Calc Crc32 On Strings

[BenJones]

hi this is a crc32 class I made see the class comments for info.
comments suggestions welcome. Hope you find it usfull.

Option Explicit On
 
'I been making a few Registration Schemes over the last few weeks
'And thought of a new way to generate a 32crc from a string,
'Or even use it to validate serials for my programs anyway was reading some papers I had 
 
'from college on crc32 I found years ago that were in C++ and decided to try and convert it
'Anyway this is what I came up with I don’t know if this is 100% right though
'But it does seem to calc some strings I test and that really want.
'If you guys think it wrong or can fix it let me know.
 
Public Class crc32
 
    'Nise long look up table.
    Private TLookup = {&H0, &H77073096, &HEE0E612C, &H990951BA, &H76DC419, &H706AF48F,
    &HE963A535, &H9E6495A3, &HEDB8832, &H79DCB8A4, &HE0D5E91E, &H97D2D988,
    &H9B64C2B, &H7EB17CBD, &HE7B82D07, &H90BF1D91, &H1DB71064, &H6AB020F2,
    &HF3B97148, &H84BE41DE, &H1ADAD47D, &H6DDDE4EB, &HF4D4B551, &H83D385C7,
    &H136C9856, &H646BA8C0, &HFD62F97A, &H8A65C9EC, &H14015C4F, &H63066CD9,
    &HFA0F3D63, &H8D080DF5, &H3B6E20C8, &H4C69105E, &HD56041E4, &HA2677172,
    &H3C03E4D1, &H4B04D447, &HD20D85FD, &HA50AB56B, &H35B5A8FA, &H42B2986C,
    &HDBBBC9D6, &HACBCF940, &H32D86CE3, &H45DF5C75, &HDCD60DCF, &HABD13D59,
    &H26D930AC, &H51DE003A, &HC8D75180, &HBFD06116, &H21B4F4B5, &H56B3C423,
    &HCFBA9599, &HB8BDA50F, &H2802B89E, &H5F058808, &HC60CD9B2, &HB10BE924,
    &H2F6F7C87, &H58684C11, &HC1611DAB, &HB6662D3D, &H76DC4190, &H1DB7106,
    &H98D220BC, &HEFD5102A, &H71B18589, &H6B6B51F, &H9FBFE4A5, &HE8B8D433,
    &H7807C9A2, &HF00F934, &H9609A88E, &HE10E9818, &H7F6A0DBB, &H86D3D2D,
    &H91646C97, &HE6635C01, &H6B6B51F4, &H1C6C6162, &H856530D8, &HF262004E,
    &H6C0695ED, &H1B01A57B, &H8208F4C1, &HF50FC457, &H65B0D9C6, &H12B7E950,
    &H8BBEB8EA, &HFCB9887C, &H62DD1DDF, &H15DA2D49, &H8CD37CF3, &HFBD44C65,
    &H4DB26158, &H3AB551CE, &HA3BC0074, &HD4BB30E2, &H4ADFA541, &H3DD895D7,
    &HA4D1C46D, &HD3D6F4FB, &H4369E96A, &H346ED9FC, &HAD678846, &HDA60B8D0,
    &H44042D73, &H33031DE5, &HAA0A4C5F, &HDD0D7CC9, &H5005713C, &H270241AA,
    &HBE0B1010, &HC90C2086, &H5768B525, &H206F85B3, &HB966D409, &HCE61E49F,
    &H5EDEF90E, &H29D9C998, &HB0D09822, &HC7D7A8B4, &H59B33D17, &H2EB40D81,
    &HB7BD5C3B, &HC0BA6CAD, &HEDB88320, &H9ABFB3B6, &H3B6E20C, &H74B1D29A,
    &HEAD54739, &H9DD277AF, &H4DB2615, &H73DC1683, &HE3630B12, &H94643B84,
    &HD6D6A3E, &H7A6A5AA8, &HE40ECF0B, &H9309FF9D, &HA00AE27, &H7D079EB1,
    &HF00F9344, &H8708A3D2, &H1E01F268, &H6906C2FE, &HF762575D, &H806567CB,
    &H196C3671, &H6E6B06E7, &HFED41B76, &H89D32BE0, &H10DA7A5A, &H67DD4ACC,
    &HF9B9DF6F, &H8EBEEFF9, &H17B7BE43, &H60B08ED5, &HD6D6A3E8, &HA1D1937E,
    &H38D8C2C4, &H4FDFF252, &HD1BB67F1, &HA6BC5767, &H3FB506DD, &H48B2364B,
    &HD80D2BDA, &HAF0A1B4C, &H36034AF6, &H41047A60, &HDF60EFC3, &HA867DF55,
    &H316E8EEF, &H4669BE79, &HCB61B38C, &HBC66831A, &H256FD2A0, &H5268E236,
    &HCC0C7795, &HBB0B4703, &H220216B9, &H5505262F, &HC5BA3BBE, &HB2BD0B28,
    &H2BB45A92, &H5CB36A04, &HC2D7FFA7, &HB5D0CF31, &H2CD99E8B, &H5BDEAE1D,
    &H9B64C2B0, &HEC63F226, &H756AA39C, &H26D930A, &H9C0906A9, &HEB0E363F,
    &H72076785, &H5005713, &H95BF4A82, &HE2B87A14, &H7BB12BAE, &HCB61B38,
    &H92D28E9B, &HE5D5BE0D, &H7CDCEFB7, &HBDBDF21, &H86D3D2D4, &HF1D4E242,
    &H68DDB3F8, &H1FDA836E, &H81BE16CD, &HF6B9265B, &H6FB077E1, &H18B74777,
    &H88085AE6, &HFF0F6A70, &H66063BCA, &H11010B5C, &H8F659EFF, &HF862AE69,
    &H616BFFD3, &H166CCF45, &HA00AE278, &HD70DD2EE, &H4E048354, &H3903B3C2,
    &HA7672661, &HD06016F7, &H4969474D, &H3E6E77DB, &HAED16A4A, &HD9D65ADC,
    &H40DF0B66, &H37D83BF0, &HA9BCAE53, &HDEBB9EC5, &H47B2CF7F, &H30B5FFE9,
    &HBDBDF21C, &HCABAC28A, &H53B39330, &H24B4A3A6, &HBAD03605, &HCDD70693,
    &H54DE5729, &H23D967BF, &HB3667A2E, &HC4614AB8, &H5D681B02, &H2A6F2B94,
    &HB40BBE37, &HC30C8EA1, &H5A05DF1B, &H2D02EF8D}
 
    Public Function Crc32CalcString(ByVal source As String) As String
        Dim crc As Integer = &HFFFFFFFF
        Dim x As Integer = 0
        Dim c As Byte = 0
 
        'Loop though the string.
        While x <= source.Length - 1
            'Get byte from char
            c = Asc(source(x))
            'This is the magic stuff that get the crc value.
            crc = (((crc And &HFFFFFF00) >> 8) And &HFFFFFF) Xor (TLookup((crc And 255) Xor c))
            'INC Counter
            x += 1
        End While
 
        crc = (Not crc)
        'Return hex value or crc value.
        Return Hex(crc)
    End Function
 
End Class

Example Code

Option Explicit On

Public Class frmmain
 
    Private Sub cmdTest_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdTest.Click
        'Declare the class.
        Dim BensCrc32 As New crc32()
 
        MessageBox.Show(BensCrc32.Crc32CalcString("This is a test"), "CRC-32-DEMO",
                        MessageBoxButtons.OK, MessageBoxIcon.Information) 'Return C07A9F32
    End Sub
 
End Class