CODEWITHSUNDEEP
.netcompressiongzip
kementeus
kementeus

Reputation: 147

Issues with .net gzip decompression stream

What could be wrong with those set of methods?

        byte[] bytes;

        using (var memory_stream = new MemoryStream())
        using (var gzip_stream = new GZipStream(memory_stream, CompressionMode.Compress))
        {
            var buffer = Encoding.Default.GetBytes("Hello nurse!");
            gzip_stream.Write(buffer, 0, buffer.Length);
            bytes = memory_stream.ToArray();
        }

        int total_read = 0;

        using (var input_stream = new MemoryStream(bytes))
        using (var gzip_stream = new GZipStream(input_stream, CompressionMode.Decompress, true))
        {
            int read;
            var buffer = new byte[4096];
            while ((read = gzip_stream.Read(buffer, 0, buffer.Length)) != 0) {
                total_read += read;
            }
        }

        Debug.WriteLine(bytes);
        Debug.WriteLine(total_read);

The gzipStr is a valid Gzipped Stream (I could compress it successfully with GzipStream() Compress).

Why is total_read always 0??? is gzip stream decompressing my stream? am I doing something wrong?

What am I doing wrong here???!!!

Upvotes: 1

Views: 1029

Answers (1)

Matthew Flaschen
Matthew Flaschen

Reputation: 284786

You forgot to flush. :) Note that Encoding.Default should not generally be used in production. In the below, replace it with Encoding.UTF8 (or whatever's appropriate). Finally, of course, the below santiy-check only works if everything fits in a single buffer. But now you should get the idea.

kementeus indicated my previous code here didn't help, so below is the exact code I used:

public class GzipBug
{
    public static void Main(String[] a)
    {
        byte[] bytes;
    byte[] buffer;

    Encoding encoding = Encoding.UTF8;

        using (var memory_stream = new MemoryStream())
        using (var gzip_stream = new GZipStream(memory_stream, CompressionMode.Compress))
        {
            buffer = encoding.GetBytes("Hello nurse!");
            gzip_stream.Write(buffer, 0, buffer.Length);
        gzip_stream.Flush();
        bytes = memory_stream.ToArray();
        }

        int total_read = 0;

        using (var input_stream = new MemoryStream(bytes))
        using (var gzip_stream = new GZipStream(input_stream, CompressionMode.Decompress, true))
        {
        int read;
            buffer = new byte[4096];
            while ((read = gzip_stream.Read(buffer, 0, buffer.Length)) != 0) {
        total_read += read;
            }
        }

        Debug.WriteLine(encoding.GetString(buffer, 0, total_read));
        Debug.WriteLine(total_read);

    }
}

It is compiled with: gmcs -d:DEBUG -langversion:linq -debug+ GzipBug.cs and run as: MONO_TRACE_LISTENER=Console.Out GzipBug.exe

(you can remove the MONO_TRACE_LISTENER bit)

Upvotes: 2

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