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comparison src/com/jcraft/jzlib/CRC32.java @ 357:46c2115ae1c8

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update jzlib to a21be20213d66eff15904d925e9b721956a01ef7
author Carl Byington <carl@five-ten-sg.com>
date Fri, 01 Aug 2014 13:34:58 -0700
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356:5e91b559b5fe 357:46c2115ae1c8
1 /* -*-mode:java; c-basic-offset:2; -*- */
2 /*
3 Copyright (c) 2011 ymnk, JCraft,Inc. All rights reserved.
4
5 Redistribution and use in source and binary forms, with or without
6 modification, are permitted provided that the following conditions are met:
7
8 1. Redistributions of source code must retain the above copyright notice,
9 this list of conditions and the following disclaimer.
10
11 2. Redistributions in binary form must reproduce the above copyright
12 notice, this list of conditions and the following disclaimer in
13 the documentation and/or other materials provided with the distribution.
14
15 3. The names of the authors may not be used to endorse or promote products
16 derived from this software without specific prior written permission.
17
18 THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES,
19 INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
20 FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL JCRAFT,
21 INC. OR ANY CONTRIBUTORS TO THIS SOFTWARE BE LIABLE FOR ANY DIRECT, INDIRECT,
22 INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
23 LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
24 OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
25 LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
26 NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
27 EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
28 */
29 /*
30 * This program is based on zlib-1.1.3, so all credit should go authors
31 * Jean-loup Gailly(jloup@gzip.org) and Mark Adler(madler@alumni.caltech.edu)
32 * and contributors of zlib.
33 */
34
35 package com.jcraft.jzlib;
36
37 final public class CRC32 implements Checksum {
38
39 /*
40 * The following logic has come from RFC1952.
41 */
42 private int v = 0;
43 private static int[] crc_table = null;
44 static {
45 crc_table = new int[256];
46 for (int n = 0; n < 256; n++) {
47 int c = n;
48 for (int k = 8; --k >= 0; ) {
49 if ((c & 1) != 0)
50 c = 0xedb88320 ^ (c >>> 1);
51 else
52 c = c >>> 1;
53 }
54 crc_table[n] = c;
55 }
56 }
57
58 public void update (byte[] buf, int index, int len) {
59 int c = ~v;
60 while (--len >= 0)
61 c = crc_table[(c^buf[index++])&0xff]^(c >>> 8);
62 v = ~c;
63 }
64
65 public void reset(){
66 v = 0;
67 }
68
69 public void reset(long vv){
70 v = (int)(vv&0xffffffffL);
71 }
72
73 public long getValue(){
74 return (long)(v&0xffffffffL);
75 }
76
77 // The following logic has come from zlib.1.2.
78 private static final int GF2_DIM = 32;
79 static long combine(long crc1, long crc2, long len2){
80 long row;
81 long[] even = new long[GF2_DIM];
82 long[] odd = new long[GF2_DIM];
83
84 // degenerate case (also disallow negative lengths)
85 if (len2 <= 0)
86 return crc1;
87
88 // put operator for one zero bit in odd
89 odd[0] = 0xedb88320L; // CRC-32 polynomial
90 row = 1;
91 for (int n = 1; n < GF2_DIM; n++) {
92 odd[n] = row;
93 row <<= 1;
94 }
95
96 // put operator for two zero bits in even
97 gf2_matrix_square(even, odd);
98
99 // put operator for four zero bits in odd
100 gf2_matrix_square(odd, even);
101
102 // apply len2 zeros to crc1 (first square will put the operator for one
103 // zero byte, eight zero bits, in even)
104 do {
105 // apply zeros operator for this bit of len2
106 gf2_matrix_square(even, odd);
107 if ((len2 & 1)!=0)
108 crc1 = gf2_matrix_times(even, crc1);
109 len2 >>= 1;
110
111 // if no more bits set, then done
112 if (len2 == 0)
113 break;
114
115 // another iteration of the loop with odd and even swapped
116 gf2_matrix_square(odd, even);
117 if ((len2 & 1)!=0)
118 crc1 = gf2_matrix_times(odd, crc1);
119 len2 >>= 1;
120
121 // if no more bits set, then done
122 } while (len2 != 0);
123
124 /* return combined crc */
125 crc1 ^= crc2;
126 return crc1;
127 }
128
129 private static long gf2_matrix_times(long[] mat, long vec){
130 long sum = 0;
131 int index = 0;
132 while (vec!=0) {
133 if ((vec & 1)!=0)
134 sum ^= mat[index];
135 vec >>= 1;
136 index++;
137 }
138 return sum;
139 }
140
141 static final void gf2_matrix_square(long[] square, long[] mat) {
142 for (int n = 0; n < GF2_DIM; n++)
143 square[n] = gf2_matrix_times(mat, mat[n]);
144 }
145
146 /*
147 private java.util.zip.CRC32 crc32 = new java.util.zip.CRC32();
148
149 public void update(byte[] buf, int index, int len){
150 if(buf==null) {crc32.reset();}
151 else{crc32.update(buf, index, len);}
152 }
153 public void reset(){
154 crc32.reset();
155 }
156 public void reset(long init){
157 if(init==0L){
158 crc32.reset();
159 }
160 else{
161 System.err.println("unsupported operation");
162 }
163 }
164 public long getValue(){
165 return crc32.getValue();
166 }
167 */
168 public CRC32 copy(){
169 CRC32 foo = new CRC32();
170 foo.v = this.v;
171 return foo;
172 }
173
174 public static int[] getCRC32Table(){
175 int[] tmp = new int[crc_table.length];
176 System.arraycopy(crc_table, 0, tmp, 0, tmp.length);
177 return tmp;
178 }
179 }