1 /*

     2  * Copyright (c) 1996, 2013, Oracle and/or its affiliates. All rights reserved.

     3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

     4  *

     5  * This code is free software; you can redistribute it and/or modify it

     6  * under the terms of the GNU General Public License version 2 only, as

     7  * published by the Free Software Foundation.  Oracle designates this

     8  * particular file as subject to the "Classpath" exception as provided

     9  * by Oracle in the LICENSE file that accompanied this code.

    10  *

    11  * This code is distributed in the hope that it will be useful, but WITHOUT

    12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

    13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

    14  * version 2 for more details (a copy is included in the LICENSE file that

    15  * accompanied this code).

    16  *

    17  * You should have received a copy of the GNU General Public License version

    18  * 2 along with this work; if not, write to the Free Software Foundation,

    19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

    20  *

    21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

    22  * or visit www.oracle.com if you need additional information or have any

    23  * questions.

    24  */

    25 

    26 package java.util.zip;

    27 

    28 import java.nio.ByteBuffer;

    29 import sun.nio.ch.DirectBuffer;

    30 

    31 /**

    32  * A class that can be used to compute the CRC-32 of a data stream.

    33  *

    34  * <p> Passing a {@code null} argument to a method in this class will cause

    35  * a {@link NullPointerException} to be thrown.

    36  *

    37  * @see         Checksum

    38  * @author      David Connelly

    39  */

    40 public

    41 class CRC32 implements Checksum {

    42     private int crc;

    43 

    44     /**

    45      * Creates a new CRC32 object.

    46      */

    47     public CRC32() {

    48     }

    49 

    50 

    51     /**

    52      * Updates the CRC-32 checksum with the specified byte (the low

    53      * eight bits of the argument b).

    54      *

    55      * @param b the byte to update the checksum with

    56      */

    57     public void update(int b) {

    58         crc = update(crc, b);

    59     }

    60 

    61     /**

    62      * Updates the CRC-32 checksum with the specified array of bytes.

    63      *

    64      * @throws  ArrayIndexOutOfBoundsException

    65      *          if {@code off} is negative, or {@code len} is negative,

    66      *          or {@code off+len} is greater than the length of the

    67      *          array {@code b}

    68      */

    69     public void update(byte[] b, int off, int len) {

    70         if (b == null) {

    71             throw new NullPointerException();

    72         }

    73         if (off < 0 || len < 0 || off > b.length - len) {

    74             throw new ArrayIndexOutOfBoundsException();

    75         }

    76         crc = updateBytes(crc, b, off, len);

    77     }

    78 

    79     /**

    80      * Updates the CRC-32 checksum with the specified array of bytes.

    81      *

    82      * @param b the array of bytes to update the checksum with

    83      */

    84     public void update(byte[] b) {

    85         crc = updateBytes(crc, b, 0, b.length);

    86     }

    87 

    88     /**

    89      * Updates the checksum with the bytes from the specified buffer.

    90      *

    91      * The checksum is updated using

    92      * buffer.{@link java.nio.Buffer#remaining() remaining()}

    93      * bytes starting at

    94      * buffer.{@link java.nio.Buffer#position() position()}

    95      * Upon return, the buffer's position will

    96      * be updated to its limit; its limit will not have been changed.

    97      *

    98      * @param buffer the ByteBuffer to update the checksum with

    99      * @since 1.8

   100      */

   101     public void update(ByteBuffer buffer) {

   102         int pos = buffer.position();

   103         int limit = buffer.limit();

   104         assert (pos <= limit);

   105         int rem = limit - pos;

   106         if (rem <= 0)

   107             return;

   108         if (buffer instanceof DirectBuffer) {

   109             crc = updateByteBuffer(crc, ((DirectBuffer)buffer).address(), pos, rem);

   110         } else if (buffer.hasArray()) {

   111             crc = updateBytes(crc, buffer.array(), pos + buffer.arrayOffset(), rem);

   112         } else {

   113             byte[] b = new byte[rem];

   114             buffer.get(b);

   115             crc = updateBytes(crc, b, 0, b.length);

   116         }

   117         buffer.position(limit);

   118     }

   119 

   120     /**

   121      * Resets CRC-32 to initial value.

   122      */

   123     public void reset() {

   124         crc = 0;

   125     }

   126 

   127     /**

   128      * Returns CRC-32 value.

   129      */

   130     public long getValue() {

   131         return (long)crc & 0xffffffffL;

   132     }

   133 

   134     private native static int update(int crc, int b);

   135     private native static int updateBytes(int crc, byte[] b, int off, int len);

   136 

   137     private native static int updateByteBuffer(int adler, long addr,

   138                                                int off, int len);

   139 }