Upload files directly to s3

s3upload.js

function upload (req, res) {    
    var Formidable = require('formidable'),
        form = new Formidable.IncomingForm();

    form.encoding = 'utf-8';
    form.onPart = function (part) {
      if (!part.filename) {
        form.handlePart(part);
      } else {
        (function () {
          var file = {filename: part.filename, mime: part.mime, length: 0, hash: require('crypto').createHash('md5'), buffers: []};

          part.on('data', function (buf) {
            file.buffers.push(buf);
            file.length += buf.length;
            file.hash.update(buf);
          });

          part.on('end', function () {
            form.emit('file', part.name, file);
          });
        }());
      }
    };

    form.parse(req, function (err, fields, files) {
      var client = require('knox').createClient(require('../config/services').s3),
          buffer = new Buffer(files.file.length),
          file_name = files.file.hash.digest('hex'),
          length = 0;

      files.file.buffers.forEach(function (buf) {
        buf.copy(buffer, length, 0);
        length += buf.length;
      });

      client.put(file_name, {
        'Content-Length': buffer.length,
        'Content-Type': 'text/plain'
      }).end(buffer);
    });
}