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    1   /*
    2    * Copyright (c) 1997, 2006, Oracle and/or its affiliates. All rights reserved.
    3    * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
    4    *
    5    * This code is free software; you can redistribute it and/or modify it
    6    * under the terms of the GNU General Public License version 2 only, as
    7    * published by the Free Software Foundation.  Oracle designates this
    8    * particular file as subject to the "Classpath" exception as provided
    9    * by Oracle in the LICENSE file that accompanied this code.
   10    *
   11    * This code is distributed in the hope that it will be useful, but WITHOUT
   12    * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
   13    * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
   14    * version 2 for more details (a copy is included in the LICENSE file that
   15    * accompanied this code).
   16    *
   17    * You should have received a copy of the GNU General Public License version
   18    * 2 along with this work; if not, write to the Free Software Foundation,
   19    * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   20    *
   21    * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
   22    * or visit www.oracle.com if you need additional information or have any
   23    * questions.
   24    */
   25   
   26   package java.security;
   27   
   28   import java.nio.ByteBuffer;
   29   
   30   import sun.security.jca.JCAUtil;
   31   
   32   /**
   33    * This class defines the <i>Service Provider Interface</i> (<b>SPI</b>)
   34    * for the <code>MessageDigest</code> class, which provides the functionality
   35    * of a message digest algorithm, such as MD5 or SHA. Message digests are
   36    * secure one-way hash functions that take arbitrary-sized data and output a
   37    * fixed-length hash value.
   38    *
   39    * <p> All the abstract methods in this class must be implemented by a
   40    * cryptographic service provider who wishes to supply the implementation
   41    * of a particular message digest algorithm.
   42    *
   43    * <p> Implementations are free to implement the Cloneable interface.
   44    *
   45    * @author Benjamin Renaud
   46    *
   47    *
   48    * @see MessageDigest
   49    */
   50   
   51   public abstract class MessageDigestSpi {
   52   
   53       // for re-use in engineUpdate(ByteBuffer input)
   54       private byte[] tempArray;
   55   
   56       /**
   57        * Returns the digest length in bytes.
   58        *
   59        * <p>This concrete method has been added to this previously-defined
   60        * abstract class. (For backwards compatibility, it cannot be abstract.)
   61        *
   62        * <p>The default behavior is to return 0.
   63        *
   64        * <p>This method may be overridden by a provider to return the digest
   65        * length.
   66        *
   67        * @return the digest length in bytes.
   68        *
   69        * @since 1.2
   70        */
   71       protected int engineGetDigestLength() {
   72           return 0;
   73       }
   74   
   75       /**
   76        * Updates the digest using the specified byte.
   77        *
   78        * @param input the byte to use for the update.
   79        */
   80       protected abstract void engineUpdate(byte input);
   81   
   82       /**
   83        * Updates the digest using the specified array of bytes,
   84        * starting at the specified offset.
   85        *
   86        * @param input the array of bytes to use for the update.
   87        *
   88        * @param offset the offset to start from in the array of bytes.
   89        *
   90        * @param len the number of bytes to use, starting at
   91        * <code>offset</code>.
   92        */
   93       protected abstract void engineUpdate(byte[] input, int offset, int len);
   94   
   95       /**
   96        * Update the digest using the specified ByteBuffer. The digest is
   97        * updated using the <code>input.remaining()</code> bytes starting
   98        * at <code>input.position()</code>.
   99        * Upon return, the buffer's position will be equal to its limit;
  100        * its limit will not have changed.
  101        *
  102        * @param input the ByteBuffer
  103        * @since 1.5
  104        */
  105       protected void engineUpdate(ByteBuffer input) {
  106           if (input.hasRemaining() == false) {
  107               return;
  108           }
  109           if (input.hasArray()) {
  110               byte[] b = input.array();
  111               int ofs = input.arrayOffset();
  112               int pos = input.position();
  113               int lim = input.limit();
  114               engineUpdate(b, ofs + pos, lim - pos);
  115               input.position(lim);
  116           } else {
  117               int len = input.remaining();
  118               int n = JCAUtil.getTempArraySize(len);
  119               if ((tempArray == null) || (n > tempArray.length)) {
  120                   tempArray = new byte[n];
  121               }
  122               while (len > 0) {
  123                   int chunk = Math.min(len, tempArray.length);
  124                   input.get(tempArray, 0, chunk);
  125                   engineUpdate(tempArray, 0, chunk);
  126                   len -= chunk;
  127               }
  128           }
  129       }
  130   
  131       /**
  132        * Completes the hash computation by performing final
  133        * operations such as padding. Once <code>engineDigest</code> has
  134        * been called, the engine should be reset (see
  135        * {@link #engineReset() engineReset}).
  136        * Resetting is the responsibility of the
  137        * engine implementor.
  138        *
  139        * @return the array of bytes for the resulting hash value.
  140        */
  141       protected abstract byte[] engineDigest();
  142   
  143       /**
  144        * Completes the hash computation by performing final
  145        * operations such as padding. Once <code>engineDigest</code> has
  146        * been called, the engine should be reset (see
  147        * {@link #engineReset() engineReset}).
  148        * Resetting is the responsibility of the
  149        * engine implementor.
  150        *
  151        * This method should be abstract, but we leave it concrete for
  152        * binary compatibility.  Knowledgeable providers should override this
  153        * method.
  154        *
  155        * @param buf the output buffer in which to store the digest
  156        *
  157        * @param offset offset to start from in the output buffer
  158        *
  159        * @param len number of bytes within buf allotted for the digest.
  160        * Both this default implementation and the SUN provider do not
  161        * return partial digests.  The presence of this parameter is solely
  162        * for consistency in our API's.  If the value of this parameter is less
  163        * than the actual digest length, the method will throw a DigestException.
  164        * This parameter is ignored if its value is greater than or equal to
  165        * the actual digest length.
  166        *
  167        * @return the length of the digest stored in the output buffer.
  168        *
  169        * @exception DigestException if an error occurs.
  170        *
  171        * @since 1.2
  172        */
  173       protected int engineDigest(byte[] buf, int offset, int len)
  174                                                   throws DigestException {
  175   
  176           byte[] digest = engineDigest();
  177           if (len < digest.length)
  178                   throw new DigestException("partial digests not returned");
  179           if (buf.length - offset < digest.length)
  180                   throw new DigestException("insufficient space in the output "
  181                                             + "buffer to store the digest");
  182           System.arraycopy(digest, 0, buf, offset, digest.length);
  183           return digest.length;
  184       }
  185   
  186       /**
  187        * Resets the digest for further use.
  188        */
  189       protected abstract void engineReset();
  190   
  191       /**
  192        * Returns a clone if the implementation is cloneable.
  193        *
  194        * @return a clone if the implementation is cloneable.
  195        *
  196        * @exception CloneNotSupportedException if this is called on an
  197        * implementation that does not support <code>Cloneable</code>.
  198        */
  199       public Object clone() throws CloneNotSupportedException {
  200           if (this instanceof Cloneable) {
  201               return super.clone();
  202           } else {
  203               throw new CloneNotSupportedException();
  204           }
  205       }
  206   }

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