1 /* 2 * Copyright (c) 1996, 2015, 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 import jdk.internal.HotSpotIntrinsicCandidate; 32 33 /** 34 * A class that can be used to compute the Adler-32 checksum of a data 35 * stream. An Adler-32 checksum is almost as reliable as a CRC-32 but 36 * can be computed much faster. 37 * 38 * <p> Passing a {@code null} argument to a method in this class will cause 39 * a {@link NullPointerException} to be thrown.</p> 40 * 41 * @author David Connelly 42 * @since 1.1 43 */ 44 public class Adler32 implements Checksum { 45 46 private int adler = 1; 47 48 /** 49 * Creates a new Adler32 object. 50 */ Adler32()51 public Adler32() { 52 } 53 54 /** 55 * Updates the checksum with the specified byte (the low eight 56 * bits of the argument b). 57 */ 58 @Override update(int b)59 public void update(int b) { 60 adler = update(adler, b); 61 } 62 63 /** 64 * Updates the checksum with the specified array of bytes. 65 * 66 * @throws ArrayIndexOutOfBoundsException 67 * if {@code off} is negative, or {@code len} is negative, or 68 * {@code off+len} is negative or greater than the length of 69 * the array {@code b}. 70 */ 71 @Override update(byte[] b, int off, int len)72 public void update(byte[] b, int off, int len) { 73 if (b == null) { 74 throw new NullPointerException(); 75 } 76 if (off < 0 || len < 0 || off > b.length - len) { 77 throw new ArrayIndexOutOfBoundsException(); 78 } 79 adler = updateBytes(adler, b, off, len); 80 } 81 82 /** 83 * Updates the checksum with the bytes from the specified buffer. 84 * 85 * The checksum is updated with the remaining bytes in the buffer, starting 86 * at the buffer's position. Upon return, the buffer's position will be 87 * updated to its limit; its limit will not have been changed. 88 * 89 * @since 1.8 90 */ 91 @Override update(ByteBuffer buffer)92 public void update(ByteBuffer buffer) { 93 int pos = buffer.position(); 94 int limit = buffer.limit(); 95 assert (pos <= limit); 96 int rem = limit - pos; 97 if (rem <= 0) 98 return; 99 if (buffer instanceof DirectBuffer) { 100 adler = updateByteBuffer(adler, ((DirectBuffer)buffer).address(), pos, rem); 101 } else if (buffer.hasArray()) { 102 adler = updateBytes(adler, buffer.array(), pos + buffer.arrayOffset(), rem); 103 } else { 104 byte[] b = new byte[Math.min(buffer.remaining(), 4096)]; 105 while (buffer.hasRemaining()) { 106 int length = Math.min(buffer.remaining(), b.length); 107 buffer.get(b, 0, length); 108 update(b, 0, length); 109 } 110 } 111 buffer.position(limit); 112 } 113 114 /** 115 * Resets the checksum to initial value. 116 */ 117 @Override reset()118 public void reset() { 119 adler = 1; 120 } 121 122 /** 123 * Returns the checksum value. 124 */ 125 @Override getValue()126 public long getValue() { 127 return (long)adler & 0xffffffffL; 128 } 129 update(int adler, int b)130 private static native int update(int adler, int b); 131 132 @HotSpotIntrinsicCandidate updateBytes(int adler, byte[] b, int off, int len)133 private static native int updateBytes(int adler, byte[] b, int off, 134 int len); 135 @HotSpotIntrinsicCandidate updateByteBuffer(int adler, long addr, int off, int len)136 private static native int updateByteBuffer(int adler, long addr, 137 int off, int len); 138 139 static { ZipUtils.loadLibrary()140 ZipUtils.loadLibrary(); 141 } 142 } 143