How to use System.IO.Compression to read/write ZIP files?

Question

I know there are libraries out there for working with ZIP files. And, you can alternatively use the functionality built into Windows for working ZIP files.

But, I\'m

Answer 1

Yes, I've used it in the past. I sub-classed DataSet once to support persisting itself out to a file (via the ReadXML/WriteXML method). As an added bonus, I decided to allow it to be, optionally, compressed if desired (this, as you all should already know, is extremely effective with textual data like XML).

I used the GZipStream class (it was my understanding at the time that the related DeflateStream was merely GZip without header information, or some such — I'm sure someone could correct me on this). It works quite simply by piggy-backing on top of another stream and thus you then use the GZipStream in its place. In my case, it was piggy-backing on a FileStream.

Given a MemoryStream to be filled with the output of myDataSet.WriteXML(), I did something like the following:

if (CompressData)
{
    // Write to memory
    mStream = new MemoryStream();
    Save(mStream);
    mStream.Seek(0, SeekOrigin.Begin);

    // Filter that through a GZipStream and then to file
    fStream = new FileStream(Path.Combine(CacheFilePath, FileName + ".gz"),
                             FileMode.OpenOrCreate);
    zipStream = new GZipStream(fStream, CompressionMode.Compress, true);

    Pump(mStream, zipStream);
}
else
{
    // Write straight to file
    fStream = new FileStream(Path.Combine(CacheFilePath, FileName),
                             FileMode.OpenOrCreate);
    Save(fStream);
}

Where Save() and Pump() are simple methods like the following:

private void Pump(Stream input, Stream output)
{
    int n;
    byte[] bytes = new byte[4096]; // 4KiB at a time

    while ((n = input.Read(bytes, 0, bytes.Length)) != 0)
    {
        output.Write(bytes, 0, n);
    }
}

public void Save(Stream stream)
{
    AcceptChanges();

    WriteXml(stream, XmlWriteMode.WriteSchema);
}