DeflateStream Class

Definition

Provides methods and properties for compressing and decompressing streams by using the Deflate algorithm.

public class DeflateStream : System.IO.Stream
Inheritance

Inherited Members

System.IO.Stream

System.MarshalByRefObject

System.Object

Examples

The following example shows how to use the DeflateStream class to compress and decompress a directory of files.

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

public class Program
{
    static string directoryPath = @"c:\temp";
    public static void Main()
    {
        
        DirectoryInfo directorySelected = new DirectoryInfo(directoryPath);
           Compress(directorySelected);
    	

        foreach (FileInfo fileToDecompress in directorySelected.GetFiles("*.cmp"))
        {
            Decompress(fileToDecompress);
        }
    }

    public static void Compress(DirectoryInfo directorySelected)
    {
        
     
        foreach (FileInfo file in directorySelected.GetFiles("*.xml"))
        using (FileStream originalFileStream = file.OpenRead())
        {
            if ((File.GetAttributes(file.FullName) & FileAttributes.Hidden)
                != FileAttributes.Hidden & file.Extension != ".cmp")
            {
                using (FileStream compressedFileStream = File.Create(file.FullName + ".cmp"))
                {
                    using (DeflateStream compressionStream = new DeflateStream(compressedFileStream, CompressionMode.Compress))
                    {
                        originalFileStream.CopyTo(compressionStream);
                    }
                }

                FileInfo info = new FileInfo(directoryPath + "\\" + file.Name + ".cmp");
                Console.WriteLine("Compressed {0} from {1} to {2} bytes.", file.Name, file.Length, info.Length);
            }
        }
    }

    public static void Decompress(FileInfo fileToDecompress)
    {
        using (FileStream originalFileStream = fileToDecompress.OpenRead())
        {
            string currentFileName = fileToDecompress.FullName;
            string newFileName = currentFileName.Remove(currentFileName.Length - fileToDecompress.Extension.Length);

            using (FileStream decompressedFileStream = File.Create(newFileName))
        	{
                using (DeflateStream decompressionStream = new DeflateStream(originalFileStream, CompressionMode.Decompress))
        	    {
                    decompressionStream.CopyTo(decompressedFileStream);
                    Console.WriteLine("Decompressed: {0}", fileToDecompress.Name);
        	    }
        	}
        }
    }
}
Imports System.IO
Imports System.IO.Compression

Public Class Program
    Shared directoryPath As String = "c:\temp"
    Public Shared Sub Main()

        Dim directorySelected As New DirectoryInfo(directoryPath)
        Compress(directorySelected)


        For Each fileToDecompress As FileInfo In directorySelected.GetFiles("*.cmp")
            Decompress(fileToDecompress)
        Next
    End Sub

    Public Shared Sub Compress(directorySelected As DirectoryInfo)

        For Each file__1 As FileInfo In directorySelected.GetFiles("*.xml")
            Using originalFileStream As FileStream = file__1.OpenRead()
                If (File.GetAttributes(file__1.FullName) And FileAttributes.Hidden) <> FileAttributes.Hidden And file__1.Extension <> ".cmp" Then
                    Using compressedFileStream As FileStream = File.Create(file__1.FullName & ".cmp")
                        Using compressionStream As Compression.DeflateStream = New DeflateStream(compressedFileStream, CompressionMode.Compress)
                            originalFileStream.CopyTo(compressionStream)
                        End Using
                    End Using

                    Dim info As New FileInfo(directoryPath & "\" & file__1.Name & ".cmp")
                    Console.WriteLine("Compressed {0} from {1} to {2} bytes.", file__1.Name, file__1.Length, info.Length)
                End If
            End Using
        Next
    End Sub

    Public Shared Sub Decompress(fileToDecompress As FileInfo)
        Using originalFileStream As FileStream = fileToDecompress.OpenRead()
            Dim currentFileName As String = fileToDecompress.FullName
            Dim newFileName As String = currentFileName.Remove(currentFileName.Length - fileToDecompress.Extension.Length)

            Using decompressedFileStream As FileStream = File.Create(newFileName)
                Using decompressionStream As New DeflateStream(originalFileStream, CompressionMode.Decompress)
                    decompressionStream.CopyTo(decompressedFileStream)
                    Console.WriteLine("Decompressed: {0}", fileToDecompress.Name)
                End Using
            End Using
        End Using
    End Sub
End Class

Remarks

This class represents the Deflate algorithm, which is an industry-standard algorithm for lossless file compression and decompression. Starting with the .NET Framework 4.5, the DeflateStream class uses the zlib library. As a result, it provides a better compression algorithm and, in most cases, a smaller compressed file than it provides in earlier versions of the .NET Framework.

This class does not inherently provide functionality for adding files to or extracting files from zip archives. To work with zip archives, use the ZipArchive and the ZipArchiveEntry classes.

The DeflateStream class uses the same compression algorithm as the gzip data format used by the GZipStream class.

The compression functionality in DeflateStream and GZipStream is exposed as a stream. Data is read on a byte-by-byte basis, so it is not possible to perform multiple passes to determine the best method for compressing entire files or large blocks of data. The DeflateStream and GZipStream classes are best used on uncompressed sources of data. If the source data is already compressed, using these classes may actually increase the size of the stream.

Constructors

DeflateStream(Stream, CompressionLevel)

Initializes a new instance of the DeflateStream class by using the specified stream and compression level.

DeflateStream(Stream, CompressionMode)

Initializes a new instance of the DeflateStream class by using the specified stream and compression mode.

DeflateStream(Stream, CompressionLevel, Boolean)

Initializes a new instance of the DeflateStream class by using the specified stream and compression level, and optionally leaves the stream open.

DeflateStream(Stream, CompressionMode, Boolean)

Initializes a new instance of the DeflateStream class by using the specified stream and compression mode, and optionally leaves the stream open.

Properties

BaseStream

Gets a reference to the underlying stream.

CanRead

Gets a value indicating whether the stream supports reading while decompressing a file.

CanSeek

Gets a value indicating whether the stream supports seeking.

CanWrite

Gets a value indicating whether the stream supports writing.

Length

This property is not supported and always throws a NotSupportedException.

Position

This property is not supported and always throws a NotSupportedException.

Methods

BeginRead(Byte[], Int32, Int32, AsyncCallback, Object)

Begins an asynchronous read operation. (Consider using the ReadAsync(Byte[], Int32, Int32) method instead.)

BeginWrite(Byte[], Int32, Int32, AsyncCallback, Object)

Begins an asynchronous write operation. (Consider using the WriteAsync(Byte[], Int32, Int32) method instead.)

Dispose(Boolean)

Releases the unmanaged resources used by the DeflateStream and optionally releases the managed resources.

EndRead(IAsyncResult)

Waits for the pending asynchronous read to complete. (Consider using the ReadAsync(Byte[], Int32, Int32) method instead.)

EndWrite(IAsyncResult)

Ends an asynchronous write operation. (Consider using the WriteAsync(Byte[], Int32, Int32) method instead.)

Flush()

The current implementation of this method has no functionality.

Read(Byte[], Int32, Int32)

Reads a number of decompressed bytes into the specified byte array.

ReadAsync(Byte[], Int32, Int32, CancellationToken)
Seek(Int64, SeekOrigin)

This operation is not supported and always throws a NotSupportedException.

SetLength(Int64)

This operation is not supported and always throws a NotSupportedException.

Write(Byte[], Int32, Int32)

Writes compressed bytes to the underlying stream from the specified byte array.

WriteAsync(Byte[], Int32, Int32, CancellationToken)