Re: Re: Deflate Encoding

Hi,

  I wrote a sample application which compresses/decompresses a simple text file, which works fine for text files or any file stored locally.  The methods are as follows:

//For Compression using Deflate
private void compressFile(string inFile, string outFile)
        {
            System.IO.FileStream inFileStream = new System.IO.FileStream(inFile, System.IO.FileMode.Open);            
            System.IO.FileStream outFileStream = new System.IO.FileStream(outFile, System.IO.FileMode.Create);            
            System.IO.Compression.DeflateStream outZStream = new System.IO.Compression.DeflateStream(outFileStream,System.IO.Compression.CompressionMode.Compress);
            try
            {
                byte[] buffer = new byte[2000];
                int len;
                while ((len = inFileStream.Read(buffer, 0, 2000)) > 0)
                {
                    outZStream.Write(buffer, 0, len);
                }
                outZStream.Flush();
            }
            finally
            {
                outZStream.Close();
                outFileStream.Close();
                inFileStream.Close();
            }
        }

//For Decompression using Deflate
private void decompressFile(string inFile, string outFile)
        {
System.IO.FileStream inFileStream = new System.IO.FileStream(inFile, System.IO.FileMode.Open);
            System.IO.FileStream outFileStream = new System.IO.FileStream(outFile, System.IO.FileMode.Create);
System.IO.Compression.DeflateStream outZStream = new System.IO.Compression.DeflateStream(inFileStream,System.IO.Compression.CompressionMode.Decompress,true);

            byte[] buffer = new byte[327680];
            using (MemoryStream ms = new MemoryStream())
            {
                while (true)
                {
                    int read = outZStream.Read(buffer, 0, buffer.Length);
                    if (read <= 0)
                    {
                        buffer = ms.ToArray();
                        break;
                    }
                    ms.Write(buffer, 0, read);
                }
                ms.Flush();
                ms.Close();
            }
            outFileStream.Write(buffer, 0, buffer.Length);
            outZStream.Flush();
            
            outFileStream.Flush();
            outZStream.Close();
            outFileStream.Close();
}

This above code works fine.  I tried to dump the compressed stream on to a file which I get after handshake.  I tried to match the bytes using HexEditor of both the dump and the local compressed file, both are different.

Got stuck here.  Please provide inputs.

Thanx,
Waugh
                        
[email protected] wrote:                                  Quoting mark W <[email protected]> from ml.gnutella.dev-forum:
 :API ---- I am using .Net based Api something like this:
 :
 :Byte [] buffer; // it has compressed data 
 :Byte[] deComp;//Decompressed data
 :Stream streamObj = new System.IO.Compression.DeflateStream(new
 :MemoryStream(buffer), CompressionMode.Decompress);
 :streamObj.Read(deComp,0,buffer.Length);
 :streamObj.close;
 
 Hah! The error is obvious!!
 
 Try to find it.  In the small snippet you have posted above, there is
 a grave logic bug.  Unless you can find it, you're not up with the
 task of writing a Gnutella client. :-)
 
 You can formulate your hypothesis here, to increase your understanding,
 but I won't tell you the bug because that would kill your learning process.
 
 Good luck.
 
 Raphael
 
     
                       

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