decoder/vorbis: use single global ov_callbacks constant

src/decoder/vorbis_decoder_plugin.c

@@ -97,6 +97,13 @@ static long ogg_tell_cb(void *data)
 	return (long)vis->input_stream->offset;
 }
 
+static const ov_callbacks vorbis_is_callbacks = {
+	.read_func = ogg_read_cb,
+	.seek_func = ogg_seek_cb,
+	.close_func = ogg_close_cb,
+	.tell_func = ogg_tell_cb,
+};
+
 static const char *
 vorbis_strerror(int code)
 {
@@ -251,7 +258,6 @@ vorbis_stream_decode(struct decoder *decoder,
 {
 	GError *error = NULL;
 	OggVorbis_File vf;
-	ov_callbacks callbacks;
 	struct vorbis_input_stream vis;
 	struct audio_format audio_format;
 	float total_time;
@@ -275,11 +281,8 @@ vorbis_stream_decode(struct decoder *decoder,
 	vis.input_stream = input_stream;
 	vis.seekable = oggvorbis_seekable(input_stream);
 
-	callbacks.read_func = ogg_read_cb;
-	callbacks.seek_func = ogg_seek_cb;
-	callbacks.close_func = ogg_close_cb;
-	callbacks.tell_func = ogg_tell_cb;
-	if ((ret = ov_open_callbacks(&vis, &vf, NULL, 0, callbacks)) < 0) {
+	if ((ret = ov_open_callbacks(&vis, &vf, NULL, 0,
+				     vorbis_is_callbacks)) < 0) {
 		if (decoder_get_command(decoder) != DECODE_COMMAND_NONE)
 			return;