CODEWITHSUNDEEP
c#stringappendgzipgzipstream
Brendan Gooden
Brendan Gooden

Reputation: 1561

Cannot append value to string C#

I've got two methods in my Windows Forms application for parsing some gzip encoded strings.

Here are my two methods, which both return the same value. 

public static async Task<string> DecodeGzipAsync(string str)
{
    var values = new Dictionary<string, string>
    {
        { "data", str }
    };

    var content = new FormUrlEncodedContent(values);

    var client = new HttpClient();

    var response = await client.PostAsync("http://www.txtwizard.net/compression/decompress/gz", content);

    var json = await response.Content.ReadAsStringAsync();

    var result = JsonConvert.DeserializeObject<GzipData>(json);

    return result.DecompressedData;
}

public static string DecodeGzip(string str)
{
    byte[] gzBuffer = Convert.FromBase64String(str);

    using (MemoryStream ms = new MemoryStream())
    {
        int msgLength = BitConverter.ToInt32(gzBuffer, 0);
        ms.Write(gzBuffer, 0, gzBuffer.Length);

        byte[] buffer = new byte[msgLength];

        ms.Position = 0;

        using (GZipStream zip = new GZipStream(ms, CompressionMode.Decompress))
        {
            zip.Read(buffer, 0, buffer.Length);
        }

        return Encoding.UTF8.GetString(buffer);

    }

And then I call these two methods from my main form.

var string1 = await Utilities.DecodeGzipAsync(xml.InnerText);
var string1Concat = string.Concat("<Connotes>", string1, "</Connotes>");

var string2 = Utilities.DecodeGzip(xml.InnerText);
var string2Concat = string.Concat("<Connotes>", string2, "</Connotes>");

Where xml.InnerText is

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

The results I get are really frustrating (and weird!)

string1 and string2 both return the same string, however string1Concat and string2Concat return different results.

string1Concat = "<Connotes>" + string1 + "</Connotes>"

string2Concat = "<Connotes>" + string2  // Notice how it is missing the concatenation on the end

What might be causing this behaviour? I have tried changing the encoding to ASCII and UTF8 but both give the same results.

Any help is much appreciated!

Upvotes: 1

Views: 256

Answers (1)

Christoph Fink
Christoph Fink

Reputation: 23113

This was a little tricky, but I found the problem/solution:
You convert the array of the size of the compressed data to a string at Encoding.UTF8.GetString(buffer). This will create a string which a length of 559903 instead of the correct 9209. If you create a new byte-array with the actually read bytes it is working:

public static string DecodeGzip(string str)
{
    byte[] gzBuffer = Convert.FromBase64String(str);

    using (MemoryStream ms = new MemoryStream())
    {
        int msgLength = BitConverter.ToInt32(gzBuffer, 0);
        ms.Write(gzBuffer, 0, gzBuffer.Length);

        byte[] buffer = new byte[msgLength];

        ms.Position = 0;
        int length;
        using (GZipStream zip = new GZipStream(ms, CompressionMode.Decompress))
        {
            length = zip.Read(buffer, 0, buffer.Length);
        }

        var data = new byte[length];
        Array.Copy(buffer, data, length);
        return Encoding.UTF8.GetString(data);   
    }
}

Upvotes: 3

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