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C# / C Sharp » Security » CRCScreenshots 
A utility class to compute CRC32
 
// HtmlAgilityPack V1.0 - Simon Mourier <simon underscore mourier at hotmail dot com>
using System;
using System.IO;

namespace HtmlAgilityPack
{
  /// <summary>
  /// A utility class to compute CRC32.
  /// </summary>
  public class Crc32
  {
    private uint _crc32 = 0;
    static private uint[] crc_32_tab =  // CRC polynomial 0xedb88320 
      {
        0x000000000x770730960xee0e612c0x990951ba0x076dc4190x706af48f,
        0xe963a5350x9e6495a30x0edb88320x79dcb8a40xe0d5e91e0x97d2d988,
        0x09b64c2b0x7eb17cbd0xe7b82d070x90bf1d910x1db710640x6ab020f2,
        0xf3b971480x84be41de0x1adad47d0x6ddde4eb0xf4d4b5510x83d385c7,
        0x136c98560x646ba8c00xfd62f97a0x8a65c9ec0x14015c4f0x63066cd9,
        0xfa0f3d630x8d080df50x3b6e20c80x4c69105e0xd56041e40xa2677172,
        0x3c03e4d10x4b04d4470xd20d85fd0xa50ab56b0x35b5a8fa0x42b2986c,
        0xdbbbc9d60xacbcf9400x32d86ce30x45df5c750xdcd60dcf0xabd13d59,
        0x26d930ac0x51de003a0xc8d751800xbfd061160x21b4f4b50x56b3c423,
        0xcfba95990xb8bda50f0x2802b89e0x5f0588080xc60cd9b20xb10be924,
        0x2f6f7c870x58684c110xc1611dab0xb6662d3d0x76dc41900x01db7106,
        0x98d220bc0xefd5102a0x71b185890x06b6b51f0x9fbfe4a50xe8b8d433,
        0x7807c9a20x0f00f9340x9609a88e0xe10e98180x7f6a0dbb0x086d3d2d,
        0x91646c970xe6635c010x6b6b51f40x1c6c61620x856530d80xf262004e,
        0x6c0695ed0x1b01a57b0x8208f4c10xf50fc4570x65b0d9c60x12b7e950,
        0x8bbeb8ea0xfcb9887c0x62dd1ddf0x15da2d490x8cd37cf30xfbd44c65,
        0x4db261580x3ab551ce0xa3bc00740xd4bb30e20x4adfa5410x3dd895d7,
        0xa4d1c46d0xd3d6f4fb0x4369e96a0x346ed9fc0xad6788460xda60b8d0,
        0x44042d730x33031de50xaa0a4c5f0xdd0d7cc90x5005713c0x270241aa,
        0xbe0b10100xc90c20860x5768b5250x206f85b30xb966d4090xce61e49f,
        0x5edef90e0x29d9c9980xb0d098220xc7d7a8b40x59b33d170x2eb40d81,
        0xb7bd5c3b0xc0ba6cad0xedb883200x9abfb3b60x03b6e20c0x74b1d29a,
        0xead547390x9dd277af0x04db26150x73dc16830xe3630b120x94643b84,
        0x0d6d6a3e0x7a6a5aa80xe40ecf0b0x9309ff9d0x0a00ae270x7d079eb1,
        0xf00f93440x8708a3d20x1e01f2680x6906c2fe0xf762575d0x806567cb,
        0x196c36710x6e6b06e70xfed41b760x89d32be00x10da7a5a0x67dd4acc,
        0xf9b9df6f0x8ebeeff90x17b7be430x60b08ed50xd6d6a3e80xa1d1937e,
        0x38d8c2c40x4fdff2520xd1bb67f10xa6bc57670x3fb506dd0x48b2364b,
        0xd80d2bda0xaf0a1b4c0x36034af60x41047a600xdf60efc30xa867df55,
        0x316e8eef0x4669be790xcb61b38c0xbc66831a0x256fd2a00x5268e236,
        0xcc0c77950xbb0b47030x220216b90x5505262f0xc5ba3bbe0xb2bd0b28,
        0x2bb45a920x5cb36a040xc2d7ffa70xb5d0cf310x2cd99e8b0x5bdeae1d,
        0x9b64c2b00xec63f2260x756aa39c0x026d930a0x9c0906a90xeb0e363f,
        0x720767850x050057130x95bf4a820xe2b87a140x7bb12bae0x0cb61b38,
        0x92d28e9b0xe5d5be0d0x7cdcefb70x0bdbdf210x86d3d2d40xf1d4e242,
        0x68ddb3f80x1fda836e0x81be16cd0xf6b9265b0x6fb077e10x18b74777,
        0x88085ae60xff0f6a700x66063bca0x11010b5c0x8f659eff0xf862ae69,
        0x616bffd30x166ccf450xa00ae2780xd70dd2ee0x4e0483540x3903b3c2,
        0xa76726610xd06016f70x4969474d0x3e6e77db0xaed16a4a0xd9d65adc,
        0x40df0b660x37d83bf00xa9bcae530xdebb9ec50x47b2cf7f0x30b5ffe9,
        0xbdbdf21c0xcabac28a0x53b393300x24b4a3a60xbad036050xcdd70693,
        0x54de57290x23d967bf0xb3667a2e0xc4614ab80x5d681b020x2a6f2b94,
        0xb40bbe370xc30c8ea10x5a05df1b0x2d02ef8d 
      };      

    static private uint UPDC32(byte octet, uint crc)
    {
      return (crc_32_tab[((crc)^((byte)octet)) 0xff((crc>> 8));
    }

    internal uint CheckSum
    {
      get
      {
        return _crc32;
      }
      set
      {
        _crc32 = value;
      }
    }

    internal uint AddToCRC32(int c)
    {
      return AddToCRC32((ushort)c);
    }

    internal uint AddToCRC32(ushort c)
    {
      byte lowByte, hiByte;
      lowByte = (byte)(c & 0x00ff);
      hiByte = (byte)(c >> 8);
      _crc32 = UPDC32(hiByte, _crc32);
      _crc32 = UPDC32(lowByte, _crc32);
      return ~_crc32;
    }

    /// <summary>
    /// Compute a checksum for a given string.
    /// </summary>
    /// <param name="text">The string to compute the checksum for.</param>
    /// <returns>The computed checksum.</returns>
    static public uint CRC32String(string text)
    {
      uint oldcrc32;
      oldcrc32 = 0xFFFFFFFF;        
      int len = text.Length;
      ushort uCharVal;
      byte lowByte, hiByte;
        
      for int i=0; len>0; i++)
      {
        --len;
        uCharVal = text[len];
        unchecked
        {
          lowByte = (byte)(uCharVal & 0x00ff);
          hiByte = (byte)(uCharVal >> 8);
        }
        oldcrc32 = UPDC32(hiByte, oldcrc32);
        oldcrc32 = UPDC32(lowByte, oldcrc32);
      }

      return ~oldcrc32;
    }

    /// <summary>
    /// Compute a checksum for a given array of bytes.
    /// </summary>
    /// <param name="bytes">The array of bytes to compute the checksum for.</param>
    /// <returns>The computed checksum.</returns>
    static public uint CRC32Bytes(byte[] bytes)
    {
      uint oldcrc32;
      oldcrc32 = 0xFFFFFFFF;        
      int len = bytes.Length;
        
      for int i=0; len>0; i++)
      {
        --len;
        oldcrc32 = UPDC32(bytes[len], oldcrc32);
      }
      return ~oldcrc32;
    }
  }
}

   
  
Related examples in the same category
1.This class is responsible for calculating the crc32 value of a byte buffer and returning it as a hexadecimal string.
2.Generate a table for a byte-wise 32-bit CRC calculation on the polynomial: 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.
3.Calculates a 32 bit Cyclic Redundancy Checksum (CRC) using the same polynomial used by Zip.
4.Do CRC32 hashing.
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