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Encoder Class

Converts a set of characters into a sequence of bytes.

Namespace: System.Text
Assembly: mscorlib (in mscorlib.dll)

'Declaration
<SerializableAttribute> _
<ComVisibleAttribute(True)> _
Public MustInherit Class Encoder
'Usage
Dim instance As Encoder

/** @attribute SerializableAttribute() */ 
/** @attribute ComVisibleAttribute(true) */ 
public abstract class Encoder
SerializableAttribute 
ComVisibleAttribute(true) 
public abstract class Encoder
Not applicable.

To obtain an instance of an implementation of the Encoder class, the application should use the GetEncoder method of an Encoding implementation.

The GetByteCount method determines how many bytes result in encoding a set of Unicode characters, and the GetBytes method performs the actual encoding. There are several versions of both of these methods available in the Encoder class.

A Encoder object maintains state information between successive calls to GetBytes or Convert methods so that it can correctly encode character sequences that span blocks. The Encoder also preserves trailing characters at the end of data blocks and uses the trailing characters in the next encoding operation. For example, a data block might end with an unmatched high surrogate, and the matching low surrogate might be in the next data block. Therefore, GetDecoder and GetEncoder are useful for network transmission and file operations, because those operations often deal with blocks of data instead of a complete data stream.

NoteNote:

When the application is done with a stream of data it should make sure that the state information is flushed by setting the flush parameter to true in the appropriate method call. If an exception occurs or if the application switches streams, it should call Reset to clear the internal state of the Encoder object.

Version Considerations

A Decoder or Encoder object can be serialized during a conversion operation. The state of the object is retained if it is deserialized in the same version of the .NET Framework, but lost if it is deserialized in another version.

Notes to Inheritors: When your application inherits from this class, it must override all the members.

The following example demonstrates how to convert an array of Unicode characters into blocks of bytes using a specified encoding. For comparison, the array of characters is first encoded using UTF7Encoding. Next, the array of characters is encoded using an Encoder.

Imports System
Imports System.Text
Imports Microsoft.VisualBasic
Imports Microsoft.VisualBasic.Strings

Class EncoderTest
    
    Public Shared Sub Main()
        ' Unicode characters.
        ' ChrW(35)  = #
        ' ChrW(37)  = %
        ' ChrW(928) = Pi
        ' ChrW(931) = Sigma
        Dim chars() As Char = {ChrW(35), ChrW(37), ChrW(928), ChrW(931)}
        
        ' Encode characters using an Encoding object.
        Dim encoding As Encoding = Encoding.UTF7
        Console.WriteLine( _
            "Using Encoding" & _
            ControlChars.NewLine & _
            "--------------" _
        )
        
        ' Encode complete array for comparison.
        Dim allCharactersFromEncoding As Byte() = encoding.GetBytes(chars)
        Console.WriteLine("All characters encoded:")
        ShowArray(allCharactersFromEncoding)
        
        ' Encode characters, one-by-one.
        ' The Encoding object will NOT maintain state between calls.
        Dim firstchar As Byte() = encoding.GetBytes(chars, 0, 1)
        Console.WriteLine("First character:")
        ShowArray(firstchar)
        
        Dim secondchar As Byte() = encoding.GetBytes(chars, 1, 1)
        Console.WriteLine("Second character:")
        ShowArray(secondchar)
        
        Dim thirdchar As Byte() = encoding.GetBytes(chars, 2, 1)
        Console.WriteLine("Third character:")
        ShowArray(thirdchar)
        
        Dim fourthchar As Byte() = encoding.GetBytes(chars, 3, 1)
        Console.WriteLine("Fourth character:")
        ShowArray(fourthchar)
        
        
        ' Now, encode characters using an Encoder object.
        Dim encoder As Encoder = encoding.GetEncoder()
        Console.WriteLine( _
            "Using Encoder" & _
            ControlChars.NewLine & _
            "-------------" _
        )
        
        ' Encode complete array for comparison.
        Dim allCharactersFromEncoder( _
            encoder.GetByteCount(chars, 0, chars.Length, True) _
        ) As Byte
        encoder.GetBytes(chars, 0, chars.Length, allCharactersFromEncoder, 0, True)
        Console.WriteLine("All characters encoded:")
        ShowArray(allCharactersFromEncoder)
        
        ' Do not flush state; i.e. maintain state between calls.
        Dim bFlushState As Boolean = False
        
        ' Encode characters one-by-one.
        ' By maintaining state, the Encoder will not store extra bytes in the output.
        Dim firstcharNoFlush( _
            encoder.GetByteCount(chars, 0, 1, bFlushState) _
        ) As Byte
        encoder.GetBytes(chars, 0, 1, firstcharNoFlush, 0, bFlushState)
        Console.WriteLine("First character:")
        ShowArray(firstcharNoFlush)
        
        Dim secondcharNoFlush( _
            encoder.GetByteCount(chars, 1, 1, bFlushState) _
        ) As Byte
        encoder.GetBytes(chars, 1, 1, secondcharNoFlush, 0, bFlushState)
        Console.WriteLine("Second character:")
        ShowArray(secondcharNoFlush)
        
        Dim thirdcharNoFlush( _
            encoder.GetByteCount(chars, 2, 1, bFlushState) _
        ) As Byte
        encoder.GetBytes(chars, 2, 1, thirdcharNoFlush, 0, bFlushState)
        Console.WriteLine("Third character:")
        ShowArray(thirdcharNoFlush)
        
        ' Must flush state on last call to GetBytes().
        bFlushState = True
        
        Dim fourthcharNoFlush( _
            encoder.GetByteCount(chars, 3, 1, bFlushState) _
        ) As Byte
        encoder.GetBytes(chars, 3, 1, fourthcharNoFlush, 0, bFlushState)
        Console.WriteLine("Fourth character:")
        ShowArray(fourthcharNoFlush)
    End Sub 'Main
    
    
    Public Shared Sub ShowArray(theArray As Array)
        Dim o As Object
        For Each o In  theArray
            Console.Write("[{0}]", o)
        Next o
        Console.WriteLine(ControlChars.NewLine)
    End Sub 'ShowArray
End Class 'EncoderTest

import System.*;
import System.Text.*;

class EncoderTest
{
    public static void main(String[] args)
    {
        // The characters to encode.
        char chars[] = new char[] {
            '\u0023', // #
            '\u0025', // %
            '\u03a0', // Pi
            '\u03a3'  // Sigma
        };

        // Encode characters using an Encoding object.
        Encoding encoding = Encoding.get_UTF7();
        Console.WriteLine("Using Encoding\n--------------");

        // Encode complete array for comparison.
        ubyte allCharactersFromEncoding[] = encoding.GetBytes(chars);
        Console.WriteLine("All characters encoded:");
        ShowArray(allCharactersFromEncoding);

        // Encode characters, one-by-one.
        // The Encoding object will NOT maintain state between calls.
        ubyte firstchar[] = encoding.GetBytes(chars, 0, 1);
        Console.WriteLine("First character:");
        ShowArray(firstchar);

        ubyte secondchar[] = encoding.GetBytes(chars, 1, 1);
        Console.WriteLine("Second character:");
        ShowArray(secondchar);

        ubyte thirdchar[] = encoding.GetBytes(chars, 2, 1);
        Console.WriteLine("Third character:");
        ShowArray(thirdchar);

        ubyte fourthchar[] = encoding.GetBytes(chars, 3, 1);
        Console.WriteLine("Fourth character:");
        ShowArray(fourthchar);

        // Now, encode characters using an Encoder object.
        Encoder encoder = encoding.GetEncoder();
        Console.WriteLine("Using Encoder\n-------------");

        // Encode complete array for comparison.
        ubyte allCharactersFromEncoder[] = new 
                ubyte[encoder.GetByteCount(chars, 0, chars.length, true)];
        encoder.GetBytes(chars, 0, chars.length,
                allCharactersFromEncoder, 0, true);
        Console.WriteLine("All characters encoded:");
        ShowArray(allCharactersFromEncoder);

        // Do not flush state; i.e. maintain state between calls.
        boolean bFlushState = false;

        // Encode characters one-by-one.
        // By maintaining state, the Encoder will not store 
        // extra bytes in the output.
        ubyte firstcharNoFlush[] = new 
                ubyte[encoder.GetByteCount(chars, 0, 1, bFlushState)];
        encoder.GetBytes(chars, 0, 1, firstcharNoFlush, 0, bFlushState);
        Console.WriteLine("First character:");
        ShowArray(firstcharNoFlush);

        ubyte secondcharNoFlush[] = new 
                ubyte[encoder.GetByteCount(chars, 1, 1, bFlushState)];
        encoder.GetBytes(chars, 1, 1, secondcharNoFlush, 0, bFlushState);
        Console.WriteLine("Second character:");
        ShowArray(secondcharNoFlush);

        ubyte thirdcharNoFlush[] = new 
                ubyte[encoder.GetByteCount(chars, 2, 1, bFlushState)];
        encoder.GetBytes(chars, 2, 1, thirdcharNoFlush, 0, bFlushState);
        Console.WriteLine("Third character:");
        ShowArray(thirdcharNoFlush);

        // Must flush state on last call to GetBytes().
        bFlushState = true;

        ubyte fourthcharNoFlush[] = new 
                ubyte[encoder.GetByteCount(chars, 3, 1, bFlushState)];
        encoder.GetBytes(chars, 3, 1, fourthcharNoFlush, 0, bFlushState);
        Console.WriteLine("Fourth character:");
        ShowArray(fourthcharNoFlush);
    } //main

    public static void ShowArray(Array theArray)
    {
        Object o = null;
        for(int iCtr = 0; iCtr < theArray.get_Length(); iCtr++) {
            o = theArray.get_Item(iCtr);
            Console.Write("[{0}]", o);
        }
        Console.WriteLine("\n");
    } //ShowArray
} //EncoderTest

System.Object
  System.Text.Encoder

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Windows 98, Windows Server 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0, 1.0

XNA Framework

Supported in: 1.0

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