grpc/include/grpc++/impl/codegen/fc_unary.h

/*
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#ifndef GRPCXX_IMPL_CODEGEN_FC_UNARY_H
#define GRPCXX_IMPL_CODEGEN_FC_UNARY_H

#include <grpc++/impl/codegen/call.h>
#include <grpc++/impl/codegen/completion_queue.h>
#include <grpc++/impl/codegen/core_codegen_interface.h>
#include <grpc++/impl/codegen/method_handler_impl.h>
#include <grpc++/impl/codegen/server_context.h>

namespace grpc {

/// A class to represent a flow-controlled unary call. This is something
/// of a hybrid between conventional unary and streaming. This is invoked
/// through a unary call on the client side, but the server responds to it
/// as though it were a single-ping-pong streaming call. The server can use
/// the \a NextMessageSize method to determine an upper-bound on the size of
/// the message.
/// A key difference relative to streaming: an FCUnary must have exactly 1 Read
/// and exactly 1 Write, in that order, to function correctly.
/// Otherwise, the RPC is in error.
template <class RequestType, class ResponseType>
  class FCUnary GRPC_FINAL {
 public:
 FCUnary(Call* call, ServerContext* ctx): call_(call), ctx_(ctx), read_done_(false), write_done_(false) {}
  ~FCUnary() {}
  bool NextMessageSize(uint32_t *sz) {
    *sz = call_->max_message_size();
    return true;
  }
  bool Read(RequestType *request) {
    if (read_done_) {
      return false;      
    }
    read_done_ = true;
    CallOpSet<CallOpRecvMessage<RequestType>> ops;
    ops.RecvMessage(request);
    call_->PerformOps(&ops);
    return call_->cq()->Pluck(&ops) && ops.got_message;
  }
  bool Write(const ResponseType& response) {return Write(response, WriteOptions());}
  bool Write(const ResponseType& response, const WriteOptions& options) {
    if (write_done_ || !read_done_) {
      return false;      
    }
    write_done_ = true;
    CallOpSet<CallOpSendInitialMetadata, CallOpSendMessage> ops;
    if (!ops.SendMessage(response, options).ok()) {
      return false;
    }
    if (!ctx_->sent_initial_metadata_) {
      ops.SendInitialMetadata(ctx_->initial_metadata_,
                              ctx_->initial_metadata_flags());
      ctx_->sent_initial_metadata_ = true;
    } else {
      return false;
    }
    call_->PerformOps(&ops);
    return call_->cq()->Pluck(&ops);    
  }
 private:
  Call* const call_;
  ServerContext* const ctx_;
  bool read_done_;
  bool write_done_;
};

}  // namespace grpc

#endif  // GRPCXX_IMPL_CODEGEN_FC_UNARY_H