grpc/include/grpc++/completion_queue.h

/*
 *
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#ifndef __GRPCPP_COMPLETION_QUEUE_H__
#define __GRPCPP_COMPLETION_QUEUE_H__

struct grpc_completion_queue;

namespace grpc {

class CompletionQueue;

class CompletionQueueTag {
 public:
  enum FinalizeResultOutput {
    SUCCEED,
    FAIL,
    SWALLOW,
  };

  virtual FinalizeResultOutput FinalizeResult(bool status) = 0;

 private:
  friend class CompletionQueue;
  void *user_tag_;
};

// grpc_completion_queue wrapper class
class CompletionQueue {
 public:
  CompletionQueue();
  ~CompletionQueue();

  // Blocking read from queue.
  // Returns true if an event was received, false if the queue is ready
  // for destruction.
  bool Next(void **tag, bool *ok);

  bool Pluck(void *tag);

  // Prepare a tag for the C api
  // Given a tag we'd like to receive from Next, what tag should we pass
  // down to the C api?
  // Usage example:
  //   grpc_call_start_batch(..., cq.PrepareTagForC(tag));
  // Allows attaching some work to be executed before the original tag
  // is returned.
  // MUST be used for all events that could be surfaced through this
  // wrapping API
  void *PrepareTagForC(CompletionQueueTag *cq_tag, void *user_tag) {
    cq_tag->user_tag_ = user_tag;
    return cq_tag;
  }

  // Shutdown has to be called, and the CompletionQueue can only be
  // destructed when false is returned from Next().
  void Shutdown();

  grpc_completion_queue* cq() { return cq_; }

 private:
  grpc_completion_queue* cq_;  // owned
};

}  // namespace grpc

#endif  // __GRPCPP_COMPLETION_QUEUE_H__