package gnu.crypto.hash;

// ----------------------------------------------------------------------------
// $Id: IMessageDigest.java,v 1.11 2005/10/06 04:24:14 rsdio Exp $
//
// Copyright (C) 2001, 2002, Free Software Foundation, Inc.
//
// This file is part of GNU Crypto.
//
// GNU Crypto is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2, or (at your option)
// any later version.
//
// GNU Crypto 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 for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; see the file COPYING.  If not, write to the
//
//    Free Software Foundation Inc.,
//    51 Franklin Street, Fifth Floor,
//    Boston, MA 02110-1301
//    USA
//
// Linking this library statically or dynamically with other modules is
// making a combined work based on this library.  Thus, the terms and
// conditions of the GNU General Public License cover the whole
// combination.
//
// As a special exception, the copyright holders of this library give
// you permission to link this library with independent modules to
// produce an executable, regardless of the license terms of these
// independent modules, and to copy and distribute the resulting
// executable under terms of your choice, provided that you also meet,
// for each linked independent module, the terms and conditions of the
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// ----------------------------------------------------------------------------

/**
 * <p>The basic visible methods of any hash algorithm.</p>
 *
 * <p>A hash (or message digest) algorithm produces its output by iterating a
 * basic compression function on blocks of data.</p>
 *
 * @version $Revision: 1.11 $
 */
public interface IMessageDigest extends Cloneable {

   // Constants
   // -------------------------------------------------------------------------

   // Methods
   // -------------------------------------------------------------------------

   /**
    * <p>Returns the canonical name of this algorithm.</p>
    *
    * @return the canonical name of this instance.
    */
   String name();

   /**
    * <p>Returns the output length in bytes of this message digest algorithm.</p>
    *
    * @return the output length in bytes of this message digest algorithm.
    */
   int hashSize();

   /**
    * <p>Returns the algorithm's (inner) block size in bytes.</p>
    *
    * @return the algorithm's inner block size in bytes.
    */
   int blockSize();

   /**
    * <p>Continues a message digest operation using the input byte.</p>
    *
    * @param b the input byte to digest.
    */
   void update(byte b);

   /**
    * <p>Continues a message digest operation, by filling the buffer, processing
    * data in the algorithm's HASH_SIZE-bit block(s), updating the context and
    * count, and buffering the remaining bytes in buffer for the next
    * operation.</p>
    *
    * @param in the input block.
    */
   void update(byte[] in);

   /**
    * <p>Continues a message digest operation, by filling the buffer, processing
    * data in the algorithm's HASH_SIZE-bit block(s), updating the context and
    * count, and buffering the remaining bytes in buffer for the next
    * operation.</p>
    *
    * @param in the input block.
    * @param offset start of meaningful bytes in input block.
    * @param length number of bytes, in input block, to consider.
    */
   void update(byte[] in, int offset, int length);

   /**
    * <p>Completes the message digest by performing final operations such as
    * padding and resetting the instance.</p>
    *
    * @return the array of bytes representing the hash value.
    */
   byte[] digest();

   /**
    * <p>Resets the current context of this instance clearing any eventually cached
    * intermediary values.</p>
    */
   void reset();

   /**
    * <p>A basic test. Ensures that the digest of a pre-determined message is equal
    * to a known pre-computed value.</p>
    *
    * @return <tt>true</tt> if the implementation passes a basic self-test.
    * Returns <tt>false</tt> otherwise.
    */
   boolean selfTest();

   /**
    * <p>Returns a clone copy of this instance.</p>
    *
    * @return a clone copy of this instance.
    */
   Object clone();
}
