FromBase64Transform Class

Definition

Namespace:

System.Security.Cryptography

Assembly:

System.Security.Cryptography.dll

Source:

Base64Transforms.cs

Converts a CryptoStream from base 64.

public ref class FromBase64Transform : IDisposable, System::Security::Cryptography::ICryptoTransform

public class FromBase64Transform : IDisposable, System.Security.Cryptography.ICryptoTransform

type FromBase64Transform = class
    interface IDisposable
    interface ICryptoTransform

Public Class FromBase64Transform
Implements ICryptoTransform, IDisposable

Inheritance

Object

FromBase64Transform

Implements

IDisposable ICryptoTransform

Examples

The following example decodes a base 64-encoded file to an output text file.

using namespace System;
using namespace System::IO;
using namespace System::Security::Cryptography;
class MyMainClass
{
public:
   static void DecodeFromFile( String^ inFileName, String^ outFileName )
   {
      FromBase64Transform^ myTransform = gcnew FromBase64Transform( FromBase64TransformMode::IgnoreWhiteSpaces );
      array<Byte>^myOutputBytes = gcnew array<Byte>(myTransform->OutputBlockSize);
      
      //Open the input and output files.
      FileStream^ myInputFile = gcnew FileStream( inFileName,FileMode::Open,FileAccess::Read );
      FileStream^ myOutputFile = gcnew FileStream( outFileName,FileMode::Create,FileAccess::Write );
      
      //Retrieve the file contents into a Byte array.
      array<Byte>^myInputBytes = gcnew array<Byte>(myInputFile->Length);
      myInputFile->Read( myInputBytes, 0, myInputBytes->Length );
      
      //Transform the data in chunks the size of InputBlockSize.
      int i = 0;
      while ( myInputBytes->Length - i > 4 )
      {
         myTransform->TransformBlock( myInputBytes, i, 4, myOutputBytes, 0 );
         
         /*myTransform->InputBlockSize*/
         i += 4;
         
         /*myTransform->InputBlockSize*/
         myOutputFile->Write( myOutputBytes, 0, myTransform->OutputBlockSize );
      }

      
      //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();
      myInputFile->Close();
      myOutputFile->Close();
   }

};

int main()
{
   MyMainClass * m = new MyMainClass;
   
   //Insert your file names into this method call.
   m->DecodeFromFile(  "c:\\encoded.txt",  "c:\\roundtrip.txt" );
}

using System;
using System.IO;
using System.Security.Cryptography;

class Members
{
    [STAThread]
    static void Main(string[] args)
    {
        string appPath = (System.IO.Directory.GetCurrentDirectory() );
        appPath = appPath + "..\\\\..\\\\..\\";
        // Insert your file names into this method call.
        EncodeFromFile(appPath + "program.cs", appPath + "code.enc");
        DecodeFromFile(appPath + "code.enc", appPath + "roundtrip.txt");
    }

    // Read in the specified source file and write out an encoded target file.
    private static void EncodeFromFile(string sourceFile, string targetFile) 
    {
        // Verify members.cs exists at the specified directory.
        if (!File.Exists(sourceFile))
        {
            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;
        }

        // Retrieve the input and output file streams.
        using (FileStream inputFileStream =
            new FileStream(sourceFile, FileMode.Open, FileAccess.Read))
        {
            using (FileStream outputFileStream =
                new FileStream(targetFile, FileMode.Create, FileAccess.Write))
            {

                // Create a new ToBase64Transform object to convert to base 64.
                ToBase64Transform base64Transform = new ToBase64Transform();

                // Create a new byte array with the size of the output block size.
                byte[] outputBytes = new byte[base64Transform.OutputBlockSize];

                // Retrieve the file contents into a byte array.
                byte[] inputBytes = new byte[inputFileStream.Length];
                inputFileStream.Read(inputBytes, 0, inputBytes.Length);

                // Verify that multiple blocks can not be transformed.
                if (!base64Transform.CanTransformMultipleBlocks)
                {
                    // Initialize the offset size.
                    int inputOffset = 0;

                    // Iterate through inputBytes transforming by blockSize.
                    int inputBlockSize = base64Transform.InputBlockSize;

                    while (inputBytes.Length - inputOffset > inputBlockSize)
                    {
                        base64Transform.TransformBlock(
                            inputBytes,
                            inputOffset,
                            inputBytes.Length - inputOffset,
                            outputBytes,
                            0);

                        inputOffset += base64Transform.InputBlockSize;
                        outputFileStream.Write(
                            outputBytes,
                            0,
                            base64Transform.OutputBlockSize);
                    }

                    // 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);
                }

                // Determine if the current transform can be reused.
                if (!base64Transform.CanReuseTransform)
                {
                    // Free any used resources.
                    base64Transform.Clear();
                }
            }
        }
    }

        public static void DecodeFromFile(string inFileName, string outFileName)
        {
            using (FromBase64Transform myTransform = new FromBase64Transform(FromBase64TransformMode.IgnoreWhiteSpaces))
            {

                byte[] myOutputBytes = new byte[myTransform.OutputBlockSize];

                // Open the input and output files.
                using (FileStream myInputFile = new FileStream(inFileName, FileMode.Open, FileAccess.Read))
                {
                    using (FileStream myOutputFile = new FileStream(outFileName, FileMode.Create, FileAccess.Write))
                    {

                        // Retrieve the file contents into a byte array. 
                        byte[] myInputBytes = new byte[myInputFile.Length];
                        myInputFile.Read(myInputBytes, 0, myInputBytes.Length);

                        // Transform the data in chunks the size of InputBlockSize. 
                        int i = 0;
                        while (myInputBytes.Length - i > 4/*myTransform.InputBlockSize*/)
                        {
                            int bytesWritten = myTransform.TransformBlock(myInputBytes, i, 4/*myTransform.InputBlockSize*/, myOutputBytes, 0);
                            i += 4/*myTransform.InputBlockSize*/;
                            myOutputFile.Write(myOutputBytes, 0, bytesWritten);
                        }

                        // 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();
                    }
                }
            }
        }
}

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

Remarks

Base 64 Content-Transfer-Encoding represents arbitrary bit sequences in a form that is not human readable.

Constructors

FromBase64Transform()	Initializes a new instance of the FromBase64Transform class.
FromBase64Transform(FromBase64TransformMode)	Initializes a new instance of the FromBase64Transform class with the specified transformation mode.

Properties

CanReuseTransform	Gets a value indicating whether the current transform can be reused.
CanTransformMultipleBlocks	Gets a value that indicates whether multiple blocks can be transformed.
InputBlockSize	Gets the input block size.
OutputBlockSize	Gets the output block size.

Methods

Clear()	Releases all resources used by the FromBase64Transform.
Dispose()	Releases all resources used by the current instance of the FromBase64Transform class.
Dispose(Boolean)	Releases the unmanaged resources used by the FromBase64Transform and optionally releases the managed resources.
Equals(Object)	Determines whether the specified object is equal to the current object. (Inherited from Object)
Finalize()	Releases the unmanaged resources used by the FromBase64Transform.
GetHashCode()	Serves as the default hash function. (Inherited from Object)
GetType()	Gets the Type of the current instance. (Inherited from Object)
MemberwiseClone()	Creates a shallow copy of the current Object. (Inherited from Object)
ToString()	Returns a string that represents the current object. (Inherited from Object)
TransformBlock(Byte[], Int32, Int32, Byte[], Int32)	Converts the specified region of the input byte array from base 64 and copies the result to the specified region of the output byte array.
TransformFinalBlock(Byte[], Int32, Int32)	Converts the specified region of the specified byte array from base 64.

See also

• Cryptographic Services