* @return 0 in case of success, a negative value corresponding to an
* AVERROR code in case of failure
*/
-int ffio_rewind_with_probe_data(AVIOContext *s, unsigned char *buf, int buf_size);
+int ffio_rewind_with_probe_data(AVIOContext *s, unsigned char **buf, int buf_size);
uint64_t ffio_read_varlen(AVIOContext *bc);