CODEWITHSUNDEEP
c#zip
Tu Nguyen
Tu Nguyen

Reputation: 33

Save a zip file to memory and unzip file from stream and get content

I am currently working on integrating Amazon Prime on our system and being stuck at getting the label back as ZPL format.

Basically, Amazon returns a base64 string, we will need to convert that string to a byte array, then save that array as a *.gzip file. From that gzip file, we can extract the content and get the zpl label content.

My question is, how we can do all of above without storing any temp files to system. I have researched some solutions but none is working for me.

My current code as below:

var str = "base64string";    
var label = Convert.FromBase64String(str);

using (var memoryStream = new MemoryStream())
{
    using (var archive = new ZipArchive(memoryStream, ZipArchiveMode.Create, true))
    {
        var demoFile = archive.CreateEntry("label.zip");

        var entryStream = demoFile.Open();

        using (var bw = new BinaryWriter(entryStream))
        {
            bw.Write(label);
        }

        var data = new MemoryStream();

        using (var zip = ZipFile.Read(entryStream))
        {
            zip["label"].Extract(data);
        }

        data.Seek(0, SeekOrigin.Begin);

        entryStream.Close();
    }

    using (var fileStream = new FileStream(@"D:\test.zip", FileMode.Create))
    {
        memoryStream.Seek(0, SeekOrigin.Begin);
        memoryStream.CopyTo(fileStream);
    }
}

If I save the file as test.zip, I can successfully get the label back. But if I try to extract it directly to another stream, I get an error

A stream from ZipArchiveEntry has been disposed

Upvotes: 2

Views: 7739

Answers (2)

Tu Nguyen
Tu Nguyen

Reputation: 33

I was overthinking it. I finally found a simple way to do it. We just need to convert that base64 string to bytes array and use GzipStream to directly decompress it. I leave the solution here in case someone needs it. Thanks!

var label = Convert.FromBase64String(str);

        using (var compressedStream = new MemoryStream(label))
        using (var zipStream = new GZipStream(compressedStream, CompressionMode.Decompress))
        using (var resultStream = new MemoryStream())
        {
            zipStream.CopyTo(resultStream);
            return resultStream.ToArray();
        }

Upvotes: 1

PaulG
PaulG

Reputation: 14021

I've done something similar, taking PNG label data from a zipped web response. This is how I went about that

using (WebClient webClient = new WebClient()) 
{
    // Download. Expect this to be a zip file
    byte[] data = webClient.DownloadData(urlString);

    MemoryStream memoryStream = new MemoryStream(data);

    ZipArchive zipArchive = new ZipArchive(memoryStream);

    foreach (var zipEntry in zipArchive.Entries)
    {
        // Can check file name here and ignore anything in zip we're not expecting
        if (!zipEntry.Name.EndsWith(".png")) continue;

        // Open zip entry as stream
        Stream extractedFile = zipEntry.Open();

        // Convert stream to memory stream
        MemoryStream extractedMemoryStream = new MemoryStream();
        extractedFile.CopyTo(extractedMemoryStream);

        // At this point the extractedMemoryStream is a sequence of bytes containing image data. 
        // In this test project I'm pushing that into a bitmap image, just to see something on screen, but could as easily be written to a file or passed for storage to sql or whatever.
        BitmapDecoder decoder = PngBitmapDecoder.Create(extractedMemoryStream, BitmapCreateOptions.None, BitmapCacheOption.OnLoad);
        BitmapFrame frame = decoder.Frames.First();
        frame.Freeze();
        this.LabelImage.Source = frame;
    }
}

Upvotes: 4

Related Questions