/* * Copyright (c) 1997, 2006, 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 * or visit www.oracle.com if you need additional information or have any * questions. */ package java.security; import java.nio.ByteBuffer; import sun.security.jca.JCAUtil; /** * This class defines the <i>Service Provider Interface</i> (<b>SPI</b>) * for the <code>MessageDigest</code> class, which provides the functionality * of a message digest algorithm, such as MD5 or SHA. Message digests are * secure one-way hash functions that take arbitrary-sized data and output a * fixed-length hash value. * * <p> All the abstract methods in this class must be implemented by a * cryptographic service provider who wishes to supply the implementation * of a particular message digest algorithm. * * <p> Implementations are free to implement the Cloneable interface. * * @author Benjamin Renaud * * * @see MessageDigest */ public abstract class MessageDigestSpi {     // for re-use in engineUpdate(ByteBuffer input)    private byte[] tempArray;     /**     * Returns the digest length in bytes.     *     * <p>This concrete method has been added to this previously-defined     * abstract class. (For backwards compatibility, it cannot be abstract.)     *     * <p>The default behavior is to return 0.     *     * <p>This method may be overridden by a provider to return the digest     * length.     *     * @return the digest length in bytes.     *     * @since 1.2     */    protected int engineGetDigestLength() {        return 0;    }     /**     * Updates the digest using the specified byte.     *     * @param input the byte to use for the update.     */    protected abstract void engineUpdate(byte input);     /**     * Updates the digest using the specified array of bytes,     * starting at the specified offset.     *     * @param input the array of bytes to use for the update.     *     * @param offset the offset to start from in the array of bytes.     *     * @param len the number of bytes to use, starting at     * <code>offset</code>.     */    protected abstract void engineUpdate(byte[] input, int offset, int len);     /**     * Update the digest using the specified ByteBuffer. The digest is     * updated using the <code>input.remaining()</code> bytes starting     * at <code>input.position()</code>.     * Upon return, the buffer's position will be equal to its limit;     * its limit will not have changed.     *     * @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();            int n = JCAUtil.getTempArraySize(len);            if ((tempArray == null) || (n > tempArray.length)) {                tempArray = new byte[n];            }            while (len > 0) {                int chunk = Math.min(len, tempArray.length);                input.get(tempArray, 0, chunk);                engineUpdate(tempArray, 0, chunk);                len -= chunk;            }        }    }     /**     * Completes the hash computation by performing final     * operations such as padding. Once <code>engineDigest</code> has     * been called, the engine should be reset (see     * {@link #engineReset() engineReset}).     * Resetting is the responsibility of the     * engine implementor.     *     * @return the array of bytes for the resulting hash value.     */    protected abstract byte[] engineDigest();     /**     * Completes the hash computation by performing final     * operations such as padding. Once <code>engineDigest</code> has     * been called, the engine should be reset (see     * {@link #engineReset() engineReset}).     * Resetting is the responsibility of the     * engine implementor.     *     * This method should be abstract, but we leave it concrete for     * binary compatibility.  Knowledgeable providers should override this     * method.     *     * @param buf the output buffer in which to store the digest     *     * @param offset offset to start from in the output buffer     *     * @param len number of bytes within buf allotted for the digest.     * Both this default implementation and the SUN provider do not     * return partial digests.  The presence of this parameter is solely     * for consistency in our API's.  If the value of this parameter is less     * than the actual digest length, the method will throw a DigestException.     * This parameter is ignored if its value is greater than or equal to     * the actual digest length.     *     * @return the length of the digest stored in the output buffer.     *     * @exception DigestException if an error occurs.     *     * @since 1.2     */    protected int engineDigest(byte[] buf, int offset, int len)                                                throws DigestException {         byte[] digest = engineDigest();        if (len < digest.length)                throw new DigestException("partial digests not returned");        if (buf.length - offset < digest.length)                throw new DigestException("insufficient space in the output "                                          + "buffer to store the digest");        System.arraycopy(digest, 0, buf, offset, digest.length);        return digest.length;    }     /**     * Resets the digest for further use.     */    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();        }    }}