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−#!/usr/bin/env python
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−#
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−# Copyright 2007 Google Inc.
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−#
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−# Licensed under the Apache License, Version 2.0 (the "License");
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−# you may not use this file except in compliance with the License.
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−# You may obtain a copy of the License at
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−#
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−#     http://www.apache.org/licenses/LICENSE-2.0
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−#
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−# Unless required by applicable law or agreed to in writing, software
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−# distributed under the License is distributed on an "AS IS" BASIS,
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−# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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−# See the License for the specific language governing permissions and
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−# limitations under the License.
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−#
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−
+
−"""Base class for implementing RPC of API proxy stubs."""
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−
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−
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−
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−
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−
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−import sys
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−
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−
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−class RPC(object):
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−  """Base class for implementing RPC of API proxy stubs.
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−
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−  To implement a RPC to make real asynchronous API call:
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−    - Extend this class.
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−    - Override _MakeCallImpl and/or _WaitImpl to do a real asynchronous call.
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−  """
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−
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−  IDLE = 0
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−  RUNNING = 1
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−  FINISHING = 2
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−
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−  def __init__(self, package=None, call=None, request=None, response=None,
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−               callback=None, deadline=None, stub=None):
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−    """Constructor for the RPC object.
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−
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−    All arguments are optional, and simply set members on the class.
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−    These data members will be overriden by values passed to MakeCall.
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−
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−    Args:
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−      package: string, the package for the call
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−      call: string, the call within the package
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−      request: ProtocolMessage instance, appropriate for the arguments
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−      response: ProtocolMessage instance, appropriate for the response
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−      callback: callable, called when call is complete
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−      deadline: A double specifying the deadline for this call as the number of
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−                seconds from the current time. Ignored if non-positive.
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−      stub: APIProxyStub instance, used in default _WaitImpl to do real call
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−    """
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−    self.__exception = None
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−    self.__state = RPC.IDLE
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−    self.__traceback = None
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−
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−    self.package = package
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−    self.call = call
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−    self.request = request
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−    self.response = response
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−    self.callback = callback
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−    self.deadline = deadline
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−    self.stub = stub
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−
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−  def MakeCall(self, package=None, call=None, request=None, response=None,
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−               callback=None, deadline=None):
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−    """Makes an asynchronous (i.e. non-blocking) API call within the
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−    specified package for the specified call method.
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−
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−    It will call the _MakeRealCall to do the real job.
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−
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−    Args:
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−      Same as constructor; see __init__.
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−
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−    Raises:
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−      TypeError or AssertionError if an argument is of an invalid type.
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−      AssertionError or RuntimeError is an RPC is already in use.
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−    """
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−    self.callback = callback or self.callback
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−    self.package = package or self.package
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−    self.call = call or self.call
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−    self.request = request or self.request
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−    self.response = response or self.response
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−    self.deadline = deadline or self.deadline
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−
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−    assert self.__state is RPC.IDLE, ('RPC for %s.%s has already been started' %
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−                                      (self.package, self.call))
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−    assert self.callback is None or callable(self.callback)
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−    self._MakeCallImpl()
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−
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−  def Wait(self):
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−    """Waits on the API call associated with this RPC."""
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−    assert self.__state is not RPC.IDLE, ('RPC for %s.%s has not been started' %
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−                                          (self.package, self.call))
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−    rpc_completed = self._WaitImpl()
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−
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−    assert rpc_completed, ('RPC for %s.%s was not completed, and no other ' +
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−                           'exception was raised ' % (self.package, self.call))
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−
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−  def CheckSuccess(self):
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−    """If there was an exception, raise it now.
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−
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−    Raises:
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−      Exception of the API call or the callback, if any.
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−    """
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−    if self.exception and self.__traceback:
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−      raise self.exception.__class__, self.exception, self.__traceback
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−    elif self.exception:
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−      raise self.exception
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−
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−  @property
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−  def exception(self):
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−    return self.__exception
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−
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−  @property
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−  def state(self):
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−    return self.__state
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−
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−  def _MakeCallImpl(self):
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−    """Override this method to implement a real asynchronous call rpc."""
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−    self.__state = RPC.RUNNING
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−
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−  def _WaitImpl(self):
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−    """Override this method to implement a real asynchronous call rpc.
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−
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−    Returns:
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−      True if the async call was completed successfully.
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−    """
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−    try:
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−      try:
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−        self.stub.MakeSyncCall(self.package, self.call,
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−                               self.request, self.response)
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−      except Exception, e:
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−        self.__exception = e
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−    finally:
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−      self.__state = RPC.FINISHING
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−      self.__Callback()
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−
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−    return True
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−
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−  def __Callback(self):
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−    if self.callback:
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−      try:
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−        self.callback()
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−      except:
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−        exc_class, self.__exception, self.__traceback = sys.exc_info()
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−        self.__exception._appengine_apiproxy_rpc = self
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−        raise