path: root/contrib/libs/protobuf/src/google/protobuf/service.h

// Protocol Buffers - Google's data interchange format 
// Copyright 2008 Google Inc.  All rights reserved. 
// https://developers.google.com/protocol-buffers/ 
// 
// Redistribution and use in source and binary forms, with or without 
// modification, are permitted provided that the following conditions are 
// met: 
// 
//     * Redistributions of source code must retain the above copyright 
// notice, this list of conditions and the following disclaimer. 
//     * Redistributions in binary form must reproduce the above 
// copyright notice, this list of conditions and the following disclaimer 
// in the documentation and/or other materials provided with the 
// distribution. 
//     * Neither the name of Google Inc. nor the names of its 
// contributors may be used to endorse or promote products derived from 
// this software without specific prior written permission. 
// 
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 
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// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 
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// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 
 
// 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

#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 TProtoStringType 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 TProtoStringType& 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__