1 // CRC32.cs - Computes CRC32 data checksum of a data stream
\r
2 // Copyright (C) 2001 Mike Krueger
\r
4 // This file was translated from java, it was part of the GNU Classpath
\r
5 // Copyright (C) 1999, 2000, 2001 Free Software Foundation, Inc.
\r
7 // This program is free software; you can redistribute it and/or
\r
8 // modify it under the terms of the GNU General Public License
\r
9 // as published by the Free Software Foundation; either version 2
\r
10 // of the License, or (at your option) any later version.
\r
12 // This program is distributed in the hope that it will be useful,
\r
13 // but WITHOUT ANY WARRANTY; without even the implied warranty of
\r
14 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
\r
15 // GNU General Public License for more details.
\r
17 // You should have received a copy of the GNU General Public License
\r
18 // along with this program; if not, write to the Free Software
\r
19 // Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
\r
21 // Linking this library statically or dynamically with other modules is
\r
22 // making a combined work based on this library. Thus, the terms and
\r
23 // conditions of the GNU General Public License cover the whole
\r
26 // As a special exception, the copyright holders of this library give you
\r
27 // permission to link this library with independent modules to produce an
\r
28 // executable, regardless of the license terms of these independent
\r
29 // modules, and to copy and distribute the resulting executable under
\r
30 // terms of your choice, provided that you also meet, for each linked
\r
31 // independent module, the terms and conditions of the license of that
\r
32 // module. An independent module is a module which is not derived from
\r
33 // or based on this library. If you modify this library, you may extend
\r
34 // this exception to your version of the library, but you are not
\r
35 // obligated to do so. If you do not wish to do so, delete this
\r
36 // exception statement from your version.
\r
40 namespace ICSharpCode.SharpZipLib.Checksums
\r
44 /// Generate a table for a byte-wise 32-bit CRC calculation on the polynomial:
\r
45 /// x^32+x^26+x^23+x^22+x^16+x^12+x^11+x^10+x^8+x^7+x^5+x^4+x^2+x+1.
\r
47 /// Polynomials over GF(2) are represented in binary, one bit per coefficient,
\r
48 /// with the lowest powers in the most significant bit. Then adding polynomials
\r
49 /// is just exclusive-or, and multiplying a polynomial by x is a right shift by
\r
50 /// one. If we call the above polynomial p, and represent a byte as the
\r
51 /// polynomial q, also with the lowest power in the most significant bit (so the
\r
52 /// byte 0xb1 is the polynomial x^7+x^3+x+1), then the CRC is (q*x^32) mod p,
\r
53 /// where a mod b means the remainder after dividing a by b.
\r
55 /// This calculation is done using the shift-register method of multiplying and
\r
56 /// taking the remainder. The register is initialized to zero, and for each
\r
57 /// incoming bit, x^32 is added mod p to the register if the bit is a one (where
\r
58 /// x^32 mod p is p+x^32 = x^26+...+1), and the register is multiplied mod p by
\r
59 /// x (which is shifting right by one and adding x^32 mod p if the bit shifted
\r
60 /// out is a one). We start with the highest power (least significant bit) of
\r
61 /// q and repeat for all eight bits of q.
\r
63 /// The table is simply the CRC of all possible eight bit values. This is all
\r
64 /// the information needed to generate CRC's on data a byte at a time for all
\r
65 /// combinations of CRC register values and incoming bytes.
\r
67 public sealed class Crc32 : IChecksum
\r
69 readonly static uint CrcSeed = 0xFFFFFFFF;
\r
71 readonly static uint[] CrcTable = new uint[] {
\r
72 0x00000000, 0x77073096, 0xEE0E612C, 0x990951BA, 0x076DC419,
\r
73 0x706AF48F, 0xE963A535, 0x9E6495A3, 0x0EDB8832, 0x79DCB8A4,
\r
74 0xE0D5E91E, 0x97D2D988, 0x09B64C2B, 0x7EB17CBD, 0xE7B82D07,
\r
75 0x90BF1D91, 0x1DB71064, 0x6AB020F2, 0xF3B97148, 0x84BE41DE,
\r
76 0x1ADAD47D, 0x6DDDE4EB, 0xF4D4B551, 0x83D385C7, 0x136C9856,
\r
77 0x646BA8C0, 0xFD62F97A, 0x8A65C9EC, 0x14015C4F, 0x63066CD9,
\r
78 0xFA0F3D63, 0x8D080DF5, 0x3B6E20C8, 0x4C69105E, 0xD56041E4,
\r
79 0xA2677172, 0x3C03E4D1, 0x4B04D447, 0xD20D85FD, 0xA50AB56B,
\r
80 0x35B5A8FA, 0x42B2986C, 0xDBBBC9D6, 0xACBCF940, 0x32D86CE3,
\r
81 0x45DF5C75, 0xDCD60DCF, 0xABD13D59, 0x26D930AC, 0x51DE003A,
\r
82 0xC8D75180, 0xBFD06116, 0x21B4F4B5, 0x56B3C423, 0xCFBA9599,
\r
83 0xB8BDA50F, 0x2802B89E, 0x5F058808, 0xC60CD9B2, 0xB10BE924,
\r
84 0x2F6F7C87, 0x58684C11, 0xC1611DAB, 0xB6662D3D, 0x76DC4190,
\r
85 0x01DB7106, 0x98D220BC, 0xEFD5102A, 0x71B18589, 0x06B6B51F,
\r
86 0x9FBFE4A5, 0xE8B8D433, 0x7807C9A2, 0x0F00F934, 0x9609A88E,
\r
87 0xE10E9818, 0x7F6A0DBB, 0x086D3D2D, 0x91646C97, 0xE6635C01,
\r
88 0x6B6B51F4, 0x1C6C6162, 0x856530D8, 0xF262004E, 0x6C0695ED,
\r
89 0x1B01A57B, 0x8208F4C1, 0xF50FC457, 0x65B0D9C6, 0x12B7E950,
\r
90 0x8BBEB8EA, 0xFCB9887C, 0x62DD1DDF, 0x15DA2D49, 0x8CD37CF3,
\r
91 0xFBD44C65, 0x4DB26158, 0x3AB551CE, 0xA3BC0074, 0xD4BB30E2,
\r
92 0x4ADFA541, 0x3DD895D7, 0xA4D1C46D, 0xD3D6F4FB, 0x4369E96A,
\r
93 0x346ED9FC, 0xAD678846, 0xDA60B8D0, 0x44042D73, 0x33031DE5,
\r
94 0xAA0A4C5F, 0xDD0D7CC9, 0x5005713C, 0x270241AA, 0xBE0B1010,
\r
95 0xC90C2086, 0x5768B525, 0x206F85B3, 0xB966D409, 0xCE61E49F,
\r
96 0x5EDEF90E, 0x29D9C998, 0xB0D09822, 0xC7D7A8B4, 0x59B33D17,
\r
97 0x2EB40D81, 0xB7BD5C3B, 0xC0BA6CAD, 0xEDB88320, 0x9ABFB3B6,
\r
98 0x03B6E20C, 0x74B1D29A, 0xEAD54739, 0x9DD277AF, 0x04DB2615,
\r
99 0x73DC1683, 0xE3630B12, 0x94643B84, 0x0D6D6A3E, 0x7A6A5AA8,
\r
100 0xE40ECF0B, 0x9309FF9D, 0x0A00AE27, 0x7D079EB1, 0xF00F9344,
\r
101 0x8708A3D2, 0x1E01F268, 0x6906C2FE, 0xF762575D, 0x806567CB,
\r
102 0x196C3671, 0x6E6B06E7, 0xFED41B76, 0x89D32BE0, 0x10DA7A5A,
\r
103 0x67DD4ACC, 0xF9B9DF6F, 0x8EBEEFF9, 0x17B7BE43, 0x60B08ED5,
\r
104 0xD6D6A3E8, 0xA1D1937E, 0x38D8C2C4, 0x4FDFF252, 0xD1BB67F1,
\r
105 0xA6BC5767, 0x3FB506DD, 0x48B2364B, 0xD80D2BDA, 0xAF0A1B4C,
\r
106 0x36034AF6, 0x41047A60, 0xDF60EFC3, 0xA867DF55, 0x316E8EEF,
\r
107 0x4669BE79, 0xCB61B38C, 0xBC66831A, 0x256FD2A0, 0x5268E236,
\r
108 0xCC0C7795, 0xBB0B4703, 0x220216B9, 0x5505262F, 0xC5BA3BBE,
\r
109 0xB2BD0B28, 0x2BB45A92, 0x5CB36A04, 0xC2D7FFA7, 0xB5D0CF31,
\r
110 0x2CD99E8B, 0x5BDEAE1D, 0x9B64C2B0, 0xEC63F226, 0x756AA39C,
\r
111 0x026D930A, 0x9C0906A9, 0xEB0E363F, 0x72076785, 0x05005713,
\r
112 0x95BF4A82, 0xE2B87A14, 0x7BB12BAE, 0x0CB61B38, 0x92D28E9B,
\r
113 0xE5D5BE0D, 0x7CDCEFB7, 0x0BDBDF21, 0x86D3D2D4, 0xF1D4E242,
\r
114 0x68DDB3F8, 0x1FDA836E, 0x81BE16CD, 0xF6B9265B, 0x6FB077E1,
\r
115 0x18B74777, 0x88085AE6, 0xFF0F6A70, 0x66063BCA, 0x11010B5C,
\r
116 0x8F659EFF, 0xF862AE69, 0x616BFFD3, 0x166CCF45, 0xA00AE278,
\r
117 0xD70DD2EE, 0x4E048354, 0x3903B3C2, 0xA7672661, 0xD06016F7,
\r
118 0x4969474D, 0x3E6E77DB, 0xAED16A4A, 0xD9D65ADC, 0x40DF0B66,
\r
119 0x37D83BF0, 0xA9BCAE53, 0xDEBB9EC5, 0x47B2CF7F, 0x30B5FFE9,
\r
120 0xBDBDF21C, 0xCABAC28A, 0x53B39330, 0x24B4A3A6, 0xBAD03605,
\r
121 0xCDD70693, 0x54DE5729, 0x23D967BF, 0xB3667A2E, 0xC4614AB8,
\r
122 0x5D681B02, 0x2A6F2B94, 0xB40BBE37, 0xC30C8EA1, 0x5A05DF1B,
\r
126 internal static uint ComputeCrc32(uint oldCrc, byte bval)
\r
128 return (uint)(Crc32.CrcTable[(oldCrc ^ bval) & 0xFF] ^ (oldCrc >> 8));
\r
132 /// The crc data checksum so far.
\r
137 /// Returns the CRC32 data checksum computed so far.
\r
139 public long Value {
\r
149 /// Resets the CRC32 data checksum as if no update was ever called.
\r
151 public void Reset()
\r
157 /// Updates the checksum with the int bval.
\r
159 /// <param name = "bval">
\r
160 /// the byte is taken as the lower 8 bits of bval
\r
162 public void Update(int bval)
\r
165 crc = CrcTable[(crc ^ bval) & 0xFF] ^ (crc >> 8);
\r
170 /// Updates the checksum with the bytes taken from the array.
\r
172 /// <param name="buffer">
\r
173 /// buffer an array of bytes
\r
175 public void Update(byte[] buffer)
\r
177 Update(buffer, 0, buffer.Length);
\r
181 /// Adds the byte array to the data checksum.
\r
183 /// <param name = "buf">
\r
184 /// the buffer which contains the data
\r
186 /// <param name = "off">
\r
187 /// the offset in the buffer where the data starts
\r
189 /// <param name = "len">
\r
190 /// the length of the data
\r
192 public void Update(byte[] buf, int off, int len)
\r
195 throw new ArgumentNullException("buf");
\r
198 if (off < 0 || len < 0 || off + len > buf.Length) {
\r
199 throw new ArgumentOutOfRangeException();
\r
204 while (--len >= 0) {
\r
205 crc = CrcTable[(crc ^ buf[off++]) & 0xFF] ^ (crc >> 8);
\r