jaroslav@609: /*
jaroslav@609:  * Copyright (c) 1996, 2005, Oracle and/or its affiliates. All rights reserved.
jaroslav@609:  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
jaroslav@609:  *
jaroslav@609:  * This code is free software; you can redistribute it and/or modify it
jaroslav@609:  * under the terms of the GNU General Public License version 2 only, as
jaroslav@609:  * published by the Free Software Foundation.  Oracle designates this
jaroslav@609:  * particular file as subject to the "Classpath" exception as provided
jaroslav@609:  * by Oracle in the LICENSE file that accompanied this code.
jaroslav@609:  *
jaroslav@609:  * This code is distributed in the hope that it will be useful, but WITHOUT
jaroslav@609:  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
jaroslav@609:  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
jaroslav@609:  * version 2 for more details (a copy is included in the LICENSE file that
jaroslav@609:  * accompanied this code).
jaroslav@609:  *
jaroslav@609:  * You should have received a copy of the GNU General Public License version
jaroslav@609:  * 2 along with this work; if not, write to the Free Software Foundation,
jaroslav@609:  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
jaroslav@609:  *
jaroslav@609:  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
jaroslav@609:  * or visit www.oracle.com if you need additional information or have any
jaroslav@609:  * questions.
jaroslav@609:  */
jaroslav@609: 
jaroslav@609: package java.util.zip;
jaroslav@609: 
jaroslav@609: /**
jaroslav@609:  * A class that can be used to compute the CRC-32 of a data stream.
jaroslav@609:  *
jaroslav@609:  * @see         Checksum
jaroslav@609:  * @author      David Connelly
jaroslav@609:  */
jaroslav@609: public
jaroslav@609: class CRC32 implements Checksum {
jaroslav@609:     private int crc;
jaroslav@609: 
jaroslav@609:     /**
jaroslav@609:      * Creates a new CRC32 object.
jaroslav@609:      */
jaroslav@609:     public CRC32() {
jaroslav@609:     }
jaroslav@609: 
jaroslav@609: 
jaroslav@609:     /**
jaroslav@609:      * Updates the CRC-32 checksum with the specified byte (the low
jaroslav@609:      * eight bits of the argument b).
jaroslav@609:      *
jaroslav@609:      * @param b the byte to update the checksum with
jaroslav@609:      */
jaroslav@609:     public void update(int b) {
jaroslav@609:         crc = update(crc, b);
jaroslav@609:     }
jaroslav@609: 
jaroslav@609:     /**
jaroslav@609:      * Updates the CRC-32 checksum with the specified array of bytes.
jaroslav@609:      */
jaroslav@609:     public void update(byte[] b, int off, int len) {
jaroslav@609:         if (b == null) {
jaroslav@609:             throw new NullPointerException();
jaroslav@609:         }
jaroslav@609:         if (off < 0 || len < 0 || off > b.length - len) {
jaroslav@609:             throw new ArrayIndexOutOfBoundsException();
jaroslav@609:         }
jaroslav@609:         crc = updateBytes(crc, b, off, len);
jaroslav@609:     }
jaroslav@609: 
jaroslav@609:     /**
jaroslav@609:      * Updates the CRC-32 checksum with the specified array of bytes.
jaroslav@609:      *
jaroslav@609:      * @param b the array of bytes to update the checksum with
jaroslav@609:      */
jaroslav@609:     public void update(byte[] b) {
jaroslav@609:         crc = updateBytes(crc, b, 0, b.length);
jaroslav@609:     }
jaroslav@609: 
jaroslav@609:     /**
jaroslav@609:      * Resets CRC-32 to initial value.
jaroslav@609:      */
jaroslav@609:     public void reset() {
jaroslav@609:         crc = 0;
jaroslav@609:     }
jaroslav@609: 
jaroslav@609:     /**
jaroslav@609:      * Returns CRC-32 value.
jaroslav@609:      */
jaroslav@609:     public long getValue() {
jaroslav@609:         return (long)crc & 0xffffffffL;
jaroslav@609:     }
jaroslav@609: 
jaroslav@609:     private native static int update(int crc, int b);
jaroslav@609:     private native static int updateBytes(int crc, byte[] b, int off, int len);
jaroslav@609: }