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 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.</p> 36 * 37 * @author David Connelly 38 */ 39 public 40 class CRC32 implements Checksum { 41 private int crc; 42 43 /** 44 * Creates a new CRC32 object. 45 */ 46 public CRC32() { 47 } 48 49 50 /** 51 * Updates the CRC-32 checksum with the specified byte (the low 52 * eight bits of the argument b). 53 */ 54 @Override 55 public void update(int b) { 56 crc = update(crc, b); 57 } 58 59 /** 60 * Updates the CRC-32 checksum with the specified array of bytes. 61 * 62 * @throws ArrayIndexOutOfBoundsException 63 * if {@code off} is negative, or {@code len} is negative, or 64 * {@code off+len} is negative or greater than the length of 65 * the array {@code b}. 66 */ 67 @Override 68 public void update(byte[] b, int off, int len) { 69 if (b == null) { 70 throw new NullPointerException(); 71 } 72 if (off < 0 || len < 0 || off > b.length - len) { 73 throw new ArrayIndexOutOfBoundsException(); 74 } 75 crc = updateBytes(crc, b, off, len); 76 } 77 78 /** 79 * Updates the CRC-32 checksum with the bytes from the specified buffer. 80 * 81 * The checksum is updated with the remaining bytes in the buffer, starting 82 * at the buffer's position. Upon return, the buffer's position will be 83 * updated to its limit; its limit will not have been changed. 84 * 85 * @since 1.8 86 */ 87 @Override 88 public void update(ByteBuffer buffer) { 89 int pos = buffer.position(); 90 int limit = buffer.limit(); 91 assert (pos <= limit); 92 int rem = limit - pos; 93 if (rem <= 0) 94 return; 95 if (buffer instanceof DirectBuffer) { 96 crc = updateByteBuffer(crc, ((DirectBuffer)buffer).address(), pos, rem); 97 } else if (buffer.hasArray()) { 98 crc = updateBytes(crc, buffer.array(), pos + buffer.arrayOffset(), rem); 99 } else { 100 byte[] b = new byte[Math.min(buffer.remaining(), 4096)]; 101 while (buffer.hasRemaining()) { 102 int length = Math.min(buffer.remaining(), b.length); 103 buffer.get(b, 0, length); 104 update(b, 0, length); 105 } 106 } 107 buffer.position(limit); 108 } 109 110 /** 111 * Resets CRC-32 to initial value. 112 */ 113 @Override 114 public void reset() { 115 crc = 0; 116 } 117 118 /** 119 * Returns CRC-32 value. 120 */ 121 @Override 122 public long getValue() { 123 return (long)crc & 0xffffffffL; 124 } 125 126 private native static int update(int crc, int b); 127 private native static int updateBytes(int crc, byte[] b, int off, int len); 128 129 private native static int updateByteBuffer(int adler, long addr, 130 int off, int len); 131 }