Add a start anchor parameter to sqfs_dir_reader_find_by_path

It optionally allows code that does tree traversal to start at an
inode that it obtained previously and makes it easier to keep state
externally.

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

2 files changed, 14 insertions, 4 deletions

diff --git a/include/sqfs/dir_reader.h b/include/sqfs/dir_reader.h
index 8071ef4..82121ed 100644
--- a/include/sqfs/dir_reader.h
+++ b/include/sqfs/dir_reader.h
@@ -269,11 +269,14 @@ SQFS_API int sqfs_dir_reader_get_root_inode(sqfs_dir_reader_t *rd,
 					    sqfs_inode_generic_t **inode);
 
 /**
- * @brief Find an inode through path traversal from the root node downwards.
+ * @brief Find an inode through path traversal starting from the root or a
+ *        given node downwards.
  *
  * @memberof sqfs_dir_reader_t
  *
  * @param rd A pointer to a directory reader.
+ * @param start If not NULL, path traversal starts at this node downwards. If
+ *              set to NULL, start at the root node.
  * @param path A path to resolve into an inode. Forward or backward slashes can
  *             be used to separate path components. Resolving '.' or '..' is
  *             not supported.
@@ -283,6 +286,7 @@ SQFS_API int sqfs_dir_reader_get_root_inode(sqfs_dir_reader_t *rd,
  * @return Zero on success, an @ref E_SQFS_ERROR value on failure.
  */
 SQFS_API int sqfs_dir_reader_find_by_path(sqfs_dir_reader_t *rd,
+					  const sqfs_inode_generic_t *start,
 					  const char *path,
 					  sqfs_inode_generic_t **out);
 
diff --git a/lib/sqfs/dir_reader.c b/lib/sqfs/dir_reader.c
index bda7d7a..8eae5bd 100644
--- a/lib/sqfs/dir_reader.c
+++ b/lib/sqfs/dir_reader.c
@@ -210,15 +210,21 @@ int sqfs_dir_reader_get_root_inode(sqfs_dir_reader_t *rd,
 					   block_start, offset, inode);
 }
 
-int sqfs_dir_reader_find_by_path(sqfs_dir_reader_t *rd, const char *path,
-				 sqfs_inode_generic_t **out)
+int sqfs_dir_reader_find_by_path(sqfs_dir_reader_t *rd,
+				 const sqfs_inode_generic_t *start,
+				 const char *path, sqfs_inode_generic_t **out)
 {
 	sqfs_inode_generic_t *inode;
 	sqfs_dir_entry_t *ent;
 	const char *ptr;
 	int ret;
 
-	ret = sqfs_dir_reader_get_root_inode(rd, &inode);
+	if (start == NULL) {
+		ret = sqfs_dir_reader_get_root_inode(rd, &inode);
+	} else {
+		ret = sqfs_inode_copy(start, &inode);
+	}
+
 	if (ret)
 		return ret;