THUAI6/CAPI/cpp/grpc/include/google/protobuf/service.h

// Protocol Buffers - Google's data interchange format
// Copyright 2008 Google Inc.  All rights reserved.
// https://developers.google.com/protocol-buffers/
//
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//
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// Author: kenton@google.com (Kenton Varda)
//  Based on original Protocol Buffers design by
//  Sanjay Ghemawat, Jeff Dean, and others.
//
// DEPRECATED:  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.
//
//
// When you use the protocol compiler to compile a service definition, it
// generates two classes:  An abstract interface for the service (with
// methods matching the service definition) and a "stub" implementation.
// A stub is just a type-safe wrapper around an RpcChannel which emulates a
// local implementation of the service.
//
// For example, the service definition:
//   service MyService {
//     rpc Foo(MyRequest) returns(MyResponse);
//   }
// will generate abstract interface "MyService" and class "MyService::Stub".
// You could implement a MyService as follows:
//   class MyServiceImpl : public MyService {
//    public:
//     MyServiceImpl() {}
//     ~MyServiceImpl() {}
//
//     // implements MyService ---------------------------------------
//
//     void Foo(google::protobuf::RpcController* controller,
//              const MyRequest* request,
//              MyResponse* response,
//              Closure* done) {
//       // ... read request and fill in response ...
//       done->Run();
//     }
//   };
// You would then register an instance of MyServiceImpl with your RPC server
// implementation.  (How to do that depends on the implementation.)
//
// To call a remote MyServiceImpl, first you need an RpcChannel connected to it.
// How to construct a channel depends, again, on your RPC implementation.
// Here we use a hypothetical "MyRpcChannel" as an example:
//   MyRpcChannel channel("rpc:hostname:1234/myservice");
//   MyRpcController controller;
//   MyServiceImpl::Stub stub(&channel);
//   FooRequest request;
//   FooResponse response;
//
//   // ... fill in request ...
//
//   stub.Foo(&controller, request, &response, NewCallback(HandleResponse));
//
// On Thread-Safety:
//
// Different RPC implementations may make different guarantees about what
// threads they may run callbacks on, and what threads the application is
// allowed to use to call the RPC system.  Portable software should be ready
// for callbacks to be called on any thread, but should not try to call the
// RPC system from any thread except for the ones on which it received the
// callbacks.  Realistically, though, simple software will probably want to
// use a single-threaded RPC system while high-end software will want to
// use multiple threads.  RPC implementations should provide multiple
// choices.

#ifndef GOOGLE_PROTOBUF_SERVICE_H__
#define GOOGLE_PROTOBUF_SERVICE_H__

#include <string>
#include <google/protobuf/stubs/callback.h>
#include <google/protobuf/stubs/common.h>

#ifdef SWIG
#error "You cannot SWIG proto headers"
#endif

// Must be included last.
#include <google/protobuf/port_def.inc>

namespace google
{
    namespace protobuf
    {

        // Defined in this file.
        class Service;
        class RpcController;
        class RpcChannel;

        // Defined in other files.
        class Descriptor;         // descriptor.h
        class ServiceDescriptor;  // descriptor.h
        class MethodDescriptor;   // descriptor.h
        class Message;            // message.h

        // Abstract base interface for protocol-buffer-based RPC services.  Services
        // themselves are abstract interfaces (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 Reflection).
        class PROTOBUF_EXPORT Service
        {
        public:
            inline Service()
            {
            }
            virtual ~Service();

            // When constructing a stub, you may pass STUB_OWNS_CHANNEL as the second
            // parameter to the constructor to tell it to delete its RpcChannel when
            // destroyed.
            enum ChannelOwnership
            {
                STUB_OWNS_CHANNEL,
                STUB_DOESNT_OWN_CHANNEL
            };

            // Get the ServiceDescriptor describing this service and its methods.
            virtual const ServiceDescriptor* GetDescriptor() = 0;

            // Call a method of the service specified by MethodDescriptor.  This is
            // normally implemented as a simple switch() that calls the standard
            // definitions of the service's methods.
            //
            // Preconditions:
            // * method->service() == GetDescriptor()
            // * request and response are of the exact same classes as the objects
            //   returned by GetRequestPrototype(method) and
            //   GetResponsePrototype(method).
            // * After the call has started, the request must not be modified and the
            //   response must not be accessed at all until "done" is called.
            // * "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.  Server-side Service
            //   implementations are expected to accept whatever type of RpcController
            //   the server-side RPC implementation uses.
            //
            // 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 succeeded, "response" contains the response returned by
            //   the server.
            // * If the RPC failed, "response"'s contents are undefined.  The
            //   RpcController can be queried to determine if an error occurred and
            //   possibly to get more information about the error.
            virtual void CallMethod(const MethodDescriptor* method, RpcController* controller, const Message* request, Message* response, Closure* done) = 0;

            // CallMethod() requires that the request and response passed in are of a
            // particular subclass of Message.  GetRequestPrototype() and
            // GetResponsePrototype() get the default instances of these required types.
            // You can then call Message::New() on these instances to construct mutable
            // objects which you can then pass to CallMethod().
            //
            // Example:
            //   const MethodDescriptor* method =
            //     service->GetDescriptor()->FindMethodByName("Foo");
            //   Message* request  = stub->GetRequestPrototype (method)->New();
            //   Message* response = stub->GetResponsePrototype(method)->New();
            //   request->ParseFromString(input);
            //   service->CallMethod(method, *request, response, callback);
            virtual const Message& GetRequestPrototype(
                const MethodDescriptor* method
            ) const = 0;
            virtual const Message& GetResponsePrototype(
                const MethodDescriptor* method
            ) const = 0;

        private:
            GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(Service);
        };

        // 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).
        class PROTOBUF_EXPORT RpcController
        {
        public:
            inline RpcController()
            {
            }
            virtual ~RpcController();

            // Client-side methods ---------------------------------------------
            // These calls may be made from the client side only.  Their results
            // are undefined on the server side (may crash).

            // Resets the RpcController to its initial state so that it may be reused in
            // a new call.  Must not be called while an RPC is in progress.
            virtual void Reset() = 0;

            // 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.
            virtual bool Failed() const = 0;

            // If Failed() is true, returns a human-readable description of the error.
            virtual std::string ErrorText() const = 0;

            // 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.
            virtual void StartCancel() = 0;

            // Server-side methods ---------------------------------------------
            // These calls may be made from the server side only.  Their results
            // are undefined on the client side (may crash).

            // 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().
            virtual void SetFailed(const std::string& reason) = 0;

            // 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.
            virtual bool IsCanceled() const = 0;

            // 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.
            virtual void NotifyOnCancel(Closure* callback) = 0;

        private:
            GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(RpcController);
        };

        // 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 call an RpcChannel directly, but instead construct a stub Service
        // wrapping it.  Example:
        //   RpcChannel* channel = new MyRpcChannel("remotehost.example.com:1234");
        //   MyService* service = new MyService::Stub(channel);
        //   service->MyMethod(request, &response, callback);
        class PROTOBUF_EXPORT RpcChannel
        {
        public:
            inline RpcChannel()
            {
            }
            virtual ~RpcChannel();

            // 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 and response objects
            // need not be of any specific class as long as their descriptors are
            // method->input_type() and method->output_type().
            virtual void CallMethod(const MethodDescriptor* method, RpcController* controller, const Message* request, Message* response, Closure* done) = 0;

        private:
            GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(RpcChannel);
        };

    }  // namespace protobuf
}  // namespace google

#include <google/protobuf/port_undef.inc>

#endif  // GOOGLE_PROTOBUF_SERVICE_H__