UTF32Encoding.GetMaxCharCount メソッドとは何？わかりやすく解説 Weblio辞書

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.NET Framework クラスライブラリリファレンス

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UTF32Encoding.GetMaxCharCount メソッド

メモ : このメソッドは、.NET Framework version 2.0 で新しく追加されたものです。

指定したバイト数をデコードすることによって生成される最大文字数を計算します。

名前空間: System.Text
アセンブリ: mscorlib (mscorlib.dll 内)
構文

Visual Basic (宣言)

Public Overrides Function
 GetMaxCharCount ( _
    byteCount As Integer _
) As Integer

Visual Basic (使用法)

Dim instance As UTF32Encoding
Dim byteCount As Integer
Dim returnValue As Integer

returnValue = instance.GetMaxCharCount(byteCount)

public override int GetMaxCharCount (
    int byteCount
)

C++

public:
virtual int GetMaxCharCount (
    int byteCount
) override

public int GetMaxCharCount (
    int byteCount
)

JScript

public override function GetMaxCharCount (
    byteCount : int
) : int

パラメータ

byteCount: デコードするバイト数。

戻り値
指定したバイト数をデコードすることによって生成される最大文字数。

例外

例外の種類	条件
ArgumentOutOfRangeException	byteCount が 0 未満です。または結果の文字数が、int として返すことのできる最大数を超えています。

例外の種類

条件

ArgumentOutOfRangeException

byteCount が 0 未満です。

または

結果の文字数が、int として返すことのできる最大数を超えています。

解説

GetChars が生成した文字を格納するために必要な正確な配列サイズを計算するには、GetCharCount を使用します。最大配列サイズを計算するには、GetMaxCharCount を使用します。通常、GetMaxCharCount メソッドの方が高速に実行されるのに対し、GetCharCount メソッドの方が使用メモリが少なくて済みます。

使用例

次のコード例は、文字列をバイト配列にエンコードし、そのバイトを文字配列にデコードします。

Visual Basic

Imports System
Imports System.Text
Imports Microsoft.VisualBasic

Public Class SamplesUTF32Encoding   

   Public Shared Sub Main()

      ' Create two instances of UTF32Encoding: one with little-endian
 byte order and one with big-endian byte order.
      Dim u32LE As New UTF32Encoding(False,
 True, True)
      Dim u32BE As New UTF32Encoding(True,
 True, True)


      ' Create byte arrays from the same 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)
      '    a high-surrogate value (U+D8FF)
      '    a low-surrogate value (U+DCFF)
      Dim myStr As String
 = "za" & ChrW(&H0306) & ChrW(&H01FD)
 & ChrW(&H03B2) & ChrW(&HD8FF) & ChrW(&HDCFF)

      ' barrBE uses the big-endian byte order.
      ' NOTE: In Visual Basic, arrays contain one extra element by default.
      '       The following line creates an array with the exact number
 of elements required.
      Dim barrBE(u32BE.GetByteCount(myStr) - 1) As
 Byte
      u32BE.GetBytes(myStr, 0, myStr.Length, barrBE, 0)

      ' barrLE uses the little-endian byte order.
      ' NOTE: In Visual Basic, arrays contain one extra element by default.
      '       The following line creates an array with the exact number
 of elements required.
      Dim barrLE(u32LE.GetByteCount(myStr) - 1) As
 Byte
      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)


      ' Decode the byte arrays using an encoding with a different byte
 order.
      Console.Write("BE array with LE encoding : ")
      Try
         PrintCountsAndChars(barrBE, u32LE)
      Catch e As System.ArgumentException
         Console.WriteLine(e.Message)
      End Try

      Console.Write("LE array with BE encoding : ")
      Try
         PrintCountsAndChars(barrLE, u32BE)
      Catch e As System.ArgumentException
         Console.WriteLine(e.Message)
      End Try

   End Sub 'Main


   Public Shared Sub PrintCountsAndChars(bytes()
 As Byte, enc As Encoding)

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

      ' Display the exact character count.
      Dim iCC As Integer
 = enc.GetCharCount(bytes)
      Console.Write(" {0,-3}", iCC)

      ' Display the maximum character count.
      Dim iMCC As Integer
 = enc.GetMaxCharCount(bytes.Length)
      Console.Write(" {0,-3} :", iMCC)

      ' Decode the bytes and display the characters.
      Dim chars(iCC) As Char
      enc.GetChars(bytes, 0, bytes.Length, chars, 0)
      Console.WriteLine(chars)

   End Sub 'PrintCountsAndChars
 

End Class 'SamplesUTF32Encoding

using System;
using System.Text;

public class SamplesUTF32Encoding  {

   public static void Main()
  {

      // Create two instances of UTF32Encoding: one with little-endian
 byte order and one with big-endian byte order.
      UTF32Encoding u32LE = new UTF32Encoding( false,
 true, true );
      UTF32Encoding u32BE = new UTF32Encoding( true,
 true, true );


      // Create byte arrays from the same 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)
      //    a high-surrogate value (U+D8FF)
      //    a low-surrogate value (U+DCFF)
      String myStr = "za\u0306\u01FD\u03B2\uD8FF\uDCFF";

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

      // barrLE uses 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 );


      // Decode the byte arrays using an encoding with a different byte
 order.
      Console.Write( "BE array with LE encoding : " );
      try  {
         PrintCountsAndChars( barrBE, u32LE );
      }
      catch ( System.ArgumentException e )  {
         Console.WriteLine( e.Message );
      }

      Console.Write( "LE array with BE encoding : " );
      try  {
         PrintCountsAndChars( barrLE, u32BE );
      }
      catch ( System.ArgumentException e )  {
         Console.WriteLine( e.Message );
      }

   }


   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 = new char[iCC];
      enc.GetChars( bytes, 0, bytes.Length, chars, 0 );
      Console.WriteLine( chars );

   }

}

C++

using namespace System;
using namespace System::Text;
void PrintCountsAndChars( array<Byte>^bytes, Encoding^ enc
 );
int main()
{
   
   // Create two instances of UTF32Encoding: one with little-endian
 byte order and one with big-endian byte order.
   UTF32Encoding^ u32LE = gcnew UTF32Encoding( false,true,true
 );
   UTF32Encoding^ u32BE = gcnew UTF32Encoding( true,true,true
 );
   
   // Create byte arrays from the same 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 = L"za\u0306\u01FD\u03B2\xD8FF\xDCFF";
   
   // barrBE uses the big-endian byte order.
   array<Byte>^barrBE = gcnew array<Byte>(u32BE->GetByteCount( myStr
 ));
   u32BE->GetBytes( myStr, 0, myStr->Length, barrBE, 0 );
   
   // barrLE uses the little-endian byte order.
   array<Byte>^barrLE = gcnew array<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 );
   
   // Decode the byte arrays using an encoding with a different byte
 order.
   Console::Write( "BE array with LE encoding : " );
   try
   {
      PrintCountsAndChars( barrBE, u32LE );
   }
   catch ( System::ArgumentException^ e ) 
   {
      Console::WriteLine( e->Message );
   }

   Console::Write( "LE array with BE encoding : " );
   try
   {
      PrintCountsAndChars( barrLE, u32BE );
   }
   catch ( System::ArgumentException^ e ) 
   {
      Console::WriteLine( e->Message );
   }

}

void PrintCountsAndChars( array<Byte>^bytes, Encoding^ enc
 )
{
   
   // Display the name of the encoding used.
   Console::Write( "{0,-25} :", enc );
   
   // 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.
   array<Char>^chars = gcnew array<Char>(iCC);
   enc->GetChars( bytes, 0, bytes->Length, chars, 0 );
   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 : 7   14  :za???
LE array with LE encoding : System.Text.UTF32Encoding : 7   14  :za???
BE array with LE encoding : System.Text.UTF32Encoding :Invalid byte was found at
 byte index 3.
LE array with BE encoding : System.Text.UTF32Encoding :Invalid byte was found at
 byte index 3.

*/

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

public class SamplesUTF32Encoding
{
    public static void main(String[]
 args)
    {
        // Create two instances of UTF32Encoding: one with little-endian
        // byte order and one with big-endian byte order.
        UTF32Encoding u32LE = new UTF32Encoding(false,
 true, true);
        UTF32Encoding u32BE = new UTF32Encoding(true,
 true, true);

        // Create byte arrays from the same 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)
        //    a high-surrogate value (U+D8FF)
        //    a low-surrogate value (U+DCFF)
        String myStr = "za\u0306\u01FD\u03B2\uD8FF\uDCFF";

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

        // barrLE uses 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);

        // Decode the byte arrays using an encoding with a 
        // different byte order.
        Console.Write("BE array with LE encoding : ");
        try {
            PrintCountsAndChars(barrBE, u32LE);
        }
        catch(System.ArgumentException e) {
            Console.WriteLine(e.get_Message());
        }
        Console.Write("LE array with BE encoding : ");
        try {
            PrintCountsAndChars(barrLE, u32BE);
        }
        catch(System.ArgumentException e) {
            Console.WriteLine(e.get_Message());
        }
    } //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[] = new char[iCC];
        enc.GetChars(bytes, 0, bytes.length, chars, 0);
        Console.WriteLine(chars);
    } //PrintCountsAndChars
} //SamplesUTF32Encoding

プラットフォーム

バージョン情報

.NET Framework
サポート対象 : 2.0

参照

関連項目
UTF32Encoding クラス
UTF32Encoding メンバ
System.Text 名前空間
GetChars
GetString
GetCharCount
GetDecoder

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UTF32Encoding.GetMaxCharCount メソッドとは？ わかりやすく解説

UTF32Encoding.GetMaxCharCount メソッド

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UTF32Encoding.GetMaxCharCount メソッドとは？わかりやすく解説