1 /* 2 * Copyright (c) 1996, 2020, 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.lang.ref.Reference; 29 import java.nio.ByteBuffer; 30 import java.util.Objects; 31 32 import sun.nio.ch.DirectBuffer; 33 import jdk.internal.vm.annotation.IntrinsicCandidate; 34 35 /** 36 * A class that can be used to compute the CRC-32 of a data stream. 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 CRC32 implements Checksum { 45 private int crc; 46 47 /** 48 * Creates a new CRC32 object. 49 */ CRC32()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 update(int b)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 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 crc = updateBytes(crc, b, off, len); 80 } 81 82 // Android-changed: method kept during jdk17u update for compatibility. 83 /** 84 * Updates the CRC-32 checksum with the specified array of bytes. 85 * 86 * @param b the array of bytes to update the checksum with 87 */ 88 @Override update(byte[] b)89 public void update(byte[] b) { 90 crc = updateBytes(crc, b, 0, b.length); 91 } 92 93 /** 94 * Updates the CRC-32 checksum with the bytes from the specified buffer. 95 * 96 * The checksum is updated with the remaining bytes in the buffer, starting 97 * at the buffer's position. Upon return, the buffer's position will be 98 * updated to its limit; its limit will not have been changed. 99 * 100 * @since 1.8 101 */ 102 @Override update(ByteBuffer buffer)103 public void update(ByteBuffer buffer) { 104 int pos = buffer.position(); 105 int limit = buffer.limit(); 106 assert (pos <= limit); 107 int rem = limit - pos; 108 if (rem <= 0) 109 return; 110 if (buffer.isDirect()) { 111 try { 112 crc = updateByteBuffer(crc, ((DirectBuffer)buffer).address(), pos, rem); 113 } finally { 114 Reference.reachabilityFence(buffer); 115 } 116 } else if (buffer.hasArray()) { 117 crc = updateBytes(crc, buffer.array(), pos + buffer.arrayOffset(), rem); 118 } else { 119 byte[] b = new byte[Math.min(buffer.remaining(), 4096)]; 120 while (buffer.hasRemaining()) { 121 int length = Math.min(buffer.remaining(), b.length); 122 buffer.get(b, 0, length); 123 update(b, 0, length); 124 } 125 } 126 buffer.position(limit); 127 } 128 129 /** 130 * Resets CRC-32 to initial value. 131 */ 132 @Override reset()133 public void reset() { 134 crc = 0; 135 } 136 137 /** 138 * Returns CRC-32 value. 139 */ 140 @Override getValue()141 public long getValue() { 142 return (long)crc & 0xffffffffL; 143 } 144 145 @IntrinsicCandidate update(int crc, int b)146 private static native int update(int crc, int b); 147 updateBytes(int crc, byte[] b, int off, int len)148 private static int updateBytes(int crc, byte[] b, int off, int len) { 149 updateBytesCheck(b, off, len); 150 return updateBytes0(crc, b, off, len); 151 } 152 153 @IntrinsicCandidate updateBytes0(int crc, byte[] b, int off, int len)154 private static native int updateBytes0(int crc, byte[] b, int off, int len); 155 updateBytesCheck(byte[] b, int off, int len)156 private static void updateBytesCheck(byte[] b, int off, int len) { 157 if (len <= 0) { 158 return; // not an error because updateBytesImpl won't execute if len <= 0 159 } 160 161 Objects.requireNonNull(b); 162 163 if (off < 0 || off >= b.length) { 164 throw new ArrayIndexOutOfBoundsException(off); 165 } 166 167 int endIndex = off + len - 1; 168 if (endIndex < 0 || endIndex >= b.length) { 169 throw new ArrayIndexOutOfBoundsException(endIndex); 170 } 171 } 172 updateByteBuffer(int alder, long addr, int off, int len)173 private static int updateByteBuffer(int alder, long addr, 174 int off, int len) { 175 updateByteBufferCheck(addr); 176 return updateByteBuffer0(alder, addr, off, len); 177 } 178 179 @IntrinsicCandidate updateByteBuffer0(int alder, long addr, int off, int len)180 private static native int updateByteBuffer0(int alder, long addr, 181 int off, int len); 182 updateByteBufferCheck(long addr)183 private static void updateByteBufferCheck(long addr) { 184 // Performs only a null check because bounds checks 185 // are not easy to do on raw addresses. 186 if (addr == 0L) { 187 throw new NullPointerException(); 188 } 189 } 190 } 191