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 java.util.Objects; 30 31 import sun.nio.ch.DirectBuffer; 32 import jdk.internal.HotSpotIntrinsicCandidate; 33 34 /** 35 * A class that can be used to compute the CRC-32 of a data stream. 36 * 37 * <p> Passing a {@code null} argument to a method in this class will cause 38 * a {@link NullPointerException} to be thrown.</p> 39 * 40 * @author David Connelly 41 * @since 1.1 42 */ 43 public 44 class CRC32 implements Checksum { 45 private int crc; 46 47 /** 48 * Creates a new CRC32 object. 49 */ 50 public CRC32() { 51 } 52 53 54 /** 55 * Updates the CRC-32 checksum with the specified byte (the low 56 * eight bits of the argument b). 57 */ 58 @Override 59 public void update(int b) { 60 crc = update(crc, b); 61 } 62 63 /** 64 * Updates the CRC-32 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 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 crc = updateBytes(crc, b, off, len); 80 } 81 82 /** 83 * Updates the CRC-32 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 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 crc = updateByteBuffer(crc, ((DirectBuffer)buffer).address(), pos, rem); 101 } else if (buffer.hasArray()) { 102 crc = updateBytes(crc, 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 CRC-32 to initial value. 116 */ 117 @Override 118 public void reset() { 119 crc = 0; 120 } 121 122 /** 123 * Returns CRC-32 value. 124 */ 125 @Override 126 public long getValue() { 127 return (long)crc & 0xffffffffL; 128 } 129 130 @HotSpotIntrinsicCandidate 131 private static native int update(int crc, int b); 132 133 private static int updateBytes(int crc, byte[] b, int off, int len) { 134 updateBytesCheck(b, off, len); 135 return updateBytes0(crc, b, off, len); 136 } 137 138 @HotSpotIntrinsicCandidate 139 private static native int updateBytes0(int crc, byte[] b, int off, int len); 140 141 private static void updateBytesCheck(byte[] b, int off, int len) { 142 if (len <= 0) { 143 return; // not an error because updateBytesImpl won't execute if len <= 0 144 } 145 146 Objects.requireNonNull(b); 147 148 if (off < 0 || off >= b.length) { 149 throw new ArrayIndexOutOfBoundsException(off); 150 } 151 152 int endIndex = off + len - 1; 153 if (endIndex < 0 || endIndex >= b.length) { 154 throw new ArrayIndexOutOfBoundsException(endIndex); 155 } 156 } 157 158 private static int updateByteBuffer(int alder, long addr, 159 int off, int len) { 160 updateByteBufferCheck(addr); 161 return updateByteBuffer0(alder, addr, off, len); 162 } 163 164 @HotSpotIntrinsicCandidate 165 private static native int updateByteBuffer0(int alder, long addr, 166 int off, int len); 167 168 private static void updateByteBufferCheck(long addr) { 169 // Performs only a null check because bounds checks 170 // are not easy to do on raw addresses. 171 if (addr == 0L) { 172 throw new NullPointerException(); 173 } 174 } 175 }