Encoder.Convert Encoder.Convert Encoder.Convert Encoder.Convert Method

定義

バッファーまたは配列に格納されている Unicode 文字を、エンコード済みバイト シーケンスに変換します。Converts a buffer or array of Unicode characters to an encoded byte sequence.

オーバーロード

Convert(ReadOnlySpan<Char>, Span<Byte>, Boolean, Int32, Int32, Boolean) Convert(ReadOnlySpan<Char>, Span<Byte>, Boolean, Int32, Int32, Boolean) Convert(ReadOnlySpan<Char>, Span<Byte>, Boolean, Int32, Int32, Boolean) Convert(ReadOnlySpan<Char>, Span<Byte>, Boolean, Int32, Int32, Boolean)
Convert(Char*, Int32, Byte*, Int32, Boolean, Int32, Int32, Boolean) Convert(Char*, Int32, Byte*, Int32, Boolean, Int32, Int32, Boolean) Convert(Char*, Int32, Byte*, Int32, Boolean, Int32, Int32, Boolean)

バッファーに格納されている Unicode 文字をエンコード済みバイト シーケンスに変換し、その結果を別のバッファーに格納します。Converts a buffer of Unicode characters to an encoded byte sequence and stores the result in another buffer.

Convert(Char[], Int32, Int32, Byte[], Int32, Int32, Boolean, Int32, Int32, Boolean) Convert(Char[], Int32, Int32, Byte[], Int32, Int32, Boolean, Int32, Int32, Boolean) Convert(Char[], Int32, Int32, Byte[], Int32, Int32, Boolean, Int32, Int32, Boolean) Convert(Char[], Int32, Int32, Byte[], Int32, Int32, Boolean, Int32, Int32, Boolean)

Unicode 文字の配列をエンコード済みバイト シーケンスに変換し、その結果をバイト配列に格納します。Converts an array of Unicode characters to an encoded byte sequence and stores the result in an array of bytes.

Convert(ReadOnlySpan<Char>, Span<Byte>, Boolean, Int32, Int32, Boolean) Convert(ReadOnlySpan<Char>, Span<Byte>, Boolean, Int32, Int32, Boolean) Convert(ReadOnlySpan<Char>, Span<Byte>, Boolean, Int32, Int32, Boolean) Convert(ReadOnlySpan<Char>, Span<Byte>, Boolean, Int32, Int32, Boolean)

public:
 virtual void Convert(ReadOnlySpan<char> chars, Span<System::Byte> bytes, bool flush, [Runtime::InteropServices::Out] int % charsUsed, [Runtime::InteropServices::Out] int % bytesUsed, [Runtime::InteropServices::Out] bool % completed);
public virtual void Convert (ReadOnlySpan<char> chars, Span<byte> bytes, bool flush, out int charsUsed, out int bytesUsed, out bool completed);
abstract member Convert : ReadOnlySpan<char> * Span<byte> * bool * int * int * bool -> unit
override this.Convert : ReadOnlySpan<char> * Span<byte> * bool * int * int * bool -> unit
Public Overridable Sub Convert (chars As ReadOnlySpan(Of Char), bytes As Span(Of Byte), flush As Boolean, ByRef charsUsed As Integer, ByRef bytesUsed As Integer, ByRef completed As Boolean)

パラメーター

bytes
Span<Byte>
charsUsed
Int32 Int32 Int32 Int32
bytesUsed
Int32 Int32 Int32 Int32

Convert(Char*, Int32, Byte*, Int32, Boolean, Int32, Int32, Boolean) Convert(Char*, Int32, Byte*, Int32, Boolean, Int32, Int32, Boolean) Convert(Char*, Int32, Byte*, Int32, Boolean, Int32, Int32, Boolean)

重要

この API は CLS 準拠ではありません。

CLS 準拠の代替
System.Text.Encoder.Convert(Char[], Int32, Int32, Byte[], Int32, Int32, Boolean, Int32, Int32, Boolean)

バッファーに格納されている Unicode 文字をエンコード済みバイト シーケンスに変換し、その結果を別のバッファーに格納します。Converts a buffer of Unicode characters to an encoded byte sequence and stores the result in another buffer.

public:
 virtual void Convert(char* chars, int charCount, System::Byte* bytes, int byteCount, bool flush, [Runtime::InteropServices::Out] int % charsUsed, [Runtime::InteropServices::Out] int % bytesUsed, [Runtime::InteropServices::Out] bool % completed);
[System.CLSCompliant(false)]
[System.Runtime.InteropServices.ComVisible(false)]
[System.Security.SecurityCritical]
public virtual void Convert (char* chars, int charCount, byte* bytes, int byteCount, bool flush, out int charsUsed, out int bytesUsed, out bool completed);
abstract member Convert : nativeptr<char> * int * nativeptr<byte> * int * bool * int * int * bool -> unit
override this.Convert : nativeptr<char> * int * nativeptr<byte> * int * bool * int * int * bool -> unit

パラメーター

chars
Char*

UTF-16 でエンコードされた変換対象の文字の文字列のアドレス。The address of a string of UTF-16 encoded characters to convert.

charCount
Int32 Int32 Int32 Int32

変換する chars 内の文字の数。The number of characters in chars to convert.

bytes
Byte*

変換後のバイトを格納するバッファーのアドレス。The address of a buffer to store the converted bytes.

byteCount
Int32 Int32 Int32 Int32

変換に使用する bytes 内の最大バイト数。The maximum number of bytes in bytes to use in the conversion.

flush
Boolean Boolean Boolean Boolean

これ以上データの変換を行わないことを示す場合は true。それ以外の場合は falsetrue to indicate no further data is to be converted; otherwise, false.

charsUsed
Int32 Int32 Int32 Int32

このメソッドから制御が戻るときに、chars で変換に使用された文字数を格納します。When this method returns, contains the number of characters from chars that were used in the conversion. このパラメーターは初期化せずに渡されます。This parameter is passed uninitialized.

bytesUsed
Int32 Int32 Int32 Int32

このメソッドから制御が戻るときに、変換に使用されたバイト数を格納します。When this method returns, contains the number of bytes that were used in the conversion. このパラメーターは初期化せずに渡されます。This parameter is passed uninitialized.

completed
Boolean Boolean Boolean Boolean

このメソッドから制御が戻るときに、charCount で指定したすべての文字が変換された場合は true。それ以外の場合は falseWhen this method returns, contains true if all the characters specified by charCount were converted; otherwise, false. このパラメーターは初期化せずに渡されます。This parameter is passed uninitialized.

例外

chars または bytesnull (Nothing) です。chars or bytes is null (Nothing).

charCount または byteCount が 0 未満です。charCount or byteCount is less than zero.

出力バッファーが小さすぎて、変換した入力を格納できません。The output buffer is too small to contain any of the converted input. 出力バッファーは、GetByteCount メソッドで示されるサイズ以上である必要があります。The output buffer should be greater than or equal to the size indicated by the GetByteCount method.

フォールバックが発生しました (完全な説明については、「 .NET Framework における文字エンコーディング 」を参照してください)。A fallback occurred (see Character Encoding in the .NET Framework for fuller explanation) および-and- FallbackEncoderExceptionFallback に設定されます。Fallback is set to EncoderExceptionFallback.

注釈

オブジェクトは、 Encoderの呼び出しの間に状態Convertを保存することに注意してください。Remember that the Encoder object saves state between calls to Convert. データストリームを使用してアプリケーションを実行する場合、状態情報がflushフラッシュさtrueれるように、パラメーターをに設定する必要があります。When the application is done with a stream of data, it should set the flush parameter to true to make sure that the state information is flushed. この設定では、エンコーダーはデータブロックの末尾の無効なバイトを無視し、内部バッファーをクリアします。With this setting, the encoder ignores invalid bytes at the end of the data block and clears the internal buffer. サロゲートペアの上位サロゲートなど、論理ユニットの一部であるその他の処理済みデータは、現在のフォールバック設定に従って変換されます。Any remaining processed data that is part of a logical unit, such as the high surrogate of a surrogate pair, is converted according to the current fallback settings.

Convertメソッドは、ファイルまたはストリームから読み取ったデータなど、任意の量の入力をエンコードするためにループで使用されるように設計されています。The Convert method is designed to be used in a loop to encode an arbitrary amount of input, such as data read from a file or stream. エンコーディング操作の出力は、固定サイズのバッファーに格納されます。It stores the output of the encoding operation in a fixed-size buffer. GetBytesでは、出力バッファーのサイズが十分でない場合にConvert例外がスローされますが、可能な限り多くの領域がいっぱいになり、読み取った文字と書き込まれたバイト数が返されます。GetBytes will throw an exception if the output buffer isn't large enough, but Convert will fill as much space as possible and return the chars read and bytes written. さらにコメントEncoding.GetBytesについては、「」を参照してください。Also see the Encoding.GetBytes topic for more comments.

出力completedパラメーターは、入力バッファー内のすべてのデータが変換され、出力バッファーに格納されたかどうかを示します。The completed output parameter indicates whether all the data in the input buffer was converted and stored in the output buffer. パラメーターで指定charCountしたfalse文字数が、 byteCountパラメーターで指定されたバイト数を超えることなく変換できない場合、このパラメーターはに設定されます。This parameter is set to false if the number of characters specified by the charCount parameter cannot be converted without exceeding the number of bytes specified by the byteCount parameter. このような状況では、アプリケーションは出力バッファーの内容を使用するか、新しい出力バッファーを提供charsし、パラメーター charsUsedによって指定された文字数だけパラメーター Convertをインクリメントしてから、メソッドを再度呼び出します。残りの入力を処理します。In that situation, the application should use the contents of the output buffer or provide a new output buffer, increment the chars parameter by the number of characters specified by the charsUsed parameter, then call the Convert method again to process the remaining input.

completedパラメーター charsUsed falseとパラメーターcharCountが等しい場合でも、パラメーターをに設定することもできます。The completed parameter can also be set to false, even though the charsUsed and charCount parameters are equal. この状況は、 Encoder charsバッファーに格納されていないデータがオブジェクトにまだ存在する場合に発生します。This situation occurs if there is still data in the Encoder object that has not been stored in the chars buffer.

セキュリティ

SecurityCriticalAttribute
直前の呼び出し元に完全信頼が必要です。Requires full trust for the immediate caller. このメンバーは、部分的に信頼されているコードまたは透過的なコードでは使用できません。This member cannot be used by partially trusted or transparent code.

Convert(Char[], Int32, Int32, Byte[], Int32, Int32, Boolean, Int32, Int32, Boolean) Convert(Char[], Int32, Int32, Byte[], Int32, Int32, Boolean, Int32, Int32, Boolean) Convert(Char[], Int32, Int32, Byte[], Int32, Int32, Boolean, Int32, Int32, Boolean) Convert(Char[], Int32, Int32, Byte[], Int32, Int32, Boolean, Int32, Int32, Boolean)

Unicode 文字の配列をエンコード済みバイト シーケンスに変換し、その結果をバイト配列に格納します。Converts an array of Unicode characters to an encoded byte sequence and stores the result in an array of bytes.

public:
 virtual void Convert(cli::array <char> ^ chars, int charIndex, int charCount, cli::array <System::Byte> ^ bytes, int byteIndex, int byteCount, bool flush, [Runtime::InteropServices::Out] int % charsUsed, [Runtime::InteropServices::Out] int % bytesUsed, [Runtime::InteropServices::Out] bool % completed);
[System.Runtime.InteropServices.ComVisible(false)]
public virtual void Convert (char[] chars, int charIndex, int charCount, byte[] bytes, int byteIndex, int byteCount, bool flush, out int charsUsed, out int bytesUsed, out bool completed);
abstract member Convert : char[] * int * int * byte[] * int * int * bool * int * int * bool -> unit
override this.Convert : char[] * int * int * byte[] * int * int * bool * int * int * bool -> unit
Public Overridable Sub Convert (chars As Char(), charIndex As Integer, charCount As Integer, bytes As Byte(), byteIndex As Integer, byteCount As Integer, flush As Boolean, ByRef charsUsed As Integer, ByRef bytesUsed As Integer, ByRef completed As Boolean)

パラメーター

chars
Char[]

変換する文字の配列。An array of characters to convert.

charIndex
Int32 Int32 Int32 Int32

変換する chars の最初の要素。The first element of chars to convert.

charCount
Int32 Int32 Int32 Int32

変換する chars の要素の数。The number of elements of chars to convert.

bytes
Byte[]

変換後のバイトを格納する配列。An array where the converted bytes are stored.

byteIndex
Int32 Int32 Int32 Int32

データを格納する bytes の最初の要素。The first element of bytes in which data is stored.

byteCount
Int32 Int32 Int32 Int32

変換に使用する bytes 内の最大要素数。The maximum number of elements of bytes to use in the conversion.

flush
Boolean Boolean Boolean Boolean

これ以上データの変換を行わないことを示す場合は true。それ以外の場合は falsetrue to indicate no further data is to be converted; otherwise, false.

charsUsed
Int32 Int32 Int32 Int32

このメソッドから制御が戻るときに、chars で変換に使用された文字数を格納します。When this method returns, contains the number of characters from chars that were used in the conversion. このパラメーターは初期化せずに渡されます。This parameter is passed uninitialized.

bytesUsed
Int32 Int32 Int32 Int32

このメソッドから制御が戻るときに、変換の結果生成されたバイト数を格納します。When this method returns, contains the number of bytes that were produced by the conversion. このパラメーターは初期化せずに渡されます。This parameter is passed uninitialized.

completed
Boolean Boolean Boolean Boolean

このメソッドから制御が戻るときに、charCount で指定したすべての文字が変換された場合は true。それ以外の場合は falseWhen this method returns, contains true if all the characters specified by charCount were converted; otherwise, false. このパラメーターは初期化せずに渡されます。This parameter is passed uninitialized.

例外

chars または bytesnull (Nothing) です。chars or bytes is null (Nothing).

charIndexcharCountbyteIndex、または byteCount が 0 未満です。charIndex, charCount, byteIndex, or byteCount is less than zero.

- または --or- chars - charIndex の長さは charCount 未満です。The length of chars - charIndex is less than charCount.

- または --or- bytes - byteIndex の長さは byteCount 未満です。The length of bytes - byteIndex is less than byteCount.

出力バッファーが小さすぎて、変換した入力を格納できません。The output buffer is too small to contain any of the converted input. 出力バッファーは、GetByteCount メソッドで示されるサイズ以上である必要があります。The output buffer should be greater than or equal to the size indicated by the GetByteCount method.

フォールバックが発生しました (完全な説明については、「 .NET Framework における文字エンコーディング 」を参照してください)。A fallback occurred (see Character Encoding in the .NET Framework for fuller explanation) および-and- FallbackEncoderExceptionFallback に設定されます。Fallback is set to EncoderExceptionFallback.

次の例ではConvert 、メソッドを使用して utf-16 文字のファイルを utf-8 に変換し、 Convertメソッドを使用して utf-8 文字を utf-16 文字に戻します。The following example uses the Convert method to convert a file of UTF-16 characters to UTF-8, then uses the Convert method to convert the UTF-8 characters back to UTF-16 characters.

// This code example demonstrates the Encoder.Convert() and Decoder.Convert methods. 
// This example uses files for input and output, but any source that can be expressed
// as a stream can be used instead.

    using System;
    using System.Text;
    using System.IO;

    public class Sample
    {
    static void Main(string[] args)
        {
// Create a large file of UTF-16 encoded Unicode characters. The file is named Example.txt, 
// and is used as input to the Encoder.Convert() method. 

            CreateTestFile("Example.txt");

 
// Using an input file of UTF-16 encoded characters named Example.txt, create an output file 
// of UTF-8 encoded bytes named UTF8.txt.

            EncoderConvert("Example.txt", "UTF8.txt", Encoding.UTF8);

// Using an input file of UTF-8 encoded bytes named UTF8.txt, create an output file 
// of UTF-16 encoded characters named UTF16.txt.

            DecoderConvert("UTF8.txt", "UTF16.txt", Encoding.UTF8);
        }

// --------------------------------------------------------------------------------------------
// Use the Encoder.Convert() method to convert a file of characters to a file of encoded bytes.
// --------------------------------------------------------------------------------------------
        static void EncoderConvert(String inputFileName, String outputFileName, Encoding enc)
        {
// Convert an input file of characters to an output file of encoded bytes.
// StreamWriter could convert the input file for us, but we'll perform the conversion 
// ourselves.

            FileStream fs = new FileStream(outputFileName, FileMode.Create);
            BinaryWriter outputFile = new BinaryWriter(fs);

// StreamReader will detect Unicode encoding from the Byte Order Mark that heads the input file.
            StreamReader inputFile = new StreamReader(inputFileName);

// Get an Encoder.
            Encoder encoder = enc.GetEncoder();
            
// Guarantee the output buffer large enough to convert a few characters.
            int UseBufferSize = 64;
            if (UseBufferSize < enc.GetMaxByteCount(10))
                    UseBufferSize = enc.GetMaxByteCount(10);
            byte[] bytes = new byte[UseBufferSize];

// Intentionally make the input character buffer larger than the output byte buffer so the 
// conversion loop executes more than one cycle. 

            char[] chars = new char[UseBufferSize * 4];
            int charsRead;
            do
            {
// Read at most the number of characters that will fit in the input buffer. The return 
// value is the actual number of characters read, or zero if no characters remain. 
                charsRead = inputFile.Read(chars, 0, UseBufferSize * 4);
   
                bool completed = false;
                int charIndex = 0;
                int charsUsed;
                int bytesUsed;

                while (!completed)
                {
// If this is the last input data, flush the encoder's internal buffer and state.

                    bool flush = (charsRead == 0);
                    encoder.Convert(chars, charIndex, charsRead - charIndex,
                                    bytes, 0, UseBufferSize, flush,
                                    out charsUsed, out bytesUsed, out completed);

// The conversion produced the number of bytes indicated by bytesUsed. Write that number
// of bytes to the output file.
                    outputFile.Write(bytes, 0, bytesUsed);

// Increment charIndex to the next block of characters in the input buffer, if any, to convert.
                    charIndex += charsUsed;
                }
            }
            while(charsRead != 0);

            outputFile.Close();
            fs.Close();
            inputFile.Close();
        }

// --------------------------------------------------------------------------------------------
// Use the Decoder.Convert() method to convert a file of encoded bytes to a file of characters.
// --------------------------------------------------------------------------------------------
        static void DecoderConvert(String inputFileName, String outputFileName, Encoding enc)
        {
// Convert an input file of of encoded bytes to an output file characters.
// StreamWriter could convert the input file for us, but we'll perform the conversion 
// ourselves.

            StreamWriter outputFile = new StreamWriter(outputFileName, false, Encoding.Unicode);

// Read the input as a binary file so we can detect the Byte Order Mark.
            FileStream fs = new FileStream(inputFileName, FileMode.Open);
            BinaryReader inputFile = new BinaryReader(fs);

// Get a Decoder.
            Decoder decoder = enc.GetDecoder();
            
// Guarantee the output buffer large enough to convert a few characters.
            int UseBufferSize = 64;
            if (UseBufferSize < enc.GetMaxCharCount(10))
                    UseBufferSize = enc.GetMaxCharCount(10);
            char[] chars = new char[UseBufferSize];

// Intentionally make the input byte buffer larger than the output character buffer so the 
// conversion loop executes more than one cycle. 

            byte[] bytes = new byte[UseBufferSize * 4];
            int bytesRead;
            do
            {
// Read at most the number of bytes that will fit in the input buffer. The 
// return value is the actual number of bytes read, or zero if no bytes remain. 

                bytesRead = inputFile.Read(bytes, 0, UseBufferSize * 4);
   
                bool completed = false;
                int byteIndex = 0;
                int bytesUsed;
                int charsUsed;

                while (!completed)
                {
// If this is the last input data, flush the decoder's internal buffer and state.

                    bool flush = (bytesRead == 0);
                    decoder.Convert(bytes, byteIndex, bytesRead - byteIndex,
                                    chars, 0, UseBufferSize, flush,
                                    out bytesUsed, out charsUsed, out completed);

// The conversion produced the number of characters indicated by charsUsed. Write that number
// of characters to the output file.

                    outputFile.Write(chars, 0, charsUsed);

// Increment byteIndex to the next block of bytes in the input buffer, if any, to convert.
                    byteIndex += bytesUsed;
                }
            }
            while(bytesRead != 0);

            outputFile.Close();
            fs.Close();
            inputFile.Close();
        }        

// --------------------------------------------------------------------------------------------
// Create a large file of UTF-16 encoded Unicode characters. 
// --------------------------------------------------------------------------------------------
        static void CreateTestFile(String FileName)
        {
// StreamWriter defaults to UTF-8 encoding so explicitly specify Unicode, that is, 
// UTF-16, encoding.
            StreamWriter file = new StreamWriter(FileName, false, Encoding.Unicode);

// Write a line of text 100 times.
            for (int i = 0; i < 100; i++)
            {
                file.WriteLine("This is an example input file used by the convert example.");
            }

// Write Unicode characters from U+0000 to, but not including, the surrogate character range.
            for (char c = (char)0; c < (char)0xD800; c++)
            {
                file.Write(c);
            }
            file.Close();
        }
    }

/*
This code example produces the following results:

(Execute the -dir- console window command and examine the files created.)

Example.txt, which contains 122,594 bytes (61,297 UTF-16 encoded characters).
UTF8.txt, which contains 169,712 UTF-8 encoded bytes.
UTF16.txt, which contains 122,594 bytes (61,297 UTF-16 encoded characters).

(Execute the -comp- console window command and compare the two Unicode files.)

>comp example.txt utf16.txt /L
Comparing example.txt and utf16.txt...
Files compare OK

(The two files are equal.)

*/
' This code example demonstrates the Encoder.Convert() and Decoder.Convert methods. 
' This example uses files for input and output, but any source that can be expressed
' as a stream can be used instead.

Imports System.Text
Imports System.IO

Public Class Sample
    Shared Sub Main(ByVal args() As String) 
        ' Create a large file of UTF-16 encoded Unicode characters. The file is named Example.txt, 
        ' and is used as input to the Encoder.Convert() method. 
        CreateTestFile("Example.txt")
        
        
        ' Using an input file of UTF-16 encoded characters named Example.txt, create an output file 
        ' of UTF-8 encoded bytes named UTF8.txt.
        EncoderConvert("Example.txt", "UTF8.txt", Encoding.UTF8)
        
        ' Using an input file of UTF-8 encoded bytes named UTF8.txt, create an output file 
        ' of UTF-16 encoded characters named UTF16.txt.
        DecoderConvert("UTF8.txt", "UTF16.txt", Encoding.UTF8)
    
    End Sub
    
    ' --------------------------------------------------------------------------------------------
    ' Use the Encoder.Convert() method to convert a file of characters to a file of encoded bytes.
    ' --------------------------------------------------------------------------------------------
    Shared Sub EncoderConvert(ByVal inputFileName As String, ByVal outputFileName As String, ByVal enc As Encoding) 
        ' Convert an input file of characters to an output file of encoded bytes.
        ' StreamWriter could convert the input file for us, but we'll perform the conversion 
        ' ourselves.
        Dim fs As New FileStream(outputFileName, FileMode.Create)
        Dim outputFile As New BinaryWriter(fs)
        
        ' StreamReader will detect Unicode encoding from the Byte Order Mark that heads the input file.
        Dim inputFile As New StreamReader(inputFileName)
        
        ' Get an Encoder.
        Dim encoder As Encoder = enc.GetEncoder()
        
        ' Guarantee the output buffer large enough to convert a few characters.
        Dim UseBufferSize As Integer = 64
        If UseBufferSize < enc.GetMaxByteCount(10) Then
            UseBufferSize = enc.GetMaxByteCount(10)
        End If
        Dim bytes(UseBufferSize) As Byte
        
        ' Intentionally make the input character buffer larger than the output byte buffer so the 
        ' conversion loop executes more than one cycle. 
        Dim chars(UseBufferSize * 4) As Char
        Dim charsRead As Integer
        Do
            ' Read at most the number of characters that will fit in the input buffer. The return 
            ' value is the actual number of characters read, or zero if no characters remain. 
            charsRead = inputFile.Read(chars, 0, UseBufferSize * 4)
            
            Dim completed As Boolean = False
            Dim charIndex As Integer = 0
            Dim charsUsed As Integer
            Dim bytesUsed As Integer
            
            While Not completed
                ' If this is the last input data, flush the encoder's internal buffer and state.
                Dim flush As Boolean = charsRead = 0
                encoder.Convert(chars, charIndex, charsRead - charIndex, bytes, 0, UseBufferSize, flush, charsUsed, bytesUsed, completed)
                
                ' The conversion produced the number of bytes indicated by bytesUsed. Write that number
                ' of bytes to the output file.
                outputFile.Write(bytes, 0, bytesUsed)
                
                ' Increment charIndex to the next block of characters in the input buffer, if any, to convert.
                charIndex += charsUsed
            End While
        Loop While charsRead <> 0
        
        outputFile.Close()
        fs.Close()
        inputFile.Close()
    
    End Sub
    
    ' --------------------------------------------------------------------------------------------
    ' Use the Decoder.Convert() method to convert a file of encoded bytes to a file of characters.
    ' --------------------------------------------------------------------------------------------
    Shared Sub DecoderConvert(ByVal inputFileName As String, ByVal outputFileName As String, ByVal enc As Encoding) 
        ' Convert an input file of of encoded bytes to an output file characters.
        ' StreamWriter could convert the input file for us, but we'll perform the conversion 
        ' ourselves.
        Dim outputFile As New StreamWriter(outputFileName, False, Encoding.Unicode)
        
        ' Read the input as a binary file so we can detect the Byte Order Mark.
        Dim fs As New FileStream(inputFileName, FileMode.Open)
        Dim inputFile As New BinaryReader(fs)
        
        ' Get a Decoder.
        Dim decoder As Decoder = enc.GetDecoder()
        
        ' Guarantee the output buffer large enough to convert a few characters.
        Dim UseBufferSize As Integer = 64
        If UseBufferSize < enc.GetMaxCharCount(10) Then
            UseBufferSize = enc.GetMaxCharCount(10)
        End If
        Dim chars(UseBufferSize) As Char
        
        ' Intentionally make the input byte buffer larger than the output character buffer so the 
        ' conversion loop executes more than one cycle. 
        Dim bytes(UseBufferSize * 4) As Byte
        Dim bytesRead As Integer
        Do
            ' Read at most the number of bytes that will fit in the input buffer. The 
            ' return value is the actual number of bytes read, or zero if no bytes remain. 
            bytesRead = inputFile.Read(bytes, 0, UseBufferSize * 4)
            
            Dim completed As Boolean = False
            Dim byteIndex As Integer = 0
            Dim bytesUsed As Integer
            Dim charsUsed As Integer
            
            While Not completed
                ' If this is the last input data, flush the decoder's internal buffer and state.
                Dim flush As Boolean = bytesRead = 0
                decoder.Convert(bytes, byteIndex, bytesRead - byteIndex, chars, 0, UseBufferSize, flush, bytesUsed, charsUsed, completed)
                
                ' The conversion produced the number of characters indicated by charsUsed. Write that number
                ' of characters to the output file.
                outputFile.Write(chars, 0, charsUsed)
                
                ' Increment byteIndex to the next block of bytes in the input buffer, if any, to convert.
                byteIndex += bytesUsed
            End While
        Loop While bytesRead <> 0
        
        outputFile.Close()
        fs.Close()
        inputFile.Close()
    
    End Sub
    
    ' --------------------------------------------------------------------------------------------
    ' Create a large file of UTF-16 encoded Unicode characters. 
    ' --------------------------------------------------------------------------------------------
    Shared Sub CreateTestFile(ByVal FileName As String) 
        ' StreamWriter defaults to UTF-8 encoding so explicitly specify Unicode, that is, 
        ' UTF-16, encoding.
        Dim file As New StreamWriter(FileName, False, Encoding.Unicode)
        
        ' Write a line of text 100 times.
        Dim i As Integer
        For i = 0 To 99
            file.WriteLine("This is an example input file used by the convert example.")
        Next i
        
        ' Write Unicode characters from U+0000 to, but not including, the surrogate character range.
        Dim c As Integer
        For c = 0 To &HD800
            file.Write(ChrW(c))
        Next c
        file.Close()
    
    End Sub
End Class

'
'This code example produces the following results:
'
'(Execute the -dir- console window command and examine the files created.)
'
'Example.txt, which contains 122,594 bytes (61,297 UTF-16 encoded characters).
'UTF8.txt, which contains 169,712 UTF-8 encoded bytes.
'UTF16.txt, which contains 122,594 bytes (61,297 UTF-16 encoded characters).
'
'(Execute the -comp- console window command and compare the two Unicode files.)
'
'>comp example.txt utf16.txt /L
'Comparing example.txt and utf16.txt...
'Files compare OK
'
'(The two files are equal.)
'

注釈

オブジェクトは、 Encoderの呼び出しの間に状態Convertを保存することに注意してください。Remember that the Encoder object saves state between calls to Convert. データストリームを使用してアプリケーションを実行する場合、状態情報がflushフラッシュさtrueれるように、パラメーターをに設定する必要があります。When the application is done with a stream of data, it should set the flush parameter to true to make sure that the state information is flushed. この設定では、エンコーダーはデータブロックの末尾の無効なバイトを無視し、内部バッファーをクリアします。With this setting, the encoder ignores invalid bytes at the end of the data block and clears the internal buffer. サロゲートペアの上位サロゲートなど、論理ユニットの一部であるその他の処理済みデータは、現在のフォールバック設定に従って変換されます。Any remaining processed data that is part of a logical unit, such as the high surrogate of a surrogate pair, is converted according to the current fallback settings.

Convertメソッドは、ファイルまたはストリームから読み取ったデータなど、任意の量の入力をデコードするためにループで使用されるように設計されています。The Convert method is designed to be used in a loop to decode an arbitrary amount of input, such as data read from a file or stream. エンコーディング操作の出力は、固定サイズのバッファーに格納されます。It stores the output of the encoding operation in a fixed-size buffer. GetBytesでは、出力バッファーのサイズが十分でない場合にConvert例外がスローされますが、可能な限り多くの領域がいっぱいになり、読み取った文字と書き込まれたバイト数が返されます。GetBytes will throw an exception if the output buffer isn't large enough, but Convert will fill as much space as possible and return the chars read and bytes written. さらにコメントEncoding.GetBytesについては、「」を参照してください。Also see the Encoding.GetBytes topic for more comments.

出力completedパラメーターは、入力バッファー内のすべてのデータが変換され、出力バッファーに格納されたかどうかを示します。The completed output parameter indicates whether all the data in the input buffer was converted and stored in the output buffer. パラメーターで指定charCountしたfalse文字数が、 byteCountパラメーターで指定されたバイト数を超えることなく変換できない場合、このパラメーターはに設定されます。This parameter is set to false if the number of characters specified by the charCount parameter cannot be converted without exceeding the number of bytes specified by the byteCount parameter. このような状況では、アプリケーションは出力バッファーの内容を使用するか、新しい出力バッファーを提供charsし、パラメーター charsUsedによって指定された文字数だけパラメーター Convertをインクリメントしてから、メソッドを再度呼び出します。残りの入力を処理します。In that situation, the application should use the contents of the output buffer or provide a new output buffer, increment the chars parameter by the number of characters specified by the charsUsed parameter, then call the Convert method again to process the remaining input.

completedパラメーター charsUsed falseとパラメーターcharCountが等しい場合でも、パラメーターをに設定することもできます。The completed parameter can also be set to false, even though the charsUsed and charCount parameters are equal. この状況は、 Encoder charsバッファーに格納されていないデータがオブジェクトにまだ存在する場合に発生します。This situation occurs if there is still data in the Encoder object that has not been stored in the chars buffer.

適用対象