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 */ CRC32()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 */ update(int b)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 */ update(byte[] b, int off, int len)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 */ update(byte[] b)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 */ update(ByteBuffer buffer)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 */ reset()123 public void reset() { 124 crc = 0; 125 } 126 127 /** 128 * Returns CRC-32 value. 129 */ getValue()130 public long getValue() { 131 return (long)crc & 0xffffffffL; 132 } 133 update(int crc, int b)134 private native static int update(int crc, int b); updateBytes(int crc, byte[] b, int off, int len)135 private native static int updateBytes(int crc, byte[] b, int off, int len); 136 updateByteBuffer(int adler, long addr, int off, int len)137 private native static int updateByteBuffer(int adler, long addr, 138 int off, int len); 139 } 140