Javascript GZIP and btoa and decompress with C# - base64

Question

i am developing an application where i compress large JSON data using pako.gzip and then use the btoa function to make it base64string in order to post the data to the server. In the javascript i wrote:
var data = JSON.stringify(JSONData);
var ZippedData = pako.gzip(data, { to: 'string' });
var base64String = btoa(ZippedData);
/* post to server*/
$http.post("URL?base64StringParam=" + base64String").then(function (response) {
//do stuff
});
the problem is that i need to decompress the data again in C# code after posting in order to do other workings on it. In the C# code i wrote:
byte[] data = Convert.FromBase64String(base64StringParam);
string decodedString = System.Text.ASCIIEncoding.ASCII.GetString(data);
Encoding enc = Encoding.Unicode;
MemoryStream stream = new MemoryStream(enc.GetBytes(decodedString));
GZipStream decompress = new GZipStream(stream, CompressionMode.Decompress);
string plainDef = "";
and i get the error here
using (var sr = new StreamReader(decompress))
{
plainDef = sr.ReadToEnd();
}
Found invalid data while decoding.
any help to decompress the data back in C# will be appreciated
EDIT:to sum up what needed to be done
javascript does the following:
Plain text >> to >> gzip bytes >> to >> base64 string
i need C# to do the reverse:
Base64 >> to >> unzip bytes >> to >> plain text

Answer 1

Assuming the following js:
dataToCommitString = btoa(pako.gzip(dataToCommitString, { to: "string" }));
This is the correct c# code to compress/decompress with GZip: Taken from https://stackoverflow.com/a/7343623/679334
using System;
using System.Collections.Generic;
using System.IO;
using System.IO.Compression;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace YourNamespace
{
public class GZipCompressor : ICompressor
{
private static void CopyTo(Stream src, Stream dest)
{
byte[] bytes = new byte[4096];
int cnt;
while ((cnt = src.Read(bytes, 0, bytes.Length)) != 0)
{
dest.Write(bytes, 0, cnt);
}
}
public byte[] Zip(string str)
{
var bytes = Encoding.UTF8.GetBytes(str);
using (var msi = new MemoryStream(bytes))
using (var mso = new MemoryStream())
{
using (var gs = new GZipStream(mso, CompressionMode.Compress))
{
//msi.CopyTo(gs);
CopyTo(msi, gs);
}
return mso.ToArray();
}
}
public string Unzip(byte[] bytes)
{
using (var msi = new MemoryStream(bytes))
using (var mso = new MemoryStream())
{
using (var gs = new GZipStream(msi, CompressionMode.Decompress))
{
//gs.CopyTo(mso);
CopyTo(gs, mso);
}
return Encoding.UTF8.GetString(mso.ToArray());
}
}
}
}
Calling it as follows:
value = _compressor.Unzip(Convert.FromBase64CharArray(value.ToCharArray(), 0, value.Length));

Answer 2

In client use:
let output = pako.gzip(JSON.stringify(obj));
send as: 'Content-Type': 'application/octet-stream'
=====================
then in C#:
[HttpPost]
[Route("ReceiveCtImage")]
public int ReceiveCtImage([FromBody] byte[] data)
{
var json = Decompress(data);
return 1;
}
public static string Decompress(byte[] data)
{
// Read the last 4 bytes to get the length
byte[] lengthBuffer = new byte[4];
Array.Copy(data, data.Length - 4, lengthBuffer, 0, 4);
int uncompressedSize = BitConverter.ToInt32(lengthBuffer, 0);
var buffer = new byte[uncompressedSize];
using (var ms = new MemoryStream(data))
{
using (var gzip = new GZipStream(ms, CompressionMode.Decompress))
{
gzip.Read(buffer, 0, uncompressedSize);
}
}
string json = Encoding.UTF8.GetString(buffer);
return json;
}