Improve ABI backward & forward compatibillity

 - Padd the compressor config union
    - 128 bytes aught to be enough for everyone, i.e. future compressors.
    - Insist that the padding space is initialized to 0. If a field gets
      added to an existing compressor, it can test for 0 as a sentinel
      value.
 - Add a size field to the hook structure, aka "the Microsoft way".
    - The explanation is in the comment.
    - Don't make the Microsoft mistake of checking for >=, insist on *exact*
      size match. Future users will need a fallback if their hooks are
      rejected. But at least they will be rejected instead of silently not
      being used.
 - Add an unsupported flag check to the dir tree reader.
 - Add a basic abi unit test that, for now, checks the size of the compressor
   config struct fields.

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

1 files changed, 2 insertions, 0 deletions

diff --git a/include/sqfs/dir_reader.h b/include/sqfs/dir_reader.h
index 8377fdd..ec84d98 100644
--- a/include/sqfs/dir_reader.h
+++ b/include/sqfs/dir_reader.h
@@ -99,6 +99,8 @@ typedef enum {
 	 * of parent nodes with the subtree stored at the end.
 	 */
 	SQFS_TREE_STORE_PARENTS = 0x40,
+
+	SQFS_TREE_ALL_FLAGS = 0x7F,
 } E_SQFS_TREE_FILTER_FLAGS;
 
 /**