AVOptions: add flags for read/read-only options

doc/APIchanges

@@ -13,6 +13,10 @@ libavutil:     2013-12-xx
 
 API changes, most recent first:
 
+2014-xx-xx - xxxxxxx - lavu 53.04.0  - opt.h
+  Add AV_OPT_FLAG_EXPORT and AV_OPT_FLAG_READONLY to mark options meant (only)
+  for reading.
+
 2014-xx-xx - xxxxxxx - lavu 53.03.01 - opt.h
   Deprecate unused AV_OPT_FLAG_METADATA.
 

libavutil/opt.c

@@ -213,7 +213,7 @@ int av_opt_set(void *obj, const char *name, const char *val, int search_flags)
     const AVOption *o = av_opt_find2(obj, name, NULL, 0, search_flags, &target_obj);
     if (!o || !target_obj)
         return AVERROR_OPTION_NOT_FOUND;
-    if (!val)
+    if (!val || o->flags & AV_OPT_FLAG_READONLY)
         return AVERROR(EINVAL);
 
     dst = ((uint8_t*)target_obj) + o->offset;
@@ -235,7 +235,7 @@ int av_opt_set(void *obj, const char *name, const char *val, int search_flags)
 #define OPT_EVAL_NUMBER(name, opttype, vartype)\
     int av_opt_eval_ ## name(void *obj, const AVOption *o, const char *val, vartype *name ## _out)\
     {\
-        if (!o || o->type != opttype)\
+        if (!o || o->type != opttype || o->flags & AV_OPT_FLAG_READONLY)\
             return AVERROR(EINVAL);\
         return set_string_number(obj, obj, o, val, name ## _out);\
     }
@@ -256,6 +256,9 @@ static int set_number(void *obj, const char *name, double num, int den, int64_t
     if (!o || !target_obj)
         return AVERROR_OPTION_NOT_FOUND;
 
+    if (o->flags & AV_OPT_FLAG_READONLY)
+        return AVERROR(EINVAL);
+
     dst = ((uint8_t*)target_obj) + o->offset;
     return write_number(obj, o, dst, num, den, intnum);
 }
@@ -286,7 +289,7 @@ int av_opt_set_bin(void *obj, const char *name, const uint8_t *val, int len, int
     if (!o || !target_obj)
         return AVERROR_OPTION_NOT_FOUND;
 
-    if (o->type != AV_OPT_TYPE_BINARY)
+    if (o->type != AV_OPT_TYPE_BINARY || o->flags & AV_OPT_FLAG_READONLY)
         return AVERROR(EINVAL);
 
     ptr = av_malloc(len);
@@ -479,6 +482,8 @@ static void opt_list(void *obj, void *av_log_obj, const char *unit,
         av_log(av_log_obj, AV_LOG_INFO, "%c", (opt->flags & AV_OPT_FLAG_VIDEO_PARAM   ) ? 'V' : '.');
         av_log(av_log_obj, AV_LOG_INFO, "%c", (opt->flags & AV_OPT_FLAG_AUDIO_PARAM   ) ? 'A' : '.');
         av_log(av_log_obj, AV_LOG_INFO, "%c", (opt->flags & AV_OPT_FLAG_SUBTITLE_PARAM) ? 'S' : '.');
+        av_log(av_log_obj, AV_LOG_INFO, "%c", (opt->flags & AV_OPT_FLAG_EXPORT)         ? 'X' : '.');
+        av_log(av_log_obj, AV_LOG_INFO, "%c", (opt->flags & AV_OPT_FLAG_READONLY)       ? 'R' : '.');
 
         if (opt->help)
             av_log(av_log_obj, AV_LOG_INFO, " %s", opt->help);
@@ -505,6 +510,9 @@ void av_opt_set_defaults(void *s)
 {
     const AVOption *opt = NULL;
     while ((opt = av_opt_next(s, opt)) != NULL) {
+        if (opt->flags & AV_OPT_FLAG_READONLY)
+            continue;
+
         switch (opt->type) {
             case AV_OPT_TYPE_CONST:
                 /* Nothing to be done here */

libavutil/opt.h

@@ -268,6 +268,15 @@ typedef struct AVOption {
 #define AV_OPT_FLAG_AUDIO_PARAM     8
 #define AV_OPT_FLAG_VIDEO_PARAM     16
 #define AV_OPT_FLAG_SUBTITLE_PARAM  32
+/**
+ * The option is inteded for exporting values to the caller.
+ */
+#define AV_OPT_FLAG_EXPORT          64
+/**
+ * The option may not be set through the AVOptions API, only read.
+ * This flag only makes sense when AV_OPT_FLAG_EXPORT is also set.
+ */
+#define AV_OPT_FLAG_READONLY        128
 //FIXME think about enc-audio, ... style flags
 
     /**

libavutil/version.h

@@ -54,8 +54,8 @@
  */
 
 #define LIBAVUTIL_VERSION_MAJOR 53
-#define LIBAVUTIL_VERSION_MINOR  3
-#define LIBAVUTIL_VERSION_MICRO  1
+#define LIBAVUTIL_VERSION_MINOR  4
+#define LIBAVUTIL_VERSION_MICRO  0
 
 #define LIBAVUTIL_VERSION_INT   AV_VERSION_INT(LIBAVUTIL_VERSION_MAJOR, \
                                                LIBAVUTIL_VERSION_MINOR, \