text: # Protocol Buffers - Google's data interchange format
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  """DEPRECATED:  Declares the RPC service interfaces.
  
  This module declares the abstract interfaces underlying proto2 RPC
  services.  These are intended to be independent of any particular RPC
  implementation, so that proto2 services can be used on top of a variety
  of implementations.  Starting with version 2.3.0, RPC implementations should
  not try to build on these, but should instead provide code generator plugins
  which generate code specific to the particular RPC implementation.  This way
  the generated code can be more appropriate for the implementation in use
  and can avoid unnecessary layers of indirection.
  """
  
  __author__ = 'petar@google.com (Petar Petrov)'
  
  
  class RpcException(Exception):
    """Exception raised on failed blocking RPC method call."""
    pass
  
  
  class Service(object):
  
    """Abstract base interface for protocol-buffer-based RPC services.
  
    Services themselves are abstract classes (implemented either by servers or as
    stubs), but they subclass this base interface. The methods of this
    interface can be used to call the methods of the service without knowing
    its exact type at compile time (analogous to the Message interface).
    """
  
    def GetDescriptor():
      """Retrieves this service's descriptor."""
      raise NotImplementedError
  
    def CallMethod(self, method_descriptor, rpc_controller,
                   request, done):
      """Calls a method of the service specified by method_descriptor.
  
      If "done" is None then the call is blocking and the response
      message will be returned directly.  Otherwise the call is asynchronous
      and "done" will later be called with the response value.
  
      In the blocking case, RpcException will be raised on error.
  
      Preconditions:
  
      * method_descriptor.service == GetDescriptor
      * request is of the exact same classes as returned by
        GetRequestClass(method).
      * After the call has started, the request must not be modified.
      * "rpc_controller" is of the correct type for the RPC implementation being
        used by this Service.  For stubs, the "correct type" depends on the
        RpcChannel which the stub is using.
  
      Postconditions:
  
      * "done" will be called when the method is complete.  This may be
        before CallMethod() returns or it may be at some point in the future.
      * If the RPC failed, the response value passed to "done" will be None.
        Further details about the failure can be found by querying the
        RpcController.
      """
      raise NotImplementedError
  
    def GetRequestClass(self, method_descriptor):
      """Returns the class of the request message for the specified method.
  
      CallMethod() requires that the request is of a particular subclass of
      Message. GetRequestClass() gets the default instance of this required
      type.
  
      Example:
        method = service.GetDescriptor().FindMethodByName("Foo")
        request = stub.GetRequestClass(method)()
        request.ParseFromString(input)
        service.CallMethod(method, request, callback)
      """
      raise NotImplementedError
  
    def GetResponseClass(self, method_descriptor):
      """Returns the class of the response message for the specified method.
  
      This method isn't really needed, as the RpcChannel's CallMethod constructs
      the response protocol message. It's provided anyway in case it is useful
      for the caller to know the response type in advance.
      """
      raise NotImplementedError
  
  
  class RpcController(object):
  
    """An RpcController mediates a single method call.
  
    The primary purpose of the controller is to provide a way to manipulate
    settings specific to the RPC implementation and to find out about RPC-level
    errors. The methods provided by the RpcController interface are intended
    to be a "least common denominator" set of features which we expect all
    implementations to support.  Specific implementations may provide more
    advanced features (e.g. deadline propagation).
    """
  
    # Client-side methods below
  
    def Reset(self):
      """Resets the RpcController to its initial state.
  
      After the RpcController has been reset, it may be reused in
      a new call. Must not be called while an RPC is in progress.
      """
      raise NotImplementedError
  
    def Failed(self):
      """Returns true if the call failed.
  
      After a call has finished, returns true if the call failed.  The possible
      reasons for failure depend on the RPC implementation.  Failed() must not
      be called before a call has finished.  If Failed() returns true, the
      contents of the response message are undefined.
      """
      raise NotImplementedError
  
    def ErrorText(self):
      """If Failed is true, returns a human-readable description of the error."""
      raise NotImplementedError
  
    def StartCancel(self):
      """Initiate cancellation.
  
      Advises the RPC system that the caller desires that the RPC call be
      canceled.  The RPC system may cancel it immediately, may wait awhile and
      then cancel it, or may not even cancel the call at all.  If the call is
      canceled, the "done" callback will still be called and the RpcController
      will indicate that the call failed at that time.
      """
      raise NotImplementedError
  
    # Server-side methods below
  
    def SetFailed(self, reason):
      """Sets a failure reason.
  
      Causes Failed() to return true on the client side.  "reason" will be
      incorporated into the message returned by ErrorText().  If you find
      you need to return machine-readable information about failures, you
      should incorporate it into your response protocol buffer and should
      NOT call SetFailed().
      """
      raise NotImplementedError
  
    def IsCanceled(self):
      """Checks if the client cancelled the RPC.
  
      If true, indicates that the client canceled the RPC, so the server may
      as well give up on replying to it.  The server should still call the
      final "done" callback.
      """
      raise NotImplementedError
  
    def NotifyOnCancel(self, callback):
      """Sets a callback to invoke on cancel.
  
      Asks that the given callback be called when the RPC is canceled.  The
      callback will always be called exactly once.  If the RPC completes without
      being canceled, the callback will be called after completion.  If the RPC
      has already been canceled when NotifyOnCancel() is called, the callback
      will be called immediately.
  
      NotifyOnCancel() must be called no more than once per request.
      """
      raise NotImplementedError
  
  
  class RpcChannel(object):
  
    """Abstract interface for an RPC channel.
  
    An RpcChannel represents a communication line to a service which can be used
    to call that service's methods.  The service may be running on another
    machine. Normally, you should not use an RpcChannel directly, but instead
    construct a stub {@link Service} wrapping it.  Example:
  
    Example:
      RpcChannel channel = rpcImpl.Channel("remotehost.example.com:1234")
      RpcController controller = rpcImpl.Controller()
      MyService service = MyService_Stub(channel)
      service.MyMethod(controller, request, callback)
    """
  
    def CallMethod(self, method_descriptor, rpc_controller,
                   request, response_class, done):
      """Calls the method identified by the descriptor.
  
      Call the given method of the remote service.  The signature of this
      procedure looks the same as Service.CallMethod(), but the requirements
      are less strict in one important way:  the request object doesn't have to
      be of any specific class as long as its descriptor is method.input_type.
      """
      raise NotImplementedError
  