I am getting InvalidDataException: Unknown block type. Stream might be corrupted exception.

I created a zip file using the following code:

     string filename = Server.MapPath("wizard.txt");

     FileStream infile = File.OpenRead(filename);
        byte[] buffer = new byte[infile.Length];
        infile.Read(buffer,0, (int) infile.Length);
        infile.Close();

        FileStream outfile = File.Create(
           Path.ChangeExtension(filename,"zip"));

        GZipStream gzipStream =
           new GZipStream(outfile, CompressionMode.Compress);
        gzipStream.Write(buffer, 0, buffer.Length);
        gzipStream.Close();

I unzip the zipped file using the following code:


        string filename = Server.MapPath("wizard.zip");

        FileStream infile = File.OpenRead(filename);
        DeflateStream deflateStream =
            new DeflateStream(infile, CompressionMode.Decompress);
        byte[] buffer = new byte[infile.Length + 100];

        int offset = 0;
        int totalCount = 0;
        while (true)
        {
            int bytesRead = deflateStream.Read(buffer, 0, 100);
            if (bytesRead == 0)
            { break; }

            offset += bytesRead;
            totalCount += bytesRead;
        }

        FileStream outfile = File.Create(
           Path.ChangeExtension(filename, "txt"));
        outfile.Write(buffer, 0, buffer.Length);
        outfile.Close();

I get the following Exception. Any advice?


Stack Trace:


[InvalidDataException: Unknown block type. Stream might be corrupted.]
   System.IO.Compression.Inflater.Decode() +407
   System.IO.Compression.Inflater.Inflate(Byte[] bytes, Int32 offset, Int32 length) +127
   System.IO.Compression.DeflateStream.Read(Byte[] array, Int32 offset, Int32 count) +134
   _Default.Page_Load(Object sender, EventArgs e) in c:\Surinder\Book Notes\ASPNet\Ch24\21\Default.aspx.cs:28
   System.Web.Util.CalliHelper.EventArgFunctionCaller (IntPtr fp, Object o, Object t, EventArgs e) +13
   System.Web.Util.CalliEventHandlerDelegateProxy.Cal lback(Object sender, EventArgs e) +45
   System.Web.UI.Control.OnLoad(EventArgs e) +80
   System.Web.UI.Control.LoadRecursive() +49
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +3745

GZipStream and DeflateStream are different compression methods - they are not compatible.

If you compress using GZipStream then decompress using GZipStream as well.

/- Sam Judson : Wrox Technical Editor -/

Thanks S.J. As per your suggestion the following solution worked for me.

        // Read the file we are going to compress into a FileStream
        string filename = Server.MapPath("wizard.zip");

        FileStream infile = File.OpenRead(filename);
        GZipStream gzipStream = new GZipStream(infile, CompressionMode.Decompress);

        byte[] buffer = new byte[infile.Length + 100];

        gzipStream.Read(buffer, 0, (int) infile.Length);
        string x = Encoding.ASCII.GetString(buffer);

And also, just so you are aware, there is a difference between a 'zip' file and a file created using the GZipStream compression (technically a GZip file).

Also, GZip and Deflate use the same algorithm to compress data, but GZip includes header details at the start of the data stream, hence why they are not compatible.

http://en.wikipedia.org/wiki/Gzip
http://en.wikipedia.org/wiki/DEFLATE
http://en.wikipedia.org/wiki/ZIP_%28file_format%29

/- Sam Judson : Wrox Technical Editor -/