1 /* 2 * Copyright (c) 1996, 2014, 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 Adler-32 checksum of a data 33 * stream. An Adler-32 checksum is almost as reliable as a CRC-32 but 34 * can be computed much faster. 35 * 36 * <p> Passing a {@code null} argument to a method in this class will cause 37 * a {@link NullPointerException} to be thrown.</p> 38 * 39 * @author David Connelly 40 */ 41 public 42 class Adler32 implements Checksum { 43 44 private int adler = 1; 45 46 /** 47 * Creates a new Adler32 object. 48 */ 49 public Adler32() { 50 } 51 52 /** 53 * Updates the checksum with the specified byte (the low eight 54 * bits of the argument b). 55 */ 56 @Override 57 public void update(int b) { 58 adler = update(adler, b); 59 } 60 61 /** 62 * Updates the checksum with the specified array of bytes. 63 * 64 * @throws ArrayIndexOutOfBoundsException 65 * if {@code off} is negative, or {@code len} is negative, or 66 * {@code off+len} is negative or greater than the length of 67 * the array {@code b}. 68 */ 69 @Override 70 public void update(byte[] b, int off, int len) { 71 if (b == null) { 72 throw new NullPointerException(); 73 } 74 if (off < 0 || len < 0 || off > b.length - len) { 75 throw new ArrayIndexOutOfBoundsException(); 76 } 77 adler = updateBytes(adler, b, off, len); 78 } 79 80 /** 81 * Updates the checksum with the bytes from the specified buffer. 82 * 83 * The checksum is updated with the remaining bytes in the buffer, starting 84 * at the buffer's position. Upon return, the buffer's position will be 85 * updated to its limit; its limit will not have been changed. 86 * 87 * @since 1.8 88 */ 89 @Override 90 public void update(ByteBuffer buffer) { 91 int pos = buffer.position(); 92 int limit = buffer.limit(); 93 assert (pos <= limit); 94 int rem = limit - pos; 95 if (rem <= 0) 96 return; 97 if (buffer instanceof DirectBuffer) { 98 adler = updateByteBuffer(adler, ((DirectBuffer)buffer).address(), pos, rem); 99 } else if (buffer.hasArray()) { 100 adler = updateBytes(adler, buffer.array(), pos + buffer.arrayOffset(), rem); 101 } else { 102 byte[] b = new byte[Math.min(buffer.remaining(), 4096)]; 103 while (buffer.hasRemaining()) { 104 int length = Math.min(buffer.remaining(), b.length); 105 buffer.get(b, 0, length); 106 update(b, 0, length); 107 } 108 } 109 buffer.position(limit); 110 } 111 112 /** 113 * Resets the checksum to initial value. 114 */ 115 @Override 116 public void reset() { 117 adler = 1; 118 } 119 120 /** 121 * Returns the checksum value. 122 */ 123 @Override 124 public long getValue() { 125 return (long)adler & 0xffffffffL; 126 } 127 128 private native static int update(int adler, int b); 129 private native static int updateBytes(int adler, byte[] b, int off, 130 int len); 131 private native static int updateByteBuffer(int adler, long addr, 132 int off, int len); 133 }