Vb.net 生成MD5和SHA1
我正在使用下面的函数为SQL备份文件生成MD5\SH1哈希。 这工作得很好,有进度报告等,但如果使用大文件,速度会很慢 我是否可以在生成SH1的同时生成MD5,而不必两次处理该文件,从而使所用时间加倍?如何将MD5结果转换为SHA1Vb.net 生成MD5和SHA1,vb.net,Vb.net,我正在使用下面的函数为SQL备份文件生成MD5\SH1哈希。 这工作得很好,有进度报告等,但如果使用大文件,速度会很慢 我是否可以在生成SH1的同时生成MD5,而不必两次处理该文件,从而使所用时间加倍?如何将MD5结果转换为SHA1 Imports System Imports System.IO Imports System.Security.Cryptography Imports System.Text Public Class ASyncFileHashAlgorithm Prote
Imports System
Imports System.IO
Imports System.Security.Cryptography
Imports System.Text
Public Class ASyncFileHashAlgorithm
Protected hashAlgorithm As HashAlgorithm
Protected m_hash As Byte()
Protected cancel As Boolean = False
Protected m_bufferSize As Integer = 4096
Public Delegate Sub FileHashingProgressHandler(ByVal sender As Object, _
ByVal e As FileHashingProgressArgs)
Public Event FileHashingProgress As FileHashingProgressHandler
Public Sub New(ByVal hashAlgorithm As HashAlgorithm)
Me.hashAlgorithm = hashAlgorithm
End Sub
Public Function ComputeHash(ByVal stream As Stream) As Byte()
cancel = False
m_hash = Nothing
Dim _bufferSize As Integer = m_bufferSize
' this makes it impossible to change the buffer size while computing
Dim readAheadBuffer As Byte(), buffer As Byte()
Dim readAheadBytesRead As Integer, bytesRead As Integer
Dim size As Long, totalBytesRead As Long = 0
size = stream.Length
readAheadBuffer = New Byte(_bufferSize - 1) {}
readAheadBytesRead = stream.Read(readAheadBuffer, 0, _
readAheadBuffer.Length)
totalBytesRead += readAheadBytesRead
Do
bytesRead = readAheadBytesRead
buffer = readAheadBuffer
readAheadBuffer = New Byte(_bufferSize - 1) {}
readAheadBytesRead = stream.Read(readAheadBuffer, 0, _
readAheadBuffer.Length)
totalBytesRead += readAheadBytesRead
If readAheadBytesRead = 0 Then
hashAlgorithm.TransformFinalBlock(buffer, 0, bytesRead)
Else
hashAlgorithm.TransformBlock(buffer, 0, bytesRead, buffer, 0)
End If
RaiseEvent FileHashingProgress(Me, New _
FileHashingProgressArgs(totalBytesRead, size))
Loop While readAheadBytesRead <> 0 AndAlso Not cancel
If cancel Then
Return InlineAssignHelper(m_hash, Nothing)
End If
Return InlineAssignHelper(m_hash, hashAlgorithm.Hash)
End Function
Public Property BufferSize() As Integer
Get
Return m_bufferSize
End Get
Set(ByVal value As Integer)
m_bufferSize = value
End Set
End Property
Public ReadOnly Property Hash() As Byte()
Get
Return m_hash
End Get
End Property
'Public Sub Cancel()
' cancel = True
'End Sub
Public Overrides Function ToString() As String
Dim hex As String = ""
For Each b As Byte In Hash
hex += b.ToString("x2")
Next
Return hex
End Function
Private Shared Function InlineAssignHelper(Of T)(ByRef target As T, _
ByVal value As T) As T
target = value
Return value
End Function
End Class
Public Class FileHashingProgressArgs
Inherits EventArgs
Public Property TotalBytesRead() As Long
Get
Return m_TotalBytesRead
End Get
Set(ByVal value As Long)
m_TotalBytesRead = Value
End Set
End Property
Private m_TotalBytesRead As Long
Public Property Size() As Long
Get
Return m_Size
End Get
Set(ByVal value As Long)
m_Size = Value
End Set
End Property
Private m_Size As Long
Public Sub New(ByVal totalBytesRead__1 As Long, ByVal size__2 As Long)
TotalBytesRead = totalBytesRead__1
Size = size__2
End Sub
End Class
您的
ToString
方法可能会为大型字符串创建巨大的开销,因为串联非常昂贵(它会创建大型临时缓冲区),而且您经常这样做。改用StringBuilder
(用正确的大小初始化)。出于好奇,为什么要同时使用这两个哈希函数?这还不够吗?您不能将MD5转换为SHA,反之亦然。这两个值都会生成并传递给使用MD5或SHA验证备份的客户端。在理想的世界里,他们都会使用一种方法!
Shared hasher As New ASyncFileHashAlgorithm(SHA1.Create())
Private Function Test(Byval (strFilePathAndName, as String)
Dim stream As IO.Stream = DirectCast(File.Open(strFilePathAndName, _
FileMode.Open), Stream)
AddHandler hasher.FileHashingProgress, _
AddressOf OnFileHashingProgress
Dim t = New Thread(AddressOf hasher.ComputeHash)
t.Start(stream)
While t.IsAlive
Application.DoEvents()
End While
'LblMD5.Text = hasher.ToString???
LblSHA1.Text = hasher.ToString
stream.Dispose()
End Sub
Public Sub OnFileHashingProgress(ByVal sender As Object, _
ByVal e As FileHashingProgressArgs)
SetControlPropertyValue(uxChildForm.ProgressBar, "Position", _
CInt(e.TotalBytesRead / e.Size * 100))
End Sub