/* Checksum.java - Interface to compute a data checksum
   Copyright (C) 1999, 2000, 2001 Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
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any later version.

GNU Classpath 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 GNU Classpath; 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
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terms of your choice, provided that you also meet, for each linked
independent module, the terms and conditions of the license of that
module.  An independent module is a module which is not derived from
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this exception to your version of the library, but you are not
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exception statement from your version. */

package java.util.zip;

/*
 * Written using on-line Java Platform 1.2 API Specification, as well
 * as "The Java Class Libraries", 2nd edition (Addison-Wesley, 1998).
 * Status:  Believed complete and correct.
 */

/**
 * Interface to compute a data checksum used by checked input/output streams.
 * A data checksum can be updated by one byte or with a byte array. After each
 * update the value of the current checksum can be returned by calling
 * <code>getValue</code>. The complete checksum object can also be reset
 * so it can be used again with new data.
 *
 * @see CheckedInputStream
 * @see CheckedOutputStream
 *
 * @author Per Bothner
 * @author Jochen Hoenicke
 */
public interface Checksum
{
  /**
   * Returns the data checksum computed so far.
   */
  long getValue();

  /**
   * Resets the data checksum as if no update was ever called.
   */
  void reset();

  /**
   * Adds one byte to the data checksum.
   *
   * @param bval the data value to add. The high byte of the int is ignored.
   */
  void update (int bval);

  /**
   * Adds the byte array to the data checksum.
   *
   * @param buf the buffer which contains the data
   * @param off the offset in the buffer where the data starts
   * @param len the length of the data
   */
  void update (byte[] buf, int off, int len);
}
