Man page 9 : relay_file_read_start_pos

relay_file_read_start_pos - find the first available byte to read

size_t relay_file_read_start_pos(size_t  read_pos , struct rchan_buf *  buf );

read_pos
    file read position

buf
    relay channel buffer

If the read_pos is in the middle of padding, return the position of the first actually available byte, otherwise return the original value.