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.NET Framework 3.5
 CompressionMode Enumeration

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Microsoft Visual Studio 2008/.NET Framework 3.5

Other versions are also available for the following:
.NET Framework Class Library
CompressionMode Enumeration

Specifies whether to compress or decompress the underlying stream.

Namespace:  System.IO.Compression
Assembly:  System (in System.dll)
Visual Basic (Declaration)
Public Enumeration CompressionMode
Visual Basic (Usage)
Dim instance As CompressionMode
C#
public enum CompressionMode
Visual C++
public enum class CompressionMode
JScript
public enum CompressionMode
Member nameDescription
Supported by the .NET Compact FrameworkSupported by the XNA FrameworkDecompress Decompresses the underlying stream.
Supported by the .NET Compact FrameworkSupported by the XNA FrameworkCompress Compresses the underlying stream.

This enumeration is used with the GZipStream and DeflateStream classes.

The following code example uses the CompressionMode enumeration with the GZipStream class to compress and decompress a file.

Visual Basic
Imports System
Imports System.IO
Imports System.IO.Compression



Public Class GZipTest
    Shared msg As String
    Private Const buffer_size As Integer = 100

    Public Shared Function ReadAllBytesFromStream(ByVal stream As Stream, ByVal 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, buffer_size)
            If bytesRead = 0 Then
                Exit While
            End If
            offset += bytesRead
            totalCount += bytesRead
        End While
        Return totalCount
    End Function 'ReadAllBytesFromStream


    Public Shared Function CompareData(ByVal buf1() As Byte, ByVal len1 As Integer, ByVal buf2() As Byte, ByVal 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(ByVal 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 + buffer_size) 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
{
    private const int buffer_size = 100;

    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, buffer_size);
            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 + buffer_size];
            // 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]);
        }
    }
}
    

Visual 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 ] );
   }
}


Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0

.NET Compact Framework

Supported in: 3.5

XNA Framework

Supported in: 3.0
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