text: # Copyright 2015-present MongoDB, Inc.
  #
  # Licensed under the Apache License, Version 2.0 (the "License");
  # you may not use this file except in compliance with the License.
  # You may obtain a copy of the License at
  #
  # http://www.apache.org/licenses/LICENSE-2.0
  #
  # Unless required by applicable law or agreed to in writing, software
  # distributed under the License is distributed on an "AS IS" BASIS,
  # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  # See the License for the specific language governing permissions and
  # limitations under the License.
  
  """Tools for representing raw BSON documents.
  """
  
  import collections
  
  from bson import _UNPACK_INT, _iterate_elements
  from bson.py3compat import iteritems
  from bson.codec_options import (
      DEFAULT_CODEC_OPTIONS as DEFAULT, _RAW_BSON_DOCUMENT_MARKER)
  from bson.errors import InvalidBSON
  
  
  class RawBSONDocument(collections.Mapping):
      """Representation for a MongoDB document that provides access to the raw
      BSON bytes that compose it.
  
      Only when a field is accessed or modified within the document does
      RawBSONDocument decode its bytes.
      """
  
      __slots__ = ('__raw', '__inflated_doc', '__codec_options')
      _type_marker = _RAW_BSON_DOCUMENT_MARKER
  
      def __init__(self, bson_bytes, codec_options=None):
          """Create a new :class:`RawBSONDocument`.
  
          :Parameters:
            - `bson_bytes`: the BSON bytes that compose this document
            - `codec_options` (optional): An instance of
              :class:`~bson.codec_options.CodecOptions`.
  
          .. versionchanged:: 3.5
            If a :class:`~bson.codec_options.CodecOptions` is passed in, its
            `document_class` must be :class:`RawBSONDocument`.
          """
          self.__raw = bson_bytes
          self.__inflated_doc = None
          # Can't default codec_options to DEFAULT_RAW_BSON_OPTIONS in signature,
          # it refers to this class RawBSONDocument.
          if codec_options is None:
              codec_options = DEFAULT_RAW_BSON_OPTIONS
          elif codec_options.document_class is not RawBSONDocument:
              raise TypeError(
                  "RawBSONDocument cannot use CodecOptions with document "
                  "class %s" % (codec_options.document_class, ))
          self.__codec_options = codec_options
  
      @property
      def raw(self):
          """The raw BSON bytes composing this document."""
          return self.__raw
  
      def items(self):
          """Lazily decode and iterate elements in this document."""
          return iteritems(self.__inflated)
  
      @property
      def __inflated(self):
          if self.__inflated_doc is None:
              # We already validated the object's size when this document was
              # created, so no need to do that again. We still need to check the
              # size of all the elements and compare to the document size.
              object_size = _UNPACK_INT(self.__raw[:4])[0] - 1
              position = 0
              self.__inflated_doc = {}
              for key, value, position in _iterate_elements(
                      self.__raw, 4, object_size, self.__codec_options):
                  self.__inflated_doc[key] = value
              if position != object_size:
                  raise InvalidBSON('bad object or element length')
          return self.__inflated_doc
  
      def __getitem__(self, item):
          return self.__inflated[item]
  
      def __iter__(self):
          return iter(self.__inflated)
  
      def __len__(self):
          return len(self.__inflated)
  
      def __eq__(self, other):
          if isinstance(other, RawBSONDocument):
              return self.__raw == other.raw
          return NotImplemented
  
      def __repr__(self):
          return ("RawBSONDocument(%r, codec_options=%r)"
                  % (self.raw, self.__codec_options))
  
  
  DEFAULT_RAW_BSON_OPTIONS = DEFAULT.with_options(document_class=RawBSONDocument)
  