Class Object

Class Object#

Inheritance Relationships#

Derived Types#

Class Documentation#

class Object#

Base class of all object containers.

Sub-class of objects should declare the following static constexpr fields:

  • _type_index: Static type index of the object, if assigned to TypeIndex::kTVMFFIDynObject the type index will be assigned during runtime. Runtime type index can be accessed by ObjectType::TypeIndex();

  • _type_key: The unique string identifier of the type.

  • _type_final: Whether the type is terminal type(there is no subclass of the type in the object system). This field is automatically set by macro TVM_FFI_DECLARE_OBJECT_INFO_FINAL It is still OK to sub-class a terminal object type T and construct it using make_object. But IsInstance check will only show that the object type is T(instead of the sub-class).

  • _type_mutable: Whether we would like to expose cast to non-constant pointer ObjectType* from Any/AnyView. By default, we set to false so it is not exposed.

The following two fields are necessary for base classes that can be sub-classed.

  • _type_child_slots: Number of reserved type index slots for child classes. Used for runtime optimization for type checking in IsInstance. If an object’s type_index is within range of [type_index, type_index + _type_child_slots] Then the object can be quickly decided as sub-class of the current object class. If not, a fallback mechanism is used to check the global type table. Recommendation: set to estimate number of children needed.

  • _type_child_slots_can_overflow: Whether we can add additional child classes even if the number of child classes exceeds the _type_child_slots. A fallback mechanism to check type table will be used. Recommendation: set to false for optimal runtime speed if we know exact number of children.

Two macros are used to declare helper functions in the object:

  • Use TVM_FFI_DECLARE_OBJECT_INFO for object classes that can be sub-classed.

  • Use TVM_FFI_DECLARE_OBJECT_INFO_FINAL for object classes that cannot be sub-classed.

New objects can be created using make_object function. Which will automatically populate the type_index and deleter of the object.

Subclassed by tvm::ffi::ArrayObj, tvm::ffi::ErrorObj, tvm::ffi::FunctionObj, tvm::ffi::MapObj, tvm::ffi::ModuleObj, tvm::ffi::ShapeObj, tvm::ffi::TensorObj, tvm::ffi::details::BytesObjBase, tvm::ffi::reflection::AccessPathObj, tvm::ffi::reflection::AccessStepObj

Public Functions

inline Object()#
template<typename TargetType>
inline bool IsInstance() const#

Check if the object is an instance of TargetType.

Template Parameters:

TargetType – The target type to be checked.

Returns:

Whether the target type is true.

inline int32_t type_index() const#
Returns:

The internal runtime type index of the object.

inline std::string GetTypeKey() const#

Note

this operation is expensive, can be used for error reporting.

Returns:

the type key of the object.

inline uint64_t GetTypeKeyHash() const#
Returns:

A hash value of the return of GetTypeKey.

inline bool unique() const#
Returns:

Whether the object.use_count() == 1.

inline uint64_t use_count() const#

Note

We use STL style naming to be consistent with known API in shared_ptr.

Returns:

The usage count of the cell.

Public Static Functions

static inline std::string TypeIndex2Key(int32_t tindex)#

Get the type key of the corresponding index from runtime.

Parameters:

tindex – The type index.

Returns:

the result.

static inline int32_t RuntimeTypeIndex()#

Get the runtime allocated type index of the type.

Note

Getting this information may need dynamic calls into a global table.

static inline int32_t _GetOrAllocRuntimeTypeIndex()#

Internal function to get or allocate a runtime index.

Public Static Attributes

static constexpr const char *_type_key = StaticTypeKey::kTVMFFIObject#

The type key of the class.

static constexpr bool _type_final = false#

Whether the class is final.

static constexpr bool _type_mutable = false#

Whether allow mutable access to fields.

static constexpr uint32_t _type_child_slots = 0#

The number of child slots of the class to pre-allocate to this type.

static constexpr bool _type_child_slots_can_overflow = true#

Whether allow additional children beyond pre-specified by _type_child_slots.

static constexpr int32_t _type_index = TypeIndex::kTVMFFIObject#

The static type index of the class.

static constexpr int32_t _type_depth = 0#

The static depth of the class in the object hierarchy.

static constexpr TVMFFISEqHashKind _type_s_eq_hash_kind = kTVMFFISEqHashKindUnsupported#

The structural equality and hash kind of the type.

Protected Attributes

TVMFFIObject header_#

header field that is the common prefix of all objects

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