How to use the mime.charsets function in mime

// redirect directory in case index.html is present
    } else if (stat.isDirectory()) {
      if (!redirect) return next();
      url = parse(req.originalUrl);
      res.statusCode = 301;
      res.setHeader('Location', url.pathname + '/');
      res.end('Redirecting to ' + url.pathname + '/');
      return;
    }

    // header fields
    if (!res.getHeader('Date')) res.setHeader('Date', new Date().toUTCString());
    if (!res.getHeader('Cache-Control')) res.setHeader('Cache-Control', 'public, max-age=' + (maxAge / 1000));
    if (!res.getHeader('Last-Modified')) res.setHeader('Last-Modified', stat.mtime.toUTCString());
    if (!res.getHeader('Content-Type')) {
      var charset = mime.charsets.lookup(type);
      res.setHeader('Content-Type', type + (charset ? '; charset=' + charset : ''));
    }
    res.setHeader('Accept-Ranges', 'bytes');

    // conditional GET support
    if (utils.conditionalGET(req)) {
      if (!utils.modified(req, res)) {
        req.emit('static');
        return utils.notModified(res);
      }
    }

    var opts = {}
      , len = stat.size;

    // we have a Range request

: next(err);
    // redirect directory in case index.html is present
    } else if (stat.isDirectory()) {
      if (!redirect) return next();
      res.statusCode = 301;
      res.setHeader('Location', url.pathname + '/');
      res.end('Redirecting to ' + url.pathname + '/');
      return;
    }

    // header fields
    if (!res.getHeader('Date')) res.setHeader('Date', new Date().toUTCString());
    if (!res.getHeader('Cache-Control')) res.setHeader('Cache-Control', 'public, max-age=' + (maxAge / 1000));
    if (!res.getHeader('Last-Modified')) res.setHeader('Last-Modified', stat.mtime.toUTCString());
    if (!res.getHeader('Content-Type')) {
      var charset = mime.charsets.lookup(type);
      res.setHeader('Content-Type', type + (charset ? '; charset=' + charset : ''));
    }
    res.setHeader('Accept-Ranges', 'bytes');

    // conditional GET support
    if (utils.conditionalGET(req)) {
      if (!utils.modified(req, res)) {
        req.emit('static');
        return utils.notModified(res);
      }
    }

    var opts = {}
      , len = stat.size;

    // we have a Range request

});
    };

    // prepare gzip exclude option
    var gzipExclude = options.gzipExclude || [];
    if (!_.isArray(gzipExclude)) {
      gzipExclude = [];
    }

    // If gzip is enabled and file not in gzip exclude array,
    // gzip the file into a temp file and then perform the upload.
    if (options.gzip && gzipExclude.indexOf(path.extname(src)) === -1) {
      headers['Content-Encoding'] = 'gzip';
      headers['Content-Type'] = headers['Content-Type'] || mime.lookup(src);

      var charset = mime.charsets.lookup(headers['Content-Type'], null);
      if (charset) {
        headers['Content-Type'] += '; charset=' + charset;
      }

      var tmp = new Tempfile();
      var input = fs.createReadStream(src);
      var output = fs.createWriteStream(tmp.path);

      // Gzip the file and upload when done.
      input.pipe(zlib.createGzip()).pipe(output)
        .on('error', function (err) {
          dfd.reject(makeError(MSG_ERR_UPLOAD, prettySrc, err));
        })
        .on('close', function () {
          // Update the src to point to the newly created .gz file.
          src = tmp.path;

res.setHeader('Content-Length', stat.size);
      res.setHeader('Cache-Control', 'public, max-age=' + (maxAge / 1000));
      res.setHeader('Last-Modified', stat.mtime.toUTCString());
      res.setHeader('ETag', utils.etag(stat));

      // conditional GET support
      if (utils.conditionalGET(req)) {
        if (!utils.modified(req, res)) {
          return utils.notModified(res);
        }
      }
    }

    // header fields
    if (!res.getHeader('content-type')) {
      var charset = mime.charsets.lookup(type);
      res.setHeader('Content-Type', type + (charset ? '; charset=' + charset : ''));
    }
    res.setHeader('Accept-Ranges', 'bytes');

    // transfer
    if (head) return res.end();

    var stream = fs.createReadStream(path, opts);
    stream.pipe(res);
    req.on('close', function(){ stream.destroy(); });

    // callback
    if (fn) {
      function callback(err) { done || fn(err); done = true }
      req.on('close', callback);
      req.socket.on('error', callback);

SendStream.prototype.type = function(path){
  var res = this.res;
  if (res.getHeader('Content-Type')) return;
  var type = mime.lookup(path);
  var charset = mime.charsets.lookup(type);
  debug('content-type %s', type);
  res.setHeader('Content-Type', type + (charset ? '; charset=' + charset : ''));
};

SendStream.prototype.type = function(path){
  var res = this.res;
  if (res.getHeader('Content-Type')) return;
  var type = mime.lookup(path);
  var charset = mime.charsets.lookup(type);
  debug('content-type %s', type);
  res.setHeader('Content-Type', type + (charset ? '; charset=' + charset : ''));
};

SendStream.prototype.type = function(path){
  var res = this.res;
  if (res.getHeader('Content-Type')) return;
  var type = mime.lookup(path);
  var charset = mime.charsets.lookup(type);
  debug('content-type %s', type);
  res.setHeader('Content-Type', type + (charset ? '; charset=' + charset : ''));
};

SendStream.prototype.type = function(path){
  var res = this.res;
  if (res.getHeader('Content-Type')) return;
  var type = mime.lookup(path);
  var charset = mime.charsets.lookup(type);
  debug('content-type %s', type);
  res.setHeader('Content-Type', type + (charset ? '; charset=' + charset : ''));
};

SendStream.prototype.type = function type (path) {
  var res = this.res

  if (res.getHeader('Content-Type')) return

  var type = mime.lookup(path)

  if (!type) {
    debug('no content-type')
    return
  }

  var charset = mime.charsets.lookup(type)

  debug('content-type %s', type)
  res.setHeader('Content-Type', type + (charset ? '; charset=' + charset : ''))
}

SendStream.prototype.type = function(path){
  var res = this.res;
  if (res.getHeader('Content-Type')) return;
  var type = mime.lookup(path);
  var charset = mime.charsets.lookup(type);
  debug('content-type %s', type);
  res.setHeader('Content-Type', type + (charset ? '; charset=' + charset : ''));
};