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package javax.crypto;

import java.security.*;
import java.security.spec.*;

import java.nio.ByteBuffer;


This class defines the Service Provider Interface (SPI)
for the Mac 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.

 Implementations are free to implement the Cloneable interface.

Author:Jan Luehe
Since:1.4
/**
 * 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.

/**
     * Constructor for subclasses to call.
     */
    public MacSpi() {}

    
Returns the length of the MAC in bytes.

Returns:the MAC length in bytes.
/**
     * 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.

Params:
  • key – the (secret) key.
  • params – the algorithm parameters.
Throws:
/**
     * 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.

Params:
  • input – the input byte to be processed.
/**
     * Processes the given byte.
     *
     * @param input the input byte to be processed.
     */
    protected abstract void engineUpdate(byte input);

    
Processes the first len bytes in input,
starting at offset inclusive.

Params:
  • input – the input buffer.
  • offset – the offset in input where the input starts.
  • len – the number of bytes to process.
/**
     * 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 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.

Params:
  • input – the ByteBuffer
Since:1.5
/**
     * 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.

Returns:the MAC result.
/**
     * 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.

/**
     * 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.

Throws:
Returns:a clone if the implementation is cloneable.
/**
     * 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();
        }
    }
}