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 * Copyright (c) 1998, 2020, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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 */

package javax.crypto;

import java.security.*;

import java.security.spec.*;

import java.nio.ByteBuffer;

/**

 * This class defines the <i>Service Provider Interface</i> (<b>SPI</b>)

 * for the <code>Mac</code> class.

 * All the abstract methods in this class must be implemented by each

 * cryptographic service provider who wishes to supply the implementation

 * of a particular MAC algorithm.

 *

 * <p> Implementations are free to implement the Cloneable interface.

 *

 * @author Jan Luehe

 *

 * @since 1.4

 */

public abstract class MacSpi {

    /**

     * Constructor for subclasses to call.

     */

    public MacSpi() {}

    /**

     * Returns the length of the MAC in bytes.

     *

     * @return the MAC length in bytes.

     */

    protected abstract int engineGetMacLength();

    /**

     * Initializes the MAC with the given (secret) key and algorithm

     * parameters.

     *

     * @param key the (secret) key.

     * @param params the algorithm parameters.

     *

     * @exception InvalidKeyException if the given key is inappropriate for

     * initializing this MAC.

     * @exception InvalidAlgorithmParameterException if the given algorithm

     * parameters are inappropriate for this MAC.

     */

    protected abstract void engineInit(Key key,

                                       AlgorithmParameterSpec params)

        throws InvalidKeyException, InvalidAlgorithmParameterException ;

    /**

     * Processes the given byte.

     *

     * @param input the input byte to be processed.

     */

    protected abstract void engineUpdate(byte input);

    /**

     * Processes the first <code>len</code> bytes in <code>input</code>,

     * starting at <code>offset</code> inclusive.

     *

     * @param input the input buffer.

     * @param offset the offset in <code>input</code> where the input starts.

     * @param len the number of bytes to process.

     */

    protected abstract void engineUpdate(byte[] input, int offset, int len);

    /**

     * Processes <code>input.remaining()</code> bytes in the ByteBuffer

     * <code>input</code>, starting at <code>input.position()</code>.

     * Upon return, the buffer's position will be equal to its limit;

     * its limit will not have changed.

     *

     * <p>Subclasses should consider overriding this method if they can

     * process ByteBuffers more efficiently than byte arrays.

     *

     * @param input the ByteBuffer

     * @since 1.5

     */

    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;

            }

        }

    }

    /**

     * Completes the MAC computation and resets the MAC for further use,

     * maintaining the secret key that the MAC was initialized with.

     *

     * @return the MAC result.

     */

    protected abstract byte[] engineDoFinal();

    /**

     * Resets the MAC for further use, maintaining the secret key that the

     * MAC was initialized with.

     */

    protected abstract void engineReset();

    /**

     * Returns a clone if the implementation is cloneable.

     *

     * @return a clone if the implementation is cloneable.

     *

     * @exception CloneNotSupportedException if this is called

     * on an implementation that does not support <code>Cloneable</code>.

     */

    public Object clone() throws CloneNotSupportedException {

        if (this instanceof Cloneable) {

            return super.clone();

        } else {

            throw new CloneNotSupportedException();

        }

    }

}