add NONE, clairfy RESERVED

1 files changed, 7 insertions, 1 deletions

diff --git a/src/include/extractor.h b/src/include/extractor.h
index 78fe627..9f24735 100644
--- a/src/include/extractor.h
+++ b/src/include/extractor.h
@@ -124,8 +124,14 @@ enum EXTRACTOR_MetaFormat
  */
 enum EXTRACTOR_MetaType
 {
-  /* fundamental types */
+  /* available to application for marking an `enum EXTRACTOR_MetaType` as not
+     carrying any meaningful value - never used by libextractor */
+  EXTRACTOR_METATYPE_NONE = -1,
+
+  /* reserved should be used as a terminator (like the '\0'-terminator for strings)
+     and is never used directly by libextractor */
   EXTRACTOR_METATYPE_RESERVED = 0,
+
   EXTRACTOR_METATYPE_MIMETYPE = 1,
   EXTRACTOR_METATYPE_FILENAME = 2,
   EXTRACTOR_METATYPE_COMMENT = 3,