public Location lookup(Object keyBase, long keyOffset, int keyLength) {
        safeLookup(keyBase, keyOffset, keyLength, loc);
        return loc;
    }
Looks up a key, and return a {@link Location} handle that can be used to test existence
and read/write values.

This function always return the same {@link Location} instance to avoid object allocation.
indexr-query-opt/src/main/java/org/apache/spark/unsafe/map/BytesToBytesMap.java