1# Protocol Buffers - Google's data interchange format 
    2# Copyright 2008 Google Inc.  All rights reserved. 
    3# 
    4# Use of this source code is governed by a BSD-style 
    5# license that can be found in the LICENSE file or at 
    6# https://developers.google.com/open-source/licenses/bsd 
    7 
    8"""Contains _ExtensionDict class to represent extensions. 
    9""" 
    10 
    11from google.protobuf.internal import type_checkers 
    12from google.protobuf.descriptor import FieldDescriptor 
    13 
    14 
    15def _VerifyExtensionHandle(message, extension_handle): 
    16  """Verify that the given extension handle is valid.""" 
    17 
    18  if not isinstance(extension_handle, FieldDescriptor): 
    19    raise KeyError('HasExtension() expects an extension handle, got: %s' % 
    20                   extension_handle) 
    21 
    22  if not extension_handle.is_extension: 
    23    raise KeyError('"%s" is not an extension.' % extension_handle.full_name) 
    24 
    25  if not extension_handle.containing_type: 
    26    raise KeyError('"%s" is missing a containing_type.' 
    27                   % extension_handle.full_name) 
    28 
    29  if extension_handle.containing_type is not message.DESCRIPTOR: 
    30    raise KeyError('Extension "%s" extends message type "%s", but this ' 
    31                   'message is of type "%s".' % 
    32                   (extension_handle.full_name, 
    33                    extension_handle.containing_type.full_name, 
    34                    message.DESCRIPTOR.full_name)) 
    35 
    36 
    37# TODO: Unify error handling of "unknown extension" crap. 
    38# TODO: Support iteritems()-style iteration over all 
    39# extensions with the "has" bits turned on? 
    40class _ExtensionDict(object): 
    41 
    42  """Dict-like container for Extension fields on proto instances. 
    43 
    44  Note that in all cases we expect extension handles to be 
    45  FieldDescriptors. 
    46  """ 
    47 
    48  def __init__(self, extended_message): 
    49    """ 
    50    Args: 
    51      extended_message: Message instance for which we are the Extensions dict. 
    52    """ 
    53    self._extended_message = extended_message 
    54 
    55  def __getitem__(self, extension_handle): 
    56    """Returns the current value of the given extension handle.""" 
    57 
    58    _VerifyExtensionHandle(self._extended_message, extension_handle) 
    59 
    60    result = self._extended_message._fields.get(extension_handle) 
    61    if result is not None: 
    62      return result 
    63 
    64    if extension_handle.is_repeated: 
    65      result = extension_handle._default_constructor(self._extended_message) 
    66    elif extension_handle.cpp_type == FieldDescriptor.CPPTYPE_MESSAGE: 
    67      message_type = extension_handle.message_type 
    68      if not hasattr(message_type, '_concrete_class'): 
    69        # pylint: disable=g-import-not-at-top 
    70        from google.protobuf import message_factory 
    71        message_factory.GetMessageClass(message_type) 
    72      if not hasattr(extension_handle.message_type, '_concrete_class'): 
    73        from google.protobuf import message_factory 
    74        message_factory.GetMessageClass(extension_handle.message_type) 
    75      result = extension_handle.message_type._concrete_class() 
    76      try: 
    77        result._SetListener(self._extended_message._listener_for_children) 
    78      except ReferenceError: 
    79        pass 
    80    else: 
    81      # Singular scalar -- just return the default without inserting into the 
    82      # dict. 
    83      return extension_handle.default_value 
    84 
    85    # Atomically check if another thread has preempted us and, if not, swap 
    86    # in the new object we just created.  If someone has preempted us, we 
    87    # take that object and discard ours. 
    88    # WARNING:  We are relying on setdefault() being atomic.  This is true 
    89    #   in CPython but we haven't investigated others.  This warning appears 
    90    #   in several other locations in this file. 
    91    result = self._extended_message._fields.setdefault( 
    92        extension_handle, result) 
    93 
    94    return result 
    95 
    96  def __eq__(self, other): 
    97    if not isinstance(other, self.__class__): 
    98      return False 
    99 
    100    my_fields = self._extended_message.ListFields() 
    101    other_fields = other._extended_message.ListFields() 
    102 
    103    # Get rid of non-extension fields. 
    104    my_fields = [field for field in my_fields if field.is_extension] 
    105    other_fields = [field for field in other_fields if field.is_extension] 
    106 
    107    return my_fields == other_fields 
    108 
    109  def __ne__(self, other): 
    110    return not self == other 
    111 
    112  def __len__(self): 
    113    fields = self._extended_message.ListFields() 
    114    # Get rid of non-extension fields. 
    115    extension_fields = [field for field in fields if field[0].is_extension] 
    116    return len(extension_fields) 
    117 
    118  def __hash__(self): 
    119    raise TypeError('unhashable object') 
    120 
    121  # Note that this is only meaningful for non-repeated, scalar extension 
    122  # fields.  Note also that we may have to call _Modified() when we do 
    123  # successfully set a field this way, to set any necessary "has" bits in the 
    124  # ancestors of the extended message. 
    125  def __setitem__(self, extension_handle, value): 
    126    """If extension_handle specifies a non-repeated, scalar extension 
    127    field, sets the value of that field. 
    128    """ 
    129 
    130    _VerifyExtensionHandle(self._extended_message, extension_handle) 
    131 
    132    if (extension_handle.is_repeated or 
    133        extension_handle.cpp_type == FieldDescriptor.CPPTYPE_MESSAGE): 
    134      raise TypeError( 
    135          'Cannot assign to extension "%s" because it is a repeated or ' 
    136          'composite type.' % extension_handle.full_name) 
    137 
    138    # It's slightly wasteful to lookup the type checker each time, 
    139    # but we expect this to be a vanishingly uncommon case anyway. 
    140    type_checker = type_checkers.GetTypeChecker(extension_handle) 
    141    # pylint: disable=protected-access 
    142    self._extended_message._fields[extension_handle] = ( 
    143        type_checker.CheckValue(value)) 
    144    self._extended_message._Modified() 
    145 
    146  def __delitem__(self, extension_handle): 
    147    self._extended_message.ClearExtension(extension_handle) 
    148 
    149  def _FindExtensionByName(self, name): 
    150    """Tries to find a known extension with the specified name. 
    151 
    152    Args: 
    153      name: Extension full name. 
    154 
    155    Returns: 
    156      Extension field descriptor. 
    157    """ 
    158    descriptor = self._extended_message.DESCRIPTOR 
    159    extensions = descriptor.file.pool._extensions_by_name[descriptor] 
    160    return extensions.get(name, None) 
    161 
    162  def _FindExtensionByNumber(self, number): 
    163    """Tries to find a known extension with the field number. 
    164 
    165    Args: 
    166      number: Extension field number. 
    167 
    168    Returns: 
    169      Extension field descriptor. 
    170    """ 
    171    descriptor = self._extended_message.DESCRIPTOR 
    172    extensions = descriptor.file.pool._extensions_by_number[descriptor] 
    173    return extensions.get(number, None) 
    174 
    175  def __iter__(self): 
    176    # Return a generator over the populated extension fields 
    177    return (f[0] for f in self._extended_message.ListFields() 
    178            if f[0].is_extension) 
    179 
    180  def __contains__(self, extension_handle): 
    181    _VerifyExtensionHandle(self._extended_message, extension_handle) 
    182 
    183    if extension_handle not in self._extended_message._fields: 
    184      return False 
    185 
    186    if extension_handle.is_repeated: 
    187      return bool(self._extended_message._fields.get(extension_handle)) 
    188 
    189    if extension_handle.cpp_type == FieldDescriptor.CPPTYPE_MESSAGE: 
    190      value = self._extended_message._fields.get(extension_handle) 
    191      # pylint: disable=protected-access 
    192      return value is not None and value._is_present_in_parent 
    193 
    194    return True