text: import types
  import functools
  import zlib
  
  from pip._vendor.requests.adapters import HTTPAdapter
  
  from .controller import CacheController
  from .cache import DictCache
  from .filewrapper import CallbackFileWrapper
  
  
  class CacheControlAdapter(HTTPAdapter):
      invalidating_methods = {"PUT", "DELETE"}
  
      def __init__(
          self,
          cache=None,
          cache_etags=True,
          controller_class=None,
          serializer=None,
          heuristic=None,
          cacheable_methods=None,
          *args,
          **kw
      ):
          super(CacheControlAdapter, self).__init__(*args, **kw)
          self.cache = DictCache() if cache is None else cache
          self.heuristic = heuristic
          self.cacheable_methods = cacheable_methods or ("GET",)
  
          controller_factory = controller_class or CacheController
          self.controller = controller_factory(
              self.cache, cache_etags=cache_etags, serializer=serializer
          )
  
      def send(self, request, cacheable_methods=None, **kw):
          """
          Send a request. Use the request information to see if it
          exists in the cache and cache the response if we need to and can.
          """
          cacheable = cacheable_methods or self.cacheable_methods
          if request.method in cacheable:
              try:
                  cached_response = self.controller.cached_request(request)
              except zlib.error:
                  cached_response = None
              if cached_response:
                  return self.build_response(request, cached_response, from_cache=True)
  
              # check for etags and add headers if appropriate
              request.headers.update(self.controller.conditional_headers(request))
  
          resp = super(CacheControlAdapter, self).send(request, **kw)
  
          return resp
  
      def build_response(
          self, request, response, from_cache=False, cacheable_methods=None
      ):
          """
          Build a response by making a request or using the cache.
  
          This will end up calling send and returning a potentially
          cached response
          """
          cacheable = cacheable_methods or self.cacheable_methods
          if not from_cache and request.method in cacheable:
              # Check for any heuristics that might update headers
              # before trying to cache.
              if self.heuristic:
                  response = self.heuristic.apply(response)
  
              # apply any expiration heuristics
              if response.status == 304:
                  # We must have sent an ETag request. This could mean
                  # that we've been expired already or that we simply
                  # have an etag. In either case, we want to try and
                  # update the cache if that is the case.
                  cached_response = self.controller.update_cached_response(
                      request, response
                  )
  
                  if cached_response is not response:
                      from_cache = True
  
                  # We are done with the server response, read a
                  # possible response body (compliant servers will
                  # not return one, but we cannot be 100% sure) and
                  # release the connection back to the pool.
                  response.read(decode_content=False)
                  response.release_conn()
  
                  response = cached_response
  
              # We always cache the 301 responses
              elif response.status == 301:
                  self.controller.cache_response(request, response)
              else:
                  # Wrap the response file with a wrapper that will cache the
                  #   response when the stream has been consumed.
                  response._fp = CallbackFileWrapper(
                      response._fp,
                      functools.partial(
                          self.controller.cache_response, request, response
                      ),
                  )
                  if response.chunked:
                      super_update_chunk_length = response._update_chunk_length
  
                      def _update_chunk_length(self):
                          super_update_chunk_length()
                          if self.chunk_left == 0:
                              self._fp._close()
  
                      response._update_chunk_length = types.MethodType(
                          _update_chunk_length, response
                      )
  
          resp = super(CacheControlAdapter, self).build_response(request, response)
  
          # See if we should invalidate the cache.
          if request.method in self.invalidating_methods and resp.ok:
              cache_url = self.controller.cache_url(request.url)
              self.cache.delete(cache_url)
  
          # Give the request a from_cache attr to let people use it
          resp.from_cache = from_cache
  
          return resp
  
      def close(self):
          self.cache.close()
          super(CacheControlAdapter, self).close()
  
  