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comparison app/src/main/java/com/jcraft/jzlib/CRC32.java @ 438:d29cce60f393
migrate from Eclipse to Android Studio
author | Carl Byington <carl@five-ten-sg.com> |
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date | Thu, 03 Dec 2015 11:23:55 -0800 |
parents | src/com/jcraft/jzlib/CRC32.java@46c2115ae1c8 |
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437:208b31032318 | 438:d29cce60f393 |
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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 } |