001 /* Checksum.java - Interface to compute a data checksum
002 Copyright (C) 1999, 2000, 2001 Free Software Foundation, Inc.
003
004 This file is part of GNU Classpath.
005
006 GNU Classpath is free software; you can redistribute it and/or modify
007 it under the terms of the GNU General Public License as published by
008 the Free Software Foundation; either version 2, or (at your option)
009 any later version.
010
011 GNU Classpath is distributed in the hope that it will be useful, but
012 WITHOUT ANY WARRANTY; without even the implied warranty of
013 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
014 General Public License for more details.
015
016 You should have received a copy of the GNU General Public License
017 along with GNU Classpath; see the file COPYING. If not, write to the
018 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
019 02110-1301 USA.
020
021 Linking this library statically or dynamically with other modules is
022 making a combined work based on this library. Thus, the terms and
023 conditions of the GNU General Public License cover the whole
024 combination.
025
026 As a special exception, the copyright holders of this library give you
027 permission to link this library with independent modules to produce an
028 executable, regardless of the license terms of these independent
029 modules, and to copy and distribute the resulting executable under
030 terms of your choice, provided that you also meet, for each linked
031 independent module, the terms and conditions of the license of that
032 module. An independent module is a module which is not derived from
033 or based on this library. If you modify this library, you may extend
034 this exception to your version of the library, but you are not
035 obligated to do so. If you do not wish to do so, delete this
036 exception statement from your version. */
037
038 package 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 */
059 public 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 }