GZipStream GZipStream GZipStream GZipStream Class

Definition

public ref class GZipStream : System::IO::Stream

public class GZipStream : System.IO.Stream

type GZipStream = class
    inherit Stream

Public Class GZipStream
Inherits Stream

Inheritance

ObjectObjectObjectObject

StreamStreamStreamStream

GZipStreamGZipStreamGZipStreamGZipStream

Examples

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

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

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

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

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

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

                }
            }
        }

        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 (GZipStream decompressionStream = new GZipStream(originalFileStream, CompressionMode.Decompress))
                    {
                        decompressionStream.CopyTo(decompressedFileStream);
                        Console.WriteLine("Decompressed: {0}", fileToDecompress.Name);
                    }
                }
            }
        }
    }
}

Imports System.IO
Imports System.IO.Compression
Module Module1

    Private directoryPath As String = "c:\temp"
    Public Sub Main()
        Dim directorySelected As New DirectoryInfo(directoryPath)
        Compress(directorySelected)

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

    Public Sub Compress(directorySelected As DirectoryInfo)
        For Each fileToCompress As FileInfo In directorySelected.GetFiles()
            Using originalFileStream As FileStream = fileToCompress.OpenRead()
                If (File.GetAttributes(fileToCompress.FullName) And FileAttributes.Hidden) <> FileAttributes.Hidden And fileToCompress.Extension <> ".gz" Then
                    Using compressedFileStream As FileStream = File.Create(fileToCompress.FullName & ".gz")
                        Using compressionStream As New GZipStream(compressedFileStream, CompressionMode.Compress)

                            originalFileStream.CopyTo(compressionStream)
                        End Using
                    End Using
                    Dim info As New FileInfo(directoryPath & "\" & fileToCompress.Name & ".gz")
                    Console.WriteLine("Compressed {0} from {1} to {2} bytes.", fileToCompress.Name,
                                      fileToCompress.Length.ToString(), info.Length.ToString())

                End If
            End Using
        Next
    End Sub


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

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

Remarks

This class represents the gzip data format, which uses an industry-standard algorithm for lossless file compression and decompression. The format includes a cyclic redundancy check value for detecting data corruption. The gzip data format uses the same algorithm as the DeflateStream class, but can be extended to use other compression formats. The format can be readily implemented in a manner not covered by patents.

Starting with the .NET Framework 4.5, the DeflateStream class uses the zlib library for compression. 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.

Compressed GZipStream objects written to a file with an extension of .gz can be decompressed using many common compression tools; however, this class does not inherently provide functionality for adding files to or extracting files from zip archives.

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.

Notes to Inheritors

When you inherit from GZipStream, you must override the following members: CanSeek, CanWrite, and CanRead.

Constructors

Properties

Methods

Explicit Interface Implementations

Applies to