Node.js streaming upload (and no tmp file on disk) with Multiparty with pipe to gunzip

gistfile1.js

"use strict";

var multiparty = require('multiparty')
  , http = require('http')
  , util = require('util')
  , zlib = require('zlib');

http.createServer(function(req, res) {
  if (req.url === '/upload' && req.method === 'POST') {
    var form = new multiparty.Form();
    var gunzip = zlib.createGunzip();
    var out = '';

    form.on('part',function(part) {
      if (part.filename) {
        part.on('data', function(chunk) {
          // plain file contents goes here
        });
        part.pipe(gunzip);
        gunzip.on('data', function(data) {
          // here we have un-gzipped data
          out += data.toString();
        });
        gunzip.on('end', function() {
          // our gzipped data is json, return it
          res.writeHead(200, { 'Content-Type': 'application/json; charset=utf-8' });
          console.log('gunzip done');
          res.end(out);
        });
      }
    });
    form.on('error', function(err) {
      console.log('fail ' + err);
    });
    form.on('progress',function(bytesReceived, bytesExpected) {
      console.log(bytesReceived +'/'+ bytesExpected);
    });
    // will probably fire before gunzip end
    form.on('close',function() {
      console.log('form done');
    });
    // any form fields goes here
    form.on('field',function(name,value) {
      console.log(name+'='+value);
    });
    form.parse(req);
  }
}).listen(3000);