BLI_implicit_sharing_ptr.hh

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/* SPDX-FileCopyrightText: 2023 Blender Authors
 *
 * SPDX-License-Identifier: GPL-2.0-or-later */
 
#pragma once
 
#include <memory>
#include <utility>
 
#include "BLI_implicit_sharing.hh"
#include "BLI_struct_equality_utils.hh"
 
namespace blender {
 
template<typename T = ImplicitSharingInfo, bool IsStrong = true> class ImplicitSharingPtr {
 private:
  const T *data_ = nullptr;
 
 public:
  ImplicitSharingPtr() = default;
 
  explicit ImplicitSharingPtr(const T *data) : data_(data) {}
 
  /* Implicit conversion from nullptr. */
  ImplicitSharingPtr(std::nullptr_t) : data_(nullptr) {}
 
  ImplicitSharingPtr(const ImplicitSharingPtr &other) : data_(other.data_)
  {
    this->add_user(data_);
  }
 
  ImplicitSharingPtr(ImplicitSharingPtr &&other) : data_(other.data_)
  {
    other.data_ = nullptr;
  }
 
  ~ImplicitSharingPtr()
  {
    this->remove_user_and_delete_if_last(data_);
  }
 
  ImplicitSharingPtr &operator=(const ImplicitSharingPtr &other)
  {
    if (this == &other) {
      return *this;
    }
 
    this->remove_user_and_delete_if_last(data_);
    data_ = other.data_;
    this->add_user(data_);
    return *this;
  }
 
  ImplicitSharingPtr &operator=(ImplicitSharingPtr &&other)
  {
    if (this == &other) {
      return *this;
    }
 
    this->remove_user_and_delete_if_last(data_);
    data_ = other.data_;
    other.data_ = nullptr;
    return *this;
  }
 
  const T *operator->() const
  {
    BLI_assert(data_ != nullptr);
    return data_;
  }
 
  const T &operator*() const
  {
    BLI_assert(data_ != nullptr);
    return *data_;
  }
 
  operator bool() const
  {
    return data_ != nullptr;
  }
 
  const T *get() const
  {
    return data_;
  }
 
  const T *release()
  {
    const T *data = data_;
    data_ = nullptr;
    return data;
  }
 
  void reset()
  {
    this->remove_user_and_delete_if_last(data_);
    data_ = nullptr;
  }
 
  bool has_value() const
  {
    return data_ != nullptr;
  }
 
  uint64_t hash() const
  {
    return get_default_hash(data_);
  }
 
  static uint64_t hash_as(const T *data)
  {
    return get_default_hash(data);
  }
 
  BLI_STRUCT_EQUALITY_OPERATORS_1(ImplicitSharingPtr, data_)
 
  friend bool operator==(const T *a, const ImplicitSharingPtr &b)
  {
    return a == b.data_;
  }
 
  friend bool operator==(const ImplicitSharingPtr &a, const T *b)
  {
    return a.data_ == b;
  }
 
 private:
  static void add_user(const T *data)
  {
    if (data != nullptr) {
      if constexpr (IsStrong) {
        data->add_user();
      }
      else {
        data->add_weak_user();
      }
    }
  }
 
  static void remove_user_and_delete_if_last(const T *data)
  {
    if (data != nullptr) {
      if constexpr (IsStrong) {
        data->remove_user_and_delete_if_last();
      }
      else {
        data->remove_weak_user_and_delete_if_last();
      }
    }
  }
};
 
using WeakImplicitSharingPtr = ImplicitSharingPtr<ImplicitSharingInfo, false>;
 
class ImplicitSharingPtrAndData {
 public:
  ImplicitSharingPtr<> sharing_info;
  const void *data = nullptr;
 
  ImplicitSharingPtrAndData() = default;
  ImplicitSharingPtrAndData(ImplicitSharingPtr<> sharing_info, const void *data)
      : sharing_info(std::move(sharing_info)), data(data)
  {
  }
 
  ImplicitSharingPtrAndData(const ImplicitSharingPtrAndData &other)
      : sharing_info(other.sharing_info), data(other.data)
  {
  }
 
  ImplicitSharingPtrAndData(ImplicitSharingPtrAndData &&other)
      : sharing_info(std::move(other.sharing_info)), data(std::exchange(other.data, nullptr))
  {
  }
 
  ImplicitSharingPtrAndData &operator=(const ImplicitSharingPtrAndData &other)
  {
    if (this == &other) {
      return *this;
    }
    std::destroy_at(this);
    new (this) ImplicitSharingPtrAndData(other);
    return *this;
  }
 
  ImplicitSharingPtrAndData &operator=(ImplicitSharingPtrAndData &&other)
  {
    if (this == &other) {
      return *this;
    }
    std::destroy_at(this);
    new (this) ImplicitSharingPtrAndData(std::move(other));
    return *this;
  }
 
  ~ImplicitSharingPtrAndData()
  {
    this->data = nullptr;
  }
 
  bool has_value() const
  {
    return this->sharing_info.has_value();
  }
};
 
}  // namespace blender