# Django 1.8.18.dev20170123152445 documentation

# Source code for django.middleware.gzip

    import re

    from django.utils.cache import patch_vary_headers
    from django.utils.text import compress_sequence, compress_string

    re_accepts_gzip = re.compile(r'\bgzip\b')

    class GZipMiddleware(object):
        """
        This middleware compresses content if the browser allows gzip compression.
        It sets the Vary header accordingly, so that caches will base their storage
        on the Accept-Encoding header.
        """
        def process_response(self, request, response):
            # It's not worth attempting to compress really short responses.
            if not response.streaming and len(response.content) < 200:
                return response

            # Avoid gzipping if we've already got a content-encoding.
            if response.has_header('Content-Encoding'):
                return response

            patch_vary_headers(response, ('Accept-Encoding',))

            ae = request.META.get('HTTP_ACCEPT_ENCODING', '')
            if not re_accepts_gzip.search(ae):
                return response

            if response.streaming:
                # Delete the `Content-Length` header for streaming content, because
                # we won't know the compressed size until we stream it.
                response.streaming_content = compress_sequence(response.streaming_content)
                del response['Content-Length']
            else:
                # Return the compressed content only if it's actually shorter.
                compressed_content = compress_string(response.content)
                if len(compressed_content) >= len(response.content):
                    return response
                response.content = compressed_content
                response['Content-Length'] = str(len(response.content))

            if response.has_header('ETag'):
                response['ETag'] = re.sub('"$', ';gzip"', response['ETag'])
            response['Content-Encoding'] = 'gzip'

            return response