BLI_generic_virtual_array.hh

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/* SPDX-FileCopyrightText: 2023 Blender Authors
 *
 * SPDX-License-Identifier: GPL-2.0-or-later */
 
#pragma once

 
#include "BLI_generic_array.hh"
#include "BLI_generic_span.hh"
#include "BLI_virtual_array.hh"
 
namespace blender {
 
/* -------------------------------------------------------------------- */
 
class GVArray;
class GVArrayImpl;
class GVMutableArray;
class GVMutableArrayImpl;
 
/* A generically typed version of #VArrayImpl. */
class GVArrayImpl {
 protected:
  const CPPType *type_;
  int64_t size_;
 
 public:
  GVArrayImpl(const CPPType &type, int64_t size);
  virtual ~GVArrayImpl() = default;
 
  const CPPType &type() const;
 
  int64_t size() const;
 
  virtual void get(int64_t index, void *r_value) const;
  virtual void get_to_uninitialized(int64_t index, void *r_value) const = 0;
 
  virtual CommonVArrayInfo common_info() const;
 
  virtual void materialize(const IndexMask &mask, void *dst, bool dst_is_uninitialized) const;
  virtual void materialize_compressed(const IndexMask &mask,
                                      void *dst,
                                      bool dst_is_uninitialized) const;
 
  virtual bool try_assign_VArray(void *varray) const;
};
 
/* A generic version of #VMutableArrayImpl. */
class GVMutableArrayImpl : public GVArrayImpl {
 public:
  GVMutableArrayImpl(const CPPType &type, int64_t size) : GVArrayImpl(type, size) {}
 
  virtual void set_by_copy(int64_t index, const void *value);
  virtual void set_by_relocate(int64_t index, void *value);
  virtual void set_by_move(int64_t index, void *value) = 0;
 
  virtual void set_all(const void *src);
 
  virtual bool try_assign_VMutableArray(void *varray) const;
};

 
/* -------------------------------------------------------------------- */
 
namespace detail {
struct GVArrayAnyExtraInfo {
  const GVArrayImpl *(*get_varray)(const void *buffer) =
      [](const void * /*buffer*/) -> const GVArrayImpl * { return nullptr; };
 
  template<typename StorageT> static constexpr GVArrayAnyExtraInfo get();
};
}  // namespace detail
 
class GVMutableArray;

class GVArrayCommon {
 protected:
  using Storage = Any<detail::GVArrayAnyExtraInfo, 40, 8>;
 
  const GVArrayImpl *impl_ = nullptr;
  Storage storage_;
 
  GVArrayCommon() = default;
  GVArrayCommon(const GVArrayCommon &other);
  GVArrayCommon(GVArrayCommon &&other) noexcept;
  GVArrayCommon(const GVArrayImpl *impl);
  GVArrayCommon(std::shared_ptr<const GVArrayImpl> impl);
  ~GVArrayCommon();
 
  template<typename ImplT, typename... Args> void emplace(Args &&...args);
 
  void copy_from(const GVArrayCommon &other);
  void move_from(GVArrayCommon &&other) noexcept;
 
  const GVArrayImpl *impl_from_storage() const;
 
 public:
  const CPPType &type() const;
  operator bool() const;
 
  int64_t size() const;
  bool is_empty() const;
  IndexRange index_range() const;
 
  template<typename T> bool try_assign_VArray(VArray<T> &varray) const;
  bool may_have_ownership() const;
 
  void materialize(void *dst) const;
  void materialize(const IndexMask &mask, void *dst) const;
 
  void materialize_to_uninitialized(void *dst) const;
  void materialize_to_uninitialized(const IndexMask &mask, void *dst) const;
 
  void materialize_compressed(const IndexMask &mask, void *dst) const;
  void materialize_compressed_to_uninitialized(const IndexMask &mask, void *dst) const;
 
  CommonVArrayInfo common_info() const;

  bool is_span() const;
  GSpan get_internal_span() const;

  bool is_single() const;
  void get_internal_single(void *r_value) const;
  void get_internal_single_to_uninitialized(void *r_value) const;
 
  void get(int64_t index, void *r_value) const;
  template<typename T> T get(int64_t index) const;
  void get_to_uninitialized(int64_t index, void *r_value) const;
};

class GVArray : public GVArrayCommon {
 private:
  friend GVMutableArray;
 
 public:
  GVArray() = default;
 
  GVArray(const GVArray &other);
  GVArray(GVArray &&other) noexcept;
  GVArray(const GVArrayImpl *impl);
  GVArray(std::shared_ptr<const GVArrayImpl> impl);
 
  GVArray(varray_tag::span /*tag*/, GSpan span);
  GVArray(varray_tag::single_ref /*tag*/, const CPPType &type, int64_t size, const void *value);
  GVArray(varray_tag::single /*tag*/, const CPPType &type, int64_t size, const void *value);
 
  template<typename T> GVArray(const VArray<T> &varray);
  template<typename T> GVArray(VArray<T> &&varray);
  template<typename T> VArray<T> typed() const;
 
  template<typename ImplT, typename... Args> static GVArray from(Args &&...args);
 
  static GVArray from_single(const CPPType &type, int64_t size, const void *value);
  static GVArray from_single_ref(const CPPType &type, int64_t size, const void *value);
  static GVArray from_single_default(const CPPType &type, int64_t size);
  static GVArray from_span(GSpan span);
  static GVArray from_garray(GArray<> array);
  static GVArray from_empty(const CPPType &type);
 
  GVArray slice(IndexRange slice) const;
 
  GVArray &operator=(const GVArray &other);
  GVArray &operator=(GVArray &&other) noexcept;
 
  const GVArrayImpl *get_implementation() const
  {
    return impl_;
  }
};

class GVMutableArray : public GVArrayCommon {
 public:
  GVMutableArray() = default;
  GVMutableArray(const GVMutableArray &other);
  GVMutableArray(GVMutableArray &&other) noexcept;
  GVMutableArray(GVMutableArrayImpl *impl);
  GVMutableArray(std::shared_ptr<GVMutableArrayImpl> impl);
 
  template<typename T> GVMutableArray(const VMutableArray<T> &varray);
  template<typename T> VMutableArray<T> typed() const;
 
  template<typename ImplT, typename... Args> static GVMutableArray from(Args &&...args);
 
  static GVMutableArray from_span(GMutableSpan span);
 
  operator GVArray() const &;
  operator GVArray() && noexcept;
 
  GVMutableArray &operator=(const GVMutableArray &other);
  GVMutableArray &operator=(GVMutableArray &&other) noexcept;
 
  GMutableSpan get_internal_span() const;
 
  template<typename T> bool try_assign_VMutableArray(VMutableArray<T> &varray) const;
 
  void set_by_copy(int64_t index, const void *value);
  void set_by_move(int64_t index, void *value);
  void set_by_relocate(int64_t index, void *value);
 
  void fill(const void *value);
  void set_all(const void *src);
 
  GVMutableArrayImpl *get_implementation() const;
 
 private:
  GVMutableArrayImpl *get_impl() const;
};

 
/* -------------------------------------------------------------------- */
 
/* A generic version of VArraySpan. */
class GVArraySpan : public GSpan {
 private:
  GVArray varray_;
  void *owned_data_ = nullptr;
 
 public:
  GVArraySpan();
  GVArraySpan(GVArray varray);
  template<typename T> GVArraySpan(VArray<T> varray) : GVArraySpan(GVArray(varray)) {}
  GVArraySpan(GVArraySpan &&other);
  ~GVArraySpan();
  GVArraySpan &operator=(GVArraySpan &&other);
};
 
/* A generic version of MutableVArraySpan. */
class GMutableVArraySpan : public GMutableSpan, NonCopyable, NonMovable {
 private:
  GVMutableArray varray_;
  void *owned_data_ = nullptr;
  bool save_has_been_called_ = false;
  bool show_not_saved_warning_ = true;
 
 public:
  GMutableVArraySpan();
  GMutableVArraySpan(GVMutableArray varray, bool copy_values_to_span = true);
  GMutableVArraySpan(GMutableVArraySpan &&other);
  ~GMutableVArraySpan();
  GMutableVArraySpan &operator=(GMutableVArraySpan &&other);
 
  const GVMutableArray &varray() const;
 
  void save();
  void disable_not_applied_warning();
};

 
/* -------------------------------------------------------------------- */
 
/* Used to convert a typed virtual array into a generic one. */
template<typename T> class GVArrayImpl_For_VArray : public GVArrayImpl {
 protected:
  VArray<T> varray_;
 
 public:
  GVArrayImpl_For_VArray(VArray<T> varray)
      : GVArrayImpl(CPPType::get<T>(), varray.size()), varray_(std::move(varray))
  {
  }
 
 protected:
  void get(const int64_t index, void *r_value) const override
  {
    *static_cast<T *>(r_value) = varray_[index];
  }
 
  void get_to_uninitialized(const int64_t index, void *r_value) const override
  {
    new (r_value) T(varray_[index]);
  }
 
  void materialize(const IndexMask &mask,
                   void *dst,
                   const bool dst_is_uninitialized) const override
  {
    varray_.get_implementation()->materialize(mask, static_cast<T *>(dst), dst_is_uninitialized);
  }
 
  void materialize_compressed(const IndexMask &mask,
                              void *dst,
                              const bool dst_is_uninitialized) const override
  {
    varray_.get_implementation()->materialize_compressed(
        mask, static_cast<T *>(dst), dst_is_uninitialized);
  }
 
  bool try_assign_VArray(void *varray) const override
  {
    *(VArray<T> *)varray = varray_;
    return true;
  }
 
  CommonVArrayInfo common_info() const override
  {
    return varray_.common_info();
  }
};
 
/* Used to convert any generic virtual array into a typed one. */
template<typename T> class VArrayImpl_For_GVArray : public VArrayImpl<T> {
 protected:
  GVArray varray_;
 
 public:
  VArrayImpl_For_GVArray(GVArray varray) : VArrayImpl<T>(varray.size()), varray_(std::move(varray))
  {
    BLI_assert(varray_);
    BLI_assert(varray_.type().template is<T>());
  }
 
 protected:
  T get(const int64_t index) const override
  {
    T value;
    varray_.get(index, &value);
    return value;
  }
 
  CommonVArrayInfo common_info() const override
  {
    return varray_.common_info();
  }
 
  bool try_assign_GVArray(GVArray &varray) const override
  {
    varray = varray_;
    return true;
  }
 
  void materialize(const IndexMask &mask, T *dst, const bool dst_is_uninitialized) const override
  {
    varray_.get_implementation()->materialize(mask, dst, dst_is_uninitialized);
  }
 
  void materialize_compressed(const IndexMask &mask,
                              T *dst,
                              const bool dst_is_uninitialized) const override
  {
    varray_.get_implementation()->materialize_compressed(mask, dst, dst_is_uninitialized);
  }
};
 
/* Used to convert any typed virtual mutable array into a generic one. */
template<typename T> class GVMutableArrayImpl_For_VMutableArray : public GVMutableArrayImpl {
 protected:
  VMutableArray<T> varray_;
 
 public:
  GVMutableArrayImpl_For_VMutableArray(VMutableArray<T> varray)
      : GVMutableArrayImpl(CPPType::get<T>(), varray.size()), varray_(std::move(varray))
  {
  }
 
 protected:
  void get(const int64_t index, void *r_value) const override
  {
    *static_cast<T *>(r_value) = varray_[index];
  }
 
  void get_to_uninitialized(const int64_t index, void *r_value) const override
  {
    new (r_value) T(varray_[index]);
  }
 
  CommonVArrayInfo common_info() const override
  {
    return varray_.common_info();
  }
 
  void set_by_copy(const int64_t index, const void *value) override
  {
    const T &value_ = *(const T *)value;
    varray_.set(index, value_);
  }
 
  void set_by_relocate(const int64_t index, void *value) override
  {
    T &value_ = *static_cast<T *>(value);
    varray_.set(index, std::move(value_));
    value_.~T();
  }
 
  void set_by_move(const int64_t index, void *value) override
  {
    T &value_ = *static_cast<T *>(value);
    varray_.set(index, std::move(value_));
  }
 
  void set_all(const void *src) override
  {
    varray_.set_all(Span(static_cast<const T *>(src), size_));
  }
 
  void materialize(const IndexMask &mask,
                   void *dst,
                   const bool dst_is_uninitialized) const override
  {
    varray_.get_implementation()->materialize(mask, static_cast<T *>(dst), dst_is_uninitialized);
  }
 
  void materialize_compressed(const IndexMask &mask,
                              void *dst,
                              const bool dst_is_uninitialized) const override
  {
    varray_.get_implementation()->materialize_compressed(
        mask, static_cast<T *>(dst), dst_is_uninitialized);
  }
 
  bool try_assign_VArray(void *varray) const override
  {
    *(VArray<T> *)varray = varray_;
    return true;
  }
 
  bool try_assign_VMutableArray(void *varray) const override
  {
    *(VMutableArray<T> *)varray = varray_;
    return true;
  }
};
 
/* Used to convert an generic mutable virtual array into a typed one. */
template<typename T> class VMutableArrayImpl_For_GVMutableArray : public VMutableArrayImpl<T> {
 protected:
  GVMutableArray varray_;
 
 public:
  VMutableArrayImpl_For_GVMutableArray(GVMutableArray varray)
      : VMutableArrayImpl<T>(varray.size()), varray_(varray)
  {
    BLI_assert(varray_);
    BLI_assert(varray_.type().template is<T>());
  }
 
 private:
  T get(const int64_t index) const override
  {
    T value;
    varray_.get(index, &value);
    return value;
  }
 
  void set(const int64_t index, T value) override
  {
    varray_.set_by_relocate(index, &value);
  }
 
  CommonVArrayInfo common_info() const override
  {
    return varray_.common_info();
  }
 
  bool try_assign_GVArray(GVArray &varray) const override
  {
    varray = varray_;
    return true;
  }
 
  bool try_assign_GVMutableArray(GVMutableArray &varray) const override
  {
    varray = varray_;
    return true;
  }
 
  void materialize(const IndexMask &mask, T *dst, const bool dst_is_uninitialized) const override
  {
    varray_.get_implementation()->materialize(mask, dst, dst_is_uninitialized);
  }
 
  void materialize_compressed(const IndexMask &mask,
                              T *dst,
                              const bool dst_is_uninitialized) const override
  {
    varray_.get_implementation()->materialize_compressed(mask, dst, dst_is_uninitialized);
  }
};

 
/* -------------------------------------------------------------------- */
 
class GVArrayImpl_For_GSpan : public GVMutableArrayImpl {
 protected:
  void *data_ = nullptr;
  const int64_t element_size_;
 
 public:
  GVArrayImpl_For_GSpan(const GMutableSpan span)
      : GVMutableArrayImpl(span.type(), span.size()),
        data_(span.data()),
        element_size_(span.type().size)
  {
  }
 
 protected:
  GVArrayImpl_For_GSpan(const CPPType &type, int64_t size)
      : GVMutableArrayImpl(type, size), element_size_(type.size)
  {
  }
 
 public:
  void get(int64_t index, void *r_value) const override;
  void get_to_uninitialized(int64_t index, void *r_value) const override;
 
  void set_by_copy(int64_t index, const void *value) override;
  void set_by_move(int64_t index, void *value) override;
  void set_by_relocate(int64_t index, void *value) override;
 
  CommonVArrayInfo common_info() const override;
 
  void materialize(const IndexMask &mask, void *dst, bool dst_is_uninitialized) const override;
 
  void materialize_compressed(const IndexMask &mask,
                              void *dst,
                              bool dst_is_uninitialized) const override;
};
 
class GVArrayImpl_For_GSpan_final final : public GVArrayImpl_For_GSpan {
 public:
  using GVArrayImpl_For_GSpan::GVArrayImpl_For_GSpan;
 
 private:
  CommonVArrayInfo common_info() const override;
};
 
template<> inline constexpr bool is_trivial_extended_v<GVArrayImpl_For_GSpan_final> = true;

 
/* -------------------------------------------------------------------- */
 
class GVArrayImpl_For_SingleValueRef : public GVArrayImpl {
 protected:
  const void *value_ = nullptr;
 
 public:
  GVArrayImpl_For_SingleValueRef(const CPPType &type, const int64_t size, const void *value)
      : GVArrayImpl(type, size), value_(value)
  {
  }
 
 protected:
  GVArrayImpl_For_SingleValueRef(const CPPType &type, const int64_t size) : GVArrayImpl(type, size)
  {
  }
 
  void get(const int64_t index, void *r_value) const override;
  void get_to_uninitialized(const int64_t index, void *r_value) const override;
  CommonVArrayInfo common_info() const override;
  void materialize(const IndexMask &mask, void *dst, bool dst_is_uninitialized) const override;
  void materialize_compressed(const IndexMask &mask,
                              void *dst,
                              bool dst_is_uninitialized) const override;
};
 
class GVArrayImpl_For_SingleValueRef_final final : public GVArrayImpl_For_SingleValueRef {
 public:
  using GVArrayImpl_For_SingleValueRef::GVArrayImpl_For_SingleValueRef;
 
 private:
  CommonVArrayInfo common_info() const override;
};
 
template<>
inline constexpr bool is_trivial_extended_v<GVArrayImpl_For_SingleValueRef_final> = true;

 
/* -------------------------------------------------------------------- */
 
inline GVArrayImpl::GVArrayImpl(const CPPType &type, const int64_t size)
    : type_(&type), size_(size)
{
  BLI_assert(size_ >= 0);
}
 
inline const CPPType &GVArrayImpl::type() const
{
  return *type_;
}
 
inline int64_t GVArrayImpl::size() const
{
  return size_;
}

 
/* -------------------------------------------------------------------- */
 
inline void GVMutableArray::set_by_copy(const int64_t index, const void *value)
{
  BLI_assert(index >= 0);
  BLI_assert(index < this->size());
  this->get_impl()->set_by_copy(index, value);
}
 
inline void GVMutableArray::set_by_move(const int64_t index, void *value)
{
  BLI_assert(index >= 0);
  BLI_assert(index < this->size());
  this->get_impl()->set_by_move(index, value);
}
 
inline void GVMutableArray::set_by_relocate(const int64_t index, void *value)
{
  BLI_assert(index >= 0);
  BLI_assert(index < this->size());
  this->get_impl()->set_by_relocate(index, value);
}
 
template<typename T>
inline bool GVMutableArray::try_assign_VMutableArray(VMutableArray<T> &varray) const
{
  BLI_assert(impl_->type().is<T>());
  return this->get_impl()->try_assign_VMutableArray(&varray);
}
 
inline GVMutableArrayImpl *GVMutableArray::get_impl() const
{
  return const_cast<GVMutableArrayImpl *>(static_cast<const GVMutableArrayImpl *>(impl_));
}

 
/* -------------------------------------------------------------------- */
 
template<typename ImplT, typename... Args> inline void GVArrayCommon::emplace(Args &&...args)
{
  static_assert(std::is_base_of_v<GVArrayImpl, ImplT>);
  if constexpr (std::is_copy_constructible_v<ImplT> && Storage::template is_inline_v<ImplT>) {
    impl_ = &storage_.template emplace<ImplT>(std::forward<Args>(args)...);
  }
  else {
    std::shared_ptr<const GVArrayImpl> ptr = std::make_shared<ImplT>(std::forward<Args>(args)...);
    impl_ = &*ptr;
    storage_ = std::move(ptr);
  }
}
 
/* Copies the value at the given index into the provided storage. The `r_value` pointer is
 * expected to point to initialized memory. */
inline void GVArrayCommon::get(const int64_t index, void *r_value) const
{
  BLI_assert(index >= 0);
  BLI_assert(index < this->size());
  impl_->get(index, r_value);
}
 
template<typename T> inline T GVArrayCommon::get(const int64_t index) const
{
  BLI_assert(index >= 0);
  BLI_assert(index < this->size());
  BLI_assert(this->type().is<T>());
  T value{};
  impl_->get(index, &value);
  return value;
}
 
/* Same as `get`, but `r_value` is expected to point to uninitialized memory. */
inline void GVArrayCommon::get_to_uninitialized(const int64_t index, void *r_value) const
{
  BLI_assert(index >= 0);
  BLI_assert(index < this->size());
  impl_->get_to_uninitialized(index, r_value);
}
 
template<typename T> inline bool GVArrayCommon::try_assign_VArray(VArray<T> &varray) const
{
  BLI_assert(impl_->type().is<T>());
  return impl_->try_assign_VArray(&varray);
}
 
inline const CPPType &GVArrayCommon::type() const
{
  return impl_->type();
}
 
inline GVArrayCommon::operator bool() const
{
  return impl_ != nullptr;
}
 
inline CommonVArrayInfo GVArrayCommon::common_info() const
{
  return impl_->common_info();
}
 
inline int64_t GVArrayCommon::size() const
{
  if (impl_ == nullptr) {
    return 0;
  }
  return impl_->size();
}
 
inline bool GVArrayCommon::is_empty() const
{
  return this->size() == 0;
}


template<typename T, bool UseSingle, bool UseSpan> struct GVArrayDevirtualizer {
  const GVArrayImpl &varray_impl;
 
  template<typename Fn> bool devirtualize(const Fn &fn) const
  {
    const CommonVArrayInfo info = this->varray_impl.common_info();
    const int64_t size = this->varray_impl.size();
    if constexpr (UseSingle) {
      if (info.type == CommonVArrayInfo::Type::Single) {
        return fn(SingleAsSpan<T>(*static_cast<const T *>(info.data), size));
      }
    }
    if constexpr (UseSpan) {
      if (info.type == CommonVArrayInfo::Type::Span) {
        return fn(Span<T>(static_cast<const T *>(info.data), size));
      }
    }
    return false;
  }
};
 
/* -------------------------------------------------------------------- */
 
inline GVArray::GVArray(varray_tag::span /*tag*/, const GSpan span)
{
  /* Use const-cast because the underlying virtual array implementation is shared between const
   * and non const data. */
  GMutableSpan mutable_span{span.type(), const_cast<void *>(span.data()), span.size()};
  this->emplace<GVArrayImpl_For_GSpan_final>(mutable_span);
}
 
inline GVArray::GVArray(varray_tag::single_ref /*tag*/,
                        const CPPType &type,
                        const int64_t size,
                        const void *value)
{
  this->emplace<GVArrayImpl_For_SingleValueRef_final>(type, size, value);
}
 
namespace detail {
template<typename StorageT> constexpr GVArrayAnyExtraInfo GVArrayAnyExtraInfo::get()
{
  static_assert(std::is_base_of_v<GVArrayImpl, StorageT> ||
                is_same_any_v<StorageT, const GVArrayImpl *, std::shared_ptr<const GVArrayImpl>>);
 
  if constexpr (std::is_base_of_v<GVArrayImpl, StorageT>) {
    return {[](const void *buffer) {
      return static_cast<const GVArrayImpl *>((const StorageT *)buffer);
    }};
  }
  else if constexpr (std::is_same_v<StorageT, const GVArrayImpl *>) {
    return {[](const void *buffer) { return *(const StorageT *)buffer; }};
  }
  else if constexpr (std::is_same_v<StorageT, std::shared_ptr<const GVArrayImpl>>) {
    return {[](const void *buffer) { return ((const StorageT *)buffer)->get(); }};
  }
  else {
    BLI_assert_unreachable();
    return {};
  }
}
}  // namespace detail
 
template<typename ImplT, typename... Args> inline GVArray GVArray::from(Args &&...args)
{
  static_assert(std::is_base_of_v<GVArrayImpl, ImplT>);
  GVArray varray;
  varray.template emplace<ImplT>(std::forward<Args>(args)...);
  return varray;
}
 
template<typename T> inline GVArray::GVArray(const VArray<T> &varray) : GVArray(VArray<T>(varray))
{
}
 
template<typename T> inline GVArray::GVArray(VArray<T> &&varray)
{
  if (!varray) {
    return;
  }
  const CommonVArrayInfo info = varray.common_info();
  if (info.type == CommonVArrayInfo::Type::Single) {
    *this = GVArray::from_single(CPPType::get<T>(), varray.size(), info.data);
    return;
  }
  /* Need to check for ownership, because otherwise the referenced data can be destructed when
   * #this is destructed. */
  if (info.type == CommonVArrayInfo::Type::Span && !info.may_have_ownership) {
    *this = GVArray::from_span(GSpan(CPPType::get<T>(), info.data, varray.size()));
    return;
  }
  if (varray.try_assign_GVArray(*this)) {
    return;
  }
  *this = GVArray::from<GVArrayImpl_For_VArray<T>>(std::move(varray));
}
 
template<typename T> inline VArray<T> GVArray::typed() const
{
  if (!*this) {
    return {};
  }
  BLI_assert(impl_->type().is<T>());
  const CommonVArrayInfo info = this->common_info();
  if (info.type == CommonVArrayInfo::Type::Single) {
    return VArray<T>::from_single(*static_cast<const T *>(info.data), this->size());
  }
  /* Need to check for ownership, because otherwise the referenced data can be destructed when
   * #this is destructed. */
  if (info.type == CommonVArrayInfo::Type::Span && !info.may_have_ownership) {
    return VArray<T>::from_span(Span<T>(static_cast<const T *>(info.data), this->size()));
  }
  VArray<T> varray;
  if (this->try_assign_VArray(varray)) {
    return varray;
  }
  return VArray<T>::template from<VArrayImpl_For_GVArray<T>>(*this);
}

 
/* -------------------------------------------------------------------- */
 
template<typename ImplT, typename... Args>
inline GVMutableArray GVMutableArray::from(Args &&...args)
{
  static_assert(std::is_base_of_v<GVMutableArrayImpl, ImplT>);
  GVMutableArray varray;
  varray.emplace<ImplT>(std::forward<Args>(args)...);
  return varray;
}
 
template<typename T> inline GVMutableArray::GVMutableArray(const VMutableArray<T> &varray)
{
  if (!varray) {
    return;
  }
  const CommonVArrayInfo info = varray.common_info();
  if (info.type == CommonVArrayInfo::Type::Span && !info.may_have_ownership) {
    *this = GVMutableArray::from_span(
        GMutableSpan(CPPType::get<T>(), const_cast<void *>(info.data), varray.size()));
    return;
  }
  if (varray.try_assign_GVMutableArray(*this)) {
    return;
  }
  *this = GVMutableArray::from<GVMutableArrayImpl_For_VMutableArray<T>>(varray);
}
 
template<typename T> inline VMutableArray<T> GVMutableArray::typed() const
{
  if (!*this) {
    return {};
  }
  BLI_assert(this->type().is<T>());
  const CommonVArrayInfo info = this->common_info();
  if (info.type == CommonVArrayInfo::Type::Span && !info.may_have_ownership) {
    return VMutableArray<T>::from_span(
        MutableSpan<T>(const_cast<T *>(static_cast<const T *>(info.data)), this->size()));
  }
  VMutableArray<T> varray;
  if (this->try_assign_VMutableArray(varray)) {
    return varray;
  }
  return VMutableArray<T>::template from<VMutableArrayImpl_For_GVMutableArray<T>>(*this);
}

 
}  // namespace blender