A C# method for calculating the CRC32 checksum on an array of bytes. The code uses a CRC32 table and makes use of C#'s bitwise operators to return the checksum of the bytes passed.
1.// Example use
2.System.Text.ASCIIEncoding AsciiEncoding = new
System.Text.ASCIIEncoding();
3.byte[] Checksum = Calculate(AsciiEncoding.GetBytes(“Checksum This!”));
// String to bytes
4.MessageBox.Show(AsciiEncoding.GetString(Checksum)); // Return checksum
5.
6.// The CRC value table
7.private static readonly UInt32[] CRCTable =
8.{
9.0×00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
10.0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
11.0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
12.0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
13.0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
14.0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
15.0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
16.0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
17.0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
18.0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
19.0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
20.0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
21.0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
22.0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
23.0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
24.0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
25.0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
26.0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
27.0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
28.0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
29.0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
30.0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
31.0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
32.0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
33.0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
34.0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
35.0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
36.0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
37.0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
38.0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
39.0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
40.0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
41.0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
42.0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
43.0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
44.0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
45.0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
46.0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
47.0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
48.0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
49.0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
50.0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
51.0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
52.0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
53.0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
54.0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
55.0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
56.0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
57.0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
58.0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
59.0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
60.0x2d02ef8d
61.};
62.
63.// The method that does the magic
64.public static byte[] Calculate(byte[] Value)
65.{
66.UInt32 CRCVal = 0xffffffff;
67.for (int i = 0; i < Value.Length; i++)
68.{
69.CRCVal = (CRCVal >> 8) ^ CRCTable[(CRCVal & 0xff) ^ Value[i]];
70.}
71.CRCVal ^= 0xffffffff; // Toggle operation
72.byte[] Result = new byte[4];
73.
74.Result[0] = (byte)(CRCVal >> 24);
75.Result[1] = (byte)(CRCVal >> 16);
76.Result[2] = (byte)(CRCVal >> 8);
77.Result[3] = (byte)(CRCVal);
78.
79.return Result;
80.}
