以下代码为乐博网lob.cn从C#转化为vb.net:
Imports System
Imports System.Security.Cryptography
Public Class Crc32
Inherits HashAlgorithm
Public Const DefaultPolynomial As UInt32 = &Hedb88320
Public Const DefaultSeed As UInt32 = &Hffffffff
Private hash As UInt32
Private seed As UInt32
Private table As UInt32()
Private Shared defaultTable As UInt32()
Public Sub New()
table = InitializeTable(DefaultPolynomial)
seed = DefaultSeed
Initialize()
End Sub
Public Sub New(ByVal polynomial As UInt32, ByVal seed As UInt32)
table = InitializeTable(polynomial)
Me.seed = seed
Initialize()
End Sub
Public Overloads Overrides Sub Initialize()
hash = seed
End Sub
Protected Overloads Overrides Sub HashCore(ByVal buffer As Byte(), ByVal start As Integer, ByVal length As Integer)
hash = CalculateHash(table, hash, buffer, start, length)
End Sub
Protected Overloads Overrides Function HashFinal() As Byte()
Dim hashBuffer As Byte() = UInt32ToBigEndianBytes(Not hash)
Me.HashValue = hashBuffer
Return hashBuffer
End Function
Public Overloads Overrides ReadOnly Property HashSize() As Integer
Get
Return 32
End Get
End Property
Public Shared Function Compute(ByVal buffer As Byte()) As UInt32
Return Not CalculateHash(InitializeTable(DefaultPolynomial), DefaultSeed, buffer, 0, buffer.Length)
End Function
Public Shared Function Compute(ByVal seed As UInt32, ByVal buffer As Byte()) As UInt32
Return Not CalculateHash(InitializeTable(DefaultPolynomial), seed, buffer, 0, buffer.Length)
End Function
Public Shared Function Compute(ByVal polynomial As UInt32, ByVal seed As UInt32, ByVal buffer As Byte()) As UInt32
Return Not CalculateHash(InitializeTable(polynomial), seed, buffer, 0, buffer.Length)
End Function
Private Shared Function InitializeTable(ByVal polynomial As UInt32) As UInt32()
If polynomial = DefaultPolynomial AndAlso defaultTable IsNot Nothing Then
Return defaultTable
End If '更多vb.net源码和实例，请关注lob.cn (乐 博 网)
Dim createTable As UInt32() = New UInt32(255) {}
For i As Integer = 0 To 255
Dim entry As UInt32 = DirectCast(i, UInt32)
For j As Integer = 0 To 7
If (entry And 1) = 1 Then
entry = (entry >> 1) Xor polynomial
Else
entry = entry >> 1
End If
Next
createTable(i) = entry
Next
If polynomial = DefaultPolynomial Then
defaultTable = createTable
End If
Return createTable
End Function
Private Shared Function CalculateHash(ByVal table As UInt32(), ByVal seed As UInt32, ByVal buffer As Byte(), ByVal start As Integer, ByVal size As Integer) As UInt32
Dim crc As UInt32 = seed
For i As Integer = start To size - 1
crc = (crc >> 8) Xor table(buffer(i) Xor crc And &Hff)
Next
Return crc
End Function
Private Function UInt32ToBigEndianBytes(ByVal x As UInt32) As Byte()
Return New Byte() {CByte(((x >> 24) And &Hff)), CByte(((x >> 16) And &Hff)), CByte(((x >> 8) And &Hff)), CByte((x And &Hff))}
End Function
End Class
乐博网提示 调用方式为：
Dim crc32 As New Crc32()
Dim hash As [String] = [String].Empty
Using fs As FileStream = File.Open("c:\myfile.txt", FileMode.Open)
For Each b As Byte In crc32.ComputeHash(fs)
hash += b.ToString("x2").ToLower()
Next
End Using
Console.WriteLine("CRC-32 is {0}", hash) |
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