/*
 * Copyright 1998-2007 Sun Microsystems, Inc.  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.  Sun designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
 * CA 95054 USA or visit www.sun.com if you need additional information or
 * have any questions.
 */

package com.sun.crypto.provider;

import java.nio.ByteBuffer;

import javax.crypto.MacSpi;
import javax.crypto.SecretKey;
import java.security.*;
import java.security.spec.*;

/**
 * This is an implementation of the HMAC-MD5 algorithm.
 *
 * @author Jan Luehe
 */
public final class HmacMD5 extends MacSpi implements Cloneable {

    private HmacCore hmac;
    private static final int MD5_BLOCK_LENGTH = 64;

    /**
     * Standard constructor, creates a new HmacMD5 instance.
     * Verify the SunJCE provider in the constructor.
     *
     * @exception SecurityException if fails to verify
     * its own integrity
     */
    public HmacMD5() throws NoSuchAlgorithmException {
        if (!SunJCE.verifySelfIntegrity(this.getClass())) {
            throw new SecurityException("The SunJCE provider may have " +
                                        "been tampered.");
        }
        hmac = new HmacCore(MessageDigest.getInstance("MD5"),
                            MD5_BLOCK_LENGTH);
    }

    /**
     * Returns the length of the HMAC in bytes.
     *
     * @return the HMAC length in bytes.
     */
    protected int engineGetMacLength() {
        return hmac.getDigestLength();
    }

    /**
     * Initializes the HMAC 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 void engineInit(Key key, AlgorithmParameterSpec params)
        throws InvalidKeyException, InvalidAlgorithmParameterException {
        hmac.init(key, params);
    }

    /**
     * Processes the given byte.
     *
     * @param input the input byte to be processed.
     */
    protected void engineUpdate(byte input) {
        hmac.update(input);
    }

    /**
     * Processes the first <code>len</code> bytes in <code>input</code>,
     * starting at <code>offset</code>.
     *
     * @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 void engineUpdate(byte input[], int offset, int len) {
        hmac.update(input, offset, len);
    }

    protected void engineUpdate(ByteBuffer input) {
        hmac.update(input);
    }

    /**
     * Completes the HMAC computation and resets the HMAC for further use,
     * maintaining the secret key that the HMAC was initialized with.
     *
     * @return the HMAC result.
     */
    protected byte[] engineDoFinal() {
        return hmac.doFinal();
    }

    /**
     * Resets the HMAC for further use, maintaining the secret key that the
     * HMAC was initialized with.
     */
    protected void engineReset() {
        hmac.reset();
    }

    /*
     * Clones this object.
     */
    public Object clone() {
        HmacMD5 that = null;
        try {
            that = (HmacMD5) super.clone();
            that.hmac = (HmacCore) this.hmac.clone();
        } catch (CloneNotSupportedException e) {
        }
        return that;
    }
}