1 //
2 //
3 // Copyright 2015 gRPC authors.
4 //
5 // Licensed under the Apache License, Version 2.0 (the "License");
6 // you may not use this file except in compliance with the License.
7 // You may obtain a copy of the License at
8 //
9 // http://www.apache.org/licenses/LICENSE-2.0
10 //
11 // Unless required by applicable law or agreed to in writing, software
12 // distributed under the License is distributed on an "AS IS" BASIS,
13 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 // See the License for the specific language governing permissions and
15 // limitations under the License.
16 //
17 //
18
19 #ifndef GRPCPP_IMPL_CLIENT_UNARY_CALL_H
20 #define GRPCPP_IMPL_CLIENT_UNARY_CALL_H
21
22 #include <grpcpp/impl/call.h>
23 #include <grpcpp/impl/call_op_set.h>
24 #include <grpcpp/impl/channel_interface.h>
25 #include <grpcpp/support/config.h>
26 #include <grpcpp/support/status.h>
27
28 namespace grpc {
29
30 class ClientContext;
31 namespace internal {
32 class RpcMethod;
33
34 /// Wrapper that performs a blocking unary call. May optionally specify the base
35 /// class of the Request and Response so that the internal calls and structures
36 /// below this may be based on those base classes and thus achieve code reuse
37 /// across different RPCs (e.g., for protobuf, MessageLite would be a base
38 /// class).
39 template <class InputMessage, class OutputMessage,
40 class BaseInputMessage = InputMessage,
41 class BaseOutputMessage = OutputMessage>
BlockingUnaryCall(ChannelInterface * channel,const RpcMethod & method,grpc::ClientContext * context,const InputMessage & request,OutputMessage * result)42 Status BlockingUnaryCall(ChannelInterface* channel, const RpcMethod& method,
43 grpc::ClientContext* context,
44 const InputMessage& request, OutputMessage* result) {
45 static_assert(std::is_base_of<BaseInputMessage, InputMessage>::value,
46 "Invalid input message specification");
47 static_assert(std::is_base_of<BaseOutputMessage, OutputMessage>::value,
48 "Invalid output message specification");
49 return BlockingUnaryCallImpl<BaseInputMessage, BaseOutputMessage>(
50 channel, method, context, request, result)
51 .status();
52 }
53
54 template <class InputMessage, class OutputMessage>
55 class BlockingUnaryCallImpl {
56 public:
BlockingUnaryCallImpl(ChannelInterface * channel,const RpcMethod & method,grpc::ClientContext * context,const InputMessage & request,OutputMessage * result)57 BlockingUnaryCallImpl(ChannelInterface* channel, const RpcMethod& method,
58 grpc::ClientContext* context,
59 const InputMessage& request, OutputMessage* result) {
60 grpc::CompletionQueue cq(grpc_completion_queue_attributes{
61 GRPC_CQ_CURRENT_VERSION, GRPC_CQ_PLUCK, GRPC_CQ_DEFAULT_POLLING,
62 nullptr}); // Pluckable completion queue
63 grpc::internal::Call call(channel->CreateCall(method, context, &cq));
64 CallOpSet<CallOpSendInitialMetadata, CallOpSendMessage,
65 CallOpRecvInitialMetadata, CallOpRecvMessage<OutputMessage>,
66 CallOpClientSendClose, CallOpClientRecvStatus>
67 ops;
68 status_ = ops.SendMessagePtr(&request);
69 if (!status_.ok()) {
70 return;
71 }
72 ops.SendInitialMetadata(&context->send_initial_metadata_,
73 context->initial_metadata_flags());
74 ops.RecvInitialMetadata(context);
75 ops.RecvMessage(result);
76 ops.AllowNoMessage();
77 ops.ClientSendClose();
78 ops.ClientRecvStatus(context, &status_);
79 call.PerformOps(&ops);
80 cq.Pluck(&ops);
81 // Some of the ops might fail. If the ops fail in the core layer, status
82 // would reflect the error. But, if the ops fail in the C++ layer, the
83 // status would still be the same as the one returned by gRPC Core. This can
84 // happen if deserialization of the message fails.
85 // TODO(yashykt): If deserialization fails, but the status received is OK,
86 // then it might be a good idea to change the status to something better
87 // than StatusCode::UNIMPLEMENTED to reflect this.
88 if (!ops.got_message && status_.ok()) {
89 status_ = Status(StatusCode::UNIMPLEMENTED,
90 "No message returned for unary request");
91 }
92 }
status()93 Status status() { return status_; }
94
95 private:
96 Status status_;
97 };
98
99 } // namespace internal
100 } // namespace grpc
101
102 #endif // GRPCPP_IMPL_CLIENT_UNARY_CALL_H
103