Scrapy partial response downloader middleware

gistfile1.py

class PartialResponse(object):
    """ Downloader middleware to only return the first n bytes
    """
    def process_response(self, request, response, spider):
        max_size = getattr(spider, 'response_max_size', 0)
        if max_size and len(response.body) > max_size:
            h = response.headers.copy()
            h['Content-Length'] = max_size
            response = response.replace(
                body=response.body.encode('utf-8')[:max_size],
                encoding='utf-8',
                headers=h)

        return response

that still downloads the whole file from the server. It would be more interesting if it could actually save bandwidth…