rpc_service_method.h

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#ifndef GRPCXX_IMPL_RPC_SERVICE_METHOD_H
#define GRPCXX_IMPL_RPC_SERVICE_METHOD_H

#include <functional>
#include <map>
#include <memory>
#include <vector>

#include <grpc++/config.h>
#include <grpc++/impl/rpc_method.h>
#include <grpc++/status.h>
#include <grpc++/stream.h>

namespace grpc {
class ServerContext;
class StreamContextInterface;

// TODO(rocking): we might need to split this file into multiple ones.

// Base class for running an RPC handler.
class MethodHandler {
 public:
  virtual ~MethodHandler() {}
  struct HandlerParameter {
    HandlerParameter(Call* c, ServerContext* context,
                     const grpc::protobuf::Message* req,
                     grpc::protobuf::Message* resp)
        : call(c), server_context(context), request(req), response(resp) {}
    Call* call;
    ServerContext* server_context;
    const grpc::protobuf::Message* request;
    grpc::protobuf::Message* response;
  };
  virtual Status RunHandler(const HandlerParameter& param) = 0;
};

// A wrapper class of an application provided rpc method handler.
template <class ServiceType, class RequestType, class ResponseType>
class RpcMethodHandler : public MethodHandler {
 public:
  RpcMethodHandler(
      std::function<Status(ServiceType*, ServerContext*, const RequestType*,
                           ResponseType*)> func,
      ServiceType* service)
      : func_(func), service_(service) {}

  Status RunHandler(const HandlerParameter& param) GRPC_FINAL {
    // Invoke application function, cast proto messages to their actual types.
    return func_(service_, param.server_context,
                 dynamic_cast<const RequestType*>(param.request),
                 dynamic_cast<ResponseType*>(param.response));
  }

 private:
  // Application provided rpc handler function.
  std::function<Status(ServiceType*, ServerContext*, const RequestType*,
                       ResponseType*)> func_;
  // The class the above handler function lives in.
  ServiceType* service_;
};

// A wrapper class of an application provided client streaming handler.
template <class ServiceType, class RequestType, class ResponseType>
class ClientStreamingHandler : public MethodHandler {
 public:
  ClientStreamingHandler(
      std::function<Status(ServiceType*, ServerContext*,
                           ServerReader<RequestType>*, ResponseType*)> func,
      ServiceType* service)
      : func_(func), service_(service) {}

  Status RunHandler(const HandlerParameter& param) GRPC_FINAL {
    ServerReader<RequestType> reader(param.call, param.server_context);
    return func_(service_, param.server_context, &reader,
                 dynamic_cast<ResponseType*>(param.response));
  }

 private:
  std::function<Status(ServiceType*, ServerContext*, ServerReader<RequestType>*,
                       ResponseType*)> func_;
  ServiceType* service_;
};

// A wrapper class of an application provided server streaming handler.
template <class ServiceType, class RequestType, class ResponseType>
class ServerStreamingHandler : public MethodHandler {
 public:
  ServerStreamingHandler(
      std::function<Status(ServiceType*, ServerContext*, const RequestType*,
                           ServerWriter<ResponseType>*)> func,
      ServiceType* service)
      : func_(func), service_(service) {}

  Status RunHandler(const HandlerParameter& param) GRPC_FINAL {
    ServerWriter<ResponseType> writer(param.call, param.server_context);
    return func_(service_, param.server_context,
                 dynamic_cast<const RequestType*>(param.request), &writer);
  }

 private:
  std::function<Status(ServiceType*, ServerContext*, const RequestType*,
                       ServerWriter<ResponseType>*)> func_;
  ServiceType* service_;
};

// A wrapper class of an application provided bidi-streaming handler.
template <class ServiceType, class RequestType, class ResponseType>
class BidiStreamingHandler : public MethodHandler {
 public:
  BidiStreamingHandler(
      std::function<Status(ServiceType*, ServerContext*,
                           ServerReaderWriter<ResponseType, RequestType>*)>
          func,
      ServiceType* service)
      : func_(func), service_(service) {}

  Status RunHandler(const HandlerParameter& param) GRPC_FINAL {
    ServerReaderWriter<ResponseType, RequestType> stream(param.call,
                                                         param.server_context);
    return func_(service_, param.server_context, &stream);
  }

 private:
  std::function<Status(ServiceType*, ServerContext*,
                       ServerReaderWriter<ResponseType, RequestType>*)> func_;
  ServiceType* service_;
};

// Server side rpc method class
class RpcServiceMethod : public RpcMethod {
 public:
  // Takes ownership of the handler and two prototype objects.
  RpcServiceMethod(const char* name, RpcMethod::RpcType type,
                   MethodHandler* handler,
                   grpc::protobuf::Message* request_prototype,
                   grpc::protobuf::Message* response_prototype)
      : RpcMethod(name, type, nullptr),
        handler_(handler),
        request_prototype_(request_prototype),
        response_prototype_(response_prototype) {}

  MethodHandler* handler() { return handler_.get(); }

  grpc::protobuf::Message* AllocateRequestProto() {
    return request_prototype_->New();
  }
  grpc::protobuf::Message* AllocateResponseProto() {
    return response_prototype_->New();
  }

 private:
  std::unique_ptr<MethodHandler> handler_;
  std::unique_ptr<grpc::protobuf::Message> request_prototype_;
  std::unique_ptr<grpc::protobuf::Message> response_prototype_;
};

// This class contains all the method information for an rpc service. It is
// used for registering a service on a grpc server.
class RpcService {
 public:
  // Takes ownership.
  void AddMethod(RpcServiceMethod* method) { methods_.emplace_back(method); }

  RpcServiceMethod* GetMethod(int i) { return methods_[i].get(); }
  int GetMethodCount() const { return methods_.size(); }

 private:
  std::vector<std::unique_ptr<RpcServiceMethod>> methods_;
};

}  // namespace grpc

#endif  // GRPCXX_IMPL_RPC_SERVICE_METHOD_H