method_handler_impl.h

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#ifndef GRPCXX_IMPL_CODEGEN_METHOD_HANDLER_IMPL_H
#define GRPCXX_IMPL_CODEGEN_METHOD_HANDLER_IMPL_H

#include <grpc++/impl/codegen/core_codegen_interface.h>
#include <grpc++/impl/codegen/rpc_service_method.h>
#include <grpc++/impl/codegen/sync_stream.h>

namespace grpc {

// 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) {}

  void RunHandler(const HandlerParameter& param) final {
    RequestType req;
    Status status =
        SerializationTraits<RequestType>::Deserialize(param.request, &req);
    ResponseType rsp;
    if (status.ok()) {
      status = func_(service_, param.server_context, &req, &rsp);
    }

    GPR_CODEGEN_ASSERT(!param.server_context->sent_initial_metadata_);
    CallOpSet<CallOpSendInitialMetadata, CallOpSendMessage,
              CallOpServerSendStatus>
        ops;
    ops.SendInitialMetadata(param.server_context->initial_metadata_,
                            param.server_context->initial_metadata_flags());
    if (param.server_context->compression_level_set()) {
      ops.set_compression_level(param.server_context->compression_level());
    }
    if (status.ok()) {
      status = ops.SendMessage(rsp);
    }
    ops.ServerSendStatus(param.server_context->trailing_metadata_, status);
    param.call->PerformOps(&ops);
    param.call->cq()->Pluck(&ops);
  }

 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) {}

  void RunHandler(const HandlerParameter& param) final {
    ServerReader<RequestType> reader(param.call, param.server_context);
    ResponseType rsp;
    Status status = func_(service_, param.server_context, &reader, &rsp);

    GPR_CODEGEN_ASSERT(!param.server_context->sent_initial_metadata_);
    CallOpSet<CallOpSendInitialMetadata, CallOpSendMessage,
              CallOpServerSendStatus>
        ops;
    ops.SendInitialMetadata(param.server_context->initial_metadata_,
                            param.server_context->initial_metadata_flags());
    if (param.server_context->compression_level_set()) {
      ops.set_compression_level(param.server_context->compression_level());
    }
    if (status.ok()) {
      status = ops.SendMessage(rsp);
    }
    ops.ServerSendStatus(param.server_context->trailing_metadata_, status);
    param.call->PerformOps(&ops);
    param.call->cq()->Pluck(&ops);
  }

 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) {}

  void RunHandler(const HandlerParameter& param) final {
    RequestType req;
    Status status =
        SerializationTraits<RequestType>::Deserialize(param.request, &req);

    if (status.ok()) {
      ServerWriter<ResponseType> writer(param.call, param.server_context);
      status = func_(service_, param.server_context, &req, &writer);
    }

    CallOpSet<CallOpSendInitialMetadata, CallOpServerSendStatus> ops;
    if (!param.server_context->sent_initial_metadata_) {
      ops.SendInitialMetadata(param.server_context->initial_metadata_,
                              param.server_context->initial_metadata_flags());
      if (param.server_context->compression_level_set()) {
        ops.set_compression_level(param.server_context->compression_level());
      }
    }
    ops.ServerSendStatus(param.server_context->trailing_metadata_, status);
    param.call->PerformOps(&ops);
    param.call->cq()->Pluck(&ops);
  }

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

// A wrapper class of an application provided bidi-streaming handler.
// This also applies to server-streamed implementation of a unary method
// with the additional requirement that such methods must have done a
// write for status to be ok
// Since this is used by more than 1 class, the service is not passed in.
// Instead, it is expected to be an implicitly-captured argument of func
// (through bind or something along those lines)
template <class Streamer, bool WriteNeeded>
class TemplatedBidiStreamingHandler : public MethodHandler {
 public:
  TemplatedBidiStreamingHandler(
      std::function<Status(ServerContext*, Streamer*)> func)
      : func_(func), write_needed_(WriteNeeded) {}

  void RunHandler(const HandlerParameter& param) final {
    Streamer stream(param.call, param.server_context);
    Status status = func_(param.server_context, &stream);

    CallOpSet<CallOpSendInitialMetadata, CallOpServerSendStatus> ops;
    if (!param.server_context->sent_initial_metadata_) {
      ops.SendInitialMetadata(param.server_context->initial_metadata_,
                              param.server_context->initial_metadata_flags());
      if (param.server_context->compression_level_set()) {
        ops.set_compression_level(param.server_context->compression_level());
      }
      if (write_needed_ && status.ok()) {
        // If we needed a write but never did one, we need to mark the
        // status as a fail
        status = Status(StatusCode::INTERNAL,
                        "Service did not provide response message");
      }
    }
    ops.ServerSendStatus(param.server_context->trailing_metadata_, status);
    param.call->PerformOps(&ops);
    param.call->cq()->Pluck(&ops);
  }

 private:
  std::function<Status(ServerContext*, Streamer*)> func_;
  const bool write_needed_;
};

template <class ServiceType, class RequestType, class ResponseType>
class BidiStreamingHandler
    : public TemplatedBidiStreamingHandler<
          ServerReaderWriter<ResponseType, RequestType>, false> {
 public:
  BidiStreamingHandler(
      std::function<Status(ServiceType*, ServerContext*,
                           ServerReaderWriter<ResponseType, RequestType>*)>
          func,
      ServiceType* service)
      : TemplatedBidiStreamingHandler<
            ServerReaderWriter<ResponseType, RequestType>, false>(std::bind(
            func, service, std::placeholders::_1, std::placeholders::_2)) {}
};

template <class RequestType, class ResponseType>
class StreamedUnaryHandler
    : public TemplatedBidiStreamingHandler<
          ServerUnaryStreamer<RequestType, ResponseType>, true> {
 public:
  explicit StreamedUnaryHandler(
      std::function<Status(ServerContext*,
                           ServerUnaryStreamer<RequestType, ResponseType>*)>
          func)
      : TemplatedBidiStreamingHandler<
            ServerUnaryStreamer<RequestType, ResponseType>, true>(func) {}
};

template <class RequestType, class ResponseType>
class SplitServerStreamingHandler
    : public TemplatedBidiStreamingHandler<
          ServerSplitStreamer<RequestType, ResponseType>, false> {
 public:
  explicit SplitServerStreamingHandler(
      std::function<Status(ServerContext*,
                           ServerSplitStreamer<RequestType, ResponseType>*)>
          func)
      : TemplatedBidiStreamingHandler<
            ServerSplitStreamer<RequestType, ResponseType>, false>(func) {}
};

// Handle unknown method by returning UNIMPLEMENTED error.
class UnknownMethodHandler : public MethodHandler {
 public:
  template <class T>
  static void FillOps(ServerContext* context, T* ops) {
    Status status(StatusCode::UNIMPLEMENTED, "");
    if (!context->sent_initial_metadata_) {
      ops->SendInitialMetadata(context->initial_metadata_,
                               context->initial_metadata_flags());
      if (context->compression_level_set()) {
        ops->set_compression_level(context->compression_level());
      }
      context->sent_initial_metadata_ = true;
    }
    ops->ServerSendStatus(context->trailing_metadata_, status);
  }

  void RunHandler(const HandlerParameter& param) final {
    CallOpSet<CallOpSendInitialMetadata, CallOpServerSendStatus> ops;
    FillOps(param.server_context, &ops);
    param.call->PerformOps(&ops);
    param.call->cq()->Pluck(&ops);
  }
};

}  // namespace grpc

#endif  // GRPCXX_IMPL_CODEGEN_METHOD_HANDLER_IMPL_H