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

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UTF32Encoding.GetMaxByteCount 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。

指定した文字数をエンコードすることによって生成される最大バイト数を計算します。

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

Visual Basic (宣言)

Public Overrides Function
 GetMaxByteCount ( _
    charCount As Integer _
) As Integer

Visual Basic (使用法)

Dim instance As UTF32Encoding
Dim charCount As Integer
Dim returnValue As Integer

returnValue = instance.GetMaxByteCount(charCount)

public override int GetMaxByteCount (
    int charCount
)

C++

public:
virtual int GetMaxByteCount (
    int charCount
) override

public int GetMaxByteCount (
    int charCount
)

JScript

public override function GetMaxByteCount (
    charCount : int
) : int

パラメータ

charCount: エンコードする文字数。

戻り値
指定した文字数をエンコードすることによって生成される最大バイト数。

例外

例外の種類	条件
ArgumentOutOfRangeException	charCount 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

charCount 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

GetBytes が生成したバイト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、GetByteCount を使用します。最大配列サイズを計算するには、GetMaxByteCount を使用します。通常、GetMaxByteCount メソッドの方が高速に実行されるのに対し、GetByteCount 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、文字列のエンコードに必要なバイト数を確認し、文字列を実際にエンコードして、結果のバイトを表示します。

Visual Basic

Imports System
Imports System.Text
Imports Microsoft.VisualBasic

Public Class SamplesUTF32Encoding   

   Public Shared Sub Main()

      ' The characters to encode:
      '    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)

      ' Create instances of different encodings.
      Dim u7 As New UTF7Encoding()
      Dim u8Nobom As New
 UTF8Encoding(False, True)
      Dim u8Bom As New UTF8Encoding(True,
 True)
      Dim u32Nobom As New
 UTF32Encoding(False, False, True)
      Dim u32Bom As New
 UTF32Encoding(False, True, True)

      ' Get the byte counts and the bytes.
      PrintCountsAndBytes(myStr, u7)
      PrintCountsAndBytes(myStr, u8Nobom)
      PrintCountsAndBytes(myStr, u8Bom)
      PrintCountsAndBytes(myStr, u32Nobom)
      PrintCountsAndBytes(myStr, u32Bom)

   End Sub 'Main


   Public Shared Sub PrintCountsAndBytes(s
 As String, enc As Encoding)

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

      ' Display the exact byte count.
      Dim iBC As Integer
 = enc.GetByteCount(s)
      Console.Write(" {0,-3}", iBC)

      ' Display the maximum byte count.
      Dim iMBC As Integer
 = enc.GetMaxByteCount(s.Length)
      Console.Write(" {0,-3} :", iMBC)

      ' Get the byte order mark, if any.
      Dim preamble As Byte()
 = enc.GetPreamble()

      ' Combine the preamble and the encoded bytes.
      ' 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 bytes(preamble.Length + iBC - 1) As
 Byte
      Array.Copy(preamble, bytes, preamble.Length)
      enc.GetBytes(s, 0, s.Length, bytes, preamble.Length)

      ' Display all the encoded bytes.
      PrintHexBytes(bytes)

   End Sub 'PrintCountsAndBytes


   Public Shared Sub PrintHexBytes(bytes()
 As Byte)

      If bytes Is Nothing
 OrElse bytes.Length = 0 Then
         Console.WriteLine("<none>")
      Else
         Dim i As Integer
         For i = 0 To bytes.Length - 1
            Console.Write("{0:X2} ", bytes(i))
         Next i
         Console.WriteLine()
      End If

   End Sub 'PrintHexBytes 

End Class 'SamplesUTF32Encoding


'This code produces the following output.
'
'System.Text.UTF7Encoding  : 18  23  :7A 61 2B 41 77 59 42 2F 51 4F
 79 32 50 2F 63 2F 77 2D
'System.Text.UTF8Encoding  : 12  24  :7A 61 CC 86 C7 BD CE B2 F1 8F
 B3 BF
'System.Text.UTF8Encoding  : 12  24  :EF BB BF 7A 61 CC 86 C7 BD CE
 B2 F1 8F B3 BF
'System.Text.UTF32Encoding : 24  28  :7A 00 00 00 61 00 00 00 06 03
 00 00 FD 01 00 00 B2 03 00 00 FF FC 04 00
'System.Text.UTF32Encoding : 24  28  :FF FE 00 00 7A 00 00 00 61 00
 00 00 06 03 00 00 FD 01 00 00 B2 03 00 00 FF FC 04 00

using System;
using System.Text;

public class SamplesUTF32Encoding  {

   public static void Main()
  {

      // The characters to encode:
      //    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";

      // Create instances of different encodings.
      UTF7Encoding  u7       = new UTF7Encoding();
      UTF8Encoding  u8Nobom  = new UTF8Encoding( false,
 true );
      UTF8Encoding  u8Bom    = new UTF8Encoding( true,
  true );
      UTF32Encoding u32Nobom = new UTF32Encoding( false,
 false, true );
      UTF32Encoding u32Bom   = new UTF32Encoding( false,
 true,  true );

      // Get the byte counts and the bytes.
      PrintCountsAndBytes( myStr, u7 );
      PrintCountsAndBytes( myStr, u8Nobom );
      PrintCountsAndBytes( myStr, u8Bom );
      PrintCountsAndBytes( myStr, u32Nobom );
      PrintCountsAndBytes( myStr, u32Bom );

   }


   public static void PrintCountsAndBytes(
 String s, Encoding enc )  {

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

      // Display the exact byte count.
      int iBC  = enc.GetByteCount( s );
      Console.Write( " {0,-3}", iBC );

      // Display the maximum byte count.
      int iMBC = enc.GetMaxByteCount( s.Length );
      Console.Write( " {0,-3} :", iMBC );

      // Get the byte order mark, if any.
      byte[] preamble = enc.GetPreamble();

      // Combine the preamble and the encoded bytes.
      byte[] bytes = new byte[preamble.Length + iBC];
      Array.Copy( preamble, bytes, preamble.Length );
      enc.GetBytes( s, 0, s.Length, bytes, preamble.Length );

      // Display all the encoded bytes.
      PrintHexBytes( bytes );

   }


   public static void PrintHexBytes(
 byte[] bytes )  {

      if (( bytes == null ) || ( bytes.Length
 == 0 ))
         Console.WriteLine( "<none>" );
      else  {
         for ( int i = 0; i < bytes.Length;
 i++ )
            Console.Write( "{0:X2} ", bytes[i] );
         Console.WriteLine();
      }

   }

}


/* 
This code produces the following output.

System.Text.UTF7Encoding  : 18  23  :7A 61 2B 41 77 59 42 2F 51 4F 79 32 50 2F 63
 2F 77 2D
System.Text.UTF8Encoding  : 12  24  :7A 61 CC 86 C7 BD CE B2 F1 8F B3 BF
System.Text.UTF8Encoding  : 12  24  :EF BB BF 7A 61 CC 86 C7 BD CE B2 F1 8F B3 BF
System.Text.UTF32Encoding : 24  28  :7A 00 00 00 61 00 00 00 06 03 00 00 FD 01 00
 00 B2 03 00 00 FF FC 04 00
System.Text.UTF32Encoding : 24  28  :FF FE 00 00 7A 00 00 00 61 00 00 00 06 03 00
 00 FD 01 00 00 B2 03 00 00 FF FC 04 00

*/

C++

using namespace System;
using namespace System::Text;
void PrintCountsAndBytes( String^ s, Encoding^ enc );
void PrintHexBytes( array<Byte>^bytes );
int main()
{
   
   // The characters to encode:
   //    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 = L"za\u0306\u01FD\u03B2\xD8FF\xDCFF";
   
   // Create instances of different encodings.
   UTF7Encoding^ u7 = gcnew UTF7Encoding;
   UTF8Encoding^ u8Nobom = gcnew UTF8Encoding( false,true
 );
   UTF8Encoding^ u8Bom = gcnew UTF8Encoding( true,true
 );
   UTF32Encoding ^ u32Nobom = gcnew UTF32Encoding( false,false,true
 );
   UTF32Encoding ^ u32Bom = gcnew UTF32Encoding( false,true,true
 );
   
   // Get the byte counts and the bytes.
   PrintCountsAndBytes( myStr, u7 );
   PrintCountsAndBytes( myStr, u8Nobom );
   PrintCountsAndBytes( myStr, u8Bom );
   PrintCountsAndBytes( myStr, u32Nobom );
   PrintCountsAndBytes( myStr, u32Bom );
}

void PrintCountsAndBytes( String^ s, Encoding^ enc )
{
   
   // Display the name of the encoding used.
   Console::Write( "{0,-25} :", enc );
   
   // Display the exact byte count.
   int iBC = enc->GetByteCount( s );
   Console::Write( " {0,-3}", iBC );
   
   // Display the maximum byte count.
   int iMBC = enc->GetMaxByteCount( s->Length );
   Console::Write( " {0,-3} :", iMBC );
   
   // Get the byte order mark, if any.
   array<Byte>^preamble = enc->GetPreamble();
   
   // Combine the preamble and the encoded bytes.
   array<Byte>^bytes = gcnew array<Byte>(preamble->Length + iBC);
   Array::Copy( preamble, bytes, preamble->Length );
   enc->GetBytes( s, 0, s->Length, bytes, preamble->Length );
   
   // Display all the encoded bytes.
   PrintHexBytes( bytes );
}

void PrintHexBytes( array<Byte>^bytes )
{
   if ( (bytes == nullptr) || (bytes->Length == 0) )
      Console::WriteLine( "<none>" );
   else
   {
      for ( int i = 0; i < bytes->Length;
 i++ )
         Console::Write( "{0:X2} ", bytes[ i ] );
      Console::WriteLine();
   }
}

/* 
This code produces the following output.

System.Text.UTF7Encoding  : 18  23  :7A 61 2B 41 77 59 42 2F 51 4F 79 32 50 2F 63
 2F 77 2D
System.Text.UTF8Encoding  : 12  24  :7A 61 CC 86 C7 BD CE B2 F1 8F B3 BF
System.Text.UTF8Encoding  : 12  24  :EF BB BF 7A 61 CC 86 C7 BD CE B2 F1 8F B3 BF
System.Text.UTF32Encoding : 24  28  :7A 00 00 00 61 00 00 00 06 03 00 00 FD 01 00
 00 B2 03 00 00 FF FC 04 00
System.Text.UTF32Encoding : 24  28  :FF FE 00 00 7A 00 00 00 61 00 00 00 06 03 00
 00 FD 01 00 00 B2 03 00 00 FF FC 04 00

*/

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

public class SamplesUTF32Encoding
{
    public static void main(String[]
 args)
    {
        // The characters to encode:
        //    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";

        // Create instances of different encodings.
        UTF7Encoding u7 = new UTF7Encoding();
        UTF8Encoding u8Nobom = new UTF8Encoding(false,
 true);
        UTF8Encoding u8Bom = new UTF8Encoding(true,
 true);
        UTF32Encoding u32Nobom = new UTF32Encoding(false,
 false, true);
        UTF32Encoding u32Bom = new UTF32Encoding(false,
 true, true);

        // Get the byte counts and the bytes.
        PrintCountsAndBytes(myStr, u7);
        PrintCountsAndBytes(myStr, u8Nobom);
        PrintCountsAndBytes(myStr, u8Bom);
        PrintCountsAndBytes(myStr, u32Nobom);
        PrintCountsAndBytes(myStr, u32Bom);
    } //main
   
    public static void PrintCountsAndBytes(String
 s, Encoding enc)
    {
        // Display the name of the encoding used.
        Console.Write("{0,-25} :", enc.ToString());

        // Display the exact byte count.
        int iBC = enc.GetByteCount(s);
        Console.Write(" {0,-3}", String.valueOf(iBC));

        // Display the maximum byte count.
        int iMBC = enc.GetMaxByteCount(s.get_Length());
        Console.Write(" {0,-3} :", String.valueOf(iMBC));

        // Get the byte order mark, if any.
        ubyte preamble[] = enc.GetPreamble();

        // Combine the preamble and the encoded bytes.
        ubyte bytes[] = new ubyte[preamble.length + iBC];
        Array.Copy(preamble, bytes, preamble.length);
        enc.GetBytes(s, 0, s.get_Length(), bytes, preamble.length);

        // Display all the encoded bytes.
        PrintHexBytes(bytes);
    } //PrintCountsAndBytes
 
    public static void PrintHexBytes(ubyte
 bytes[])
    {
        if(bytes == null || bytes.length ==
 0) {
            Console.WriteLine("<none>");
        }
        else {
            for(int i = 0; i < bytes.length;
 i++) {
                Console.Write("{0:X2} ", 
                    ((System.Byte)bytes[i]).ToString("X2"));
            }
            Console.WriteLine();
        }
    } //PrintHexBytes
} //SamplesUTF32Encoding

/* 
This code produces the following output.

System.Text.UTF7Encoding  : 18  23  :7A 61 2B 41 77 59 42 2F 51 4F 79 32 50
 2F 63 2F 77 2D
System.Text.UTF8Encoding  : 12  24  :7A 61 CC 86 C7 BD CE B2 F1 8F B3 BF
System.Text.UTF8Encoding  : 12  24  :EF BB BF 7A 61 CC 86 C7 BD CE B2 F1
 8F B3 BF
System.Text.UTF32Encoding : 24  28  :7A 00 00 00 61 00 00 00 06 03 00 00
 FD 01 00 00 B2 03 00 00 FF FC 04 00
System.Text.UTF32Encoding : 24  28  :FF FE 00 00 7A 00 00 00 61 00 00 00
 06 03 00 00 FD 01 00 00 B2 03 00 00 FF FC 04 00

*/

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
GetBytes
GetByteCount
GetEncoder

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

UTF32Encoding.GetMaxByteCount メソッド

急上昇のことば

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