Question

I have a memory stream that contains a zip file in byte[] format. Is there any way I can unzip this memory stream, without any need of writing the file to disk?

In general I am using ICSharpCode.SharpZipLib.Zip.FastZip to unzip a file, but is there any way to unzip a memory stream, maybe by storing the files in another MemoryStream or in byte[] format according to the files/folders present in the zip?

Any way I can use the Memorymapped files feature in this scenario ?

Answer 1

We use DotNetZip, and I can unzip the contents of a zip file from a Stream into memory. Here’s the sample code for extracting a specifically named file from a stream (LocalCatalogZip) and returning a stream to read that file, but it’d be easy to expand on it.

private static MemoryStream UnZipCatalog()
{
    MemoryStream data = new MemoryStream();
    using (ZipFile zip = ZipFile.Read(LocalCatalogZip))
    {
        zip["ListingExport.txt"].Extract(data);
    }
    data.Seek(0, SeekOrigin.Begin);
    return data;
}

It’s not the library you’re using now, but if you can change, you can get that functionality.

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Here’s a variation which would return a Dictionary<string,MemoryStream> of for the contents of every file of a zip file.

private static Dictionary<string,MemoryStream> UnZipToMemory()
{
    var result = new Dictionary<string,MemoryStream>();
    using (ZipFile zip = ZipFile.Read(LocalCatalogZip))
    {
        foreach (ZipEntry e in zip)
        {
            MemoryStream data = new MemoryStream();
            e.Extract(data);
            result.Add(e.FileName, data);
        }
    }

    return result;
}