Advance the cursor to off and return an index that stored the same 4 bytes as b[o:o+4). This may only be called on strictly increasing sequences of offsets. A return value of -1 indicates that no other index could be found.
Return an index that less than off and stores the same 4 bytes. Unlike .get, it doesn't need to be called on increasing offsets. A return value of -1 indicates that no other index could be found.