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FromBase64Transform Class
Visual Studio 2008
Converts a CryptoStream from base 64.
Assembly: mscorlib (in mscorlib.dll)
The following example decrypts a base 64-encoded file to an output text file.
Imports System.IO Imports System.Security.Cryptography Friend Class Members <STAThread()> _ Shared Sub Main(ByVal args() As String) Dim appPath As String = (System.IO.Directory.GetCurrentDirectory()) appPath = appPath & "..\\..\\..\" ' Insert your file names into this method call. EncodeFromFile(appPath & "program.vb", appPath & "code.enc") DecodeFromFile(appPath & "code.enc", appPath & "roundtrip.txt") End Sub ' Read in the specified source file and write out an encoded target file. Private Shared Sub EncodeFromFile(ByVal sourceFile As String, ByVal targetFile As String) ' Verify members.cs exists at the specified directory. If Not File.Exists(sourceFile) Then Console.Write("Unable to locate source file located at ") Console.WriteLine(sourceFile & ".") Console.Write("Please correct the path and run the ") Console.WriteLine("sample again.") Return End If ' Retrieve the input and output file streams. Using inputFileStream As New FileStream(sourceFile, FileMode.Open, FileAccess.Read) Using outputFileStream As New FileStream(targetFile, FileMode.Create, FileAccess.Write) ' Create a new ToBase64Transform object to convert to base 64. Dim base64Transform As New ToBase64Transform() ' Create a new byte array with the size of the output block size. Dim outputBytes(base64Transform.OutputBlockSize - 1) As Byte ' Retrieve the file contents into a byte array. Dim inputBytes(inputFileStream.Length - 1) As Byte inputFileStream.Read(inputBytes, 0, inputBytes.Length) ' Verify that multiple blocks can not be transformed. If Not base64Transform.CanTransformMultipleBlocks Then ' Initializie the offset size. Dim inputOffset As Integer = 0 ' Iterate through inputBytes transforming by blockSize. Dim inputBlockSize As Integer = base64Transform.InputBlockSize Do While inputBytes.Length - inputOffset > inputBlockSize base64Transform.TransformBlock(inputBytes, inputOffset, inputBytes.Length - inputOffset, outputBytes, 0) inputOffset += base64Transform.InputBlockSize outputFileStream.Write(outputBytes, 0, base64Transform.OutputBlockSize) Loop ' Transform the final block of data. outputBytes = base64Transform.TransformFinalBlock(inputBytes, inputOffset, inputBytes.Length - inputOffset) outputFileStream.Write(outputBytes, 0, outputBytes.Length) Console.WriteLine("Created encoded file at " & targetFile) End If ' Determine if the current transform can be reused. If Not base64Transform.CanReuseTransform Then ' Free up any used resources. base64Transform.Clear() End If End Using End Using End Sub Public Shared Sub DecodeFromFile(ByVal inFileName As String, ByVal outFileName As String) Using myTransform As New FromBase64Transform(FromBase64TransformMode.IgnoreWhiteSpaces) Dim myOutputBytes(myTransform.OutputBlockSize - 1) As Byte 'Open the input and output files. Using myInputFile As New FileStream(inFileName, FileMode.Open, FileAccess.Read) Using myOutputFile As New FileStream(outFileName, FileMode.Create, FileAccess.Write) 'Retrieve the file contents into a byte array. Dim myInputBytes(myInputFile.Length - 1) As Byte myInputFile.Read(myInputBytes, 0, myInputBytes.Length) 'Transform the data in chunks the size of InputBlockSize. Dim i As Integer = 0 Do While myInputBytes.Length - i > 4 'myTransform.InputBlockSize Dim bytesWritten As Int32 = myTransform.TransformBlock(myInputBytes, i, 4, myOutputBytes, 0) 'myTransform.InputBlockSize i += 4 'myTransform.InputBlockSize myOutputFile.Write(myOutputBytes, 0, bytesWritten) Loop 'Transform the final block of data. myOutputBytes = myTransform.TransformFinalBlock(myInputBytes, i, myInputBytes.Length - i) myOutputFile.Write(myOutputBytes, 0, myOutputBytes.Length) 'Free up any used resources. myTransform.Clear() End Using End Using End Using End Sub End Class
Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98
The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
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