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 }