001/* Checksum.java - Interface to compute a data checksum
002   Copyright (C) 1999, 2000, 2001 Free Software Foundation, Inc.
003
004This file is part of GNU Classpath.
005
006GNU Classpath is free software; you can redistribute it and/or modify
007it under the terms of the GNU General Public License as published by
008the Free Software Foundation; either version 2, or (at your option)
009any later version.
010
011GNU Classpath is distributed in the hope that it will be useful, but
012WITHOUT ANY WARRANTY; without even the implied warranty of
013MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014General Public License for more details.
015
016You should have received a copy of the GNU General Public License
017along with GNU Classpath; see the file COPYING.  If not, write to the
018Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
01902110-1301 USA.
020
021Linking this library statically or dynamically with other modules is
022making a combined work based on this library.  Thus, the terms and
023conditions of the GNU General Public License cover the whole
024combination.
025
026As a special exception, the copyright holders of this library give you
027permission to link this library with independent modules to produce an
028executable, regardless of the license terms of these independent
029modules, and to copy and distribute the resulting executable under
030terms of your choice, provided that you also meet, for each linked
031independent module, the terms and conditions of the license of that
032module.  An independent module is a module which is not derived from
033or based on this library.  If you modify this library, you may extend
034this exception to your version of the library, but you are not
035obligated to do so.  If you do not wish to do so, delete this
036exception statement from your version. */
037
038package java.util.zip;
039
040/*
041 * Written using on-line Java Platform 1.2 API Specification, as well
042 * as "The Java Class Libraries", 2nd edition (Addison-Wesley, 1998).
043 * Status:  Believed complete and correct.
044 */
045
046/**
047 * Interface to compute a data checksum used by checked input/output streams.
048 * A data checksum can be updated by one byte or with a byte array. After each
049 * update the value of the current checksum can be returned by calling
050 * <code>getValue</code>. The complete checksum object can also be reset
051 * so it can be used again with new data.
052 *
053 * @see CheckedInputStream
054 * @see CheckedOutputStream
055 *
056 * @author Per Bothner
057 * @author Jochen Hoenicke
058 */
059public interface Checksum
060{
061  /**
062   * Returns the data checksum computed so far.
063   */
064  long getValue();
065
066  /**
067   * Resets the data checksum as if no update was ever called.
068   */
069  void reset();
070
071  /**
072   * Adds one byte to the data checksum.
073   *
074   * @param bval the data value to add. The high byte of the int is ignored.
075   */
076  void update (int bval);
077
078  /**
079   * Adds the byte array to the data checksum.
080   *
081   * @param buf the buffer which contains the data
082   * @param off the offset in the buffer where the data starts
083   * @param len the length of the data
084   */
085  void update (byte[] buf, int off, int len);
086}