MT#55283 distinguish between lookup and creation

While processing SDPs, we only need to look up manipulation
instructions, which means we can just return NULL if none were given,
instead of always creating the object.

Change-Id: If187c1289eb385b23b86b3aa326634efaf0ce5ad

include/call_interfaces.h

@@ -264,21 +264,25 @@ int call_interfaces_init(void);
 void call_interfaces_free(void);
 void call_interfaces_timer(void);
 
-INLINE struct sdp_manipulations *sdp_manipulations_get_by_id(sdp_ng_flags *f, enum media_type id) {
+INLINE struct sdp_manipulations *sdp_manipulations_get_by_id(const sdp_ng_flags *f, enum media_type id) {
+	if (id < 0 || id >= G_N_ELEMENTS(f->sdp_manipulations))
+		return NULL;
+	return f->sdp_manipulations[id];
+}
+INLINE struct sdp_manipulations *sdp_manipulations_get_create_by_id(sdp_ng_flags *f, enum media_type id) {
 	if (id < 0 || id >= G_N_ELEMENTS(f->sdp_manipulations))
 		return NULL;
 	if (!f->sdp_manipulations[id])
 		f->sdp_manipulations[id] = g_slice_alloc0(sizeof(*f->sdp_manipulations[id]));
 	return f->sdp_manipulations[id];
 }
-
 INLINE struct sdp_manipulations *sdp_manipulations_get_by_name(sdp_ng_flags *f, const str *s) {
 	if (!str_cmp(s, "none") || !str_cmp(s, "global"))
-		return sdp_manipulations_get_by_id(f, MT_UNKNOWN);
+		return sdp_manipulations_get_create_by_id(f, MT_UNKNOWN);
 	enum media_type id = codec_get_type(s);
 	if (id == MT_OTHER)
 		return NULL;
-	return sdp_manipulations_get_by_id(f, id);
+	return sdp_manipulations_get_create_by_id(f, id);
 }