// Copyright 2018 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef V8_OBJECTS_HEAP_OBJECT_H_
#define V8_OBJECTS_HEAP_OBJECT_H_

#include "src/common/globals.h"
#include "src/objects/instance-type.h"
#include "src/objects/objects.h"
#include "src/objects/tagged-field.h"

// Has to be the last include (doesn't have include guards):
#include "src/objects/object-macros.h"

namespace v8 {
namespace internal {

class Heap;
class PrimitiveHeapObject;
class ExternalPointerSlot;
class IndirectPointerSlot;
template <typename T>
class Tagged;

// HeapObject is the superclass for all classes describing heap allocated
// objects.
class HeapObject : public Object {
 public:
  bool is_null() const {
    return static_cast<Tagged_t>(ptr()) == static_cast<Tagged_t>(kNullAddress);
  }

  // [map]: Contains a map which contains the object's reflective
  // information.
  DECL_GETTER(map, Tagged<Map>)
  inline void set_map(Tagged<Map> value);

  // This method behaves the same as `set_map` but marks the map transition as
  // safe for the concurrent marker (object layout doesn't change) during
  // verification.
  inline void set_map_safe_transition(Tagged<Map> value);

  inline ObjectSlot map_slot() const;

  // The no-write-barrier version.  This is OK if the object is white and in
  // new space, or if the value is an immortal immutable object, like the maps
  // of primitive (non-JS) objects like strings, heap numbers etc.
  inline void set_map_no_write_barrier(Tagged<Map> value,
                                       RelaxedStoreTag = kRelaxedStore);
  inline void set_map_no_write_barrier(Tagged<Map> value, ReleaseStoreTag);
  inline void set_map_safe_transition_no_write_barrier(
      Tagged<Map> value, RelaxedStoreTag = kRelaxedStore);
  inline void set_map_safe_transition_no_write_barrier(Tagged<Map> value,
                                                       ReleaseStoreTag);

  // Access the map using acquire load and release store.
  DECL_ACQUIRE_GETTER(map, Tagged<Map>)
  inline void set_map(Tagged<Map> value, ReleaseStoreTag);
  inline void set_map_safe_transition(Tagged<Map> value, ReleaseStoreTag);

  // Compare-and-swaps map word using release store, returns true if the map
  // word was actually swapped.
  inline bool release_compare_and_swap_map_word_forwarded(
      MapWord old_map_word, Tagged<HeapObject> new_target_object);

  // Initialize the map immediately after the object is allocated.
  // Do not use this outside Heap.
  inline void set_map_after_allocation(
      Tagged<Map> value, WriteBarrierMode mode = UPDATE_WRITE_BARRIER);

  // During garbage collection, the map word of a heap object does not
  // necessarily contain a map pointer.
  DECL_RELAXED_GETTER(map_word, MapWord)
  inline void set_map_word(Tagged<Map> map, RelaxedStoreTag);
  inline void set_map_word_forwarded(Tagged<HeapObject> target_object,
                                     RelaxedStoreTag);

  // Access the map word using acquire load and release store.
  DECL_ACQUIRE_GETTER(map_word, MapWord)
  inline void set_map_word(Tagged<Map> map, ReleaseStoreTag);
  inline void set_map_word_forwarded(Tagged<HeapObject> target_object,
                                     ReleaseStoreTag);

  // This method exists to help remove GetIsolate/GetHeap from HeapObject, in a
  // way that doesn't require passing Isolate/Heap down huge call chains or to
  // places where it might not be safe to access it.
  inline ReadOnlyRoots GetReadOnlyRoots() const;
  // This version is intended to be used for the isolate values produced by
  // i::GetPtrComprCageBase(HeapObject) function which may return nullptr.
  inline ReadOnlyRoots GetReadOnlyRoots(PtrComprCageBase cage_base) const;
  // This is slower, but safe to call during bootstrapping.
  inline ReadOnlyRoots EarlyGetReadOnlyRoots() const;

  // Whether the object is in the RO heap and the RO heap is shared, or in the
  // writable shared heap.
  V8_INLINE bool InAnySharedSpace() const;

  V8_INLINE bool InWritableSharedSpace() const;

  V8_INLINE bool InReadOnlySpace() const;

  // Converts an address to a HeapObject pointer.
  static inline Tagged<HeapObject> FromAddress(Address address) {
    DCHECK_TAG_ALIGNED(address);
    return Tagged<HeapObject>::unchecked_cast(
        Tagged<Object>(address + kHeapObjectTag));
  }

  // Returns the address of this HeapObject.
  inline Address address() const { return ptr() - kHeapObjectTag; }

  // Iterates over pointers contained in the object (including the Map).
  // If it's not performance critical iteration use the non-templatized
  // version.
  void Iterate(PtrComprCageBase cage_base, ObjectVisitor* v);

  template <typename ObjectVisitor>
  inline void IterateFast(PtrComprCageBase cage_base, ObjectVisitor* v);

  template <typename ObjectVisitor>
  inline void IterateFast(Tagged<Map> map, ObjectVisitor* v);

  template <typename ObjectVisitor>
  inline void IterateFast(Tagged<Map> map, int object_size, ObjectVisitor* v);

  // Iterates over all pointers contained in the object except the
  // first map pointer.  The object type is given in the first
  // parameter. This function does not access the map pointer in the
  // object, and so is safe to call while the map pointer is modified.
  // If it's not performance critical iteration use the non-templatized
  // version.
  void IterateBody(PtrComprCageBase cage_base, ObjectVisitor* v);
  void IterateBody(Tagged<Map> map, int object_size, ObjectVisitor* v);

  template <typename ObjectVisitor>
  inline void IterateBodyFast(PtrComprCageBase cage_base, ObjectVisitor* v);

  template <typename ObjectVisitor>
  inline void IterateBodyFast(Tagged<Map> map, int object_size,
                              ObjectVisitor* v);

  // Returns the heap object's size in bytes
  DECL_GETTER(Size, int)

  // Given a heap object's map pointer, returns the heap size in bytes
  // Useful when the map pointer field is used for other purposes.
  // GC internal.
  V8_EXPORT_PRIVATE int SizeFromMap(Tagged<Map> map) const;

  template <class T, typename std::enable_if<std::is_arithmetic<T>::value ||
                                                 std::is_enum<T>::value,
                                             int>::type = 0>
  inline T ReadField(size_t offset) const {
    return ReadMaybeUnalignedValue<T>(field_address(offset));
  }

  template <class T, typename std::enable_if<std::is_arithmetic<T>::value ||
                                                 std::is_enum<T>::value,
                                             int>::type = 0>
  inline void WriteField(size_t offset, T value) const {
    return WriteMaybeUnalignedValue<T>(field_address(offset), value);
  }

  // Atomically reads a field using relaxed memory ordering. Can only be used
  // with integral types whose size is <= kTaggedSize (to guarantee alignment).
  template <class T,
            typename std::enable_if<(std::is_arithmetic<T>::value ||
                                     std::is_enum<T>::value) &&
                                        !std::is_floating_point<T>::value,
                                    int>::type = 0>
  inline T Relaxed_ReadField(size_t offset) const;

  // Atomically writes a field using relaxed memory ordering. Can only be used
  // with integral types whose size is <= kTaggedSize (to guarantee alignment).
  template <class T,
            typename std::enable_if<(std::is_arithmetic<T>::value ||
                                     std::is_enum<T>::value) &&
                                        !std::is_floating_point<T>::value,
                                    int>::type = 0>
  inline void Relaxed_WriteField(size_t offset, T value);

  // Atomically compares and swaps a field using seq cst memory ordering.
  // Contains the required logic to properly handle number comparison.
  template <typename CompareAndSwapImpl>
  static Tagged<Object> SeqCst_CompareAndSwapField(
      Tagged<Object> expected_value, Tagged<Object> new_value,
      CompareAndSwapImpl compare_and_swap_impl);

  //
  // SandboxedPointer_t field accessors.
  //
  inline Address ReadSandboxedPointerField(size_t offset,
                                           PtrComprCageBase cage_base) const;
  inline void WriteSandboxedPointerField(size_t offset,
                                         PtrComprCageBase cage_base,
                                         Address value);
  inline void WriteSandboxedPointerField(size_t offset, Isolate* isolate,
                                         Address value);

  //
  // BoundedSize field accessors.
  //
  inline size_t ReadBoundedSizeField(size_t offset) const;
  inline void WriteBoundedSizeField(size_t offset, size_t value);

  //
  // ExternalPointer_t field accessors.
  //
  template <ExternalPointerTag tag>
  inline void InitExternalPointerField(size_t offset, Isolate* isolate,
                                       Address value);
  template <ExternalPointerTag tag>
  inline Address ReadExternalPointerField(size_t offset,
                                          Isolate* isolate) const;
  template <ExternalPointerTag tag>
  inline void WriteExternalPointerField(size_t offset, Isolate* isolate,
                                        Address value);

  template <ExternalPointerTag tag>
  inline void WriteLazilyInitializedExternalPointerField(size_t offset,
                                                         Isolate* isolate,
                                                         Address value);

  inline void ResetLazilyInitializedExternalPointerField(size_t offset);

  //
  // IndirectPointer field accessors.
  //
  inline Tagged<Object> ReadIndirectPointerField(size_t offset) const;

  //
  // CodePointer field accessors.
  //
  inline void InitCodePointerTableEntryField(size_t offset, Isolate* isolate,
                                             Tagged<Code> owning_code,
                                             Address entrypoint);
  inline Address ReadCodeEntrypointField(size_t offset) const;
  inline void WriteCodeEntrypointField(size_t offset, Address value);

  // Returns the field at offset in obj, as a read/write Object reference.
  // Does no checking, and is safe to use during GC, while maps are invalid.
  // Does not invoke write barrier, so should only be assigned to
  // during marking GC.
  inline ObjectSlot RawField(int byte_offset) const;
  inline MaybeObjectSlot RawMaybeWeakField(int byte_offset) const;
  inline InstructionStreamSlot RawInstructionStreamField(int byte_offset) const;
  inline ExternalPointerSlot RawExternalPointerField(int byte_offset) const;
  inline IndirectPointerSlot RawIndirectPointerField(int byte_offset) const;

  DECL_CAST(HeapObject)

  // Return the write barrier mode for this. Callers of this function
  // must be able to present a reference to an DisallowGarbageCollection
  // object as a sign that they are not going to use this function
  // from code that allocates and thus invalidates the returned write
  // barrier mode.
  inline WriteBarrierMode GetWriteBarrierMode(
      const DisallowGarbageCollection& promise);

  // Dispatched behavior.
  void HeapObjectShortPrint(std::ostream& os);
#ifdef OBJECT_PRINT
  void PrintHeader(std::ostream& os, const char* id);
#endif
  DECL_PRINTER(HeapObject)
  EXPORT_DECL_VERIFIER(HeapObject)
#ifdef VERIFY_HEAP
  inline void VerifyObjectField(Isolate* isolate, int offset);
  inline void VerifySmiField(int offset);
  inline void VerifyMaybeObjectField(Isolate* isolate, int offset);

  // Verify a pointer is a valid HeapObject pointer that points to object
  // areas in the heap.
  static void VerifyHeapPointer(Isolate* isolate, Tagged<Object> p);
  static void VerifyCodePointer(Isolate* isolate, Tagged<Object> p);
#endif

  static inline AllocationAlignment RequiredAlignment(Tagged<Map> map);
  bool inline CheckRequiredAlignment(PtrComprCageBase cage_base) const;

  // Whether the object needs rehashing. That is the case if the object's
  // content depends on v8_flags.hash_seed. When the object is deserialized into
  // a heap with a different hash seed, these objects need to adapt.
  bool NeedsRehashing(InstanceType instance_type) const;
  bool NeedsRehashing(PtrComprCageBase cage_base) const;

  // Rehashing support is not implemented for all objects that need rehashing.
  // With objects that need rehashing but cannot be rehashed, rehashing has to
  // be disabled.
  bool CanBeRehashed(PtrComprCageBase cage_base) const;

  // Rehash the object based on the layout inferred from its map.
  template <typename IsolateT>
  void RehashBasedOnMap(IsolateT* isolate);

  // Layout description.
#define HEAP_OBJECT_FIELDS(V) \
  V(kMapOffset, kTaggedSize)  \
  /* Header size. */          \
  V(kHeaderSize, 0)

  DEFINE_FIELD_OFFSET_CONSTANTS(Object::kHeaderSize, HEAP_OBJECT_FIELDS)
#undef HEAP_OBJECT_FIELDS

  static_assert(kMapOffset == Internals::kHeapObjectMapOffset);

  using MapField = TaggedField<MapWord, HeapObject::kMapOffset>;

  inline Address GetFieldAddress(int field_offset) const;

 protected:
  OBJECT_CONSTRUCTORS(HeapObject, Object);

  inline Address field_address(size_t offset) const {
    return ptr() + offset - kHeapObjectTag;
  }

 private:
  enum class VerificationMode {
    kSafeMapTransition,
    kPotentialLayoutChange,
  };

  enum class EmitWriteBarrier {
    kYes,
    kNo,
  };

  template <EmitWriteBarrier emit_write_barrier, typename MemoryOrder>
  V8_INLINE void set_map(Tagged<Map> value, MemoryOrder order,
                         VerificationMode mode);
};

OBJECT_CONSTRUCTORS_IMPL(HeapObject, Object)
CAST_ACCESSOR(HeapObject)

// Define Tagged<HeapObject> now that HeapObject exists.
constexpr HeapObject Tagged<HeapObject>::operator*() const {
  return ToRawPtr();
}
constexpr detail::TaggedOperatorArrowRef<HeapObject>
Tagged<HeapObject>::operator->() const {
  return detail::TaggedOperatorArrowRef<HeapObject>{ToRawPtr()};
}
// Implicit conversions and explicit casts to/from raw pointers
// TODO(leszeks): Remove once we're using Tagged everywhere.
// NOLINTNEXTLINE
constexpr Tagged<HeapObject>::operator HeapObject() {
  static_assert(kTaggedCanConvertToRawObjects);
  return ToRawPtr();
}
constexpr HeapObject Tagged<HeapObject>::ToRawPtr() const {
  return HeapObject(this->ptr(), HeapObject::SkipTypeCheckTag{});
}

// Overload Is* predicates for HeapObject.
#define IS_TYPE_FUNCTION_DECL(Type)                                            \
  V8_INLINE bool Is##Type(Tagged<HeapObject> obj);                             \
  V8_INLINE bool Is##Type(Tagged<HeapObject> obj, PtrComprCageBase cage_base); \
  V8_INLINE bool Is##Type(HeapObject obj);                                     \
  V8_INLINE bool Is##Type(HeapObject obj, PtrComprCageBase cage_base);
HEAP_OBJECT_TYPE_LIST(IS_TYPE_FUNCTION_DECL)
IS_TYPE_FUNCTION_DECL(HashTableBase)
IS_TYPE_FUNCTION_DECL(SmallOrderedHashTable)
#undef IS_TYPE_FUNCTION_DECL

// Most calls to Is<Oddball> should go via the Tagged<Object> overloads, withst
// an Isolate/LocalIsolate/ReadOnlyRoots parameter.
#define IS_TYPE_FUNCTION_DECL(Type, Value, _)      \
  V8_INLINE bool Is##Type(Tagged<HeapObject> obj); \
  V8_INLINE bool Is##Type(HeapObject obj);
ODDBALL_LIST(IS_TYPE_FUNCTION_DECL)
HOLE_LIST(IS_TYPE_FUNCTION_DECL)
IS_TYPE_FUNCTION_DECL(NullOrUndefined, , /* unused */)
#undef IS_TYPE_FUNCTION_DECL

#define DECL_STRUCT_PREDICATE(NAME, Name, name)                                \
  V8_INLINE bool Is##Name(Tagged<HeapObject> obj);                             \
  V8_INLINE bool Is##Name(Tagged<HeapObject> obj, PtrComprCageBase cage_base); \
  V8_INLINE bool Is##Name(HeapObject obj);                                     \
  V8_INLINE bool Is##Name(HeapObject obj, PtrComprCageBase cage_base);
STRUCT_LIST(DECL_STRUCT_PREDICATE)
#undef DECL_STRUCT_PREDICATE

}  // namespace internal
}  // namespace v8

#include "src/objects/object-macros-undef.h"

#endif  // V8_OBJECTS_HEAP_OBJECT_H_