#ifndef TENSORFLOW_FRAMEWORK_CONTROL_FLOW_H_
#define TENSORFLOW_FRAMEWORK_CONTROL_FLOW_H_

#include "tensorflow/core/platform/port.h"
#include "tensorflow/core/platform/logging.h"
#include "tensorflow/core/lib/hash/hash.h"

namespace tensorflow {

const uint64 kIllegalFrameId = ~0uLL;
const int64 kIllegalIterId = -1;

// For the purpose of control flow, every tensor produced by TensorFlow is
// conceptually tagged by a 'FrameAndIter'. FrameAndIter consists of a
// 'frame_id' and an 'iter_id'. The tensor value it represents is produced
// in the frame with frame_id at the iteration of iter_id.
struct FrameAndIter {
  uint64 frame_id = kIllegalFrameId;
  int64 iter_id = kIllegalIterId;

  FrameAndIter() {}

  FrameAndIter(uint64 frame, int64 iter) {
    frame_id = frame;
    iter_id = iter;
  }

  bool operator==(const FrameAndIter& other) const {
    return (frame_id == other.frame_id && iter_id == other.iter_id);
  }
};

struct FrameAndIterHash {
  size_t operator()(const FrameAndIter& key) const {
    // Make sure there are no padding bytes that we don't want
    CHECK_EQ(sizeof(uint64) + sizeof(int64), sizeof(FrameAndIter));
    return Hash64(reinterpret_cast<const char*>(&key), sizeof(FrameAndIter));
  }
};

}  // namespace tensorflow

#endif  // TENSORFLOW_FRAMEWORK_CONTROL_FLOW_H_