[FFmpeg-devel] [PATCH] lavfi: add avfilter_get_class() and iteration callbacks

[Stefano Sabatini]

Allow iteration over specific filter options.
---
 libavfilter/avfilter.c |   31 +++++++++++++++++++++++++++++++
 libavfilter/avfilter.h |    6 ++++++
 2 files changed, 37 insertions(+), 0 deletions(-)

diff --git a/libavfilter/avfilter.c b/libavfilter/avfilter.c
index c698d8a..e5935cd 100644
--- a/libavfilter/avfilter.c
+++ b/libavfilter/avfilter.c
@@ -432,13 +432,44 @@ static const char *default_filter_name(void *filter_ctx)
     return ctx->name ? ctx->name : ctx->filter->name;
 }
 
+static void *filter_child_next(void *obj, void *prev)
+{
+    AVFilterContext *ctx = obj;
+    if (!prev && ctx->filter && ctx->filter->priv_class && ctx->priv)
+        return ctx->priv;
+    return NULL;
+}
+
+static const AVClass *filter_child_class_next(const AVClass *prev)
+{
+    AVFilter **filter_ptr = NULL;
+
+    /* find the filter that corresponds to prev */
+    while (prev && (filter_ptr = av_filter_next(filter_ptr)))
+        if ((*filter_ptr)->priv_class == prev)
+            break;
+
+    /* find next filter with specific options */
+    while (*(filter_ptr = av_filter_next(filter_ptr)))
+        if ((*filter_ptr)->priv_class)
+            return (*filter_ptr)->priv_class;
+    return NULL;
+}
+
 static const AVClass avfilter_class = {
     .class_name = "AVFilter",
     .item_name  = default_filter_name,
     .version    = LIBAVUTIL_VERSION_INT,
     .category   = AV_CLASS_CATEGORY_FILTER,
+    .child_next = filter_child_next,
+    .child_class_next = filter_child_class_next,
 };
 
+const AVClass *avfilter_get_class(void)
+{
+    return &avfilter_class;
+}
+
 int avfilter_open(AVFilterContext **filter_ctx, AVFilter *filter, const char *inst_name)
 {
     AVFilterContext *ret;
diff --git a/libavfilter/avfilter.h b/libavfilter/avfilter.h
index 54a0b97..07bc5a9 100644
--- a/libavfilter/avfilter.h
+++ b/libavfilter/avfilter.h
@@ -47,6 +47,10 @@ const char *avfilter_configuration(void);
  */
 const char *avfilter_license(void);
 
+/**
+ * Get the class for the AVFilterContext struct.
+ */
+const AVClass *avfilter_get_class(void);
 
 typedef struct AVFilterContext AVFilterContext;
 typedef struct AVFilterLink    AVFilterLink;
@@ -469,6 +473,8 @@ typedef struct AVFilter {
      * used for providing binary data.
      */
     int (*init_opaque)(AVFilterContext *ctx, const char *args, void *opaque);
+
+    const AVClass *priv_class;      ///< private class, containing filter specific options
 } AVFilter;
 
 /** An instance of a filter */
-- 
1.7.5.4