/* Copyright 2015 The TensorFlow Authors. All Rights Reserved.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
==============================================================================*/

#ifndef TENSORFLOW_CORE_FRAMEWORK_CONTROL_FLOW_H_
#define TENSORFLOW_CORE_FRAMEWORK_CONTROL_FLOW_H_

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

namespace tensorflow {

const uint64_t kIllegalFrameId = ~0uLL;
const int64_t 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_t frame_id = kIllegalFrameId;
  int64_t iter_id = kIllegalIterId;

  FrameAndIter() {}

  FrameAndIter(uint64_t frame, int64_t 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_t) + sizeof(int64_t), sizeof(FrameAndIter));
    return Hash64(reinterpret_cast<const char*>(&key), sizeof(FrameAndIter));
  }
};

}  // namespace tensorflow

#endif  // TENSORFLOW_CORE_FRAMEWORK_CONTROL_FLOW_H_
