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 */
42 public
43 class CRC32 implements Checksum {
44 private int crc;
45
46 /**
47 * Creates a new CRC32 object.
48 */
49 public CRC32() {
50 }
51
52
53 /**
54 * Updates the CRC-32 checksum with the specified byte (the low
55 * eight bits of the argument b).
56 */
57 @Override
58 public void update(int b) {
59 crc = update(crc, b);
60 }
61
62 /**
63 * Updates the CRC-32 checksum with the specified array of bytes.
64 *
65 * @throws ArrayIndexOutOfBoundsException
66 * if {@code off} is negative, or {@code len} is negative, or
67 * {@code off+len} is negative or greater than the length of
68 * the array {@code b}.
69 */
70 @Override
71 public void update(byte[] b, int off, int len) {
72 if (b == null) {
73 throw new NullPointerException();
74 }
75 if (off < 0 || len < 0 || off > b.length - len) {
76 throw new ArrayIndexOutOfBoundsException();
77 }
78 crc = updateBytes(crc, b, off, len);
79 }
80
81 /**
82 * Updates the CRC-32 checksum with the bytes from the specified buffer.
83 *
84 * The checksum is updated with the remaining bytes in the buffer, starting
85 * at the buffer's position. Upon return, the buffer's position will be
86 * updated to its limit; its limit will not have been changed.
87 *
88 * @since 1.8
89 */
90 @Override
91 public void update(ByteBuffer buffer) {
92 int pos = buffer.position();
93 int limit = buffer.limit();
94 assert (pos <= limit);
95 int rem = limit - pos;
96 if (rem <= 0)
97 return;
98 if (buffer instanceof DirectBuffer) {
99 crc = updateByteBuffer(crc, ((DirectBuffer)buffer).address(), pos, rem);
100 } else if (buffer.hasArray()) {
101 crc = updateBytes(crc, buffer.array(), pos + buffer.arrayOffset(), rem);
102 } else {
103 byte[] b = new byte[Math.min(buffer.remaining(), 4096)];
104 while (buffer.hasRemaining()) {
105 int length = Math.min(buffer.remaining(), b.length);
106 buffer.get(b, 0, length);
107 update(b, 0, length);
108 }
109 }
110 buffer.position(limit);
111 }
112
113 /**
114 * Resets CRC-32 to initial value.
115 */
116 @Override
117 public void reset() {
118 crc = 0;
119 }
120
121 /**
122 * Returns CRC-32 value.
123 */
124 @Override
125 public long getValue() {
126 return (long)crc & 0xffffffffL;
127 }
128
129 @HotSpotIntrinsicCandidate
130 private native static int update(int crc, int b);
131
132 private static int updateBytes(int crc, byte[] b, int off, int len) {
133 updateBytesCheck(b, off, len);
134 return updateBytesImpl(crc, b, off, len);
135 }
136
137 @HotSpotIntrinsicCandidate
138 private native static int updateBytesImpl(int crc, byte[] b, int off, int len);
139
140 private static void updateBytesCheck(byte[] b, int off, int len) {
141 if (len <= 0) {
142 return; // not an error because updateBytesImpl won't execute if len <= 0
143 }
144
145 Objects.requireNonNull(b);
146
147 if (off < 0 || off >= b.length) {
148 throw new ArrayIndexOutOfBoundsException(off);
149 }
150
151 int endIndex = off + len - 1;
152 if (endIndex < 0 || endIndex >= b.length) {
153 throw new ArrayIndexOutOfBoundsException(endIndex);
154 }
155 }
156
157 private static int updateByteBuffer(int alder, long addr,
158 int off, int len) {
159 updateByteBufferCheck(addr);
160 return updateByteBufferImpl(alder, addr, off, len);
161 }
162
163 @HotSpotIntrinsicCandidate
164 private native static int updateByteBufferImpl(int alder, long addr,
165 int off, int len);
166
167 private static void updateByteBufferCheck(long addr) {
168 // Performs only a null check because bounds checks
169 // are not easy to do on raw addresses.
170 if (addr == 0L) {
171 throw new NullPointerException();
172 }
173 }
174 }