avoptions: Add an av_opt_flag_is_set function for inspecting flag fields

Signed-off-by: Martin Storsjö <martin@martin.st>

doc/APIchanges

@@ -13,6 +13,9 @@ libavutil:   2011-04-18
 
 API changes, most recent first:
 
+2011-06-xx - xxxxxxx - lavu 51.6.0 - opt.h
+  Add av_opt_flag_is_set().
+
 2011-06-xx - xxxxxxx - lavu 51.5.0 - AVMetadata
   Move AVMetadata from lavf to lavu and rename it to
   AVDictionary -- new installed header dict.h.

libavutil/avutil.h

@@ -40,7 +40,7 @@
 #define AV_VERSION(a, b, c) AV_VERSION_DOT(a, b, c)
 
 #define LIBAVUTIL_VERSION_MAJOR 51
-#define LIBAVUTIL_VERSION_MINOR  5
+#define LIBAVUTIL_VERSION_MINOR  6
 #define LIBAVUTIL_VERSION_MICRO  0
 
 #define LIBAVUTIL_VERSION_INT   AV_VERSION_INT(LIBAVUTIL_VERSION_MAJOR, \

libavutil/opt.c

@@ -320,6 +320,16 @@ int64_t av_get_int(void *obj, const char *name, const AVOption **o_out)
     return num*intnum/den;
 }
 
+int av_opt_flag_is_set(void *obj, const char *field_name, const char *flag_name)
+{
+    const AVOption *field = av_find_opt(obj, field_name, NULL, 0, 0);
+    const AVOption *flag  = av_find_opt(obj, flag_name,  NULL, 0, 0);
+
+    if (!field || !flag || flag->type != FF_OPT_TYPE_CONST)
+        return 0;
+    return av_get_int(obj, field_name, NULL) & (int) flag->default_val.dbl;
+}
+
 static void opt_list(void *obj, void *av_log_obj, const char *unit,
                      int req_flags, int rej_flags)
 {

libavutil/opt.h

@@ -181,4 +181,14 @@ int av_set_options_string(void *ctx, const char *opts,
  */
 void av_opt_free(void *obj);
 
+/**
+ * Check whether a particular flag is set in a flags field.
+ *
+ * @param field_name the name of the flag field option
+ * @param flag_name the name of the flag to check
+ * @return non-zero if the flag is set, zero if the flag isn't set,
+ *         isn't of the right type, or the flags field doesn't exist.
+ */
+int av_opt_flag_is_set(void *obj, const char *field_name, const char *flag_name);
+
 #endif /* AVUTIL_OPT_H */