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- from django.utils.cache import patch_vary_headers
- from django.utils.deprecation import MiddlewareMixin
- from django.utils.regex_helper import _lazy_re_compile
- from django.utils.text import compress_sequence, compress_string
-
- re_accepts_gzip = _lazy_re_compile(r"\bgzip\b")
-
-
- class GZipMiddleware(MiddlewareMixin):
- """
- Compress content if the browser allows gzip compression.
- Set 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.headers["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.headers["Content-Length"] = str(len(response.content))
-
- # If there is a strong ETag, make it weak to fulfill the requirements
- # of RFC 7232 section-2.1 while also allowing conditional request
- # matches on ETags.
- etag = response.get("ETag")
- if etag and etag.startswith('"'):
- response.headers["ETag"] = "W/" + etag
- response.headers["Content-Encoding"] = "gzip"
-
- return response
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