AVOptions: add AV_OPT_SEARCH_FAKE_OBJ flag for av_opt_find().

It allows to search for options only with AVClass, without allocating
the corresponding context.

1 files changed, 9 insertions, 0 deletions

diff --git a/libavutil/opt.h b/libavutil/opt.h
index 30aa54f5b6..21dac7c569 100644
--- a/libavutil/opt.h
+++ b/libavutil/opt.h
@@ -215,6 +215,13 @@ int av_opt_set_dict(void *obj, struct AVDictionary **options);
 
 #define AV_OPT_SEARCH_CHILDREN   0x0001 /**< Search in possible children of the
                                              given object first. */
+/**
+ *  The obj passed to av_opt_find() is fake -- only a double pointer to AVClass
+ *  instead of a required pointer to a struct containing AVClass. This is
+ *  useful for searching for options without needing to allocate the corresponding
+ *  object.
+ */
+#define AV_OPT_SEARCH_FAKE_OBJ   0x0002
 
 /**
  * Look for an option in an object. Consider only options which
@@ -222,6 +229,8 @@ int av_opt_set_dict(void *obj, struct AVDictionary **options);
  *
  * @param[in] obj A pointer to a struct whose first element is a
  *                pointer to an AVClass.
+ *                Alternatively a double pointer to an AVClass, if
+ *                AV_OPT_SEARCH_FAKE_OBJ search flag is set.
  * @param[in] name The name of the option to look for.
  * @param[in] unit When searching for named constants, name of the unit
  *                 it belongs to.