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 45 class Adler32 implements Checksum { 46 47 private int adler = 1; 48 49 /** 50 * Creates a new Adler32 object. 51 */ Adler32()52 public Adler32() { 53 } 54 55 /** 56 * Updates the checksum with the specified byte (the low eight 57 * bits of the argument b). 58 */ 59 @Override update(int b)60 public void update(int b) { 61 adler = update(adler, b); 62 } 63 64 /** 65 * Updates the checksum with the specified array of bytes. 66 * 67 * @throws ArrayIndexOutOfBoundsException 68 * if {@code off} is negative, or {@code len} is negative, or 69 * {@code off+len} is negative or greater than the length of 70 * the array {@code b}. 71 */ 72 @Override update(byte[] b, int off, int len)73 public void update(byte[] b, int off, int len) { 74 if (b == null) { 75 throw new NullPointerException(); 76 } 77 if (off < 0 || len < 0 || off > b.length - len) { 78 throw new ArrayIndexOutOfBoundsException(); 79 } 80 adler = updateBytes(adler, b, off, len); 81 } 82 83 /** 84 * Updates the checksum with the bytes from the specified buffer. 85 * 86 * The checksum is updated with the remaining bytes in the buffer, starting 87 * at the buffer's position. Upon return, the buffer's position will be 88 * updated to its limit; its limit will not have been changed. 89 * 90 * @since 1.8 91 */ 92 @Override update(ByteBuffer buffer)93 public void update(ByteBuffer buffer) { 94 int pos = buffer.position(); 95 int limit = buffer.limit(); 96 assert (pos <= limit); 97 int rem = limit - pos; 98 if (rem <= 0) 99 return; 100 if (buffer instanceof DirectBuffer) { 101 adler = updateByteBuffer(adler, ((DirectBuffer)buffer).address(), pos, rem); 102 } else if (buffer.hasArray()) { 103 adler = updateBytes(adler, buffer.array(), pos + buffer.arrayOffset(), rem); 104 } else { 105 byte[] b = new byte[Math.min(buffer.remaining(), 4096)]; 106 while (buffer.hasRemaining()) { 107 int length = Math.min(buffer.remaining(), b.length); 108 buffer.get(b, 0, length); 109 update(b, 0, length); 110 } 111 } 112 buffer.position(limit); 113 } 114 115 /** 116 * Resets the checksum to initial value. 117 */ 118 @Override reset()119 public void reset() { 120 adler = 1; 121 } 122 123 /** 124 * Returns the checksum value. 125 */ 126 @Override getValue()127 public long getValue() { 128 return (long)adler & 0xffffffffL; 129 } 130 update(int adler, int b)131 private static native int update(int adler, int b); 132 133 @HotSpotIntrinsicCandidate updateBytes(int adler, byte[] b, int off, int len)134 private static native int updateBytes(int adler, byte[] b, int off, 135 int len); 136 @HotSpotIntrinsicCandidate updateByteBuffer(int adler, long addr, int off, int len)137 private static native int updateByteBuffer(int adler, long addr, 138 int off, int len); 139 140 static { ZipUtils.loadLibrary()141 ZipUtils.loadLibrary(); 142 } 143 } 144