1 files changed, 92 insertions, 0 deletions
diff --git a/pack-bitmap.c b/pack-bitmap.c
index 33e748273a..82090a6741 100644
--- a/pack-bitmap.c
+++ b/pack-bitmap.c
@@ -968,3 +968,95 @@ void test_bitmap_walk(struct rev_info *revs)
 	else
 		fprintf(stderr, "Mismatch!\n");
 }
+
+static int rebuild_bitmap(uint32_t *reposition,
+			  struct ewah_bitmap *source,
+			  struct bitmap *dest)
+{
+	uint32_t pos = 0;
+	struct ewah_iterator it;
+	eword_t word;
+
+	ewah_iterator_init(&it, source);
+
+	while (ewah_iterator_next(&word, &it)) {
+		uint32_t offset, bit_pos;
+
+		for (offset = 0; offset < BITS_IN_WORD; ++offset) {
+			if ((word >> offset) == 0)
+				break;
+
+			offset += ewah_bit_ctz64(word >> offset);
+
+			bit_pos = reposition[pos + offset];
+			if (bit_pos > 0)
+				bitmap_set(dest, bit_pos - 1);
+			else /* can't reuse, we don't have the object */
+				return -1;
+		}
+
+		pos += BITS_IN_WORD;
+	}
+	return 0;
+}
+
+int rebuild_existing_bitmaps(struct packing_data *mapping,
+			     khash_sha1 *reused_bitmaps,
+			     int show_progress)
+{
+	uint32_t i, num_objects;
+	uint32_t *reposition;
+	struct bitmap *rebuild;
+	struct stored_bitmap *stored;
+	struct progress *progress = NULL;
+
+	khiter_t hash_pos;
+	int hash_ret;
+
+	if (prepare_bitmap_git() < 0)
+		return -1;
+
+	num_objects = bitmap_git.pack->num_objects;
+	reposition = xcalloc(num_objects, sizeof(uint32_t));
+
+	for (i = 0; i < num_objects; ++i) {
+		const unsigned char *sha1;
+		struct revindex_entry *entry;
+		struct object_entry *oe;
+
+		entry = &bitmap_git.reverse_index->revindex[i];
+		sha1 = nth_packed_object_sha1(bitmap_git.pack, entry->nr);
+		oe = packlist_find(mapping, sha1, NULL);
+
+		if (oe)
+			reposition[i] = oe->in_pack_pos + 1;
+	}
+
+	rebuild = bitmap_new();
+	i = 0;
+
+	if (show_progress)
+		progress = start_progress("Reusing bitmaps", 0);
+
+	kh_foreach_value(bitmap_git.bitmaps, stored, {
+		if (stored->flags & BITMAP_FLAG_REUSE) {
+			if (!rebuild_bitmap(reposition,
+					    lookup_stored_bitmap(stored),
+					    rebuild)) {
+				hash_pos = kh_put_sha1(reused_bitmaps,
+						       stored->sha1,
+						       &hash_ret);
+				kh_value(reused_bitmaps, hash_pos) =
+					bitmap_to_ewah(rebuild);
+			}
+			bitmap_reset(rebuild);
+			display_progress(progress, ++i);
+		}
+	});
+
+	stop_progress(&progress);
+
+	free(reposition);
+	bitmap_free(rebuild);
+	return 0;
+}