text: from __future__ import absolute_import
  
  try:
      from collections.abc import Mapping, MutableMapping
  except ImportError:
      from collections import Mapping, MutableMapping
  
  # Platform-specific: No threads available
  # TODO RLock with pyqt
  class RLock:
      def __enter__(self):
          pass
  
      def __exit__(self, exc_type, exc_value, traceback):
          pass
  
  
  from collections import OrderedDict
  from .exceptions import InvalidHeader
  from .packages.six import iterkeys, itervalues, PY3
  
  
  __all__ = ["RecentlyUsedContainer", "HTTPHeaderDict"]
  
  from PyQt5.QtCore import QObject
  _Null = QObject()
  
  
  class RecentlyUsedContainer(MutableMapping):
      """
      Provides a thread-safe dict-like container which maintains up to
      ``maxsize`` keys while throwing away the least-recently-used keys beyond
      ``maxsize``.
  
      :param maxsize:
          Maximum number of recent elements to retain.
  
      :param dispose_func:
          Every time an item is evicted from the container,
          ``dispose_func(value)`` is called.  Callback which will get called
      """
  
      ContainerCls = OrderedDict
  
      def __init__(self, maxsize=10, dispose_func=None):
          self._maxsize = maxsize
          self.dispose_func = dispose_func
  
          self._container = self.ContainerCls()
          self.lock = RLock()
  
      def __getitem__(self, key):
          # Re-insert the item, moving it to the end of the eviction line.
          with self.lock:
              item = self._container.pop(key)
              self._container[key] = item
              return item
  
      def __setitem__(self, key, value):
          evicted_value = _Null
          with self.lock:
              # Possibly evict the existing value of 'key'
              evicted_value = self._container.get(key, _Null)
              self._container[key] = value
  
              # If we didn't evict an existing value, we might have to evict the
              # least recently used item from the beginning of the container.
              if len(self._container) > self._maxsize:
                  _key, evicted_value = self._container.popitem(last=False)
  
          if self.dispose_func and evicted_value is not _Null:
              self.dispose_func(evicted_value)
  
      def __delitem__(self, key):
          with self.lock:
              value = self._container.pop(key)
  
          if self.dispose_func:
              self.dispose_func(value)
  
      def __len__(self):
          with self.lock:
              return len(self._container)
  
      def __iter__(self):
          raise NotImplementedError(
              "Iteration over this class is unlikely to be threadsafe."
          )
  
      def clear(self):
          with self.lock:
              # Copy pointers to all values, then wipe the mapping
              values = list(itervalues(self._container))
              self._container.clear()
  
          if self.dispose_func:
              for value in values:
                  self.dispose_func(value)
  
      def keys(self):
          with self.lock:
              return list(iterkeys(self._container))
  
  
  class HTTPHeaderDict(MutableMapping):
      """
      :param headers:
          An iterable of field-value pairs. Must not contain multiple field names
          when compared case-insensitively.
  
      :param kwargs:
          Additional field-value pairs to pass in to ``dict.update``.
  
      A ``dict`` like container for storing HTTP Headers.
  
      Field names are stored and compared case-insensitively in compliance with
      RFC 7230. Iteration provides the first case-sensitive key seen for each
      case-insensitive pair.
  
      Using ``__setitem__`` syntax overwrites fields that compare equal
      case-insensitively in order to maintain ``dict``'s api. For fields that
      compare equal, instead create a new ``HTTPHeaderDict`` and use ``.add``
      in a loop.
  
      If multiple fields that are equal case-insensitively are passed to the
      constructor or ``.update``, the behavior is undefined and some will be
      lost.
  
      >>> headers = HTTPHeaderDict()
      >>> headers.add('Set-Cookie', 'foo=bar')
      >>> headers.add('set-cookie', 'baz=quxx')
      >>> headers['content-length'] = '7'
      >>> headers['SET-cookie']
      'foo=bar, baz=quxx'
      >>> headers['Content-Length']
      '7'
      """
  
      def __init__(self, headers=None, **kwargs):
          super(HTTPHeaderDict, self).__init__()
          self._container = OrderedDict()
          if headers is not None:
              if isinstance(headers, HTTPHeaderDict):
                  self._copy_from(headers)
              else:
                  self.extend(headers)
          if kwargs:
              self.extend(kwargs)
  
      def __setitem__(self, key, val):
          self._container[key.lower()] = [key, val]
          return self._container[key.lower()]
  
      def __getitem__(self, key):
          val = self._container[key.lower()]
          return ", ".join(val[1:])
  
      def __delitem__(self, key):
          del self._container[key.lower()]
  
      def __contains__(self, key):
          return key.lower() in self._container
  
      def __eq__(self, other):
          if not isinstance(other, Mapping) and not hasattr(other, "keys"):
              return False
          if not isinstance(other, type(self)):
              other = type(self)(other)
          return dict((k.lower(), v) for k, v in self.itermerged()) == dict(
              (k.lower(), v) for k, v in other.itermerged()
          )
  
      def __ne__(self, other):
          return not self.__eq__(other)
  
      if not PY3:  # Python 2
          iterkeys = MutableMapping.iterkeys
          itervalues = MutableMapping.itervalues
  
      __marker = object()
  
      def __len__(self):
          return len(self._container)
  
      def __iter__(self):
          # Only provide the originally cased names
          for vals in self._container.values():
              yield vals[0]
  
      def pop(self, key, default=__marker):
          """D.pop(k[,d]) -> v, remove specified key and return the corresponding value.
            If key is not found, d is returned if given, otherwise KeyError is raised.
          """
          # Using the MutableMapping function directly fails due to the private marker.
          # Using ordinary dict.pop would expose the internal structures.
          # So let's reinvent the wheel.
          try:
              value = self[key]
          except KeyError:
              if default is self.__marker:
                  raise
              return default
          else:
              del self[key]
              return value
  
      def discard(self, key):
          try:
              del self[key]
          except KeyError:
              pass
  
      def add(self, key, val):
          """Adds a (name, value) pair, doesn't overwrite the value if it already
          exists.
  
          >>> headers = HTTPHeaderDict(foo='bar')
          >>> headers.add('Foo', 'baz')
          >>> headers['foo']
          'bar, baz'
          """
          key_lower = key.lower()
          new_vals = [key, val]
          # Keep the common case aka no item present as fast as possible
          vals = self._container.setdefault(key_lower, new_vals)
          if new_vals is not vals:
              vals.append(val)
  
      def extend(self, *args, **kwargs):
          """Generic import function for any type of header-like object.
          Adapted version of MutableMapping.update in order to insert items
          with self.add instead of self.__setitem__
          """
          if len(args) > 1:
              raise TypeError(
                  "extend() takes at most 1 positional "
                  "arguments ({0} given)".format(len(args))
              )
          other = args[0] if len(args) >= 1 else ()
  
          if isinstance(other, HTTPHeaderDict):
              for key, val in other.iteritems():
                  self.add(key, val)
          elif isinstance(other, Mapping):
              for key in other:
                  self.add(key, other[key])
          elif hasattr(other, "keys"):
              for key in other.keys():
                  self.add(key, other[key])
          else:
              for key, value in other:
                  self.add(key, value)
  
          for key, value in kwargs.items():
              self.add(key, value)
  
      def getlist(self, key, default=__marker):
          """Returns a list of all the values for the named field. Returns an
          empty list if the key doesn't exist."""
          try:
              vals = self._container[key.lower()]
          except KeyError:
              if default is self.__marker:
                  return []
              return default
          else:
              return vals[1:]
  
      # Backwards compatibility for httplib
      getheaders = getlist
      getallmatchingheaders = getlist
      iget = getlist
  
      # Backwards compatibility for http.cookiejar
      get_all = getlist
  
      def __repr__(self):
          return "%s(%s)" % (type(self).__name__, dict(self.itermerged()))
  
      def _copy_from(self, other):
          for key in other:
              val = other.getlist(key)
              if isinstance(val, list):
                  # Don't need to convert tuples
                  val = list(val)
              self._container[key.lower()] = [key] + val
  
      def copy(self):
          clone = type(self)()
          clone._copy_from(self)
          return clone
  
      def iteritems(self):
          """Iterate over all header lines, including duplicate ones."""
          for key in self:
              vals = self._container[key.lower()]
              for val in vals[1:]:
                  yield vals[0], val
  
      def itermerged(self):
          """Iterate over all headers, merging duplicate ones together."""
          for key in self:
              val = self._container[key.lower()]
              yield val[0], ", ".join(val[1:])
  
      def items(self):
          return list(self.iteritems())
  
      @classmethod
      def from_httplib(cls, message):  # Python 2
          """Read headers from a Python 2 httplib message object."""
          # python2.7 does not expose a proper API for exporting multiheaders
          # efficiently. This function re-reads raw lines from the message
          # object and extracts the multiheaders properly.
          obs_fold_continued_leaders = (" ", "\t")
          headers = []
  
          for line in message.headers:
              if line.startswith(obs_fold_continued_leaders):
                  if not headers:
                      # We received a header line that starts with OWS as described
                      # in RFC-7230 S3.2.4. This indicates a multiline header, but
                      # there exists no previous header to which we can attach it.
                      raise InvalidHeader(
                          "Header continuation with no previous header: %s" % line
                      )
                  else:
                      key, value = headers[-1]
                      headers[-1] = (key, value + " " + line.strip())
                      continue
  
              key, value = line.split(":", 1)
              headers.append((key, value.strip()))
  
          return cls(headers)
  