gistfile1.js

function Dummyware(app) {
  return function(env) {
    var r = app(env);
    var istream = r.body;
    var ostream = r.body = new MemoryStream();
    async(function chunked() {
      if ( istream.canRead )
        ostream.write(istream.read(Infinity));
      if ( !istream.seenEOF )
        async(chunked);
      else ostream.closed();
    });
    return r;
  };
}

// or

function Dummyware(app) {
  return function(env) {
    var istream = new MemoryStream();
    var ostream = env["jsgi.output"];
    env["jsgi.output"] = istream;
    async(function chunked() {
      if ( istream.canRead )
        ostream.write(istream.read(Infinity));
      if ( !istream.seenEOF )
        async(chunked);
      else ostream.closed();
    });
    return app(env);
  };
}