ExtrUniquePtrHolder.h

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/*
   Copyright (C) 2002-2025 CERN for the benefit of the ATLAS collaboration
 */
 
#ifndef TRKEXTOOLS_EXTRUNIQUEPTRHOLDER_H
#define TRKEXTOOLS_EXTRUNIQUEPTRHOLDER_H

 
#include <algorithm>
#include <memory>
#include <vector>
 
namespace Trk{
 
template <typename T>
using CacheOwnedPtr = T*;
 
template <typename T>
struct ExtrUniquePtrHolder {
 
  ExtrUniquePtrHolder() = default;
  // ctor with capacity
  ExtrUniquePtrHolder(size_t capacity) { m_elements.reserve(capacity); }
  ~ExtrUniquePtrHolder() = default;
  // delete all the rest
  ExtrUniquePtrHolder(const ExtrUniquePtrHolder&) = delete;
  ExtrUniquePtrHolder(ExtrUniquePtrHolder&&) = delete;
  ExtrUniquePtrHolder& operator=(const ExtrUniquePtrHolder&) = delete;
  ExtrUniquePtrHolder& operator=(ExtrUniquePtrHolder&&) = delete;

  CacheOwnedPtr<T> push(std::unique_ptr<T> input) {
    if (input == nullptr) {
      return nullptr;
    }
    m_elements.push_back(std::move(input));
    return m_elements.back().get();
  }

  std::unique_ptr<T> move(CacheOwnedPtr<T> input) {
    if (input == nullptr) {
      return nullptr;
    }
    // start from the last as this is more likely
    auto itr = std::find_if(
        m_elements.rbegin(), m_elements.rend(),
        [&input](const std::unique_ptr<T>& x) { return x.get() == input; });
    if (itr == m_elements.crend()) {
      return nullptr;
    }
    return std::unique_ptr<T>(std::move(*itr));
  }
  // The vector of unique_ptr
  std::vector<std::unique_ptr<T>> m_elements;
};
 
}  // namespace Trk
 
#endif