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Encoding.GetMaxCharCount Method

When overridden in a derived class, calculates the maximum number of characters produced by decoding the specified number of bytes.

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

public abstract int GetMaxCharCount (
	int byteCount
)
public abstract int GetMaxCharCount (
	int byteCount
)
public abstract function GetMaxCharCount (
	byteCount : int
) : int
Not applicable.

Parameters

byteCount

The number of bytes to decode.

Return Value

The maximum number of characters produced by decoding the specified number of bytes.

Exception typeCondition

ArgumentOutOfRangeException

byteCount is less than zero.

DecoderFallbackException

A fallback occurred (see Understanding Encodings for complete explanation)

-and-

DecoderFallback is set to DecoderExceptionFallback.

To calculate the exact array size required by GetChars to store the resulting characters, the application should use GetCharCount. To calculate the maximum array size, it should use GetMaxCharCount. The GetCharCount method generally allows allocation of less memory, while the GetMaxCharCount method generally executes faster.

GetMaxCharCount retrieves a worst-case number, including the worst case for the currently selected DecoderFallback. If a fallback is chosen with a potentially large string, GetMaxCharCount retrieves large values.

In most cases, this method retrieves reasonable numbers for small strings. For large strings, you might have to choose between using very large buffers and catching errors in the rare case that a more reasonable buffer is too small. You might also want to consider a different approach using GetCharCount or System.Text.Decoder.Convert.

GetMaxCharCount has no relation to GetBytes. If your application needs a similar function to use with GetBytes, it should use GetMaxByteCount.

When using GetMaxCharCount, your application should allocate the output buffer based on the maximum size of the input buffer. If the output buffer is constrained in size, the application might use the Convert method.

Note that GetMaxCharCount considers the worst case for leftover bytes from a previous encoder operation. For most code pages, passing a value of 0 to this method retrieves values greater than or equal to 1.

NoteNote:

GetMaxCharCount(N) is not necessarily the same value as N* GetMaxCharCount(1).

Notes to Implementers: All Encoding implementations must guarantee that no buffer overflow exceptions occur if buffers are sized according to the results of this method's calculations.

The following code example encodes a string into an array of bytes, and then decodes the bytes into an array of characters.

using System;
using System.Text;

public class SamplesEncoding  {

   public static void Main()  {

      // Create two instances of UTF32Encoding: one with little-endian byte order and one with big-endian byte order.
      Encoding u32LE = Encoding.GetEncoding( "utf-32" );
      Encoding u32BE = Encoding.GetEncoding( "utf-32BE" );

      // Use a string containing the following characters:
      //    Latin Small Letter Z (U+007A)
      //    Latin Small Letter A (U+0061)
      //    Combining Breve (U+0306)
      //    Latin Small Letter AE With Acute (U+01FD)
      //    Greek Small Letter Beta (U+03B2)
      String myStr = "za\u0306\u01FD\u03B2";

      // Encode the string using the big-endian byte order.
      byte[] barrBE = new byte[u32BE.GetByteCount( myStr )];
      u32BE.GetBytes( myStr, 0, myStr.Length, barrBE, 0 );

      // Encode the string using the little-endian byte order.
      byte[] barrLE = new byte[u32LE.GetByteCount( myStr )];
      u32LE.GetBytes( myStr, 0, myStr.Length, barrLE, 0 );

      // Get the char counts, and decode the byte arrays.
      Console.Write( "BE array with BE encoding : " );
      PrintCountsAndChars( barrBE, u32BE );
      Console.Write( "LE array with LE encoding : " );
      PrintCountsAndChars( barrLE, u32LE );

   }


   public static void PrintCountsAndChars( byte[] bytes, Encoding enc )  {

      // Display the name of the encoding used.
      Console.Write( "{0,-25} :", enc.ToString() );

      // Display the exact character count.
      int iCC  = enc.GetCharCount( bytes );
      Console.Write( " {0,-3}", iCC );

      // Display the maximum character count.
      int iMCC = enc.GetMaxCharCount( bytes.Length );
      Console.Write( " {0,-3} :", iMCC );

      // Decode the bytes and display the characters.
      char[] chars = enc.GetChars( bytes );
      Console.WriteLine( chars );

   }

}


/* 
This code produces the following output.  The question marks take the place of characters that cannot be displayed at the console.

BE array with BE encoding : System.Text.UTF32Encoding : 5   12  :za??
LE array with LE encoding : System.Text.UTF32Encoding : 5   12  :za??

*/


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

public class SamplesEncoding
{
    public static void main(String[] args)
    {
        // Create two instances of UTF32Encoding: one with little-endian
        // byte order and one with big-endian byte order.
        Encoding u32LE = Encoding.GetEncoding("utf-32");
        Encoding u32BE = Encoding.GetEncoding("utf-32BE");

        // Use a string containing the following characters:
        //    Latin Small Letter Z (U+007A)
        //    Latin Small Letter A (U+0061)
        //    Combining Breve (U+0306)
        //    Latin Small Letter AE With Acute (U+01FD)
        //    Greek Small Letter Beta (U+03B2)
        String myStr = "za\u0306\u01FD\u03B2";

        // Encode the string using the big-endian byte order.
        ubyte barrBE[] = new ubyte[u32BE.GetByteCount(myStr)];
        u32BE.GetBytes(myStr, 0, myStr.get_Length(), barrBE, 0);

        // Encode the string using the little-endian byte order.
        ubyte barrLE[] = new ubyte[u32LE.GetByteCount(myStr)];
        u32LE.GetBytes(myStr, 0, myStr.get_Length(), barrLE, 0);

        // Get the char counts, and decode the byte arrays.
        Console.Write("BE array with BE encoding : ");
        PrintCountsAndChars(barrBE, u32BE);
        Console.Write("LE array with LE encoding : ");
        PrintCountsAndChars(barrLE, u32LE);
    } //main

    public static void PrintCountsAndChars(ubyte bytes[], Encoding enc)
    {
        // Display the name of the encoding used.
        Console.Write("{0,-25} :", enc.ToString());

        // Display the exact character count.
        int iCC = enc.GetCharCount(bytes);
        Console.Write(" {0,-3}", String.valueOf(iCC));

        // Display the maximum character count.
        int iMCC = enc.GetMaxCharCount(bytes.length);
        Console.Write(" {0,-3} :", String.valueOf(iMCC));

        // Decode the bytes and display the characters.
        char chars[] = enc.GetChars(bytes);
        Console.WriteLine(chars);
    } //PrintCountsAndChars
} //SamplesEncoding 

/* 
This code produces the following output.  The question marks take the place
 of characters that cannot be displayed at the console.

BE array with BE encoding : System.Text.UTF32Encoding : 5   12  :za??
LE array with LE encoding : System.Text.UTF32Encoding : 5   12  :za??

*/


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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