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CRC校验类VERSION 1.0 CLASS
BEGIN
  MultiUse = -1  'True
  Persistable = 0  'NotPersistable
  DataBindingBehavior = 0  'vbNone
  DataSourceBehavior  = 0  'vbNone
  MTSTransactionMode  = 0  'NotAnMTSObject
END
Attribute VB_Name = "CCRC32"
Attribute VB_GlobalNameSpace = False
Attribute VB_Creatable = True
Attribute VB_PredeclaredId = False
Attribute VB_Exposed = False
Option ExplicitPrivate Const mlPOLY As Long = &HEDB88320  ' starting reverse polynomial for the CRC table
Private mlcrc32table(255) As Long      ' table to hold our 256 itemsPrivate Const mclBlockSize            As Long = (64 * 1024&)  ' 64K buffer
Private Const GENERIC_READ = &H80000000
Private Const FILE_SHARE_READ = &H1
Private Const FILE_SHARE_WRITE = &H2
Private Const FILE_SHARE_DELETE = &H4
Private Const FILE_ATTRIBUTE_NORMAL = &H0
Private Const OPEN_EXISTING = 3
Private Const INVALID_HANDLE_VALUE = -1
Private Declare Function CreateFile Lib "kernel32" Alias "CreateFileA" ( _
    ByVal lpFileName As String, _
    ByVal dwDesiredAccess As Long, _
    ByVal dwShareMode As Long, _
    ByVal lpSecurityAttributes As Long, _
    ByVal dwCreationDisposition As Long, _
    ByVal dwFlagsAndAttributes As Long, _
    ByVal hTemplateFile As Long) As Long
Private Declare Function ReadFile Lib "kernel32" (ByVal hFile As Long, lpBuffer As Byte, ByVal nNumberOfBytesToRead As Long, lpNumberOfBytesRead As Long, ByVal lpOverlapped As Long) As Long
Private Declare Function GetFileSize Lib "kernel32" (ByVal hFile As Long, lpFileSizeHigh As Long) As Long
Private Declare Function CloseHandle Lib "kernel32" (ByVal hObject As Long) As LongPublic Event eProgress(ByVal iPercent As Integer)Private Sub CreateTable()
    Dim i     As Long
    Dim j     As Long
    Dim lCRC  As Long
    For i = 1 To 255
        lCRC = i
        j = 8
        Do
            If (lCRC And 1) Then
                lCRC = ((lCRC And &HFFFFFFFE) \ 2&) And &H7FFFFFFF
                lCRC = lCRC Xor mlPOLY
            Else
                lCRC = ((lCRC And &HFFFFFFFE) \ 2&) And &H7FFFFFFF
            End If
            j = j - 1
        Loop While j
        mlcrc32table(i) = lCRC
    Next i
End Sub' pass an non-empty zero based array
' this function can be slightly faster than Forward, but of course yields different results.
Public Function GetCRCFromArrayReverse(ByRef aInput() As Byte) As Long
    Dim lCRC      As Long
    Dim lCounter  As Long
    Dim lLookup   As Long
    lCounter = UBound(aInput)
    lCRC = -1
    Do
        lLookup = (lCRC And &HFF) Xor aInput(lCounter)
        lCRC = ((lCRC And &HFFFFFF00) \ &H100) And &HFFFFFF
        lCRC = lCRC Xor mlcrc32table(lLookup)
        lCounter = lCounter - 1 ' dec
    Loop While lCounter >= 0 ' jns
    GetCRCFromArrayReverse = Not lCRC
End Function' Pass a zero based array
' lCrc is typically set to -1 (&HFFFFFFFF) to start
' The return of the function is fed back to lCrc for a progressive CRC32
' This code can process in chunks, make sure to take the bitwise NOT of the return when (completely) done.
Public Function GetCRCFromArrayForward(ByVal lCRC As Long, ByVal lStartOffset As Long, ByVal lLength As Long, ByRef aInput() As Byte) As Long
    Dim lLookup   As Long
    Dim lMax      As Long
    Dim lTemp     As Long
    lMax = lStartOffset + lLength
    Do
        lLookup = (lCRC And &HFF) Xor aInput(lStartOffset)
        lCRC = ((lCRC And &HFFFFFF00) \ &H100) And &HFFFFFF   ' nasty shr 8 with vb :/
        lStartOffset = lStartOffset + 1
        lCRC = lCRC Xor mlcrc32table(lLookup)
    Loop While lStartOffset < lMax
    GetCRCFromArrayForward = lCRC
End FunctionPublic Function GetCRCFromFile(ByVal sFile As String) As Long
    Dim lCRC As Long, lFileHandle As Long, bData() As Byte, lRead As Long
    Dim lNumBlocks    As Long
    Dim lTotalBlocks  As Long
    lCRC = -1
    lFileHandle = CreateFile(sFile, _
                                GENERIC_READ, _
                                FILE_SHARE_READ Or FILE_SHARE_WRITE Or FILE_SHARE_DELETE, _
                                0, _
                                OPEN_EXISTING, _
                                FILE_ATTRIBUTE_NORMAL, _
                                0)
    If lFileHandle <> INVALID_HANDLE_VALUE Then
        lTotalBlocks = (GetFileSize(lFileHandle, 0&) + mclBlockSize - 1) \ mclBlockSize
        lNumBlocks = 1
        lRead = mclBlockSize
        Do While lRead = mclBlockSize And lNumBlocks <= lTotalBlocks
            ReDim bData(mclBlockSize - 1) As Byte
            ReadFile lFileHandle, bData(0), mclBlockSize, lRead, 0
            If lRead < mclBlockSize Then ReDim Preserve bData(lRead - 1) As Byte
            lCRC = GetCRCFromArrayForward(lCRC, 0, lRead, bData)
            RaiseEvent eProgress(CInt((lNumBlocks / lTotalBlocks) * 100))
            lNumBlocks = lNumBlocks + 1
        Loop
    End If
    If lFileHandle <> INVALID_HANDLE_VALUE Then
        CloseHandle lFileHandle
        lFileHandle = INVALID_HANDLE_VALUE
    End If
    GetCRCFromFile = Not lCRC
End FunctionPrivate Sub Class_Initialize()
    Call CreateTable
End Sub

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