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Apr 17th, 2000, 05:06 PM
#1
Any one know how to do this? Is must be very easy, every zip program ever made dose it. I looked all over for it on the net and was only able to find some ocx for vb4 that did it for like $100.
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Apr 17th, 2000, 05:56 PM
#2
Addicted Member
I found this code at http://www.dotcom2001.com/vbresources/
. There is also code for CRC16, but given the size of the code I'll just post the CRC32 here. You can look up the code yourself by finding the search area on the site mentioned above (it's a very busy design on the site so it might not that easy to find the search button) and do a search for CRC. You will get about 5 hits, 2 of which are CRC16 and CRC32.
Hope this helps. 
Code:
'CCRC32
'This class calculates the 32-bit CRC of a file or string.
' Example code for CCRC32
' http://www.dotcom2001.com/vbresources/
' To try this example, do the following:
' 1. Create a new form
' 2. Create a command button named 'cmdTest'
' 3. Paste all the code from this example to the new form's module.
' 4. Run the form
' This example assumes that the sample files are located in the
' directory named by the following constant.
Private Const mcstrExamplePath = "c:\vbsbsamp"
Private WithEvents mcrc32 As CCRC32
Private Sub cmdTest_Click()
Dim lngCRCValue As Long
Dim strString As String
' Example of creating a 32-bit CRC value for a file
mcrc32.InputFileName = mcstrExamplePath & "\sample.mdb"
lngCRCValue = mcrc32.GetCRCFromFile()
MsgBox "CRC File Value:" & lngCRCValue
' Example of creating a 32-bit CRC value for a string
strString = "One small step for [a] man; one giant leap for mankind"
lngCRCValue = mcrc32.GetCRCFromString(strString)
MsgBox "String CRC Value: " & lngCRCValue
End Sub
Private Sub Form_Load()
Set mcrc32 = New CCRC32
cmdtest.Caption = "CRC32"
End Sub
Private Sub mcrc32_Progress(sngPercentage As Single)
Debug.Print "Percent done: " & sngPercentage * 100
End Sub
'--------------------
' Class : CCRC32
' Description : This class calculates the 32-bit CRC of a file or string.
' Events
' This event is raised during file encryption. The parameter sngPercentage is
' a number between 0 and 1 representing the percentage of the file processed
Public Event Progress(sngPercentage As Single)
' Local variables to hold property values
Private m_strInputFileName As String
' Private class-specific variables
' The table of CRC Values
Private malngCRC32(256) As Long
Public Property Get InputFileName() As String
' Returns: the input file name
' Source: Total VB SourceBook 6
InputFileName = m_strInputFileName
End Property
Public Property Let InputFileName(ByVal strValue As String)
' strValue: Set the input file name
' Source: Total VB SourceBook 6
m_strInputFileName = strValue
End Property
Public Function GetCRCFromFile() As Long
' Comments : This procedure generates a CRC for the file specified in the
' InputFile property
' Parameters: None
' Returns : The calculated CRC value
'
Dim lngCRC As Long
Dim abytBuffer() As Byte
Dim lngCounter As Long
Dim lngBytesRead As Long
Dim lngFileLength As Long
Dim lngTotalBytesRead As Long
Dim intInputFile As Integer
Const cintBufferSize As Integer = &H7FFF
On Error GoTo PROC_ERR
' Construct the CRC table
ConstructCRCTable
' Get the next free file id
intInputFile = FreeFile
' Open the input file
Open m_strInputFileName For Binary Access Read As intInputFile
' Get the length of the input file
lngFileLength = LOF(intInputFile)
lngCRC = &HFFFFFFFF
' Raise the progress event, none of the file has been processed, so we pass
' zero
RaiseEvent Progress(0)
' Read data from the file
lngBytesRead = ReadFile(intInputFile, abytBuffer, cintBufferSize)
' While there is still data in the file
Do While lngBytesRead > 0
' For each byte read
For lngCounter = 0 To lngBytesRead - 1
' Update the CRC
lngCRC = UpdateCRC32(lngCRC, abytBuffer(lngCounter))
Next lngCounter
' Get the total amount of the file that has been processed
lngTotalBytesRead = lngTotalBytesRead + lngBytesRead
' Raise the progress, passing the percentage of the file processed
RaiseEvent Progress(lngTotalBytesRead / lngFileLength)
' Read the next chunk of data from the file
lngBytesRead = ReadFile(intInputFile, abytBuffer, cintBufferSize)
Loop
' Close the input file
Close intInputFile
' Return the CRC
GetCRCFromFile = Not lngCRC
PROC_EXIT:
Exit Function
PROC_ERR:
MsgBox "Error: " & Err.Number & ". " & Err.Description, , _
"GetCRCFromFile"
Resume PROC_EXIT
End Function
Public Function GetCRCFromString(strInput As String) As Long
' Comments : This procedure generates a CRC for the string specified in the
' strInput parameter
' Parameters: strInput - The string to checksum
' Returns : The calculated CRC value
'
Dim lngCRC As Long
Dim abytInput() As Byte
Dim lngCounter As Long
Dim lngInputLength As Long
Const cintUpdateBytes As Integer = 4096
On Error GoTo PROC_ERR
abytInput = strInput
lngInputLength = UBound(abytInput)
' Construct the CRC table
ConstructCRCTable
lngCRC = &HFFFFFFFF
' Raise the progress event, none of the file has been processed, so we pass
' zero
RaiseEvent Progress(0)
For lngCounter = 0 To lngInputLength
' Update the CRC
lngCRC = UpdateCRC32(lngCRC, abytInput(lngCounter))
' Raise the progress event
If lngCounter Mod cintUpdateBytes Then
RaiseEvent Progress(lngCounter / lngInputLength)
End If
Next lngCounter
' The string is done being processed
RaiseEvent Progress(1)
' Return the CRC
GetCRCFromString = Not lngCRC
PROC_EXIT:
Exit Function
PROC_ERR:
MsgBox "Error: " & Err.Number & ". " & Err.Description, , _
"GetCRCFromString"
Resume PROC_EXIT
End Function
Private Sub ConstructCRCTable()
' Comments : This procedure fills the CRC table with precalculated Values.
' This is more efficient than calculating CRC's on the fly
' Parameters: None
' Returns : Nothing
'
On Error GoTo PROC_ERR
' Fill the table with the precalculate CRC Values.
malngCRC32(0) = &H0
malngCRC32(1) = &H77073096
malngCRC32(2) = &HEE0E612C
malngCRC32(3) = &H990951BA
malngCRC32(4) = &H76DC419
malngCRC32(5) = &H706AF48F
malngCRC32(6) = &HE963A535
malngCRC32(7) = &H9E6495A3
malngCRC32(8) = &HEDB8832
malngCRC32(9) = &H79DCB8A4
malngCRC32(10) = &HE0D5E91E
malngCRC32(11) = &H97D2D988
malngCRC32(12) = &H9B64C2B
malngCRC32(13) = &H7EB17CBD
malngCRC32(14) = &HE7B82D07
malngCRC32(15) = &H90BF1D91
malngCRC32(16) = &H1DB71064
malngCRC32(17) = &H6AB020F2
malngCRC32(18) = &HF3B97148
malngCRC32(19) = &H84BE41DE
malngCRC32(20) = &H1ADAD47D
malngCRC32(21) = &H6DDDE4EB
malngCRC32(22) = &HF4D4B551
malngCRC32(23) = &H83D385C7
malngCRC32(24) = &H136C9856
malngCRC32(25) = &H646BA8C0
malngCRC32(26) = &HFD62F97A
malngCRC32(27) = &H8A65C9EC
malngCRC32(28) = &H14015C4F
malngCRC32(29) = &H63066CD9
malngCRC32(30) = &HFA0F3D63
malngCRC32(31) = &H8D080DF5
malngCRC32(32) = &H3B6E20C8
malngCRC32(33) = &H4C69105E
malngCRC32(34) = &HD56041E4
malngCRC32(35) = &HA2677172
malngCRC32(36) = &H3C03E4D1
malngCRC32(37) = &H4B04D447
malngCRC32(38) = &HD20D85FD
malngCRC32(39) = &HA50AB56B
malngCRC32(40) = &H35B5A8FA
malngCRC32(41) = &H42B2986C
malngCRC32(42) = &HDBBBC9D6
malngCRC32(43) = &HACBCF940
malngCRC32(44) = &H32D86CE3
malngCRC32(45) = &H45DF5C75
malngCRC32(46) = &HDCD60DCF
malngCRC32(47) = &HABD13D59
malngCRC32(48) = &H26D930AC
malngCRC32(49) = &H51DE003A
malngCRC32(50) = &HC8D75180
malngCRC32(51) = &HBFD06116
malngCRC32(52) = &H21B4F4B5
malngCRC32(53) = &H56B3C423
malngCRC32(54) = &HCFBA9599
malngCRC32(55) = &HB8BDA50F
malngCRC32(56) = &H2802B89E
malngCRC32(57) = &H5F058808
malngCRC32(58) = &HC60CD9B2
malngCRC32(59) = &HB10BE924
malngCRC32(60) = &H2F6F7C87
malngCRC32(61) = &H58684C11
malngCRC32(62) = &HC1611DAB
malngCRC32(63) = &HB6662D3D
malngCRC32(64) = &H76DC4190
malngCRC32(65) = &H1DB7106
malngCRC32(66) = &H98D220BC
malngCRC32(67) = &HEFD5102A
malngCRC32(68) = &H71B18589
malngCRC32(69) = &H6B6B51F
malngCRC32(70) = &H9FBFE4A5
malngCRC32(71) = &HE8B8D433
malngCRC32(72) = &H7807C9A2
malngCRC32(73) = &HF00F934
malngCRC32(74) = &H9609A88E
malngCRC32(75) = &HE10E9818
malngCRC32(76) = &H7F6A0DBB
malngCRC32(77) = &H86D3D2D
malngCRC32(78) = &H91646C97
malngCRC32(79) = &HE6635C01
malngCRC32(80) = &H6B6B51F4
malngCRC32(81) = &H1C6C6162
malngCRC32(82) = &H856530D8
malngCRC32(83) = &HF262004E
malngCRC32(84) = &H6C0695ED
malngCRC32(85) = &H1B01A57B
malngCRC32(86) = &H8208F4C1
malngCRC32(87) = &HF50FC457
malngCRC32(88) = &H65B0D9C6
malngCRC32(89) = &H12B7E950
malngCRC32(90) = &H8BBEB8EA
malngCRC32(91) = &HFCB9887C
malngCRC32(92) = &H62DD1DDF
malngCRC32(93) = &H15DA2D49
malngCRC32(94) = &H8CD37CF3
malngCRC32(95) = &HFBD44C65
malngCRC32(96) = &H4DB26158
malngCRC32(97) = &H3AB551CE
malngCRC32(98) = &HA3BC0074
malngCRC32(99) = &HD4BB30E2
malngCRC32(100) = &H4ADFA541
malngCRC32(101) = &H3DD895D7
malngCRC32(102) = &HA4D1C46D
malngCRC32(103) = &HD3D6F4FB
malngCRC32(104) = &H4369E96A
malngCRC32(105) = &H346ED9FC
malngCRC32(106) = &HAD678846
malngCRC32(107) = &HDA60B8D0
malngCRC32(108) = &H44042D73
malngCRC32(109) = &H33031DE5
malngCRC32(110) = &HAA0A4C5F
malngCRC32(111) = &HDD0D7CC9
malngCRC32(112) = &H5005713C
malngCRC32(113) = &H270241AA
malngCRC32(114) = &HBE0B1010
malngCRC32(115) = &HC90C2086
malngCRC32(116) = &H5768B525
malngCRC32(117) = &H206F85B3
malngCRC32(118) = &HB966D409
malngCRC32(119) = &HCE61E49F
malngCRC32(120) = &H5EDEF90E
malngCRC32(121) = &H29D9C998
malngCRC32(122) = &HB0D09822
malngCRC32(123) = &HC7D7A8B4
malngCRC32(124) = &H59B33D17
malngCRC32(125) = &H2EB40D81
malngCRC32(126) = &HB7BD5C3B
malngCRC32(127) = &HC0BA6CAD
malngCRC32(128) = &HEDB88320
malngCRC32(129) = &H9ABFB3B6
malngCRC32(130) = &H3B6E20C
malngCRC32(131) = &H74B1D29A
malngCRC32(132) = &HEAD54739
malngCRC32(133) = &H9DD277AF
malngCRC32(134) = &H4DB2615
malngCRC32(135) = &H73DC1683
malngCRC32(136) = &HE3630B12
malngCRC32(137) = &H94643B84
malngCRC32(138) = &HD6D6A3E
malngCRC32(139) = &H7A6A5AA8
malngCRC32(140) = &HE40ECF0B
malngCRC32(141) = &H9309FF9D
malngCRC32(142) = &HA00AE27
malngCRC32(143) = &H7D079EB1
malngCRC32(144) = &HF00F9344
malngCRC32(145) = &H8708A3D2
malngCRC32(146) = &H1E01F268
malngCRC32(147) = &H6906C2FE
malngCRC32(148) = &HF762575D
malngCRC32(149) = &H806567CB
malngCRC32(150) = &H196C3671
malngCRC32(151) = &H6E6B06E7
malngCRC32(152) = &HFED41B76
malngCRC32(153) = &H89D32BE0
malngCRC32(154) = &H10DA7A5A
malngCRC32(155) = &H67DD4ACC
malngCRC32(156) = &HF9B9DF6F
malngCRC32(157) = &H8EBEEFF9
malngCRC32(158) = &H17B7BE43
malngCRC32(159) = &H60B08ED5
malngCRC32(160) = &HD6D6A3E8
malngCRC32(161) = &HA1D1937E
malngCRC32(162) = &H38D8C2C4
malngCRC32(163) = &H4FDFF252
malngCRC32(164) = &HD1BB67F1
malngCRC32(165) = &HA6BC5767
malngCRC32(166) = &H3FB506DD
malngCRC32(167) = &H48B2364B
malngCRC32(168) = &HD80D2BDA
malngCRC32(169) = &HAF0A1B4C
malngCRC32(170) = &H36034AF6
malngCRC32(171) = &H41047A60
malngCRC32(172) = &HDF60EFC3
malngCRC32(173) = &HA867DF55
malngCRC32(174) = &H316E8EEF
malngCRC32(175) = &H4669BE79
malngCRC32(176) = &HCB61B38C
malngCRC32(177) = &HBC66831A
malngCRC32(178) = &H256FD2A0
malngCRC32(179) = &H5268E236
malngCRC32(180) = &HCC0C7795
malngCRC32(181) = &HBB0B4703
malngCRC32(182) = &H220216B9
malngCRC32(183) = &H5505262F
malngCRC32(184) = &HC5BA3BBE
malngCRC32(185) = &HB2BD0B28
malngCRC32(186) = &H2BB45A92
malngCRC32(187) = &H5CB36A04
malngCRC32(188) = &HC2D7FFA7
malngCRC32(189) = &HB5D0CF31
malngCRC32(190) = &H2CD99E8B
malngCRC32(191) = &H5BDEAE1D
malngCRC32(192) = &H9B64C2B0
malngCRC32(193) = &HEC63F226
malngCRC32(194) = &H756AA39C
malngCRC32(195) = &H26D930A
malngCRC32(196) = &H9C0906A9
malngCRC32(197) = &HEB0E363F
malngCRC32(198) = &H72076785
malngCRC32(199) = &H5005713
malngCRC32(200) = &H95BF4A82
malngCRC32(201) = &HE2B87A14
malngCRC32(202) = &H7BB12BAE
malngCRC32(203) = &HCB61B38
malngCRC32(204) = &H92D28E9B
malngCRC32(205) = &HE5D5BE0D
malngCRC32(206) = &H7CDCEFB7
malngCRC32(207) = &HBDBDF21
malngCRC32(208) = &H86D3D2D4
malngCRC32(209) = &HF1D4E242
malngCRC32(210) = &H68DDB3F8
malngCRC32(211) = &H1FDA836E
malngCRC32(212) = &H81BE16CD
malngCRC32(213) = &HF6B9265B
malngCRC32(214) = &H6FB077E1
malngCRC32(215) = &H18B74777
malngCRC32(216) = &H88085AE6
malngCRC32(217) = &HFF0F6A70
malngCRC32(218) = &H66063BCA
malngCRC32(219) = &H11010B5C
malngCRC32(220) = &H8F659EFF
malngCRC32(221) = &HF862AE69
malngCRC32(222) = &H616BFFD3
malngCRC32(223) = &H166CCF45
malngCRC32(224) = &HA00AE278
malngCRC32(225) = &HD70DD2EE
malngCRC32(226) = &H4E048354
malngCRC32(227) = &H3903B3C2
malngCRC32(228) = &HA7672661
malngCRC32(229) = &HD06016F7
malngCRC32(230) = &H4969474D
malngCRC32(231) = &H3E6E77DB
malngCRC32(232) = &HAED16A4A
malngCRC32(233) = &HD9D65ADC
malngCRC32(234) = &H40DF0B66
malngCRC32(235) = &H37D83BF0
malngCRC32(236) = &HA9BCAE53
malngCRC32(237) = &HDEBB9EC5
malngCRC32(238) = &H47B2CF7F
malngCRC32(239) = &H30B5FFE9
malngCRC32(240) = &HBDBDF21C
malngCRC32(241) = &HCABAC28A
malngCRC32(242) = &H53B39330
malngCRC32(243) = &H24B4A3A6
malngCRC32(244) = &HBAD03605
malngCRC32(245) = &HCDD70693
malngCRC32(246) = &H54DE5729
malngCRC32(247) = &H23D967BF
malngCRC32(248) = &HB3667A2E
malngCRC32(249) = &HC4614AB8
malngCRC32(250) = &H5D681B02
malngCRC32(251) = &H2A6F2B94
malngCRC32(252) = &HB40BBE37
malngCRC32(253) = &HC30C8EA1
malngCRC32(254) = &H5A05DF1B
malngCRC32(255) = &H2D02EF8D
PROC_EXIT:
Exit Sub
PROC_ERR:
MsgBox "Error: " & Err.Number & ". " & Err.Description, , _
"ConstructCRCTable"
Resume PROC_EXIT
End Sub
Private Function ReadFile( _
ByVal intFile As Integer, _
ByRef abytBuffer() As Byte, _
ByVal lngNumberOfBytes As Long) _
As Long
' Comments : Reads the specified number of bytes from the file.
' Parameters: intFile - The file to read from
' abytBuffer - The buffer to read the bytes into
' lngNumberOfBytes - The number of bytes to read
' Returns : The actual number of bytes read.
'
Dim lngLen As Long
Dim lngActualBytesRead As Long
Dim lngStart As Long
On Error GoTo PROC_ERR
' Get the starting position of the next read
lngStart = Loc(intFile) + 1
' Get the length of the file
lngLen = LOF(intFile)
' Check to see if there is more data to read from the file
If lngStart < lngLen Then
' Check to see if we are attempting to read past the end of the file
If lngStart + lngNumberOfBytes < lngLen Then
lngActualBytesRead = lngNumberOfBytes
Else
' If we are attempting to read more data than is left in the file,
' calculate how much data we should read
lngActualBytesRead = lngLen - (lngStart - 1)
End If
' Create the buffer to hold the data
ReDim abytBuffer(lngActualBytesRead - 1) As Byte
' Do the read
Get intFile, lngStart, abytBuffer
Else
' If we attempted to read past the end of file, return zero bytes read
lngActualBytesRead = 0
End If
' Return the number of bytes read
ReadFile = lngActualBytesRead
PROC_EXIT:
Exit Function
PROC_ERR:
MsgBox "Error: " & Err.Number & ". " & Err.Description, , _
"ReadFile"
Resume PROC_EXIT
End Function
Private Function UpdateCRC32(ByVal lngCRC As Long, ByVal bytByte As Byte) As Long
' Comments : This procedure calculates the new CRC based on the current CRC
' and the byte value
' Parameters: lngCRC - The current CRC value
' bytByte - The byte value to lookup
' Returns : The calculated cumulative CRC value
'
Dim intLookup As Integer
On Error GoTo PROC_ERR
' Calculate the lookup value
intLookup = (lngCRC Xor bytByte) And &HFF
' Calculate and return the new CRC value
UpdateCRC32 = (Int(lngCRC / 256) And &HFFFFFF) Xor malngCRC32(intLookup)
PROC_EXIT:
Exit Function
PROC_ERR:
MsgBox "Error: " & Err.Number & ". " & Err.Description, , _
"UpdateCRC32"
Resume PROC_EXIT
End Function
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Apr 19th, 2000, 08:53 AM
#3
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