GZipStream.CanWrite プロパティ

.NET Framework クラス ライブラリ リファレンス

GZipStream.CanWrite プロパティ

メモ : このプロパティは、.NET Framework version 2.0 で新しく追加されたものです。

ストリームが書き込みをサポートしているかどうかを示す値を取得します。

名前空間: System.IO.Compression
アセンブリ: System (system.dll 内)
構文

Visual Basic (宣言)

Public Overrides ReadOnly
 Property CanWrite As Boolean

Visual Basic (使用法)

Dim instance As GZipStream
Dim value As Boolean

value = instance.CanWrite

C#

public override bool CanWrite { get;
 }

C++

public:
virtual property bool CanWrite {
    bool get () override;
}

J#

/** @property */
public boolean get_CanWrite ()

JScript

public override function get
 CanWrite () : boolean

プロパティ値
CompressionMode 値が Compress で、基になるストリームが書き込みをサポートし、閉じられていない場合は true。それ以外の場合は false。

解説

継承時の注意 GZipStream から継承する場合、CanSeek、CanWrite、CanRead の各メンバをオーバーライドする必要があります。

使用例

GZipStream クラスを使用して、ファイルの圧縮および圧縮解除を実行するコード例を次に示します。

Visual Basic

Imports System
Imports System.IO
Imports System.IO.Compression



Public Class GZipTest
    Shared msg As String
   Public Shared Function
 ReadAllBytesFromStream(stream As Stream, buffer() As
 Byte) As Integer
      ' Use this method is used to read all bytes from a stream.
      Dim offset As Integer
 = 0
      Dim totalCount As Integer
 = 0
      While True
         Dim bytesRead As Integer
 = stream.Read(buffer, offset, 100)
         If bytesRead = 0 Then
            Exit While
         End If
         offset += bytesRead
         totalCount += bytesRead
      End While
      Return totalCount
   End Function 'ReadAllBytesFromStream
   
   
   Public Shared Function
 CompareData(buf1() As Byte, len1 As
 Integer, buf2() As Byte, len2 As Integer) As Boolean
      ' Use this method to compare data from two different buffers.
        If len1 <> len2 Then
            msg = "Number of bytes in two buffer are different"
 & len1 & ":" & len2
            MsgBox(msg)
            Return False
        End If
      
      Dim i As Integer
      For i = 0 To len1 - 1
         If buf1(i) <> buf2(i) Then
                msg = "byte " & i & "
 is different " & buf1(i) & "|"
 & buf2(i)
                MsgBox(msg)
                Return False
         End If
        Next i
        msg = "All bytes compare."
        MsgBox(msg)
        Return True
   End Function 'CompareData
   
   
   Public Shared Sub GZipCompressDecompress(filename
 As String)
        msg = "Test compression and decompression on file "
 & filename
        MsgBox(msg)

        Dim infile As FileStream
      Try
         ' Open the file as a FileStream object.
         infile = New FileStream(filename, FileMode.Open, FileAccess.Read,
 FileShare.Read)
            Dim buffer(infile.Length - 1) As
 Byte
         ' Read the file to ensure it is readable.
            Dim count As Integer
 = infile.Read(buffer, 0, buffer.Length)
         If count <> buffer.Length Then
                infile.Close()
                msg = "Test Failed: Unable to read data from file"
                MsgBox(msg)
                Return
         End If
         infile.Close()
         Dim ms As New MemoryStream()
         ' Use the newly created memory stream for the compressed data.
         Dim compressedzipStream As New
 GZipStream(ms, CompressionMode.Compress, True)
         compressedzipStream.Write(buffer, 0, buffer.Length)
         ' Close the stream.
            compressedzipStream.Close()

            msg = "Original size: " & buffer.Length
 & ", Compressed size: " & ms.Length
            MsgBox(msg)

         ' Reset the memory stream position to begin decompression.
         ms.Position = 0
         Dim zipStream As New
 GZipStream(ms, CompressionMode.Decompress)
         Dim decompressedBuffer(buffer.Length + 100) As
 Byte
         ' Use the ReadAllBytesFromStream to read the stream.
         Dim totalCount As Integer
 = GZipTest.ReadAllBytesFromStream(zipStream, decompressedBuffer)
            msg = "Decompressed " & totalCount
 & " bytes"
            MsgBox(msg)

         If Not GZipTest.CompareData(buffer,
 buffer.Length, decompressedBuffer, totalCount) Then
                msg = "Error. The two buffers did not compare."
                MsgBox(msg)

         End If
         zipStream.Close()
        Catch e As Exception
            msg = "Error: The file being read contains invalid
 data."
            MsgBox(msg)
        End Try

   End Sub 'GZipCompressDecompress
   
    Public Shared Sub Main(ByVal
 args() As String)
        Dim usageText As String
 = "Usage: GZIPTEST <inputfilename>"
        'If no file name is specified, write usage text.
        If args.Length = 0 Then
            Console.WriteLine(usageText)
        Else
            If File.Exists(args(0)) Then
                GZipCompressDecompress(args(0))
            End If
        End If
    End Sub 'Main
End Class 'GZipTest 

C#

using System;
using System.IO;
using System.IO.Compression;

public class GZipTest
{
    public static int ReadAllBytesFromStream(Stream
 stream, byte[] buffer) 
    {
    // Use this method is used to read all bytes from a stream.
    int offset = 0;
    int totalCount = 0;
        while (true) 
        {
        int bytesRead = stream.Read(buffer, offset, 100); 
            if ( bytesRead == 0) 
            {
            break; 
            }
    offset += bytesRead;
    totalCount += bytesRead; 
        }
    return totalCount;
    } 

    public static bool CompareData(byte[]
 buf1, int len1, byte[] buf2, int len2) 
    {
        // Use this method to compare data from two different buffers.
        if (len1 != len2) 
        { 
        Console.WriteLine("Number of bytes in two buffer
 are different {0}:{1}", len1, len2);
        return false;
        }

        for ( int i= 0; i< len1; i++) 
        {
            if ( buf1[i] != buf2[i]) 
            {
            Console.WriteLine("byte {0} is different {1}|{2}", i, buf1[i],
 buf2[i]);
            return false;
            }
        }
    Console.WriteLine("All bytes compare.");
    return true; 
    }

    public static void GZipCompressDecompress(string
 filename)
    {
    Console.WriteLine("Test compression and decompression on file {0}",
 filename);
    FileStream infile;
        try
        {
        // Open the file as a FileStream object.
        infile = new FileStream(filename, FileMode.Open, FileAccess.Read,
 FileShare.Read);
        byte[] buffer = new byte[infile.Length];
        // Read the file to ensure it is readable.
        int count = infile.Read(buffer, 0, buffer.Length);
            if ( count != buffer.Length) 
            {
            infile.Close();
            Console.WriteLine("Test Failed: Unable to read data from file");
 
            return;
            }
        infile.Close();
        MemoryStream ms = new MemoryStream();
        // Use the newly created memory stream for the compressed data.
        GZipStream compressedzipStream = new GZipStream(ms , CompressionMode.Compress,
 true);
        Console.WriteLine("Compression");
        compressedzipStream.Write(buffer, 0, buffer.Length);
        // Close the stream.
        compressedzipStream.Close();
        Console.WriteLine("Original size: {0}, Compressed size: {1}", buffer.Length,
 ms.Length);

        // Reset the memory stream position to begin decompression.
        ms.Position = 0;
        GZipStream zipStream = new GZipStream(ms, CompressionMode.Decompress);
        Console.WriteLine("Decompression");
        byte[] decompressedBuffer = new byte[buffer.Length + 100];
        // Use the ReadAllBytesFromStream to read the stream.
        int totalCount = GZipTest.ReadAllBytesFromStream(zipStream,
 decompressedBuffer);
        Console.WriteLine("Decompressed {0} bytes", totalCount);

        if( !GZipTest.CompareData(buffer, buffer.Length, decompressedBuffer,
 totalCount) ) 
        {
        Console.WriteLine("Error. The two buffers did not compare.");
        }
    zipStream.Close(); 
        } // end try
        catch (InvalidDataException)
        {
            Console.WriteLine("Error: The file being read contains invalid data.");
        }
        catch (FileNotFoundException)
        {
            Console.WriteLine("Error:The file specified was not found.");
        }
        catch (ArgumentException)
        {
            Console.WriteLine("Error: path is a zero-length string,
 contains only white space, or contains one or more invalid characters");
        }
        catch (PathTooLongException)
        {
            Console.WriteLine("Error: The specified path, file name, or both
 exceed the system-defined maximum length. For example, on Windows-based platforms,
 paths must be less than 248 characters, and file names must be less than 260 characters.");
        }
        catch (DirectoryNotFoundException)
        {
            Console.WriteLine("Error: The specified path is invalid, such as
 being on an unmapped drive.");
        }
        catch (IOException)
        {
            Console.WriteLine("Error: An I/O error occurred while
 opening the file.");
        }
        catch (UnauthorizedAccessException)
        {
            Console.WriteLine("Error: path specified a file that is read-only,
 the path is a directory, or caller does not have the required permissions.");
        }
        catch (IndexOutOfRangeException)
        {
            Console.WriteLine("Error: You must provide parameters for
 MyGZIP.");
        }
    }
    public static void Main(string[]
 args)
    {
        string usageText = "Usage: MYGZIP <inputfilename>";
        //If no file name is specified, write usage text.
        if (args.Length == 0)
        {
            Console.WriteLine(usageText);
        }
        else
        {
            if (File.Exists(args[0]))
                GZipCompressDecompress(args[0]);
        }
    }
}
    

C++

#using <System.dll>

using namespace System;
using namespace System::IO;
using namespace System::IO::Compression;
int ReadAllBytesFromStream( Stream^ stream, array<Byte>^buffer
 )
{
   
   // Use this method is used to read all bytes from a stream.
   int offset = 0;
   int totalCount = 0;
   for ( ; ;  )
   {
      int bytesRead = stream->Read( buffer, offset, 100 );
      if ( bytesRead == 0 )
      {
         break;
      }

      offset += bytesRead;
      totalCount += bytesRead;

   }
   return totalCount;
}

bool CompareData( array<Byte>^buf1, int
 len1, array<Byte>^buf2, int len2 )
{
   
   // Use this method to compare data from two different buffers.
   if ( len1 != len2 )
   {
      Console::WriteLine( "Number of bytes in two buffer
 are different {0}:{1}", len1, len2 );
      return false;
   }

   for ( int i = 0; i < len1; i++ )
   {
      if ( buf1[ i ] != buf2[ i ] )
      {
         Console::WriteLine( "byte {0} is different {1}|{2}", i, buf1[
 i ], buf2[ i ] );
         return false;
      }

   }
   Console::WriteLine( "All bytes compare." );
   return true;
}

void GZipCompressDecompress( String^ filename )
{
   Console::WriteLine( "Test compression and decompression on file {0}",
 filename );
   FileStream^ infile;
   try
   {
      
      // Open the file as a FileStream object.
      infile = gcnew FileStream( filename,FileMode::Open,FileAccess::Read,FileShare::Read
 );
      array<Byte>^buffer = gcnew array<Byte>((int)infile->Length);
      
      // Read the file to ensure it is readable.
      int count = infile->Read( buffer, 0, buffer->Length
 );
      if ( count != buffer->Length )
      {
         infile->Close();
         Console::WriteLine( "Test Failed: Unable to read data from file"
 );
         return;
      }
      infile->Close();
      MemoryStream^ ms = gcnew MemoryStream;
      
      // Use the newly created memory stream for the compressed data.
      GZipStream ^ compressedzipStream = gcnew GZipStream( ms,CompressionMode::Compress,true
 );
      Console::WriteLine( "Compression" );
      compressedzipStream->Write( buffer, 0, buffer->Length );
      
      // Close the stream.
      compressedzipStream->Close();
      Console::WriteLine( "Original size: {0}, Compressed size: {1}", buffer->Length,
 ms->Length );
      
      // Reset the memory stream position to begin decompression.
      ms->Position = 0;
      GZipStream ^ zipStream = gcnew GZipStream( ms,CompressionMode::Decompress );
      Console::WriteLine( "Decompression" );
      array<Byte>^decompressedBuffer = gcnew array<Byte>(buffer->Length
 + 100);
      
      // Use the ReadAllBytesFromStream to read the stream.
      int totalCount = ReadAllBytesFromStream( zipStream, decompressedBuffer
 );
      Console::WriteLine( "Decompressed {0} bytes", totalCount );
      if (  !CompareData( buffer, buffer->Length, decompressedBuffer,
 totalCount ) )
      {
         Console::WriteLine( "Error. The two buffers did not compare."
 );
      }
      zipStream->Close();
   }
   catch ( InvalidDataException ^ ) 
   {
      Console::WriteLine( "Error: The file being read contains invalid data."
 );
   }
   catch ( FileNotFoundException^ ) 
   {
      Console::WriteLine( "Error:The file specified was not found." );
   }
   catch ( ArgumentException^ ) 
   {
      Console::WriteLine( "Error: path is a zero-length string,
 contains only white space, or contains one or more invalid characters" );
   }
   catch ( PathTooLongException^ ) 
   {
      Console::WriteLine( "Error: The specified path, file name, or both exceed
 the system-defined maximum length."
      " For example, on Windows-based platforms, paths must be less than 248
 characters, and file names must be less than 260 characters." );
   }
   catch ( DirectoryNotFoundException^ ) 
   {
      Console::WriteLine( "Error: The specified path is invalid, such as being
 on an unmapped drive." );
   }
   catch ( IOException^ ) 
   {
      Console::WriteLine( "Error: An I/O error occurred while
 opening the file." );
   }
   catch ( UnauthorizedAccessException^ ) 
   {
      Console::WriteLine( "Error: path specified a file that is read-only, the
 path is a directory, or caller does not have the required permissions." );
   }
   catch ( IndexOutOfRangeException^ ) 
   {
      Console::WriteLine( "Error: You must provide parameters for
 MyGZIP." );
   }

}

int main()
{
   array<String^>^args = Environment::GetCommandLineArgs();
   String^ usageText = "Usage: MYGZIP <inputfilename>";
   
   //If no file name is specified, write usage text.
   if ( args->Length == 1 )
   {
      Console::WriteLine( usageText );
   }
   else
   {
      if ( File::Exists( args[ 1 ] ) )
            GZipCompressDecompress( args[ 1 ] );
   }
}

J#

import System.*;
import System.IO.*;
import System.IO.Compression.*;

public class GZipTest
{
    public static int ReadAllBytesFromStream(Stream
 stream, ubyte buffer[])
    {
        // Use this method is used to read all bytes from a stream.
        int offSet = 0;
        int totalCount = 0;
        while (true) {
            int bytesRead = stream.Read(buffer, offSet, 100);
            if (bytesRead == 0) {
                break;
            }
            offSet += bytesRead;
            totalCount += bytesRead;
        }
        return totalCount;
    } //ReadAllBytesFromStream

    public static boolean CompareData(ubyte
 buf1[], int len1, 
        ubyte buf2[], int len2)
    {
        // Use this method to compare data from two different buffers.
        if (len1 != len2) {
            Console.WriteLine("Number of bytes in two buffer
 are "
                + "different {0}:{1}", System.Convert.ToString(len1), 
                System.Convert.ToString(len2));
            return false;
        }
        for (int i = 0; i < len1; i++) {
            if (!(buf1.get_Item(i).Equals(buf2.get_Item(i))))
 {
                Console.WriteLine("byte {0} is different {1}|{2}", 
                    System.Convert.ToString(i), 
                    System.Convert.ToString(buf1.get_Item(i)), 
                    System.Convert.ToString(buf2.get_Item(i)));
                return false;
            }
        }
        Console.WriteLine("All bytes compare.");
        return true;
    } //CompareData

    public static void GZipCompressDecompress(String
 fileName)
    {
        Console.WriteLine("Test compression and decompression on file {0}"
,
            fileName);
        FileStream inFile;
        try {
            // Open the file as a FileStream object.
            inFile = new FileStream(fileName, FileMode.Open, 
                FileAccess.Read, FileShare.Read);
            ubyte buffer[] = new ubyte[(ubyte)inFile.get_Length()];

            // Read the file to ensure it is readable.
            int count = inFile.Read(buffer, 0, buffer.length);
            if (count != buffer.length) {
                inFile.Close();
                Console.WriteLine("Test Failed: Unable to read data from file");
                return;
            }
            inFile.Close();
            MemoryStream ms = new MemoryStream();

            // Use the newly created memory stream for the compressed
 data.
            GZipStream compressedZipStream = 
                new GZipStream(ms, CompressionMode.Compress, true);
            Console.WriteLine("Compression");
            compressedZipStream.Write(buffer, 0, buffer.length);

            // Close the stream.
            compressedZipStream.Close();
            Console.WriteLine("Original size: {0}, Compressed size: {1}",
 
                System.Convert.ToString(buffer.length), 
                System.Convert.ToString(ms.get_Length()));

            // Reset the memory stream position to begin decompression.
            ms.set_Position(0);
            GZipStream zipStream = 
                new GZipStream(ms, CompressionMode.Decompress);
            Console.WriteLine("Decompression");
            ubyte decompressedBuffer[] = new ubyte[buffer.length
 + 100];

            // Use the ReadAllBytesFromStream to read the stream.
            int totalCount = GZipTest.ReadAllBytesFromStream(zipStream,
 
                decompressedBuffer);
            Console.WriteLine("Decompressed {0} bytes", 
                System.Convert.ToString(totalCount));
            if (!(GZipTest.CompareData(buffer, buffer.length,
 
                decompressedBuffer, totalCount))) {
                Console.WriteLine("Error. The two buffers did not compare.");
            }
            zipStream.Close();
        } 
        catch (InvalidDataException exp) {
            Console.WriteLine("Error: The file being read contains"
                + " invalid data.");
        }
        catch (FileNotFoundException exp) {
            Console.WriteLine("Error:The file specified was not found.");
        }
        catch (ArgumentException exp) {
            Console.WriteLine("Error: path is a zero-length string,
 contains "
                + "only white space, or contains one or more invalid characters");
        }
        catch (PathTooLongException exp) {
            Console.WriteLine("Error: The specified path, file name, or both
 "
                + "exceed the system-defined maximum length. For example, on"
                + " Windows-based platforms, paths must be less than 248 "
                + "characters, and file names must be less than 260 characters.");
        }
        catch (DirectoryNotFoundException exp) {
            Console.WriteLine("Error: The specified path is invalid, such"
                + " as being on an unmapped drive.");
        }
        catch (IOException exp) {
            Console.WriteLine("Error: An I/O error occurred while
 "
                + "opening the file.");
        }
        catch (UnauthorizedAccessException exp) {
            Console.WriteLine("Error: path specified a file that is read-only
,"
                + " the path is a directory, or caller does not have"
                + " the required permissions.");
        }
        catch (IndexOutOfRangeException exp) {
            Console.WriteLine("Error: You must provide parameters for
 MyGZIP.");
        }
    } //GZipCompressDecompress

    public static void main(String[]
 args)
    {
        String usageText = "Usage: MYGZIP <inputfilename>";

        //If no file name is specified, write usage text.
        if (args.length == 0) {
            Console.WriteLine(usageText);
        }
        else {
            if (File.Exists(args[0])) {
                GZipCompressDecompress(args[0]);
            }
        }
    } //main
} //GZipTest

プラットフォーム

Windows 98, Windows 2000 SP4, Windows Millennium Edition, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

開発プラットフォームの中には、.NET Framework によってサポートされていないバージョンがあります。サポートされているバージョンについては、「システム要件」を参照してください。

バージョン情報

.NET Framework
サポート対象 : 2.0

参照

関連項目
GZipStream クラス
GZipStream メンバ
System.IO.Compression 名前空間