public Object clone() throws CloneNotSupportedException 
{
        if (this instanceof Cloneable) {
            return super.clone();
        } else {
            throw new CloneNotSupportedException();
        }
}

Returns a clone if the implementation is cloneable.

 abstract protected byte[] engineDoFinal()
Completes the MAC computation and resets the MAC for further use,
maintaining the secret key that the MAC was initialized with.

 abstract protected int engineGetMacLength()
Returns the length of the MAC in bytes.

 abstract protected  void engineInit(Key key,
    AlgorithmParameterSpec params) throws InvalidKeyException, InvalidAlgorithmParameterException
Initializes the MAC with the given (secret) key and algorithm
parameters.

 abstract protected  void engineReset()
Resets the MAC for further use, maintaining the secret key that the
MAC was initialized with.

 abstract protected  void engineUpdate(byte input)
Processes the given byte.

 protected  void engineUpdate(ByteBuffer input) 
{
        if (input.hasRemaining() == false) {
            return;
        }
        if (input.hasArray()) {
            byte[] b = input.array();
            int ofs = input.arrayOffset();
            int pos = input.position();
            int lim = input.limit();
            engineUpdate(b, ofs + pos, lim - pos);
            input.position(lim);
        } else {
            int len = input.remaining();
            byte[] b = new byte[CipherSpi.getTempArraySize(len)];
            while (len  > 0) {
                int chunk = Math.min(len, b.length);
                input.get(b, 0, chunk);
                engineUpdate(b, 0, chunk);
                len -= chunk;
            }
        }
}

Processes input.remaining() bytes in the ByteBuffer input, starting at input.position(). Upon return, the buffer's position will be equal to its limit; its limit will not have changed.

Subclasses should consider overriding this method if they can process ByteBuffers more efficiently than byte arrays.

 abstract protected  void engineUpdate(byte[] input,
    int offset,
    int len)
Processes the first len bytes in input,
starting at offset inclusive.