protobuf/internal/containers.py

# Protocol Buffers - Google's data interchange format
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# http://code.google.com/p/protobuf/
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"""Contains container classes to represent different protocol buffer types.

This file defines container classes which represent categories of protocol
buffer field types which need extra maintenance. Currently these categories
are:
  - Repeated scalar fields - These are all repeated fields which aren't
    composite (e.g. they are of simple types like int32, string, etc).
  - Repeated composite fields - Repeated fields which are composite. This
    includes groups and nested messages.
"""

__author__ = 'petar@google.com (Petar Petrov)'


class BaseContainer(object):

  """Base container class."""

  # Minimizes memory usage and disallows assignment to other attributes.
  __slots__ = ['_message_listener', '_values']

  def __init__(self, message_listener):
    """
    Args:
      message_listener: A MessageListener implementation.
        The RepeatedScalarFieldContainer will call this object's
        Modified() method when it is modified.
    """
    self._message_listener = message_listener
    self._values = []

  def __getitem__(self, key):
    """Retrieves item by the specified key."""
    return self._values[key]

  def __len__(self):
    """Returns the number of elements in the container."""
    return len(self._values)

  def __ne__(self, other):
    """Checks if another instance isn't equal to this one."""
    # The concrete classes should define __eq__.
    return not self == other

  def __hash__(self):
    raise TypeError('unhashable object')

  def __repr__(self):
    return repr(self._values)

  def sort(self, *args, **kwargs):
    # Continue to support the old sort_function keyword argument.
    # This is expected to be a rare occurrence, so use LBYL to avoid
    # the overhead of actually catching KeyError.
    if 'sort_function' in kwargs:
      kwargs['cmp'] = kwargs.pop('sort_function')
    self._values.sort(*args, **kwargs)


class RepeatedScalarFieldContainer(BaseContainer):

  """Simple, type-checked, list-like container for holding repeated scalars."""

  # Disallows assignment to other attributes.
  __slots__ = ['_type_checker']

  def __init__(self, message_listener, type_checker):
    """
    Args:
      message_listener: A MessageListener implementation.
        The RepeatedScalarFieldContainer will call this object's
        Modified() method when it is modified.
      type_checker: A type_checkers.ValueChecker instance to run on elements
        inserted into this container.
    """
    super(RepeatedScalarFieldContainer, self).__init__(message_listener)
    self._type_checker = type_checker

  def append(self, value):
    """Appends an item to the list. Similar to list.append()."""
    self._type_checker.CheckValue(value)
    self._values.append(value)
    if not self._message_listener.dirty:
      self._message_listener.Modified()

  def insert(self, key, value):
    """Inserts the item at the specified position. Similar to list.insert()."""
    self._type_checker.CheckValue(value)
    self._values.insert(key, value)
    if not self._message_listener.dirty:
      self._message_listener.Modified()

  def extend(self, elem_seq):
    """Extends by appending the given sequence. Similar to list.extend()."""
    if not elem_seq:
      return

    new_values = []
    for elem in elem_seq:
      self._type_checker.CheckValue(elem)
      new_values.append(elem)
    self._values.extend(new_values)
    self._message_listener.Modified()

  def MergeFrom(self, other):
    """Appends the contents of another repeated field of the same type to this
    one. We do not check the types of the individual fields.
    """
    self._values.extend(other._values)
    self._message_listener.Modified()

  def remove(self, elem):
    """Removes an item from the list. Similar to list.remove()."""
    self._values.remove(elem)
    self._message_listener.Modified()

  def __setitem__(self, key, value):
    """Sets the item on the specified position."""
    self._type_checker.CheckValue(value)
    self._values[key] = value
    self._message_listener.Modified()

  def __getslice__(self, start, stop):
    """Retrieves the subset of items from between the specified indices."""
    return self._values[start:stop]

  def __setslice__(self, start, stop, values):
    """Sets the subset of items from between the specified indices."""
    new_values = []
    for value in values:
      self._type_checker.CheckValue(value)
      new_values.append(value)
    self._values[start:stop] = new_values
    self._message_listener.Modified()

  def __delitem__(self, key):
    """Deletes the item at the specified position."""
    del self._values[key]
    self._message_listener.Modified()

  def __delslice__(self, start, stop):
    """Deletes the subset of items from between the specified indices."""
    del self._values[start:stop]
    self._message_listener.Modified()

  def __eq__(self, other):
    """Compares the current instance with another one."""
    if self is other:
      return True
    # Special case for the same type which should be common and fast.
    if isinstance(other, self.__class__):
      return other._values == self._values
    # We are presumably comparing against some other sequence type.
    return other == self._values


class RepeatedCompositeFieldContainer(BaseContainer):

  """Simple, list-like container for holding repeated composite fields."""

  # Disallows assignment to other attributes.
  __slots__ = ['_message_descriptor']

  def __init__(self, message_listener, message_descriptor):
    """
    Note that we pass in a descriptor instead of the generated directly,
    since at the time we construct a _RepeatedCompositeFieldContainer we
    haven't yet necessarily initialized the type that will be contained in the
    container.

    Args:
      message_listener: A MessageListener implementation.
        The RepeatedCompositeFieldContainer will call this object's
        Modified() method when it is modified.
      message_descriptor: A Descriptor instance describing the protocol type
        that should be present in this container.  We'll use the
        _concrete_class field of this descriptor when the client calls add().
    """
    super(RepeatedCompositeFieldContainer, self).__init__(message_listener)
    self._message_descriptor = message_descriptor

  def add(self, **kwargs):
    """Adds a new element at the end of the list and returns it. Keyword
    arguments may be used to initialize the element.
    """
    new_element = self._message_descriptor._concrete_class(**kwargs)
    new_element._SetListener(self._message_listener)
    self._values.append(new_element)
    if not self._message_listener.dirty:
      self._message_listener.Modified()
    return new_element

  def extend(self, elem_seq):
    """Extends by appending the given sequence of elements of the same type
    as this one, copying each individual message.
    """
    message_class = self._message_descriptor._concrete_class
    listener = self._message_listener
    values = self._values
    for message in elem_seq:
      new_element = message_class()
      new_element._SetListener(listener)
      new_element.MergeFrom(message)
      values.append(new_element)
    listener.Modified()

  def MergeFrom(self, other):
    """Appends the contents of another repeated field of the same type to this
    one, copying each individual message.
    """
    self.extend(other._values)

  def remove(self, elem):
    """Removes an item from the list. Similar to list.remove()."""
    self._values.remove(elem)
    self._message_listener.Modified()

  def __getslice__(self, start, stop):
    """Retrieves the subset of items from between the specified indices."""
    return self._values[start:stop]

  def __delitem__(self, key):
    """Deletes the item at the specified position."""
    del self._values[key]
    self._message_listener.Modified()

  def __delslice__(self, start, stop):
    """Deletes the subset of items from between the specified indices."""
    del self._values[start:stop]
    self._message_listener.Modified()

  def __eq__(self, other):
    """Compares the current instance with another one."""
    if self is other:
      return True
    if not isinstance(other, self.__class__):
      raise TypeError('Can only compare repeated composite fields against '
                      'other repeated composite fields.')
    return self._values == other._values