use it in your controllers

<?php 

use n3b\Bundle\Util\HttpFoundation\StreamResponse\StreamResponse,
    n3b\Bundle\Util\HttpFoundation\StreamResponse\FileWriter,
    n3b\Bundle\Util\HttpFoundation\StreamResponse\StreamWriterWrapper;

class MyController
{
    // just sending a file
    public function sendFileAction()
    {
        $response = new StreamResponse(new FileWriter(__DIR__ . '/../Resources/price.xls'));
        $response->headers->set('Content-Type', 'text/vnd.ms-excel; charset=utf-8');
        $response->headers->set('Content-Disposition', 'attachment;filename=price.xls');
    
        return $response;
    }

    // or using third-party library, that can send data direct into output stream, PhpExcel as example
    public function sendStreamAction()
    {
        $pe = new \PHPExcel();
        ...
        $writer = \PHPExcel_IOFactory::createWriter($pe, 'Excel5');

        $response = new StreamResponse(new StreamWriterWrapper($writer, 'save', 'php://output'));
        $response->headers->set('Content-Type', 'text/vnd.ms-excel; charset=utf-8');
        $response->headers->set('Content-Disposition', 'attachment;filename=stream.xls');
    
        return $response;
    }
}

also you can use your own stream wrappers

<?php

use n3b\Bundle\Util\HttpFoundation\StreamResponse\StreamResponse,
    n3b\Bundle\Util\HttpFoundation\StreamResponse\StreamWriterInterface;

class MyWrapper implements StreamWriterInterface
{
    protected $stream;

    public function __construct($stream)
    {
        if(!is_resource $stream)
            throw new \Exception();

        $this->stream = $stream;
    }

    public function write()
    {
        echo stream_get_contents($this->stream);
    }
}

class MyController
{
    public function sendStreamAction()
    {
        $streamWrapper = new MyWrapper(fopen('http://www.example.com', 'r'));
        $response = new StreamResponse($streamWrapper);

        return $response;
    }
}