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

//...
public static void CompressFile(string inputFileName, string outputFileName) 
{
    byte[] buffer = new byte[4096];
    if (File.Exists(inputFileName)) 
    {    
        using (FileStream inputFile = File.Open(inputFileName, FileMode.Open), outputFile = File.Create(outputFileName)) 
        {

            using (GZipStream gzip = new GZipStream(outputFile, CompressionMode.Compress)) 
            {
                int n = 0;
                while((n = inputFile.Read(buffer, 0, buffer.Length)) != 0) 
                {
                    gzip.Write(buffer, 0, n);
                }
            }
        }
    }
}


public static void UncompressFile(string inputFileName, string outputFileName) 
{
    byte[] buffer = new byte[4096];
    if(File.Exists(inputFileName)) 
    {
        using (FileStream intputFile = File.Open(inputFileName, FileMode.Open), outputFile = File.Create(outputFileName)) 
        {
            using (GZipStream gzip = new GZipStream(intputFile, CompressionMode.Decompress)) 
            {
                int n;
                while ((n = gzip.Read(buffer, 0, buffer.Length)) != 0) 
                {
                    outputFile.Write(buffer, 0, n);
                }
            }
        }
    }
}

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.util.zip.GZIPInputStream;
import java.util.zip.GZIPOutputStream;

public class GZIP {
    public static boolean compress(String iFilename, String oFilename){
        try {
            // prepare le gzip de sortie
            GZIPOutputStream out = new GZIPOutputStream(new FileOutputStream(oFilename));
            // ouvre le fichier d'entree
            FileInputStream in = new FileInputStream(iFilename);
            //transfere les bytes vers le gzip
            byte[] buf = new byte[1024];
            int offset;
            while ((offset = in.read(buf)) > 0) 
                out.write(buf, 0, offset);
            in.close();
        
            // On complete le fichier GZIP
            out.finish();
            out.close();
            return true;
        } catch (IOException e) {
            e.printStackTrace();
            return false;
        }
    }
    
    public static boolean uncompress(String iFilename, String oFilename){
        try {
            // Ouvre le fichier compresse
            GZIPInputStream in = new GZIPInputStream(new FileInputStream(iFilename));
            // ouvre le fichier de sortie
            OutputStream out = new FileOutputStream(oFilename);
            // transfere les byte compresse vers le fichier de sortie
            byte[] buf = new byte[1024];
            int offset;
            while ((offset = in.read(buf)) > 0)
                out.write(buf, 0, offset);
        
            // Ferme le fichier et le gzip
            in.close();
            out.close();
            return true;
        } catch (IOException e) {
            e.printStackTrace();
            return false;
        }
    }
}

Imports System.IO
Imports System.IO.Compression

Public Class HbGzip

    Public Shared Function Compress(ByVal cheminSource As String, ByVal cheminCible As String) As String
        Try
            Dim hbread As New BinaryReader(File.OpenRead(cheminSource))
            Dim F_array(hbread.BaseStream.Length) As Byte
            hbread.BaseStream.Seek(0, SeekOrigin.Begin)
            hbread.BaseStream.Read(F_array, 0, F_array.Length)
            hbread.BaseStream.Flush()
            hbread.Close()
            Dim tmpstream As FileStream = New FileStream(cheminCible, FileMode.OpenOrCreate)
            Dim gzipper As GZipStream = New GZipStream(tmpstream, CompressionMode.Compress)
            gzipper.Write(F_array, 0, F_array.Length)
            gzipper.Flush()
            gzipper.Close()
            Return "compression effectuée avec succés"
        Catch ex As Exception
            Return ex.ToString
        End Try
    End Function

    Public Shared Function Decompress(ByVal cheminSource As String, ByVal cheminCible As String) As String
        Try
            Dim bufferLen As Integer = 1024
            Dim hbread As New BinaryReader(File.OpenRead(cheminSource))
            Dim gzipper As GZipStream = New GZipStream(hbread.BaseStream, CompressionMode.Decompress)
            Dim hbwrite As New BinaryWriter(File.OpenWrite(cheminCible))
            Dim F_array(bufferLen) As Byte
            Dim readlen As Integer
            Dim flag As Boolean = True
            Do
                readlen = gzipper.Read(F_array, 0, F_array.Length)
                If readlen > 0 Then
                    flag = True
                    If readlen = (bufferLen + 1) Then hbwrite.Write(F_array, 0, readlen) Else hbwrite.Write(F_array, 0, readlen - 1)
                Else
                    flag = False
                End If
            Loop While (flag)
            hbwrite.Close()
            gzipper.Close()
            Return "decompression effectuée avec succés"
        Catch ex As Exception
            Return ex.ToString
        End Try
    End Function
End Class