1.1 --- a/emul/mini/src/main/java/java/util/zip/CRC32.java Wed Jan 30 14:03:49 2013 +0100
1.2 +++ b/emul/mini/src/main/java/java/util/zip/CRC32.java Fri Feb 01 18:02:16 2013 +0100
1.3 @@ -1,113 +1,132 @@
1.4 -/*
1.5 - * Copyright (c) 1996, 2005, Oracle and/or its affiliates. All rights reserved.
1.6 - * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
1.7 - *
1.8 - * This code is free software; you can redistribute it and/or modify it
1.9 - * under the terms of the GNU General Public License version 2 only, as
1.10 - * published by the Free Software Foundation. Oracle designates this
1.11 - * particular file as subject to the "Classpath" exception as provided
1.12 - * by Oracle in the LICENSE file that accompanied this code.
1.13 - *
1.14 - * This code is distributed in the hope that it will be useful, but WITHOUT
1.15 - * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
1.16 - * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
1.17 - * version 2 for more details (a copy is included in the LICENSE file that
1.18 - * accompanied this code).
1.19 - *
1.20 - * You should have received a copy of the GNU General Public License version
1.21 - * 2 along with this work; if not, write to the Free Software Foundation,
1.22 - * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
1.23 - *
1.24 - * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
1.25 - * or visit www.oracle.com if you need additional information or have any
1.26 - * questions.
1.27 - */
1.28 +/* CRC32.java - Computes CRC32 data checksum of a data stream
1.29 + Copyright (C) 1999. 2000, 2001 Free Software Foundation, Inc.
1.30 +
1.31 +This file is part of GNU Classpath.
1.32 +
1.33 +GNU Classpath is free software; you can redistribute it and/or modify
1.34 +it under the terms of the GNU General Public License as published by
1.35 +the Free Software Foundation; either version 2, or (at your option)
1.36 +any later version.
1.37 +
1.38 +GNU Classpath is distributed in the hope that it will be useful, but
1.39 +WITHOUT ANY WARRANTY; without even the implied warranty of
1.40 +MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
1.41 +General Public License for more details.
1.42 +
1.43 +You should have received a copy of the GNU General Public License
1.44 +along with GNU Classpath; see the file COPYING. If not, write to the
1.45 +Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
1.46 +02111-1307 USA.
1.47 +
1.48 +Linking this library statically or dynamically with other modules is
1.49 +making a combined work based on this library. Thus, the terms and
1.50 +conditions of the GNU General Public License cover the whole
1.51 +combination.
1.52 +
1.53 +As a special exception, the copyright holders of this library give you
1.54 +permission to link this library with independent modules to produce an
1.55 +executable, regardless of the license terms of these independent
1.56 +modules, and to copy and distribute the resulting executable under
1.57 +terms of your choice, provided that you also meet, for each linked
1.58 +independent module, the terms and conditions of the license of that
1.59 +module. An independent module is a module which is not derived from
1.60 +or based on this library. If you modify this library, you may extend
1.61 +this exception to your version of the library, but you are not
1.62 +obligated to do so. If you do not wish to do so, delete this
1.63 +exception statement from your version. */
1.64
1.65 package java.util.zip;
1.66
1.67 +/*
1.68 + * Written using on-line Java Platform 1.2 API Specification, as well
1.69 + * as "The Java Class Libraries", 2nd edition (Addison-Wesley, 1998).
1.70 + * The actual CRC32 algorithm is taken from RFC 1952.
1.71 + * Status: Believed complete and correct.
1.72 + */
1.73 +
1.74 /**
1.75 - * A class that can be used to compute the CRC-32 of a data stream.
1.76 + * Computes CRC32 data checksum of a data stream.
1.77 + * The actual CRC32 algorithm is described in RFC 1952
1.78 + * (GZIP file format specification version 4.3).
1.79 + * Can be used to get the CRC32 over a stream if used with checked input/output
1.80 + * streams.
1.81 *
1.82 - * @see Checksum
1.83 - * @author David Connelly
1.84 + * @see InflaterInputStream
1.85 + * @see DeflaterOutputStream
1.86 + *
1.87 + * @author Per Bothner
1.88 + * @date April 1, 1999.
1.89 */
1.90 -public
1.91 -class CRC32 implements Checksum {
1.92 - private int crc = 0xFFFFFFFF;
1.93 +public class CRC32 implements Checksum
1.94 +{
1.95 + /** The crc data checksum so far. */
1.96 + private int crc = 0;
1.97
1.98 - /**
1.99 - * Creates a new CRC32 object.
1.100 - */
1.101 - public CRC32() {
1.102 - }
1.103 + /** The fast CRC table. Computed once when the CRC32 class is loaded. */
1.104 + private static int[] crc_table = make_crc_table();
1.105
1.106 + /** Make the table for a fast CRC. */
1.107 + private static int[] make_crc_table ()
1.108 + {
1.109 + int[] crc_table = new int[256];
1.110 + for (int n = 0; n < 256; n++)
1.111 + {
1.112 + int c = n;
1.113 + for (int k = 8; --k >= 0; )
1.114 + {
1.115 + if ((c & 1) != 0)
1.116 + c = 0xedb88320 ^ (c >>> 1);
1.117 + else
1.118 + c = c >>> 1;
1.119 + }
1.120 + crc_table[n] = c;
1.121 + }
1.122 + return crc_table;
1.123 + }
1.124
1.125 - /**
1.126 - * Updates the CRC-32 checksum with the specified byte (the low
1.127 - * eight bits of the argument b).
1.128 - *
1.129 - * @param b the byte to update the checksum with
1.130 - */
1.131 - public void update(int b) {
1.132 - byte[] arr = { (byte)b };
1.133 - update(arr);
1.134 - }
1.135 + /**
1.136 + * Returns the CRC32 data checksum computed so far.
1.137 + */
1.138 + public long getValue ()
1.139 + {
1.140 + return (long) crc & 0xffffffffL;
1.141 + }
1.142
1.143 - /**
1.144 - * Updates the CRC-32 checksum with the specified array of bytes.
1.145 - */
1.146 - public void update(byte[] b, int off, int len) {
1.147 - if (b == null) {
1.148 - throw new NullPointerException();
1.149 - }
1.150 - if (off < 0 || len < 0 || off > b.length - len) {
1.151 - throw new ArrayIndexOutOfBoundsException();
1.152 - }
1.153 - crc = updateBytes(crc, b, off, len);
1.154 - }
1.155 + /**
1.156 + * Resets the CRC32 data checksum as if no update was ever called.
1.157 + */
1.158 + public void reset () { crc = 0; }
1.159
1.160 - /**
1.161 - * Updates the CRC-32 checksum with the specified array of bytes.
1.162 - *
1.163 - * @param b the array of bytes to update the checksum with
1.164 - */
1.165 - public void update(byte[] b) {
1.166 - crc = updateBytes(crc, b, 0, b.length);
1.167 - }
1.168 + /**
1.169 + * Updates the checksum with the int bval.
1.170 + *
1.171 + * @param bval (the byte is taken as the lower 8 bits of bval)
1.172 + */
1.173
1.174 - /**
1.175 - * Resets CRC-32 to initial value.
1.176 - */
1.177 - public void reset() {
1.178 - crc = 0;
1.179 - }
1.180 + public void update (int bval)
1.181 + {
1.182 + int c = ~crc;
1.183 + c = crc_table[(c ^ bval) & 0xff] ^ (c >>> 8);
1.184 + crc = ~c;
1.185 + }
1.186
1.187 - /**
1.188 - * Returns CRC-32 value.
1.189 - */
1.190 - public long getValue() {
1.191 - return (long)crc & 0xffffffffL;
1.192 - }
1.193 + /**
1.194 + * Adds the byte array to the data checksum.
1.195 + *
1.196 + * @param buf the buffer which contains the data
1.197 + * @param off the offset in the buffer where the data starts
1.198 + * @param len the length of the data
1.199 + */
1.200 + public void update (byte[] buf, int off, int len)
1.201 + {
1.202 + int c = ~crc;
1.203 + while (--len >= 0)
1.204 + c = crc_table[(c ^ buf[off++]) & 0xff] ^ (c >>> 8);
1.205 + crc = ~c;
1.206 + }
1.207
1.208 - // XXX: taken from
1.209 - // http://introcs.cs.princeton.edu/java/51data/CRC32.java.html
1.210 - private static int updateBytes(int crc, byte[] arr, int off, int len) {
1.211 - int poly = 0xEDB88320; // reverse polynomial
1.212 -
1.213 - while (len-- > 0) {
1.214 - byte b = arr[off++];
1.215 - int temp = (crc ^ b) & 0xff;
1.216 -
1.217 - // read 8 bits one at a time
1.218 - for (int i = 0; i < 8; i++) {
1.219 - if ((temp & 1) == 1) {
1.220 - temp = (temp >>> 1) ^ poly;
1.221 - } else {
1.222 - temp = (temp >>> 1);
1.223 - }
1.224 - }
1.225 - crc = (crc >>> 8) ^ temp;
1.226 - }
1.227 - return crc ^ 0xffffffff;
1.228 - }
1.229 + /**
1.230 + * Adds the complete byte array to the data checksum.
1.231 + */
1.232 + public void update (byte[] buf) { update(buf, 0, buf.length); }
1.233 }