# Protocol Buffers - Google's data interchange format
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"""Provides DescriptorPool to use as a container for proto2 descriptors.

The DescriptorPool is used in conjection with a DescriptorDatabase to maintain
a collection of protocol buffer descriptors for use when dynamically creating
message types at runtime.

For most applications protocol buffers should be used via modules generated by
the protocol buffer compiler tool. This should only be used when the type of
protocol buffers used in an application or library cannot be predetermined.

Below is a straightforward example on how to use this class:

  pool = DescriptorPool()
  file_descriptor_protos = [ ... ]
  for file_descriptor_proto in file_descriptor_protos:
    pool.Add(file_descriptor_proto)
  my_message_descriptor = pool.FindMessageTypeByName('some.package.MessageType')

The message descriptor can be used in conjunction with the message_factory
module in order to create a protocol buffer class that can be encoded and
decoded.

If you want to get a Python class for the specified proto, use the
helper functions inside google.protobuf.message_factory
directly instead of this class.
"""

__author__ = 'matthewtoia@google.com (Matt Toia)'

import collections

from google.protobuf import descriptor
from google.protobuf import descriptor_database
from google.protobuf import text_encoding


_USE_C_DESCRIPTORS = descriptor._USE_C_DESCRIPTORS  # pylint: disable=protected-access


def _NormalizeFullyQualifiedName(name):
  """Remove leading period from fully-qualified type name.

  Due to b/13860351 in descriptor_database.py, types in the root namespace are
  generated with a leading period. This function removes that prefix.

  Args:
    name: A str, the fully-qualified symbol name.

  Returns:
    A str, the normalized fully-qualified symbol name.
  """
  return name.lstrip('.')


def _OptionsOrNone(descriptor_proto):
  """Returns the value of the field `options`, or None if it is not set."""
  if descriptor_proto.HasField('options'):
    return descriptor_proto.options
  else:
    return None


def _IsMessageSetExtension(field):
  return (field.is_extension and
          field.containing_type.has_options and
          field.containing_type.GetOptions().message_set_wire_format and
          field.type == descriptor.FieldDescriptor.TYPE_MESSAGE and
          field.label == descriptor.FieldDescriptor.LABEL_OPTIONAL)


class DescriptorPool(object):
  """A collection of protobufs dynamically constructed by descriptor protos."""

  if _USE_C_DESCRIPTORS:

    def __new__(cls, descriptor_db=None):
      # pylint: disable=protected-access
      return descriptor._message.DescriptorPool(descriptor_db)

  def __init__(self, descriptor_db=None):
    """Initializes a Pool of proto buffs.

    The descriptor_db argument to the constructor is provided to allow
    specialized file descriptor proto lookup code to be triggered on demand. An
    example would be an implementation which will read and compile a file
    specified in a call to FindFileByName() and not require the call to Add()
    at all. Results from this database will be cached internally here as well.

    Args:
      descriptor_db: A secondary source of file descriptors.
    """

    self._internal_db = descriptor_database.DescriptorDatabase()
    self._descriptor_db = descriptor_db
    self._descriptors = {}
    self._enum_descriptors = {}
    self._service_descriptors = {}
    self._file_descriptors = {}
    self._toplevel_extensions = {}