uid_tracker.hpp

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/*
 * Copyright 2020 Robert Bosch GmbH
 *
 * 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.
 *
 * SPDX-License-Identifier: Apache-2.0
 */
#pragma once
#ifndef CLOE_UTILITY_UID_TRACKER_HPP_
#define CLOE_UTILITY_UID_TRACKER_HPP_

#include <cassert>     // for assert
#include <functional>  // for std::function
#include <map>         // for std::map
#include <memory>      // for std::shared_ptr
#include <set>         // for std::set
#include <vector>      // for std::vector

namespace cloe {
namespace utility {

class UniqueIDTracker {
  // Tracklet is used internally
  struct Tracklet {
    int in_id;
    int out_id;
    int age;
  };

  int ttl_;  // time to live before reusing
  std::map<int, std::shared_ptr<Tracklet>> assigned_;
  std::set<int> free_;
  std::vector<std::function<void(int in_id, int out_id)>> observers_;

 public:
  UniqueIDTracker(int min, int max, int ttl = 1) : ttl_(ttl) {
    assert(min < max);
    assert(ttl_ >= 1);  // TODO(unknown): perhaps 0 is ok too

    for (int i = min; i <= max; i++) {
      free_.insert(i);
    }
  }

  virtual ~UniqueIDTracker() = default;

  int assign(int id);

  void next_cycle();

  void add_delete_observer(void f(int in_id, int out_id)) { observers_.emplace_back(f); }
};

}  // namespace utility
}  // namespace cloe

#endif  // CLOE_UTILITY_UID_TRACKER_HPP_