/src/PcapPlusPlus/Common++/header/PointerVector.h

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#pragma once

#include <cstddef>
#include <cstdio>
#include <cstdint>
#include <stdexcept>
#include <vector>
#include <memory>
#include <type_traits>

#include "DeprecationUtils.h"

/// @file

/// @namespace pcpp
/// @brief The main namespace for the PcapPlusPlus lib
namespace pcpp
{
  namespace internal
  {
    /// @brief A helper struct to facilitate the creation of a copy of an object.
    /// @tparam T The type of object to copy.
    /// @tparam Enable Helper parameter for SFINAE.
    template <class T, class Enable = void> struct Copier
    {
      std::unique_ptr<T> operator()(const T& obj) const
      {
        return std::make_unique<T>(obj);
      }
    };

    /// @brief A specialization of Copier to facilitate the safe copying of polymorphic objects via clone() method.
    /// @tparam T The type of object to copy.
    template <class T> struct Copier<T, typename std::enable_if<std::is_polymorphic<T>::value>::type>
    {
      std::unique_ptr<T> operator()(const T& obj) const
      {
        // Clone can return unique_ptr or raw pointer.
        return std::unique_ptr<T>(std::move(obj.clone()));
      }
    };
  }  // namespace internal

  /// @class PointerVector
  /// A template class for representing a std::vector of pointers. Once (a pointer to) an element is added to this
  /// vector, the element responsibility moves to the vector, meaning the PointerVector will free the object once it's
  /// removed from the vector This class wraps std::vector and adds the capability of freeing objects once they're
  /// removed from it
  template <typename T, typename Deleter = std::default_delete<T>> class PointerVector
  {
  public:
    /// Iterator object that is used for iterating all elements in the vector
    using VectorIterator = typename std::vector<T*>::iterator;

    /// Const iterator object that is used for iterating all elements in a constant vector
    using ConstVectorIterator = typename std::vector<T*>::const_iterator;

    /// A constructor that create an empty instance of this object
    PointerVector() = default;

    /// Copies the vector along with all elements inside it.
    /// All elements inside the copied vector are duplicates and the originals remain unchanged.
    /// @param[in] other The vector to copy from.
    /// @remarks As the vector is copied via deep copy, all pointers obtained from the copied vector
    /// reference the duplicates and not the originals.
    PointerVector(const PointerVector& other) : m_Vector(deepCopyUnsafe(other.m_Vector))
    {}

    /// Move constructor. All elements along with their ownership is transferred to the new vector.
    /// @param[in] other The vector to move from.
    PointerVector(PointerVector&& other) noexcept : m_Vector(std::move(other.m_Vector))
    {
      other.m_Vector.clear();
    }

    /// A destructor for this class. The destructor frees all elements that are binded to the vector
    ~PointerVector()
    {
      freeVectorUnsafe(m_Vector);
    }

    /// A copy assignment operator. Replaces the contents with a copy of the contents of other.
    /// See copy constructor for more information on the specific copy procedure.
    /// @param[in] other The vector to copy from.
    /// @return A reference to the current object.
    PointerVector& operator=(const PointerVector& other)
    {
      // Self-assignment check.
      if (this == &other)
      {
        return *this;
      }

      // Saves a copy of the old pointer to defer cleanup.
      auto oldValues = m_Vector;
      try
      {
        m_Vector = deepCopyUnsafe(other.m_Vector);
      }
      // If an exception is thrown during the copy operation, restore old values and rethrow.
      catch (const std::exception&)
      {
        m_Vector = std::move(oldValues);
        throw;
      }
      // Free old values as the new ones have been successfully assigned.
      freeVectorUnsafe(oldValues);
      return *this;
    }

    /// A move assignment operator. Replaces the contents with those of other via move semantics.
    /// The other vector is left empty.
    /// @param[in] other The vector to move from.
    /// @return A reference to the current object.
    PointerVector& operator=(PointerVector&& other) noexcept
    {
      if (this == &other)
      {
        return *this;
      }

      // Releases all current elements.
      clear();
      // Moves the elements of the other vector.
      m_Vector = std::move(other.m_Vector);
      // Explicitly clear the other vector as the standard only guarantees an unspecified valid state after move.
      other.m_Vector.clear();
      return *this;
    }

    /// Clears all elements of the vector while freeing them
    void clear()
    {
      freeVectorUnsafe(m_Vector);
      m_Vector.clear();
    }

    /// Adding a nullptr to the vector is not allowed.
    void pushBack(std::nullptr_t element, bool freeElementOnError = true) = delete;

    /// Add a new (pointer to an) element to the vector
    /// @param[in] element A pointer to an element to assume ownership of.
    /// @param[in] freeElementOnError If set to true, the element is freed if an exception is thrown during the
    /// push.
    /// @throws std::invalid_argument The provided pointer is a nullptr.
    void pushBack(T* element, bool freeElementOnError = true)
    {
      if (element == nullptr)
      {
        throw std::invalid_argument("Element is nullptr");
      }

      try
      {
        m_Vector.push_back(element);
      }
      catch (const std::exception&)
      {
        if (freeElementOnError)
        {
          Deleter{}(element);
        }
        throw;
      }
    }

    /// Add a new element to the vector that has been managed by an unique pointer.
    /// @param[in] element A unique pointer holding an element.
    /// @throws std::invalid_argument The provided pointer is a nullptr.
    /// @remarks If pushBack throws the element is freed immediately.
    void pushBack(std::unique_ptr<T> element)
    {
      if (!element)
      {
        throw std::invalid_argument("Element is nullptr");
      }

      // Release is called after the raw pointer is already inserted into the vector to prevent
      // a memory leak if push_back throws.
      // cppcheck-suppress danglingLifetime
      m_Vector.push_back(element.get());
      element.release();
    }

    /// Get the first element of the vector
    /// @return An iterator object pointing to the first element of the vector
    VectorIterator begin()
    {
      return m_Vector.begin();
    }

    /// Get the first element of a constant vector
    /// @return A const iterator object pointing to the first element of the vector
    ConstVectorIterator begin() const
    {
      return m_Vector.begin();
    }

    /// Get the last element of the vector
    /// @return An iterator object pointing to the last element of the vector
    VectorIterator end()
    {
      return m_Vector.end();
    }

    /// Get the last element of a constant vector
    /// @return A const iterator object pointing to the last element of the vector
    ConstVectorIterator end() const
    {
      return m_Vector.end();
    }

    /// Get number of elements in the vector
    /// @return The number of elements in the vector
    size_t size() const
    {
      return m_Vector.size();
    }

    /// @brief Get the current capacity of the vector.
    /// @return The number of elements that can be held in the vector without requiring a reallocation.
    size_t capacity() const
    {
      return m_Vector.capacity();
    }

    /// @brief Reserve storage for the vector.
    /// @param[in] size The number of elements to reserve space for.
    /// @remarks This method ensures that the vector can hold at least the specified number of elements
    /// without requiring a reallocation.
    void reserve(size_t size)
    {
      m_Vector.reserve(size);
    }

    /// @return A pointer of the first element in the vector
    T* front() const
    {
      return m_Vector.front();
    }

    /// @return A pointer to the last element in the vector
    T* back() const
    {
      return m_Vector.back();
    }

    /// Removes from the vector a single element (position). Once the element is erased, it's also freed
    /// @param[in] position The position of the element to erase
    /// @return An iterator pointing to the new location of the element that followed the last element erased by the
    /// function call
    VectorIterator erase(VectorIterator position)
    {
      Deleter{}(*position);
      return m_Vector.erase(position);
    }

    /// Removes a range of elements from the vector and frees them.
    /// @param[in] first An iterator pointing to the first element in the range to erase.
    /// @param[in] last An iterator pointing to one past the last element in the range to erase.
    /// @return An iterator pointing to the new location of the element that followed the last element erased by the
    /// function call.
    VectorIterator erase(ConstVectorIterator first, ConstVectorIterator last)
    {
      for (auto iter = first; iter != last; ++iter)
      {
        Deleter{}(*iter);
      }
      return m_Vector.erase(first, last);
    }

    /// Remove an element from the vector without freeing it
    /// @param[in, out] position The position of the element to remove from the vector.
    /// The iterator is shifted to the following element after the removal is completed.
    /// @return A pointer to the element which is no longer managed by the vector. It's user responsibility to free
    /// it
    /// @deprecated Deprecated in favor of 'getAndDetach' as that function provides memory safety.
    PCPP_DEPRECATED("Please use the memory safe 'getAndDetach' instead.")
    T* getAndRemoveFromVector(VectorIterator& position)
    {
      T* result = *position;
      position = m_Vector.erase(position);
      return result;
    }

    /// Removes an element from the vector and transfers ownership to the returned unique pointer.
    /// @param[in] index The index of the element to detach.
    /// @return An unique pointer that holds ownership of the detached element.
    std::unique_ptr<T> getAndDetach(size_t index)
    {
      return getAndDetach(m_Vector.begin() + index);
    }

    /// Removes an element from the vector and transfers ownership to the returned unique pointer.
    /// @param[in, out] position An iterator pointing to the element to detach.
    /// The iterator is shifted to the following element after the detach completes.
    /// @return An unique pointer that holds ownership of the detached element.
    std::unique_ptr<T> getAndDetach(VectorIterator& position)
    {
      std::unique_ptr<T> result(*position);
      position = m_Vector.erase(position);
      return result;
    }

    /// Removes an element from the vector and transfers ownership to the returned unique pointer.
    /// @param[in] position An iterator pointing to the element to detach.
    /// @return An unique pointer that holds ownership of the detached element.
    std::unique_ptr<T> getAndDetach(const VectorIterator& position)
    {
      std::unique_ptr<T> result(*position);
      m_Vector.erase(position);
      return result;
    }

    /// Return a pointer to the element in a certain index
    /// @param[in] index The index to retrieve the element from
    /// @return The element at the specified position in the vector
    T* at(int index) const
    {
      return m_Vector.at(index);
    }

  private:
    /// Performs a copy of the vector along with its elements.
    /// The caller is responsible of freeing the copied elements.
    /// @return A vector of pointers to the newly copied elements.
    static std::vector<T*> deepCopyUnsafe(const std::vector<T*>& origin)
    {
      std::vector<T*> copyVec;
      // Allocate the vector initially to ensure no exceptions are thrown during push_back.
      copyVec.reserve(origin.size());

      try
      {
        for (const auto iter : origin)
        {
          std::unique_ptr<T> objCopy = internal::Copier<T>()(*iter);
          // There shouldn't be a memory leak as the vector is reserved.
          copyVec.push_back(objCopy.release());
        }
      }
      catch (const std::exception&)
      {
        freeVectorUnsafe(copyVec);
        throw;
      }

      return copyVec;
    }

    /// Frees all elements inside the vector.
    /// Calling this function with non-heap allocated pointers is UB.
    /// @param[in] origin The vector of elements to free.
    /// @remarks The vector's contents are not cleared and will point to invalid locations in memory.
    static void freeVectorUnsafe(const std::vector<T*>& origin)
    {
      for (auto& obj : origin)
      {
        Deleter{}(obj);
      }
    }

    std::vector<T*> m_Vector;
  };

}  // namespace pcpp

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Created: 2025-07-18 07:14