3 files changed, 96 insertions, 9 deletions

diff --git a/libavutil/log.h b/libavutil/log.h
index c1d9a6c393..18d0ddf0a8 100644
--- a/libavutil/log.h
+++ b/libavutil/log.h
@@ -73,11 +73,19 @@ typedef struct {
     int parent_log_context_offset;
 
     /**
-     * A function for extended searching, e.g. in possible
-     * children objects.
+     * Return next AVOptions-enabled child or NULL
      */
-    const struct AVOption* (*opt_find)(void *obj, const char *name, const char *unit,
-                                       int opt_flags, int search_flags);
+    void* (*child_next)(void *obj, void *prev);
+
+    /**
+     * Return an AVClass corresponding to next potential
+     * AVOptions-enabled child.
+     *
+     * The difference between child_next and this is that
+     * child_next iterates over _already existing_ objects, while
+     * child_class_next iterates over _all possible_ children.
+     */
+    const struct AVClass* (*child_class_next)(const struct AVClass *prev);
 } AVClass;
 
 /* av_log API */
diff --git a/libavutil/opt.c b/libavutil/opt.c
index 78fdf63a32..b732703c6d 100644
--- a/libavutil/opt.c
+++ b/libavutil/opt.c
@@ -583,22 +583,60 @@ int av_opt_set_dict(void *obj, AVDictionary **options)
 const AVOption *av_opt_find(void *obj, const char *name, const char *unit,
                             int opt_flags, int search_flags)
 {
-    AVClass *c = *(AVClass**)obj;
+    return av_opt_find2(obj, name, unit, opt_flags, search_flags, NULL);
+}
+
+const AVOption *av_opt_find2(void *obj, const char *name, const char *unit,
+                             int opt_flags, int search_flags, void **target_obj)
+{
+    const AVClass  *c = *(AVClass**)obj;
     const AVOption *o = NULL;
 
-    if (c->opt_find && search_flags & AV_OPT_SEARCH_CHILDREN &&
-        (o = c->opt_find(obj, name, unit, opt_flags, search_flags)))
-        return o;
+    if (search_flags & AV_OPT_SEARCH_CHILDREN) {
+        if (search_flags & AV_OPT_SEARCH_FAKE_OBJ) {
+            const AVClass *child = NULL;
+            while (child = av_opt_child_class_next(c, child))
+                if (o = av_opt_find2(&child, name, unit, opt_flags, search_flags, NULL))
+                    return o;
+        } else {
+            void *child = NULL;
+            while (child = av_opt_child_next(obj, child))
+                if (o = av_opt_find2(child, name, unit, opt_flags, search_flags, target_obj))
+                    return o;
+        }
+    }
 
     while (o = av_next_option(obj, o)) {
         if (!strcmp(o->name, name) && (o->flags & opt_flags) == opt_flags &&
             ((!unit && o->type != FF_OPT_TYPE_CONST) ||
-             (unit  && o->unit && !strcmp(o->unit, unit))))
+             (unit  && o->unit && !strcmp(o->unit, unit)))) {
+            if (target_obj) {
+                if (!(search_flags & AV_OPT_SEARCH_FAKE_OBJ))
+                    *target_obj = obj;
+                else
+                    *target_obj = NULL;
+            }
             return o;
+        }
     }
     return NULL;
 }
 
+void *av_opt_child_next(void *obj, void *prev)
+{
+    const AVClass *c = *(AVClass**)obj;
+    if (c->child_next)
+        return c->child_next(obj, prev);
+    return NULL;
+}
+
+const AVClass *av_opt_child_class_next(const AVClass *parent, const AVClass *prev)
+{
+    if (parent->child_class_next)
+        return parent->child_class_next(prev);
+    return NULL;
+}
+
 #ifdef TEST
 
 #undef printf
diff --git a/libavutil/opt.h b/libavutil/opt.h
index 50c0a33bc7..6f0a03be3c 100644
--- a/libavutil/opt.h
+++ b/libavutil/opt.h
@@ -30,6 +30,7 @@
 #include "rational.h"
 #include "avutil.h"
 #include "dict.h"
+#include "log.h"
 
 enum AVOptionType{
     FF_OPT_TYPE_FLAGS,
@@ -255,4 +256,44 @@ int av_opt_set_dict(void *obj, struct AVDictionary **options);
 const AVOption *av_opt_find(void *obj, const char *name, const char *unit,
                             int opt_flags, int search_flags);
 
+/**
+ * Look for an option in an object. Consider only options which
+ * have all the specified flags set.
+ *
+ * @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.
+ * @param opt_flags Find only options with all the specified flags set (AV_OPT_FLAG).
+ * @param search_flags A combination of AV_OPT_SEARCH_*.
+ * @param[out] target_obj if non-NULL, an object to which the option belongs will be
+ * written here. It may be different from obj if AV_OPT_SEARCH_CHILDREN is present
+ * in search_flags. This parameter is ignored if search_flags contain
+ * AV_OPT_SEARCH_FAKE_OBJ.
+ *
+ * @return A pointer to the option found, or NULL if no option
+ *         was found.
+ */
+const AVOption *av_opt_find2(void *obj, const char *name, const char *unit,
+                             int opt_flags, int search_flags, void **target_obj);
+
+/**
+ * Iterate over AVOptions-enabled children of obj.
+ *
+ * @param prev result of a previous call to this function or NULL
+ * @return next AVOptions-enabled child or NULL
+ */
+void *av_opt_child_next(void *obj, void *prev);
+
+/**
+ * Iterate over potential AVOptions-enabled children of parent.
+ *
+ * @param prev result of a previous call to this function or NULL
+ * @return AVClass corresponding to next potential child or NULL
+ */
+const AVClass *av_opt_child_class_next(const AVClass *parent, const AVClass *prev);
+
 #endif /* AVUTIL_OPT_H */