Expert: if the bit-width of this reader matches one of
java's native types, returns the underlying array
(ie, byte, short, int, long); else, returns
null. Note that when accessing the array you must
upgrade the type (bitwise AND with all ones), to
interpret the full value as unsigned. Ie,
bytes[idx]&0xFF, shorts[idx]&0xFFFF, etc.
Returns true if this implementation is backed by a
native java array.