uint64_t size;
+
+ if ((a->size != b->size) || (a->granularity != b->granularity)) {
+ return false;
+ }
+
+ if (hbitmap_count(b) == 0) {
+ return true;
+ }
+
+ /* This merge is O(size), as BITS_PER_LONG and HBITMAP_LEVELS are constant.
+ * It may be possible to improve running times for sparsely populated maps
+ * by using hbitmap_iter_next, but this is suboptimal for dense maps.
+ */
+ size = a->size;
+ for (i = HBITMAP_LEVELS - 1; i >= 0; i--) {
+ size = MAX((size + BITS_PER_LONG - 1) >> BITS_PER_LEVEL, 1);
+ for (j = 0; j < size; j++) {
+ a->levels[i][j] |= b->levels[i][j];
+ }
+ }
+
+ return true;
+}