Implement rudimentary reference counting for sqfs_object_t

Implement grab/drop functions to increase/decrease reference count
and destroy the object if the count drops to 0.

Make sure that all objects that maintain internal references actually
grab that reference, duplicate it in the copy function, drop it in
the destroy handler.

Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>

1 files changed, 10 insertions, 4 deletions

diff --git a/lib/sqfs/meta_reader.c b/lib/sqfs/meta_reader.c
index 1b48fb8..e431d40 100644
--- a/lib/sqfs/meta_reader.c
+++ b/lib/sqfs/meta_reader.c
@@ -48,6 +48,10 @@ struct sqfs_meta_reader_t {
 
 static void meta_reader_destroy(sqfs_object_t *m)
 {
+	sqfs_meta_reader_t *mr = (sqfs_meta_reader_t *)m;
+
+	sqfs_drop(mr->file);
+	sqfs_drop(mr->cmp);
 	free(m);
 }
 
@@ -58,10 +62,12 @@ static sqfs_object_t *meta_reader_copy(const sqfs_object_t *obj)
 
 	if (copy != NULL) {
 		memcpy(copy, m, sizeof(*m));
+
+		/* duplicate references */
+		copy->cmp = sqfs_grab(copy->cmp);
+		copy->file = sqfs_grab(copy->file);
 	}
 
-	/* XXX: cmp and file aren't deep-copied because m
-	        doesn't own them either. */
 	return (sqfs_object_t *)copy;
 }
 
@@ -79,8 +85,8 @@ sqfs_meta_reader_t *sqfs_meta_reader_create(sqfs_file_t *file,
 	m->block_offset = 0xFFFFFFFFFFFFFFFFUL;
 	m->start = start;
 	m->limit = limit;
-	m->file = file;
-	m->cmp = cmp;
+	m->file = sqfs_grab(file);
+	m->cmp = sqfs_grab(cmp);
 	return m;
 }