method_handler.h

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/*
 *
 * Copyright 2015 gRPC authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 */
 
#ifndef GRPCPP_IMPL_CODEGEN_METHOD_HANDLER_H
#define GRPCPP_IMPL_CODEGEN_METHOD_HANDLER_H
 
#include <grpcpp/impl/codegen/byte_buffer.h>
#include <grpcpp/impl/codegen/core_codegen_interface.h>
#include <grpcpp/impl/codegen/rpc_service_method.h>
#include <grpcpp/impl/codegen/sync_stream.h>
 
namespace grpc {
 
namespace internal {
 
// Invoke the method handler, fill in the status, and
// return whether or not we finished safely (without an exception).
// Note that exception handling is 0-cost in most compiler/library
// implementations (except when an exception is actually thrown),
// so this process doesn't require additional overhead in the common case.
// Additionally, we don't need to return if we caught an exception or not;
// the handling is the same in either case.
template <class Callable>
::grpc::Status CatchingFunctionHandler(Callable&& handler) {
#if GRPC_ALLOW_EXCEPTIONS
  try {
    return handler();
  } catch (...) {
    return ::grpc::Status(::grpc::StatusCode::UNKNOWN,
                          "Unexpected error in RPC handling");
  }
#else   // GRPC_ALLOW_EXCEPTIONS
  return handler();
#endif  // GRPC_ALLOW_EXCEPTIONS
}
 
template <class ServiceType, class RequestType, class ResponseType>
class RpcMethodHandler : public ::grpc::internal::MethodHandler {
 public:
  RpcMethodHandler(
      std::function<::grpc::Status(ServiceType*, ::grpc::ServerContext*,
                                   const RequestType*, ResponseType*)>
          func,
      ServiceType* service)
      : func_(func), service_(service) {}
 
  void RunHandler(const HandlerParameter& param) final {
    ResponseType rsp;
    ::grpc::Status status = param.status;
    if (status.ok()) {
      status = CatchingFunctionHandler([this, &param, &rsp] {
        return func_(service_,
                     static_cast<::grpc::ServerContext*>(param.server_context),
                     static_cast<RequestType*>(param.request), &rsp);
      });
      static_cast<RequestType*>(param.request)->~RequestType();
    }
 
    GPR_CODEGEN_ASSERT(!param.server_context->sent_initial_metadata_);
    ::grpc::internal::CallOpSet<::grpc::internal::CallOpSendInitialMetadata,
                                ::grpc::internal::CallOpSendMessage,
                                ::grpc::internal::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.SendMessagePtr(&rsp);
    }
    ops.ServerSendStatus(&param.server_context->trailing_metadata_, status);
    param.call->PerformOps(&ops);
    param.call->cq()->Pluck(&ops);
  }
 
  void* Deserialize(grpc_call* call, grpc_byte_buffer* req,
                    ::grpc::Status* status, void** /*handler_data*/) final {
    ::grpc::ByteBuffer buf;
    buf.set_buffer(req);
    auto* request =
        new (::grpc::g_core_codegen_interface->grpc_call_arena_alloc(
            call, sizeof(RequestType))) RequestType();
    *status =
        ::grpc::SerializationTraits<RequestType>::Deserialize(&buf, request);
    buf.Release();
    if (status->ok()) {
      return request;
    }
    request->~RequestType();
    return nullptr;
  }
 
 private:
  std::function<::grpc::Status(ServiceType*, ::grpc::ServerContext*,
                               const RequestType*, ResponseType*)>
      func_;
  // The class the above handler function lives in.
  ServiceType* service_;
};
 
template <class ServiceType, class RequestType, class ResponseType>
class ClientStreamingHandler : public ::grpc::internal::MethodHandler {
 public:
  ClientStreamingHandler(
      std::function<::grpc::Status(ServiceType*, ::grpc::ServerContext*,
                                   ServerReader<RequestType>*, ResponseType*)>
          func,
      ServiceType* service)
      : func_(func), service_(service) {}
 
  void RunHandler(const HandlerParameter& param) final {
    ServerReader<RequestType> reader(
        param.call, static_cast<::grpc::ServerContext*>(param.server_context));
    ResponseType rsp;
    ::grpc::Status status = CatchingFunctionHandler([this, &param, &reader,
                                                     &rsp] {
      return func_(service_,
                   static_cast<::grpc::ServerContext*>(param.server_context),
                   &reader, &rsp);
    });
 
    ::grpc::internal::CallOpSet<::grpc::internal::CallOpSendInitialMetadata,
                                ::grpc::internal::CallOpSendMessage,
                                ::grpc::internal::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 (status.ok()) {
      status = ops.SendMessagePtr(&rsp);
    }
    ops.ServerSendStatus(&param.server_context->trailing_metadata_, status);
    param.call->PerformOps(&ops);
    param.call->cq()->Pluck(&ops);
  }
 
 private:
  std::function<::grpc::Status(ServiceType*, ::grpc::ServerContext*,
                               ServerReader<RequestType>*, ResponseType*)>
      func_;
  ServiceType* service_;
};
 
template <class ServiceType, class RequestType, class ResponseType>
class ServerStreamingHandler : public ::grpc::internal::MethodHandler {
 public:
  ServerStreamingHandler(std::function<::grpc::Status(
                             ServiceType*, ::grpc::ServerContext*,
                             const RequestType*, ServerWriter<ResponseType>*)>
                             func,
                         ServiceType* service)
      : func_(func), service_(service) {}
 
  void RunHandler(const HandlerParameter& param) final {
    ::grpc::Status status = param.status;
    if (status.ok()) {
      ServerWriter<ResponseType> writer(
          param.call,
          static_cast<::grpc::ServerContext*>(param.server_context));
      status = CatchingFunctionHandler([this, &param, &writer] {
        return func_(service_,
                     static_cast<::grpc::ServerContext*>(param.server_context),
                     static_cast<RequestType*>(param.request), &writer);
      });
      static_cast<RequestType*>(param.request)->~RequestType();
    }
 
    ::grpc::internal::CallOpSet<::grpc::internal::CallOpSendInitialMetadata,
                                ::grpc::internal::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);
    if (param.server_context->has_pending_ops_) {
      param.call->cq()->Pluck(&param.server_context->pending_ops_);
    }
    param.call->cq()->Pluck(&ops);
  }
 
  void* Deserialize(grpc_call* call, grpc_byte_buffer* req,
                    ::grpc::Status* status, void** /*handler_data*/) final {
    ::grpc::ByteBuffer buf;
    buf.set_buffer(req);
    auto* request =
        new (::grpc::g_core_codegen_interface->grpc_call_arena_alloc(
            call, sizeof(RequestType))) RequestType();
    *status =
        ::grpc::SerializationTraits<RequestType>::Deserialize(&buf, request);
    buf.Release();
    if (status->ok()) {
      return request;
    }
    request->~RequestType();
    return nullptr;
  }
 
 private:
  std::function<::grpc::Status(ServiceType*, ::grpc::ServerContext*,
                               const RequestType*, ServerWriter<ResponseType>*)>
      func_;
  ServiceType* service_;
};
 
template <class Streamer, bool WriteNeeded>
class TemplatedBidiStreamingHandler : public ::grpc::internal::MethodHandler {
 public:
  TemplatedBidiStreamingHandler(
      std::function<::grpc::Status(::grpc::ServerContext*, Streamer*)> func)
      : func_(func), write_needed_(WriteNeeded) {}
 
  void RunHandler(const HandlerParameter& param) final {
    Streamer stream(param.call,
                    static_cast<::grpc::ServerContext*>(param.server_context));
    ::grpc::Status status = CatchingFunctionHandler([this, &param, &stream] {
      return func_(static_cast<::grpc::ServerContext*>(param.server_context),
                   &stream);
    });
 
    ::grpc::internal::CallOpSet<::grpc::internal::CallOpSendInitialMetadata,
                                ::grpc::internal::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 = ::grpc::Status(::grpc::StatusCode::INTERNAL,
                                "Service did not provide response message");
      }
    }
    ops.ServerSendStatus(&param.server_context->trailing_metadata_, status);
    param.call->PerformOps(&ops);
    if (param.server_context->has_pending_ops_) {
      param.call->cq()->Pluck(&param.server_context->pending_ops_);
    }
    param.call->cq()->Pluck(&ops);
  }
 
 private:
  std::function<::grpc::Status(::grpc::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<::grpc::Status(
                           ServiceType*, ::grpc::ServerContext*,
                           ServerReaderWriter<ResponseType, RequestType>*)>
                           func,
                       ServiceType* service)
      // TODO(vjpai): When gRPC supports C++14, move-capture func in the below
      : TemplatedBidiStreamingHandler<
            ServerReaderWriter<ResponseType, RequestType>, false>(
            [func, service](
                ::grpc::ServerContext* ctx,
                ServerReaderWriter<ResponseType, RequestType>* streamer) {
              return func(service, ctx, streamer);
            }) {}
};
 
template <class RequestType, class ResponseType>
class StreamedUnaryHandler
    : public TemplatedBidiStreamingHandler<
          ServerUnaryStreamer<RequestType, ResponseType>, true> {
 public:
  explicit StreamedUnaryHandler(
      std::function<
          ::grpc::Status(::grpc::ServerContext*,
                         ServerUnaryStreamer<RequestType, ResponseType>*)>
          func)
      : TemplatedBidiStreamingHandler<
            ServerUnaryStreamer<RequestType, ResponseType>, true>(
            std::move(func)) {}
};
 
template <class RequestType, class ResponseType>
class SplitServerStreamingHandler
    : public TemplatedBidiStreamingHandler<
          ServerSplitStreamer<RequestType, ResponseType>, false> {
 public:
  explicit SplitServerStreamingHandler(
      std::function<
          ::grpc::Status(::grpc::ServerContext*,
                         ServerSplitStreamer<RequestType, ResponseType>*)>
          func)
      : TemplatedBidiStreamingHandler<
            ServerSplitStreamer<RequestType, ResponseType>, false>(
            std::move(func)) {}
};
 
template <::grpc::StatusCode code>
class ErrorMethodHandler : public ::grpc::internal::MethodHandler {
 public:
  template <class T>
  static void FillOps(::grpc::ServerContextBase* context, T* ops) {
    ::grpc::Status status(code, "");
    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 {
    ::grpc::internal::CallOpSet<::grpc::internal::CallOpSendInitialMetadata,
                                ::grpc::internal::CallOpServerSendStatus>
        ops;
    FillOps(param.server_context, &ops);
    param.call->PerformOps(&ops);
    param.call->cq()->Pluck(&ops);
  }
 
  void* Deserialize(grpc_call* /*call*/, grpc_byte_buffer* req,
                    ::grpc::Status* /*status*/, void** /*handler_data*/) final {
    // We have to destroy any request payload
    if (req != nullptr) {
      ::grpc::g_core_codegen_interface->grpc_byte_buffer_destroy(req);
    }
    return nullptr;
  }
};
 
typedef ErrorMethodHandler<::grpc::StatusCode::UNIMPLEMENTED>
    UnknownMethodHandler;
typedef ErrorMethodHandler<::grpc::StatusCode::RESOURCE_EXHAUSTED>
    ResourceExhaustedHandler;
 
}  // namespace internal
}  // namespace grpc
 
#endif  // GRPCPP_IMPL_CODEGEN_METHOD_HANDLER_H