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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one or more
3    * contributor license agreements.  See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * The ASF licenses this file to You under the Apache License, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License.  You may obtain a copy of the License at
8    * 
9    *      http://www.apache.org/licenses/LICENSE-2.0
10   * 
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the License for the specific language governing permissions and
15   * limitations under the License.
16   */
17  package org.apache.commons.vfs.provider.bzip2;
18  
19  /*
20   * This package is based on the work done by Keiron Liddle, Aftex Software
21   * <keiron@aftexsw.com> to whom the Ant project is very grateful for his
22   * great code.
23   */
24  
25  /***
26   * A simple class the hold and calculate the CRC for sanity checking of the
27   * data.
28   *
29   * @author <a href="mailto:keiron@aftexsw.com">Keiron Liddle</a>
30   */
31  class CRC
32  {
33      private static int[] CRC32_TABLE = new int[]
34      {
35          0x00000000, 0x04c11db7, 0x09823b6e, 0x0d4326d9,
36          0x130476dc, 0x17c56b6b, 0x1a864db2, 0x1e475005,
37          0x2608edb8, 0x22c9f00f, 0x2f8ad6d6, 0x2b4bcb61,
38          0x350c9b64, 0x31cd86d3, 0x3c8ea00a, 0x384fbdbd,
39          0x4c11db70, 0x48d0c6c7, 0x4593e01e, 0x4152fda9,
40          0x5f15adac, 0x5bd4b01b, 0x569796c2, 0x52568b75,
41          0x6a1936c8, 0x6ed82b7f, 0x639b0da6, 0x675a1011,
42          0x791d4014, 0x7ddc5da3, 0x709f7b7a, 0x745e66cd,
43          0x9823b6e0, 0x9ce2ab57, 0x91a18d8e, 0x95609039,
44          0x8b27c03c, 0x8fe6dd8b, 0x82a5fb52, 0x8664e6e5,
45          0xbe2b5b58, 0xbaea46ef, 0xb7a96036, 0xb3687d81,
46          0xad2f2d84, 0xa9ee3033, 0xa4ad16ea, 0xa06c0b5d,
47          0xd4326d90, 0xd0f37027, 0xddb056fe, 0xd9714b49,
48          0xc7361b4c, 0xc3f706fb, 0xceb42022, 0xca753d95,
49          0xf23a8028, 0xf6fb9d9f, 0xfbb8bb46, 0xff79a6f1,
50          0xe13ef6f4, 0xe5ffeb43, 0xe8bccd9a, 0xec7dd02d,
51          0x34867077, 0x30476dc0, 0x3d044b19, 0x39c556ae,
52          0x278206ab, 0x23431b1c, 0x2e003dc5, 0x2ac12072,
53          0x128e9dcf, 0x164f8078, 0x1b0ca6a1, 0x1fcdbb16,
54          0x018aeb13, 0x054bf6a4, 0x0808d07d, 0x0cc9cdca,
55          0x7897ab07, 0x7c56b6b0, 0x71159069, 0x75d48dde,
56          0x6b93dddb, 0x6f52c06c, 0x6211e6b5, 0x66d0fb02,
57          0x5e9f46bf, 0x5a5e5b08, 0x571d7dd1, 0x53dc6066,
58          0x4d9b3063, 0x495a2dd4, 0x44190b0d, 0x40d816ba,
59          0xaca5c697, 0xa864db20, 0xa527fdf9, 0xa1e6e04e,
60          0xbfa1b04b, 0xbb60adfc, 0xb6238b25, 0xb2e29692,
61          0x8aad2b2f, 0x8e6c3698, 0x832f1041, 0x87ee0df6,
62          0x99a95df3, 0x9d684044, 0x902b669d, 0x94ea7b2a,
63          0xe0b41de7, 0xe4750050, 0xe9362689, 0xedf73b3e,
64          0xf3b06b3b, 0xf771768c, 0xfa325055, 0xfef34de2,
65          0xc6bcf05f, 0xc27dede8, 0xcf3ecb31, 0xcbffd686,
66          0xd5b88683, 0xd1799b34, 0xdc3abded, 0xd8fba05a,
67          0x690ce0ee, 0x6dcdfd59, 0x608edb80, 0x644fc637,
68          0x7a089632, 0x7ec98b85, 0x738aad5c, 0x774bb0eb,
69          0x4f040d56, 0x4bc510e1, 0x46863638, 0x42472b8f,
70          0x5c007b8a, 0x58c1663d, 0x558240e4, 0x51435d53,
71          0x251d3b9e, 0x21dc2629, 0x2c9f00f0, 0x285e1d47,
72          0x36194d42, 0x32d850f5, 0x3f9b762c, 0x3b5a6b9b,
73          0x0315d626, 0x07d4cb91, 0x0a97ed48, 0x0e56f0ff,
74          0x1011a0fa, 0x14d0bd4d, 0x19939b94, 0x1d528623,
75          0xf12f560e, 0xf5ee4bb9, 0xf8ad6d60, 0xfc6c70d7,
76          0xe22b20d2, 0xe6ea3d65, 0xeba91bbc, 0xef68060b,
77          0xd727bbb6, 0xd3e6a601, 0xdea580d8, 0xda649d6f,
78          0xc423cd6a, 0xc0e2d0dd, 0xcda1f604, 0xc960ebb3,
79          0xbd3e8d7e, 0xb9ff90c9, 0xb4bcb610, 0xb07daba7,
80          0xae3afba2, 0xaafbe615, 0xa7b8c0cc, 0xa379dd7b,
81          0x9b3660c6, 0x9ff77d71, 0x92b45ba8, 0x9675461f,
82          0x8832161a, 0x8cf30bad, 0x81b02d74, 0x857130c3,
83          0x5d8a9099, 0x594b8d2e, 0x5408abf7, 0x50c9b640,
84          0x4e8ee645, 0x4a4ffbf2, 0x470cdd2b, 0x43cdc09c,
85          0x7b827d21, 0x7f436096, 0x7200464f, 0x76c15bf8,
86          0x68860bfd, 0x6c47164a, 0x61043093, 0x65c52d24,
87          0x119b4be9, 0x155a565e, 0x18197087, 0x1cd86d30,
88          0x029f3d35, 0x065e2082, 0x0b1d065b, 0x0fdc1bec,
89          0x3793a651, 0x3352bbe6, 0x3e119d3f, 0x3ad08088,
90          0x2497d08d, 0x2056cd3a, 0x2d15ebe3, 0x29d4f654,
91          0xc5a92679, 0xc1683bce, 0xcc2b1d17, 0xc8ea00a0,
92          0xd6ad50a5, 0xd26c4d12, 0xdf2f6bcb, 0xdbee767c,
93          0xe3a1cbc1, 0xe760d676, 0xea23f0af, 0xeee2ed18,
94          0xf0a5bd1d, 0xf464a0aa, 0xf9278673, 0xfde69bc4,
95          0x89b8fd09, 0x8d79e0be, 0x803ac667, 0x84fbdbd0,
96          0x9abc8bd5, 0x9e7d9662, 0x933eb0bb, 0x97ffad0c,
97          0xafb010b1, 0xab710d06, 0xa6322bdf, 0xa2f33668,
98          0xbcb4666d, 0xb8757bda, 0xb5365d03, 0xb1f740b4
99      };
100 
101     private int m_globalCrc;
102 
103     protected CRC()
104     {
105         initialiseCRC();
106     }
107 
108     int getFinalCRC()
109     {
110         return ~m_globalCrc;
111     }
112 
113     void initialiseCRC()
114     {
115         m_globalCrc = 0xffffffff;
116     }
117 
118     void updateCRC( final int inCh )
119     {
120         int temp = ( m_globalCrc >> 24 ) ^ inCh;
121         if( temp < 0 )
122         {
123             temp = 256 + temp;
124         }
125         m_globalCrc = ( m_globalCrc << 8 ) ^ CRC32_TABLE[ temp ];
126     }
127 }
128