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

/*
 *
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 * modification, are permitted provided that the following conditions are
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 *
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#ifndef GRPCXX_IMPL_CODEGEN_ASYNC_STREAM_H
#define GRPCXX_IMPL_CODEGEN_ASYNC_STREAM_H

#include <grpc++/impl/codegen/call.h>
#include <grpc++/impl/codegen/channel_interface.h>
#include <grpc++/impl/codegen/core_codegen_interface.h>
#include <grpc++/impl/codegen/server_context.h>
#include <grpc++/impl/codegen/service_type.h>
#include <grpc++/impl/codegen/status.h>

namespace grpc {

class CompletionQueue;

/// Common interface for all client side asynchronous streaming.
class ClientAsyncStreamingInterface {
 public:
  virtual ~ClientAsyncStreamingInterface() {}

  /// Request notification of the reading of the initial metadata. Completion
  /// will be notified by \a tag on the associated completion queue.
  /// This call is optional, but if it is used, it cannot be used concurrently
  /// with or after the \a Read method.
  ///
  /// \param[in] tag Tag identifying this request.
  virtual void ReadInitialMetadata(void* tag) = 0;

  /// Indicate that the stream is to be finished and request notification
  /// Should not be used concurrently with other operations
  ///
  /// \param[out] status To be updated with the operation status.
  /// \param[in] tag Tag identifying this request.
  virtual void Finish(Status* status, void* tag) = 0;
};

/// An interface that yields a sequence of messages of type \a R.
template <class R>
class AsyncReaderInterface {
 public:
  virtual ~AsyncReaderInterface() {}

  /// Read a message of type \a R into \a msg. Completion will be notified by \a
  /// tag on the associated completion queue.
  /// This is thread-safe with respect to \a Write or \a WritesDone methods. It
  /// should not be called concurrently with other streaming APIs
  /// on the same stream. It is not meaningful to call it concurrently
  /// with another \a Read on the same stream since reads on the same stream
  /// are delivered in order.
  ///
  /// \param[out] msg Where to eventually store the read message.
  /// \param[in] tag The tag identifying the operation.
  virtual void Read(R* msg, void* tag) = 0;
};

/// An interface that can be fed a sequence of messages of type \a W.
template <class W>
class AsyncWriterInterface {
 public:
  virtual ~AsyncWriterInterface() {}

  /// Request the writing of \a msg with identifying tag \a tag.
  ///
  /// Only one write may be outstanding at any given time. This means that
  /// after calling Write, one must wait to receive \a tag from the completion
  /// queue BEFORE calling Write again.
  /// This is thread-safe with respect to \a Read
  ///
  /// \param[in] msg The message to be written.
  /// \param[in] tag The tag identifying the operation.
  virtual void Write(const W& msg, void* tag) = 0;

  /// Request the writing of \a msg using WriteOptions \a options with
  /// identifying tag \a tag.
  ///
  /// Only one write may be outstanding at any given time. This means that
  /// after calling Write, one must wait to receive \a tag from the completion
  /// queue BEFORE calling Write again.
  /// WriteOptions \a options is used to set the write options of this message.
  /// This is thread-safe with respect to \a Read
  ///
  /// \param[in] msg The message to be written.
  /// \param[in] options The WriteOptions to be used to write this message.
  /// \param[in] tag The tag identifying the operation.
  virtual void Write(const W& msg, WriteOptions options, void* tag) = 0;

  /// Request the writing of \a msg and coalesce it with the writing
  /// of trailing metadata, using WriteOptions \a options with identifying tag
  /// \a tag.
  ///
  /// For client, WriteLast is equivalent of performing Write and WritesDone in
  /// a single step.
  /// For server, WriteLast buffers the \a msg. The writing of \a msg is held
  /// until Finish is called, where \a msg and trailing metadata are coalesced
  /// and write is initiated. Note that WriteLast can only buffer \a msg up to
  /// the flow control window size. If \a msg size is larger than the window
  /// size, it will be sent on wire without buffering.
  ///
  /// \param[in] msg The message to be written.
  /// \param[in] options The WriteOptions to be used to write this message.
  /// \param[in] tag The tag identifying the operation.
  void WriteLast(const W& msg, WriteOptions options, void* tag) {
    Write(msg, options.set_last_message(), tag);
  }
};

template <class R>
class ClientAsyncReaderInterface : public ClientAsyncStreamingInterface,
                                   public AsyncReaderInterface<R> {};

template <class R>
class ClientAsyncReader final : public ClientAsyncReaderInterface<R> {
 public:
  /// Create a stream and write the first request out.
  template <class W>
  ClientAsyncReader(ChannelInterface* channel, CompletionQueue* cq,
                    const RpcMethod& method, ClientContext* context,
                    const W& request, void* tag)
      : context_(context), call_(channel->CreateCall(method, context, cq)) {
    init_ops_.set_output_tag(tag);
    init_ops_.SendInitialMetadata(context->send_initial_metadata_,
                                  context->initial_metadata_flags());
    // TODO(ctiller): don't assert
    GPR_CODEGEN_ASSERT(init_ops_.SendMessage(request).ok());
    init_ops_.ClientSendClose();
    call_.PerformOps(&init_ops_);
  }

  void ReadInitialMetadata(void* tag) override {
    GPR_CODEGEN_ASSERT(!context_->initial_metadata_received_);

    meta_ops_.set_output_tag(tag);
    meta_ops_.RecvInitialMetadata(context_);
    call_.PerformOps(&meta_ops_);
  }

  void Read(R* msg, void* tag) override {
    read_ops_.set_output_tag(tag);
    if (!context_->initial_metadata_received_) {
      read_ops_.RecvInitialMetadata(context_);
    }
    read_ops_.RecvMessage(msg);
    call_.PerformOps(&read_ops_);
  }

  void Finish(Status* status, void* tag) override {
    finish_ops_.set_output_tag(tag);
    if (!context_->initial_metadata_received_) {
      finish_ops_.RecvInitialMetadata(context_);
    }
    finish_ops_.ClientRecvStatus(context_, status);
    call_.PerformOps(&finish_ops_);
  }

 private:
  ClientContext* context_;
  Call call_;
  CallOpSet<CallOpSendInitialMetadata, CallOpSendMessage, CallOpClientSendClose>
      init_ops_;
  CallOpSet<CallOpRecvInitialMetadata> meta_ops_;
  CallOpSet<CallOpRecvInitialMetadata, CallOpRecvMessage<R>> read_ops_;
  CallOpSet<CallOpRecvInitialMetadata, CallOpClientRecvStatus> finish_ops_;
};

/// Common interface for client side asynchronous writing.
template <class W>
class ClientAsyncWriterInterface : public ClientAsyncStreamingInterface,
                                   public AsyncWriterInterface<W> {
 public:
  /// Signal the client is done with the writes.
  /// Thread-safe with respect to \a Read
  ///
  /// \param[in] tag The tag identifying the operation.
  virtual void WritesDone(void* tag) = 0;
};

template <class W>
class ClientAsyncWriter final : public ClientAsyncWriterInterface<W> {
 public:
  template <class R>
  ClientAsyncWriter(ChannelInterface* channel, CompletionQueue* cq,
                    const RpcMethod& method, ClientContext* context,
                    R* response, void* tag)
      : context_(context), call_(channel->CreateCall(method, context, cq)) {
    finish_ops_.RecvMessage(response);
    finish_ops_.AllowNoMessage();
    // if corked bit is set in context, we buffer up the initial metadata to
    // coalesce with later message to be sent. No op is performed.
    if (context_->initial_metadata_corked_) {
      write_ops_.SendInitialMetadata(context->send_initial_metadata_,
                                     context->initial_metadata_flags());
    } else {
      write_ops_.set_output_tag(tag);
      write_ops_.SendInitialMetadata(context->send_initial_metadata_,
                                     context->initial_metadata_flags());
      call_.PerformOps(&write_ops_);
    }
  }

  void ReadInitialMetadata(void* tag) override {
    GPR_CODEGEN_ASSERT(!context_->initial_metadata_received_);

    meta_ops_.set_output_tag(tag);
    meta_ops_.RecvInitialMetadata(context_);
    call_.PerformOps(&meta_ops_);
  }

  void Write(const W& msg, void* tag) override {
    write_ops_.set_output_tag(tag);
    // TODO(ctiller): don't assert
    GPR_CODEGEN_ASSERT(write_ops_.SendMessage(msg).ok());
    call_.PerformOps(&write_ops_);
  }

  void Write(const W& msg, WriteOptions options, void* tag) override {
    write_ops_.set_output_tag(tag);
    if (options.is_last_message()) {
      options.set_buffer_hint();
      write_ops_.ClientSendClose();
    }
    // TODO(ctiller): don't assert
    GPR_CODEGEN_ASSERT(write_ops_.SendMessage(msg, options).ok());
    call_.PerformOps(&write_ops_);
  }

  void WritesDone(void* tag) override {
    write_ops_.set_output_tag(tag);
    write_ops_.ClientSendClose();
    call_.PerformOps(&write_ops_);
  }

  void Finish(Status* status, void* tag) override {
    finish_ops_.set_output_tag(tag);
    if (!context_->initial_metadata_received_) {
      finish_ops_.RecvInitialMetadata(context_);
    }
    finish_ops_.ClientRecvStatus(context_, status);
    call_.PerformOps(&finish_ops_);
  }

 private:
  ClientContext* context_;
  Call call_;
  CallOpSet<CallOpRecvInitialMetadata> meta_ops_;
  CallOpSet<CallOpSendInitialMetadata, CallOpSendMessage, CallOpClientSendClose>
      write_ops_;
  CallOpSet<CallOpRecvInitialMetadata, CallOpGenericRecvMessage,
            CallOpClientRecvStatus>
      finish_ops_;
};

/// Client-side interface for asynchronous bi-directional streaming.
template <class W, class R>
class ClientAsyncReaderWriterInterface : public ClientAsyncStreamingInterface,
                                         public AsyncWriterInterface<W>,
                                         public AsyncReaderInterface<R> {
 public:
  /// Signal the client is done with the writes.
  /// Thread-safe with respect to \a Read
  ///
  /// \param[in] tag The tag identifying the operation.
  virtual void WritesDone(void* tag) = 0;
};

template <class W, class R>
class ClientAsyncReaderWriter final
    : public ClientAsyncReaderWriterInterface<W, R> {
 public:
  ClientAsyncReaderWriter(ChannelInterface* channel, CompletionQueue* cq,
                          const RpcMethod& method, ClientContext* context,
                          void* tag)
      : context_(context), call_(channel->CreateCall(method, context, cq)) {
    if (context_->initial_metadata_corked_) {
      // if corked bit is set in context, we buffer up the initial metadata to
      // coalesce with later message to be sent. No op is performed.
      write_ops_.SendInitialMetadata(context->send_initial_metadata_,
                                     context->initial_metadata_flags());
    } else {
      write_ops_.set_output_tag(tag);
      write_ops_.SendInitialMetadata(context->send_initial_metadata_,
                                     context->initial_metadata_flags());
      call_.PerformOps(&write_ops_);
    }
  }

  void ReadInitialMetadata(void* tag) override {
    GPR_CODEGEN_ASSERT(!context_->initial_metadata_received_);

    meta_ops_.set_output_tag(tag);
    meta_ops_.RecvInitialMetadata(context_);
    call_.PerformOps(&meta_ops_);
  }

  void Read(R* msg, void* tag) override {
    read_ops_.set_output_tag(tag);
    if (!context_->initial_metadata_received_) {
      read_ops_.RecvInitialMetadata(context_);
    }
    read_ops_.RecvMessage(msg);
    call_.PerformOps(&read_ops_);
  }

  void Write(const W& msg, void* tag) override {
    write_ops_.set_output_tag(tag);
    // TODO(ctiller): don't assert
    GPR_CODEGEN_ASSERT(write_ops_.SendMessage(msg).ok());
    call_.PerformOps(&write_ops_);
  }

  void Write(const W& msg, WriteOptions options, void* tag) override {
    write_ops_.set_output_tag(tag);
    if (options.is_last_message()) {
      options.set_buffer_hint();
      write_ops_.ClientSendClose();
    }
    // TODO(ctiller): don't assert
    GPR_CODEGEN_ASSERT(write_ops_.SendMessage(msg, options).ok());
    call_.PerformOps(&write_ops_);
  }

  void WritesDone(void* tag) override {
    write_ops_.set_output_tag(tag);
    write_ops_.ClientSendClose();
    call_.PerformOps(&write_ops_);
  }

  void Finish(Status* status, void* tag) override {
    finish_ops_.set_output_tag(tag);
    if (!context_->initial_metadata_received_) {
      finish_ops_.RecvInitialMetadata(context_);
    }
    finish_ops_.ClientRecvStatus(context_, status);
    call_.PerformOps(&finish_ops_);
  }

 private:
  ClientContext* context_;
  Call call_;
  CallOpSet<CallOpRecvInitialMetadata> meta_ops_;
  CallOpSet<CallOpRecvInitialMetadata, CallOpRecvMessage<R>> read_ops_;
  CallOpSet<CallOpSendInitialMetadata, CallOpSendMessage, CallOpClientSendClose>
      write_ops_;
  CallOpSet<CallOpRecvInitialMetadata, CallOpClientRecvStatus> finish_ops_;
};

template <class W, class R>
class ServerAsyncReaderInterface : public ServerAsyncStreamingInterface,
                                   public AsyncReaderInterface<R> {
 public:
  virtual void Finish(const W& msg, const Status& status, void* tag) = 0;

  virtual void FinishWithError(const Status& status, void* tag) = 0;
};

template <class W, class R>
class ServerAsyncReader final : public ServerAsyncReaderInterface<W, R> {
 public:
  explicit ServerAsyncReader(ServerContext* ctx)
      : call_(nullptr, nullptr, nullptr), ctx_(ctx) {}

  void SendInitialMetadata(void* tag) override {
    GPR_CODEGEN_ASSERT(!ctx_->sent_initial_metadata_);

    meta_ops_.set_output_tag(tag);
    meta_ops_.SendInitialMetadata(ctx_->initial_metadata_,
                                  ctx_->initial_metadata_flags());
    if (ctx_->compression_level_set()) {
      meta_ops_.set_compression_level(ctx_->compression_level());
    }
    ctx_->sent_initial_metadata_ = true;
    call_.PerformOps(&meta_ops_);
  }

  void Read(R* msg, void* tag) override {
    read_ops_.set_output_tag(tag);
    read_ops_.RecvMessage(msg);
    call_.PerformOps(&read_ops_);
  }

  void Finish(const W& msg, const Status& status, void* tag) override {
    finish_ops_.set_output_tag(tag);
    if (!ctx_->sent_initial_metadata_) {
      finish_ops_.SendInitialMetadata(ctx_->initial_metadata_,
                                      ctx_->initial_metadata_flags());
      if (ctx_->compression_level_set()) {
        finish_ops_.set_compression_level(ctx_->compression_level());
      }
      ctx_->sent_initial_metadata_ = true;
    }
    // The response is dropped if the status is not OK.
    if (status.ok()) {
      finish_ops_.ServerSendStatus(ctx_->trailing_metadata_,
                                   finish_ops_.SendMessage(msg));
    } else {
      finish_ops_.ServerSendStatus(ctx_->trailing_metadata_, status);
    }
    call_.PerformOps(&finish_ops_);
  }

  void FinishWithError(const Status& status, void* tag) override {
    GPR_CODEGEN_ASSERT(!status.ok());
    finish_ops_.set_output_tag(tag);
    if (!ctx_->sent_initial_metadata_) {
      finish_ops_.SendInitialMetadata(ctx_->initial_metadata_,
                                      ctx_->initial_metadata_flags());
      if (ctx_->compression_level_set()) {
        finish_ops_.set_compression_level(ctx_->compression_level());
      }
      ctx_->sent_initial_metadata_ = true;
    }
    finish_ops_.ServerSendStatus(ctx_->trailing_metadata_, status);
    call_.PerformOps(&finish_ops_);
  }

 private:
  void BindCall(Call* call) override { call_ = *call; }

  Call call_;
  ServerContext* ctx_;
  CallOpSet<CallOpSendInitialMetadata> meta_ops_;
  CallOpSet<CallOpRecvMessage<R>> read_ops_;
  CallOpSet<CallOpSendInitialMetadata, CallOpSendMessage,
            CallOpServerSendStatus>
      finish_ops_;
};

template <class W>
class ServerAsyncWriterInterface : public ServerAsyncStreamingInterface,
                                   public AsyncWriterInterface<W> {
 public:
  virtual void Finish(const Status& status, void* tag) = 0;

  /// Request the writing of \a msg and coalesce it with trailing metadata which
  /// contains \a status, using WriteOptions options with identifying tag \a
  /// tag.
  ///
  /// WriteAndFinish is equivalent of performing WriteLast and Finish in a
  /// single step.
  ///
  /// \param[in] msg The message to be written.
  /// \param[in] options The WriteOptions to be used to write this message.
  /// \param[in] status The Status that server returns to client.
  /// \param[in] tag The tag identifying the operation.
  virtual void WriteAndFinish(const W& msg, WriteOptions options,
                              const Status& status, void* tag) = 0;
};

template <class W>
class ServerAsyncWriter final : public ServerAsyncWriterInterface<W> {
 public:
  explicit ServerAsyncWriter(ServerContext* ctx)
      : call_(nullptr, nullptr, nullptr), ctx_(ctx) {}

  void SendInitialMetadata(void* tag) override {
    GPR_CODEGEN_ASSERT(!ctx_->sent_initial_metadata_);

    meta_ops_.set_output_tag(tag);
    meta_ops_.SendInitialMetadata(ctx_->initial_metadata_,
                                  ctx_->initial_metadata_flags());
    if (ctx_->compression_level_set()) {
      meta_ops_.set_compression_level(ctx_->compression_level());
    }
    ctx_->sent_initial_metadata_ = true;
    call_.PerformOps(&meta_ops_);
  }

  void EnsureInitialMetadataSent(CallOpSetInterface* ops_in) {
    CallOpSet<CallOpSendInitialMetadata>* ops =
        static_cast<CallOpSet<CallOpSendInitialMetadata>*>(ops_in);
    if (!ctx_->sent_initial_metadata_) {
      ops->SendInitialMetadata(ctx_->initial_metadata_,
                               ctx_->initial_metadata_flags());
      if (ctx_->compression_level_set()) {
        ops->set_compression_level(ctx_->compression_level());
      }
      ctx_->sent_initial_metadata_ = true;
    }
  }

  void Write(const W& msg, void* tag) override {
    write_ops_.set_output_tag(tag);
    EnsureInitialMetadataSent(&write_ops_);
    // TODO(ctiller): don't assert
    GPR_CODEGEN_ASSERT(write_ops_.SendMessage(msg).ok());
    call_.PerformOps(&write_ops_);
  }

  void Write(const W& msg, WriteOptions options, void* tag) override {
    write_ops_.set_output_tag(tag);
    if (options.is_last_message()) {
      options.set_buffer_hint();
    }

    EnsureInitialMetadataSent(&write_ops_);
    // TODO(ctiller): don't assert
    GPR_CODEGEN_ASSERT(write_ops_.SendMessage(msg, options).ok());
    call_.PerformOps(&write_ops_);
  }

  void WriteAndFinish(const W& msg, WriteOptions options, const Status& status,
                      void* tag) override {
    write_ops_.set_output_tag(tag);
    EnsureInitialMetadataSent(&write_ops_);
    options.set_buffer_hint();
    GPR_CODEGEN_ASSERT(write_ops_.SendMessage(msg, options).ok());
    write_ops_.ServerSendStatus(ctx_->trailing_metadata_, status);
    call_.PerformOps(&write_ops_);
  }

  void Finish(const Status& status, void* tag) override {
    finish_ops_.set_output_tag(tag);
    EnsureInitialMetadataSent(&finish_ops_);
    finish_ops_.ServerSendStatus(ctx_->trailing_metadata_, status);
    call_.PerformOps(&finish_ops_);
  }

 private:
  void BindCall(Call* call) override { call_ = *call; }

  Call call_;
  ServerContext* ctx_;
  CallOpSet<CallOpSendInitialMetadata> meta_ops_;
  CallOpSet<CallOpSendInitialMetadata, CallOpSendMessage,
            CallOpServerSendStatus>
      write_ops_;
  CallOpSet<CallOpSendInitialMetadata, CallOpServerSendStatus> finish_ops_;
};

/// Server-side interface for asynchronous bi-directional streaming.
template <class W, class R>
class ServerAsyncReaderWriterInterface : public ServerAsyncStreamingInterface,
                                         public AsyncWriterInterface<W>,
                                         public AsyncReaderInterface<R> {
 public:
  virtual void Finish(const Status& status, void* tag) = 0;

  /// Request the writing of \a msg and coalesce it with trailing metadata which
  /// contains \a status, using WriteOptions options with identifying tag \a
  /// tag.
  ///
  /// WriteAndFinish is equivalent of performing WriteLast and Finish in a
  /// single step.
  ///
  /// \param[in] msg The message to be written.
  /// \param[in] options The WriteOptions to be used to write this message.
  /// \param[in] status The Status that server returns to client.
  /// \param[in] tag The tag identifying the operation.
  virtual void WriteAndFinish(const W& msg, WriteOptions options,
                              const Status& status, void* tag) = 0;
};

template <class W, class R>
class ServerAsyncReaderWriter final
    : public ServerAsyncReaderWriterInterface<W, R> {
 public:
  explicit ServerAsyncReaderWriter(ServerContext* ctx)
      : call_(nullptr, nullptr, nullptr), ctx_(ctx) {}

  void SendInitialMetadata(void* tag) override {
    GPR_CODEGEN_ASSERT(!ctx_->sent_initial_metadata_);

    meta_ops_.set_output_tag(tag);
    meta_ops_.SendInitialMetadata(ctx_->initial_metadata_,
                                  ctx_->initial_metadata_flags());
    if (ctx_->compression_level_set()) {
      meta_ops_.set_compression_level(ctx_->compression_level());
    }
    ctx_->sent_initial_metadata_ = true;
    call_.PerformOps(&meta_ops_);
  }

  void EnsureInitialMetadataSent(CallOpSetInterface* ops_in) {
    CallOpSet<CallOpSendInitialMetadata>* ops =
        static_cast<CallOpSet<CallOpSendInitialMetadata>*>(ops_in);
    if (!ctx_->sent_initial_metadata_) {
      ops->SendInitialMetadata(ctx_->initial_metadata_,
                               ctx_->initial_metadata_flags());
      if (ctx_->compression_level_set()) {
        ops->set_compression_level(ctx_->compression_level());
      }
      ctx_->sent_initial_metadata_ = true;
    }
  }

  void Read(R* msg, void* tag) override {
    read_ops_.set_output_tag(tag);
    read_ops_.RecvMessage(msg);
    call_.PerformOps(&read_ops_);
  }

  void Write(const W& msg, void* tag) override {
    write_ops_.set_output_tag(tag);
    EnsureInitialMetadataSent(&write_ops_);
    // TODO(ctiller): don't assert
    GPR_CODEGEN_ASSERT(write_ops_.SendMessage(msg).ok());
    call_.PerformOps(&write_ops_);
  }

  void Write(const W& msg, WriteOptions options, void* tag) override {
    write_ops_.set_output_tag(tag);
    if (options.is_last_message()) {
      options.set_buffer_hint();
    }
    EnsureInitialMetadataSent(&write_ops_);
    GPR_CODEGEN_ASSERT(write_ops_.SendMessage(msg, options).ok());
    call_.PerformOps(&write_ops_);
  }

  void WriteAndFinish(const W& msg, WriteOptions options, const Status& status,
                      void* tag) override {
    write_ops_.set_output_tag(tag);
    EnsureInitialMetadataSent(&write_ops_);
    options.set_buffer_hint();
    GPR_CODEGEN_ASSERT(write_ops_.SendMessage(msg, options).ok());
    write_ops_.ServerSendStatus(ctx_->trailing_metadata_, status);
    call_.PerformOps(&write_ops_);
  }

  void Finish(const Status& status, void* tag) override {
    finish_ops_.set_output_tag(tag);
    EnsureInitialMetadataSent(&finish_ops_);

    finish_ops_.ServerSendStatus(ctx_->trailing_metadata_, status);
    call_.PerformOps(&finish_ops_);
  }

 private:
  friend class ::grpc::Server;

  void BindCall(Call* call) override { call_ = *call; }

  Call call_;
  ServerContext* ctx_;
  CallOpSet<CallOpSendInitialMetadata> meta_ops_;
  CallOpSet<CallOpRecvMessage<R>> read_ops_;
  CallOpSet<CallOpSendInitialMetadata, CallOpSendMessage,
            CallOpServerSendStatus>
      write_ops_;
  CallOpSet<CallOpSendInitialMetadata, CallOpServerSendStatus> finish_ops_;
};

}  // namespace grpc

#endif  // GRPCXX_IMPL_CODEGEN_ASYNC_STREAM_H