// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

#ifndef VM_RAW_OBJECT_H_
#define VM_RAW_OBJECT_H_

#include "platform/assert.h"
#include "vm/atomic.h"
#include "vm/globals.h"
#include "vm/snapshot.h"
#include "vm/token.h"
#include "vm/token_position.h"
#include "vm/verified_memory.h"

namespace dart {

// Macrobatics to define the Object hierarchy of VM implementation classes.
#define CLASS_LIST_NO_OBJECT_NOR_STRING_NOR_ARRAY(V)                           \
  V(Class)                                                                     \
  V(UnresolvedClass)                                                           \
  V(TypeArguments)                                                             \
  V(PatchClass)                                                                \
  V(Function)                                                                  \
  V(ClosureData)                                                               \
  V(RedirectionData)                                                           \
  V(Field)                                                                     \
  V(LiteralToken)                                                              \
  V(TokenStream)                                                               \
  V(Script)                                                                    \
  V(Library)                                                                   \
  V(Namespace)                                                                 \
  V(Code)                                                                      \
  V(Instructions)                                                              \
  V(ObjectPool)                                                                \
  V(PcDescriptors)                                                             \
  V(CodeSourceMap)                                                             \
  V(Stackmap)                                                                  \
  V(LocalVarDescriptors)                                                       \
  V(ExceptionHandlers)                                                         \
  V(Context)                                                                   \
  V(ContextScope)                                                              \
  V(ICData)                                                                    \
  V(MegamorphicCache)                                                          \
  V(SubtypeTestCache)                                                          \
  V(Error)                                                                     \
    V(ApiError)                                                                \
    V(LanguageError)                                                           \
    V(UnhandledException)                                                      \
    V(UnwindError)                                                             \
  V(Instance)                                                                  \
    V(LibraryPrefix)                                                           \
    V(AbstractType)                                                            \
      V(Type)                                                                  \
      V(TypeRef)                                                               \
      V(TypeParameter)                                                         \
      V(BoundedType)                                                           \
      V(MixinAppType)                                                          \
    V(Closure)                                                                 \
    V(Number)                                                                  \
      V(Integer)                                                               \
        V(Smi)                                                                 \
        V(Mint)                                                                \
        V(Bigint)                                                              \
      V(Double)                                                                \
    V(Bool)                                                                    \
    V(GrowableObjectArray)                                                     \
    V(Float32x4)                                                               \
    V(Int32x4)                                                                 \
    V(Float64x2)                                                               \
    V(TypedData)                                                               \
    V(ExternalTypedData)                                                       \
    V(Capability)                                                              \
    V(ReceivePort)                                                             \
    V(SendPort)                                                                \
    V(Stacktrace)                                                              \
    V(RegExp)                                                                  \
    V(WeakProperty)                                                            \
    V(MirrorReference)                                                         \
    V(LinkedHashMap)                                                           \
    V(UserTag)                                                                 \

#define CLASS_LIST_ARRAYS(V)                                                   \
  V(Array)                                                                     \
    V(ImmutableArray)                                                          \

#define CLASS_LIST_STRINGS(V)                                                  \
  V(String)                                                                    \
    V(OneByteString)                                                           \
    V(TwoByteString)                                                           \
    V(ExternalOneByteString)                                                   \
    V(ExternalTwoByteString)

#define CLASS_LIST_TYPED_DATA(V)                                               \
  V(Int8Array)                                                                 \
  V(Uint8Array)                                                                \
  V(Uint8ClampedArray)                                                         \
  V(Int16Array)                                                                \
  V(Uint16Array)                                                               \
  V(Int32Array)                                                                \
  V(Uint32Array)                                                               \
  V(Int64Array)                                                                \
  V(Uint64Array)                                                               \
  V(Float32Array)                                                              \
  V(Float64Array)                                                              \
  V(Float32x4Array)                                                            \
  V(Int32x4Array)                                                              \
  V(Float64x2Array)                                                            \

#define DART_CLASS_LIST_TYPED_DATA(V)                                          \
  V(Int8)                                                                      \
  V(Uint8)                                                                     \
  V(Uint8Clamped)                                                              \
  V(Int16)                                                                     \
  V(Uint16)                                                                    \
  V(Int32)                                                                     \
  V(Uint32)                                                                    \
  V(Int64)                                                                     \
  V(Uint64)                                                                    \
  V(Float32)                                                                   \
  V(Float64)                                                                   \
  V(Float32x4)                                                                 \
  V(Int32x4)                                                                   \
  V(Float64x2)

#define CLASS_LIST_FOR_HANDLES(V)                                              \
  CLASS_LIST_NO_OBJECT_NOR_STRING_NOR_ARRAY(V)                                 \
  V(Array)                                                                     \
  V(String)

#define CLASS_LIST_NO_OBJECT(V)                                                \
  CLASS_LIST_NO_OBJECT_NOR_STRING_NOR_ARRAY(V)                                 \
  CLASS_LIST_ARRAYS(V)                                                         \
  CLASS_LIST_STRINGS(V)

#define CLASS_LIST(V)                                                          \
  V(Object)                                                                    \
  CLASS_LIST_NO_OBJECT(V)


// Forward declarations.
class Isolate;
#define DEFINE_FORWARD_DECLARATION(clazz)                                      \
  class Raw##clazz;
CLASS_LIST(DEFINE_FORWARD_DECLARATION)
#undef DEFINE_FORWARD_DECLARATION


enum ClassId {
  // Illegal class id.
  kIllegalCid = 0,

  // List of Ids for predefined classes.
#define DEFINE_OBJECT_KIND(clazz)                                              \
  k##clazz##Cid,
CLASS_LIST(DEFINE_OBJECT_KIND)
#undef DEFINE_OBJECT_KIND

#define DEFINE_OBJECT_KIND(clazz)                                              \
  kTypedData##clazz##Cid,
CLASS_LIST_TYPED_DATA(DEFINE_OBJECT_KIND)
#undef DEFINE_OBJECT_KIND

#define DEFINE_OBJECT_KIND(clazz)                                              \
  kTypedData##clazz##ViewCid,
CLASS_LIST_TYPED_DATA(DEFINE_OBJECT_KIND)
#undef DEFINE_OBJECT_KIND

  kByteDataViewCid,

#define DEFINE_OBJECT_KIND(clazz)                                              \
  kExternalTypedData##clazz##Cid,
CLASS_LIST_TYPED_DATA(DEFINE_OBJECT_KIND)
#undef DEFINE_OBJECT_KIND

  kByteBufferCid,

  // The following entries do not describe a predefined class, but instead
  // are class indexes for pre-allocated instance (Null, dynamic and Void).
  kNullCid,
  kDynamicCid,
  kVoidCid,

  // The following entry does not describe a real class, but instead it is an
  // id which is used to identify free list elements in the heap.
  kFreeListElement,

  kNumPredefinedCids,
};

enum ObjectAlignment {
  // Alignment offsets are used to determine object age.
  kNewObjectAlignmentOffset = kWordSize,
  kOldObjectAlignmentOffset = 0,
  // Object sizes are aligned to kObjectAlignment.
  kObjectAlignment = 2 * kWordSize,
  kObjectAlignmentLog2 = kWordSizeLog2 + 1,
  kObjectAlignmentMask = kObjectAlignment - 1,
};

enum {
  kSmiTag = 0,
  kHeapObjectTag = 1,
  kSmiTagSize = 1,
  kSmiTagMask = 1,
  kSmiTagShift = 1,
};

enum TypedDataElementType {
#define V(name) k##name##Element,
CLASS_LIST_TYPED_DATA(V)
#undef V
};

#define SNAPSHOT_WRITER_SUPPORT()                                              \
  void WriteTo(                                                                \
      SnapshotWriter* writer, intptr_t object_id,                              \
      Snapshot::Kind kind, bool as_reference);                                 \
  friend class SnapshotWriter;                                                 \

#define VISITOR_SUPPORT(object)                                                \
  static intptr_t Visit##object##Pointers(Raw##object* raw_obj,                \
                                          ObjectPointerVisitor* visitor);

#define HEAP_PROFILER_SUPPORT()                                                \
  friend class HeapProfiler;                                                   \

#define RAW_OBJECT_IMPLEMENTATION(object)                                      \
 private:  /* NOLINT */                                                        \
  VISITOR_SUPPORT(object)                                                      \
  friend class object;                                                         \
  friend class RawObject;                                                      \
  friend class Heap;                                                           \
  friend class Simulator;                                                      \
  friend class SimulatorHelpers;                                               \
  DISALLOW_ALLOCATION();                                                       \
  DISALLOW_IMPLICIT_CONSTRUCTORS(Raw##object)

// TODO(koda): Make ptr() return const*, like Object::raw_ptr().
#define RAW_HEAP_OBJECT_IMPLEMENTATION(object)                                 \
  private:                                                                     \
    RAW_OBJECT_IMPLEMENTATION(object);                                         \
    Raw##object* ptr() const {                                                 \
      ASSERT(IsHeapObject());                                                  \
      return reinterpret_cast<Raw##object*>(                                   \
          reinterpret_cast<uword>(this) - kHeapObjectTag);                     \
    }                                                                          \
    SNAPSHOT_WRITER_SUPPORT()                                                  \
    HEAP_PROFILER_SUPPORT()                                                    \

// RawObject is the base class of all raw objects, even though it carries the
// class_ field not all raw objects are allocated in the heap and thus cannot
// be dereferenced (e.g. RawSmi).
class RawObject {
 public:
  // The tags field which is a part of the object header uses the following
  // bit fields for storing tags.
  enum TagBits {
    kMarkBit = 0,
    kCanonicalBit = 1,
    kVMHeapObjectBit = 2,
    kRememberedBit = 3,
    kReservedTagPos = 4,  // kReservedBit{100K,1M,10M}
#if defined(ARCH_IS_32_BIT)
    kReservedTagSize = 4,
    kSizeTagPos = kReservedTagPos + kReservedTagSize,  // = 8
    kSizeTagSize = 8,
    kClassIdTagPos = kSizeTagPos + kSizeTagSize,  // = 16
    kClassIdTagSize = 16,
#elif defined(ARCH_IS_64_BIT)
    kReservedTagSize = 12,
    kSizeTagPos = kReservedTagPos + kReservedTagSize,  // = 16
    kSizeTagSize = 16,
    kClassIdTagPos = kSizeTagPos + kSizeTagSize,  // = 32
    kClassIdTagSize = 32,
#else
#error Unexpected architecture word size
#endif
  };

  COMPILE_ASSERT(kClassIdTagSize == (sizeof(classid_t) * kBitsPerByte));

  // Encodes the object size in the tag in units of object alignment.
  class SizeTag {
   public:
    static const intptr_t kMaxSizeTag =
        ((1 << RawObject::kSizeTagSize) - 1) << kObjectAlignmentLog2;

    static uword encode(intptr_t size) {
      return SizeBits::encode(SizeToTagValue(size));
    }

    static intptr_t decode(uword tag) {
      return TagValueToSize(SizeBits::decode(tag));
    }

    static uword update(intptr_t size, uword tag) {
      return SizeBits::update(SizeToTagValue(size), tag);
    }

   private:
    // The actual unscaled bit field used within the tag field.
    class SizeBits :
        public BitField<uword, intptr_t, kSizeTagPos, kSizeTagSize> {};

    static intptr_t SizeToTagValue(intptr_t size) {
      ASSERT(Utils::IsAligned(size, kObjectAlignment));
      return  (size > kMaxSizeTag) ? 0 : (size >> kObjectAlignmentLog2);
    }
    static intptr_t TagValueToSize(intptr_t value) {
      return value << kObjectAlignmentLog2;
    }
  };

  class ClassIdTag :
      public BitField<uword, intptr_t, kClassIdTagPos, kClassIdTagSize> {};

  bool IsWellFormed() const {
    uword value = reinterpret_cast<uword>(this);
    return (value & kSmiTagMask) == 0 ||
        Utils::IsAligned(value - kHeapObjectTag, kWordSize);
  }
  bool IsHeapObject() const {
    ASSERT(IsWellFormed());
    uword value = reinterpret_cast<uword>(this);
    return (value & kSmiTagMask) == kHeapObjectTag;
  }
  // Assumes this is a heap object.
  bool IsNewObject() const {
    ASSERT(IsHeapObject());
    uword addr = reinterpret_cast<uword>(this);
    return (addr & kNewObjectAlignmentOffset) == kNewObjectAlignmentOffset;
  }
  // Assumes this is a heap object.
  bool IsOldObject() const {
    ASSERT(IsHeapObject());
    uword addr = reinterpret_cast<uword>(this);
    return (addr & kNewObjectAlignmentOffset) == kOldObjectAlignmentOffset;
  }

  // Like !IsHeapObject() || IsOldObject(), but compiles to a single branch.
  bool IsSmiOrOldObject() const {
    ASSERT(IsWellFormed());
    COMPILE_ASSERT(kHeapObjectTag == 1);
    COMPILE_ASSERT(kNewObjectAlignmentOffset == kWordSize);
    static const uword kNewObjectBits =
        (kNewObjectAlignmentOffset | kHeapObjectTag);
    const uword addr = reinterpret_cast<uword>(this);
    return (addr & kNewObjectBits) != kNewObjectBits;
  }

  // Support for GC marking bit.
  bool IsMarked() const {
    return MarkBit::decode(ptr()->tags_);
  }
  void SetMarkBit() {
    ASSERT(!IsMarked());
    UpdateTagBit<MarkBit>(true);
  }
  void SetMarkBitUnsynchronized() {
    ASSERT(!IsMarked());
    uword tags = ptr()->tags_;
    ptr()->tags_ = MarkBit::update(true, tags);
  }
  void ClearMarkBit() {
    ASSERT(IsMarked());
    UpdateTagBit<MarkBit>(false);
  }
  // Returns false if the bit was already set.
  // TODO(koda): Add "must use result" annotation here, after we add support.
  bool TryAcquireMarkBit() {
    return TryAcquireTagBit<MarkBit>();
  }

  // Support for object tags.
  bool IsCanonical() const {
    return CanonicalObjectTag::decode(ptr()->tags_);
  }
  void SetCanonical() {
    UpdateTagBit<CanonicalObjectTag>(true);
  }
  void ClearCanonical() {
    UpdateTagBit<CanonicalObjectTag>(false);
  }
  bool IsVMHeapObject() const {
    return VMHeapObjectTag::decode(ptr()->tags_);
  }
  void SetVMHeapObject() {
    UpdateTagBit<VMHeapObjectTag>(true);
  }

  // Support for GC remembered bit.
  bool IsRemembered() const {
    return RememberedBit::decode(ptr()->tags_);
  }
  void SetRememberedBit() {
    ASSERT(!IsRemembered());
    UpdateTagBit<RememberedBit>(true);
  }
  void SetRememberedBitUnsynchronized() {
    ASSERT(!IsRemembered());
    uword tags = ptr()->tags_;
    ptr()->tags_ = RememberedBit::update(true, tags);
  }
  void ClearRememberedBit() {
    UpdateTagBit<RememberedBit>(false);
  }
  void ClearRememberedBitUnsynchronized() {
    uword tags = ptr()->tags_;
    ptr()->tags_ = RememberedBit::update(false, tags);
  }
  // Returns false if the bit was already set.
  // TODO(koda): Add "must use result" annotation here, after we add support.
  bool TryAcquireRememberedBit() {
    return TryAcquireTagBit<RememberedBit>();
  }

#define DEFINE_IS_CID(clazz)                                                   \
  bool Is##clazz() const { return ((GetClassId() == k##clazz##Cid)); }
CLASS_LIST(DEFINE_IS_CID)
#undef DEFINE_IS_CID

#define DEFINE_IS_CID(clazz)                                                   \
  bool IsTypedData##clazz() const {                                            \
    return ((GetClassId() == kTypedData##clazz##Cid));                         \
  }                                                                            \
  bool IsTypedDataView##clazz() const {                                        \
    return ((GetClassId() == kTypedData##clazz##ViewCid));                     \
  }                                                                            \
  bool IsExternalTypedData##clazz() const {                                    \
    return ((GetClassId() == kExternalTypedData##clazz##Cid));                 \
  }
CLASS_LIST_TYPED_DATA(DEFINE_IS_CID)
#undef DEFINE_IS_CID

  bool IsStringInstance() const {
    return IsStringClassId(GetClassId());
  }
  bool IsDartInstance() const {
    return (!IsHeapObject() || (GetClassId() >= kInstanceCid));
  }
  bool IsFreeListElement() const {
    return ((GetClassId() == kFreeListElement));
  }

  intptr_t Size() const {
    uword tags = ptr()->tags_;
    intptr_t result = SizeTag::decode(tags);
    if (result != 0) {
      ASSERT(result == SizeFromClass());
      return result;
    }
    result = SizeFromClass();
    ASSERT(result > SizeTag::kMaxSizeTag);
    return result;
  }

  bool Contains(uword addr) const {
    intptr_t this_size = Size();
    uword this_addr = RawObject::ToAddr(this);
    return (addr >= this_addr) && (addr < (this_addr + this_size));
  }

  void Validate(Isolate* isolate) const;
  intptr_t VisitPointers(ObjectPointerVisitor* visitor);
  bool FindObject(FindObjectVisitor* visitor);

  static RawObject* FromAddr(uword addr) {
    // We expect the untagged address here.
    ASSERT((addr & kSmiTagMask) != kHeapObjectTag);
    return reinterpret_cast<RawObject*>(addr + kHeapObjectTag);
  }

  static uword ToAddr(const RawObject* raw_obj) {
    return reinterpret_cast<uword>(raw_obj->ptr());
  }

  static bool IsVMHeapObject(intptr_t value) {
    return VMHeapObjectTag::decode(value);
  }

  static bool IsCanonical(intptr_t value) {
    return CanonicalObjectTag::decode(value);
  }

  // Class Id predicates.
  static bool IsErrorClassId(intptr_t index);
  static bool IsNumberClassId(intptr_t index);
  static bool IsIntegerClassId(intptr_t index);
  static bool IsStringClassId(intptr_t index);
  static bool IsOneByteStringClassId(intptr_t index);
  static bool IsTwoByteStringClassId(intptr_t index);
  static bool IsExternalStringClassId(intptr_t index);
  static bool IsBuiltinListClassId(intptr_t index);
  static bool IsTypedDataClassId(intptr_t index);
  static bool IsTypedDataViewClassId(intptr_t index);
  static bool IsExternalTypedDataClassId(intptr_t index);
  static bool IsInternalVMdefinedClassId(intptr_t index);
  static bool IsVariableSizeClassId(intptr_t index);
  static bool IsImplicitFieldClassId(intptr_t index);

  static intptr_t NumberOfTypedDataClasses();

 private:
  uword tags_;  // Various object tags (bits).

  class MarkBit : public BitField<uword, bool, kMarkBit, 1> {};

  class RememberedBit : public BitField<uword, bool, kRememberedBit, 1> {};

  class CanonicalObjectTag : public BitField<uword, bool, kCanonicalBit, 1> {};

  class VMHeapObjectTag : public BitField<uword, bool, kVMHeapObjectBit, 1> {};

  class ReservedBits : public
      BitField<uword, intptr_t, kReservedTagPos, kReservedTagSize> {};

  // TODO(koda): After handling tags_, return const*, like Object::raw_ptr().
  RawObject* ptr() const {
    ASSERT(IsHeapObject());
    return reinterpret_cast<RawObject*>(
        reinterpret_cast<uword>(this) - kHeapObjectTag);
  }

  intptr_t SizeFromClass() const;

  intptr_t GetClassId() const {
    uword tags = ptr()->tags_;
    return ClassIdTag::decode(tags);
  }

  template<class TagBitField>
  void UpdateTagBit(bool value) {
    uword tags = ptr()->tags_;
    uword old_tags;
    do {
      old_tags = tags;
      uword new_tags = TagBitField::update(value, old_tags);
      tags = AtomicOperations::CompareAndSwapWord(
          &ptr()->tags_, old_tags, new_tags);
    } while (tags != old_tags);
  }

  template<class TagBitField>
  bool TryAcquireTagBit() {
    uword tags = ptr()->tags_;
    uword old_tags;
    do {
      old_tags = tags;
      if (TagBitField::decode(tags)) return false;
      uword new_tags = TagBitField::update(true, old_tags);
      tags = AtomicOperations::CompareAndSwapWord(
          &ptr()->tags_, old_tags, new_tags);
    } while (tags != old_tags);
    return true;
  }

  // All writes to heap objects should ultimately pass through one of the
  // methods below or their counterparts in Object, to ensure that the
  // write barrier is correctly applied.

  template<typename type>
  void StorePointer(type const* addr, type value) {
#if defined(DEBUG)
    ValidateOverwrittenPointer(*addr);
#endif  // DEBUG
    VerifiedMemory::Write(const_cast<type*>(addr), value);
    // Filter stores based on source and target.
    if (!value->IsHeapObject()) return;
    if (value->IsNewObject() && this->IsOldObject() &&
        !this->IsRemembered()) {
      this->SetRememberedBit();
      Thread::Current()->StoreBufferAddObject(this);
    }
  }

  // Use for storing into an explicitly Smi-typed field of an object
  // (i.e., both the previous and new value are Smis).
  void StoreSmi(RawSmi* const* addr, RawSmi* value) {
#if defined(DEBUG)
    ValidateOverwrittenSmi(*addr);
#endif  // DEBUG
    // Can't use Contains, as array length is initialized through this method.
    ASSERT(reinterpret_cast<uword>(addr) >= RawObject::ToAddr(this));
    VerifiedMemory::Write(const_cast<RawSmi**>(addr), value);
  }

  void InitializeSmi(RawSmi* const* addr, RawSmi* value) {
    // Can't use Contains, as array length is initialized through this method.
    ASSERT(reinterpret_cast<uword>(addr) >= RawObject::ToAddr(this));
    // This is an initializing store, so any previous content is OK.
    VerifiedMemory::Accept(reinterpret_cast<uword>(addr), kWordSize);
    VerifiedMemory::Write(const_cast<RawSmi**>(addr), value);
  }

#if defined(DEBUG)
  static void ValidateOverwrittenPointer(RawObject* raw);
  static void ValidateOverwrittenSmi(RawSmi* raw);
#endif  // DEBUG

  friend class Api;
  friend class ApiMessageReader;  // GetClassId
  friend class Array;
  friend class Bigint;
  friend class ByteBuffer;
  friend class Closure;
  friend class Code;
  friend class Double;
  friend class ForwardPointersVisitor;  // StorePointer
  friend class FreeListElement;
  friend class Function;
  friend class GCMarker;
  friend class ExternalTypedData;
  friend class ForwardList;
  friend class GrowableObjectArray;  // StorePointer
  friend class Heap;
  friend class HeapMapAsJSONVisitor;
  friend class ClassStatsVisitor;
  template<bool> friend class MarkingVisitorBase;
  friend class Mint;
  friend class Object;
  friend class OneByteString;  // StoreSmi
  friend class RawCode;
  friend class RawExternalTypedData;
  friend class RawInstructions;
  friend class RawInstance;
  friend class RawTypedData;
  friend class Scavenger;
  friend class ScavengerVisitor;
  friend class SizeExcludingClassVisitor;  // GetClassId
  friend class InstanceAccumulator;  // GetClassId
  friend class RetainingPathVisitor;  // GetClassId
  friend class SkippedCodeFunctions;  // StorePointer
  friend class InstructionsReader;  // tags_ check
  friend class AssemblyInstructionsWriter;
  friend class BlobInstructionsWriter;
  friend class SnapshotReader;
  friend class SnapshotWriter;
  friend class String;
  friend class Type;  // GetClassId
  friend class TypedData;
  friend class TypedDataView;
  friend class WeakProperty;  // StorePointer
  friend class Instance;  // StorePointer
  friend class StackFrame;  // GetCodeObject assertion.
  friend class CodeLookupTableBuilder;  // profiler
  friend class NativeEntry;  // GetClassId
  friend class Simulator;
  friend class SimulatorHelpers;

  DISALLOW_ALLOCATION();
  DISALLOW_IMPLICIT_CONSTRUCTORS(RawObject);
};


class RawClass : public RawObject {
 public:
  enum ClassFinalizedState {
    kAllocated = 0,  // Initial state.
    kPreFinalized,  // VM classes: size precomputed, but no checks done.
    kFinalized,  // Class parsed, finalized and ready for use.
    kRefinalizeAfterPatch,  // Class needs to be refinalized (patched).
  };

 private:
  RAW_HEAP_OBJECT_IMPLEMENTATION(Class);

  RawObject** from() { return reinterpret_cast<RawObject**>(&ptr()->name_); }
  RawString* name_;
  NOT_IN_PRODUCT(RawString* user_name_);
  RawArray* functions_;
  RawArray* functions_hash_table_;
  RawArray* fields_;
  RawArray* offset_in_words_to_field_;
  RawArray* interfaces_;  // Array of AbstractType.
  RawScript* script_;
  RawLibrary* library_;
  RawTypeArguments* type_parameters_;  // Array of TypeParameter.
  RawAbstractType* super_type_;
  RawType* mixin_;  // Generic mixin type, e.g. M<T>, not M<int>.
  RawFunction* signature_function_;  // Associated function for typedef class.
  RawArray* constants_;  // Canonicalized const instances of this class.
  RawType* canonical_type_;  // Canonical type for this class.
  RawArray* invocation_dispatcher_cache_;  // Cache for dispatcher functions.
  RawCode* allocation_stub_;  // Stub code for allocation of instances.
  RawGrowableObjectArray* direct_subclasses_;  // Array of Class.
  RawArray* dependent_code_;  // CHA optimized codes.
  RawObject** to() {
    return reinterpret_cast<RawObject**>(&ptr()->dependent_code_);
  }
  RawObject** to_snapshot(Snapshot::Kind kind) {
    switch (kind) {
      case Snapshot::kCore:
      case Snapshot::kScript:
      case Snapshot::kAppWithJIT:
      case Snapshot::kAppNoJIT:
        return reinterpret_cast<RawObject**>(&ptr()->direct_subclasses_);
      case Snapshot::kMessage:
      case Snapshot::kNone:
      case Snapshot::kInvalid:
        break;
    }
    UNREACHABLE();
    return NULL;
  }

  cpp_vtable handle_vtable_;
  TokenPosition token_pos_;
  int32_t instance_size_in_words_;  // Size if fixed len or 0 if variable len.
  int32_t type_arguments_field_offset_in_words_;  // Offset of type args fld.
  int32_t next_field_offset_in_words_;  // Offset of the next instance field.
  classid_t id_;  // Class Id, also index in the class table.
  int16_t num_type_arguments_;  // Number of type arguments in flattened vector.
  int16_t num_own_type_arguments_;  // Number of non-overlapping type arguments.
  uint16_t num_native_fields_;  // Number of native fields in class.
  uint16_t state_bits_;

  friend class Instance;
  friend class Isolate;
  friend class Object;
  friend class RawInstance;
  friend class RawInstructions;
  friend class SnapshotReader;
};


class RawUnresolvedClass : public RawObject {
  RAW_HEAP_OBJECT_IMPLEMENTATION(UnresolvedClass);

  RawObject** from() {
    return reinterpret_cast<RawObject**>(&ptr()->library_prefix_);
  }
  RawLibraryPrefix* library_prefix_;  // Library prefix qualifier for the ident.
  RawString* ident_;  // Name of the unresolved identifier.
  RawObject** to() {
    return reinterpret_cast<RawObject**>(&ptr()->ident_);
  }
  TokenPosition token_pos_;
};


class RawTypeArguments : public RawObject {
 private:
  RAW_HEAP_OBJECT_IMPLEMENTATION(TypeArguments);

  RawObject** from() {
    return reinterpret_cast<RawObject**>(&ptr()->instantiations_);
  }
  // The instantiations_ array remains empty for instantiated type arguments.
  RawArray* instantiations_;  // Array of paired canonical vectors:
                              // Even index: instantiator.
                              // Odd index: instantiated (without bound error).
  // Instantiations leading to bound errors do not get cached.
  RawSmi* length_;

  RawSmi* hash_;

  // Variable length data follows here.
  RawAbstractType* const* types() const {
    OPEN_ARRAY_START(RawAbstractType*, RawAbstractType*);
  }
  RawAbstractType** types() {
    OPEN_ARRAY_START(RawAbstractType*, RawAbstractType*);
  }
  RawObject** to(intptr_t length) {
    return reinterpret_cast<RawObject**>(&ptr()->types()[length - 1]);
  }

  friend class SnapshotReader;
};


class RawPatchClass : public RawObject {
 private:
  RAW_HEAP_OBJECT_IMPLEMENTATION(PatchClass);

  RawObject** from() {
    return reinterpret_cast<RawObject**>(&ptr()->patched_class_);
  }
  RawClass* patched_class_;
  RawClass* origin_class_;
  RawScript* script_;
  RawObject** to() {
    return reinterpret_cast<RawObject**>(&ptr()->script_);
  }

  friend class Function;
};


class RawFunction : public RawObject {
 public:
  enum Kind {
    kRegularFunction,
    kClosureFunction,
    kSignatureFunction,  // represents a signature only without actual code.
    kGetterFunction,     // represents getter functions e.g: get foo() { .. }.
    kSetterFunction,     // represents setter functions e.g: set foo(..) { .. }.
    kConstructor,
    kImplicitGetter,     // represents an implicit getter for fields.
    kImplicitSetter,     // represents an implicit setter for fields.
    kImplicitStaticFinalGetter,  // represents an implicit getter for static
                                 // final fields (incl. static const fields).
    kMethodExtractor,  // converts method into implicit closure on the receiver.
    kNoSuchMethodDispatcher,  // invokes noSuchMethod.
    kInvokeFieldDispatcher,  // invokes a field as a closure.
    kIrregexpFunction,   // represents a generated irregexp matcher function.
  };

  enum AsyncModifier {
    kNoModifier = 0x0,
    kAsyncBit   = 0x1,
    kGeneratorBit =  0x2,
    kAsync      = kAsyncBit,
    kSyncGen    = kGeneratorBit,
    kAsyncGen   = kAsyncBit | kGeneratorBit,
  };

 private:
  // So that the SkippedCodeFunctions::DetachCode can null out the code fields.
  friend class SkippedCodeFunctions;
  friend class Class;
  RAW_HEAP_OBJECT_IMPLEMENTATION(Function);
  static bool ShouldVisitCode(RawCode* raw_code);
  static bool CheckUsageCounter(RawFunction* raw_fun);

  RawObject** from() { return reinterpret_cast<RawObject**>(&ptr()->name_); }
  RawString* name_;
  RawObject* owner_;  // Class or patch class or mixin class
                      // where this function is defined.
  RawAbstractType* result_type_;
  RawArray* parameter_types_;
  RawArray* parameter_names_;
  RawObject* data_;  // Additional data specific to the function kind.
  RawObject** to_snapshot() {
    return reinterpret_cast<RawObject**>(&ptr()->data_);
  }
  RawArray* ic_data_array_;  // ICData of unoptimized code.
  RawObject** to_no_code() {
    return reinterpret_cast<RawObject**>(&ptr()->ic_data_array_);
  }
  RawCode* code_;  // Currently active code.
  RawCode* unoptimized_code_;  // Unoptimized code, keep it after optimization.
  RawObject** to() {
    return reinterpret_cast<RawObject**>(&ptr()->unoptimized_code_);
  }
  uword entry_point_;

  TokenPosition token_pos_;
  TokenPosition end_token_pos_;
  int32_t usage_counter_;  // Incremented while function is running.
  int16_t num_fixed_parameters_;
  int16_t num_optional_parameters_;  // > 0: positional; < 0: named.
  int8_t deoptimization_counter_;
  int8_t was_compiled_;
  uint32_t kind_tag_;  // See Function::KindTagBits.
  uint16_t optimized_instruction_count_;
  uint16_t optimized_call_site_count_;
};


class RawClosureData : public RawObject {
 private:
  RAW_HEAP_OBJECT_IMPLEMENTATION(ClosureData);

  RawObject** from() {
    return reinterpret_cast<RawObject**>(&ptr()->context_scope_);
  }
  RawContextScope* context_scope_;
  RawFunction* parent_function_;  // Enclosing function of this local function.
  RawType* signature_type_;
  RawInstance* closure_;  // Closure object for static implicit closures.
  RawObject** to() {
    return reinterpret_cast<RawObject**>(&ptr()->closure_);
  }

  friend class Function;
};


class RawRedirectionData : public RawObject {
 private:
  RAW_HEAP_OBJECT_IMPLEMENTATION(RedirectionData);

  RawObject** from() {
    return reinterpret_cast<RawObject**>(&ptr()->type_);
  }
  RawType* type_;
  RawString* identifier_;
  RawFunction* target_;
  RawObject** to() {
    return reinterpret_cast<RawObject**>(&ptr()->target_);
  }
};


class RawField : public RawObject {
  RAW_HEAP_OBJECT_IMPLEMENTATION(Field);

  RawObject** from() { return reinterpret_cast<RawObject**>(&ptr()->name_); }
  RawString* name_;
  RawObject* owner_;  // Class or patch class or mixin class
                      // where this field is defined or original field.
  RawAbstractType* type_;
  union {
    RawInstance* static_value_;  // Value for static fields.
    RawSmi* offset_;  // Offset in words for instance fields.
  } value_;
  union {
    // When precompiling we need to save the static initializer function here
    // so that code for it can be generated.
    RawFunction* precompiled_;  // Static initializer function - precompiling.
    // When generating script snapshots after running the application it is
    // necessary to save the initial value of static fields so that we can
    // restore the value back to the original initial value.
    RawInstance* saved_value_;  // Saved initial value - static fields.
  } initializer_;
  RawSmi* guarded_list_length_;
  RawArray* dependent_code_;
  RawObject** to() {
    return reinterpret_cast<RawObject**>(&ptr()->dependent_code_);
  }
  RawObject** to_snapshot(Snapshot::Kind kind) {
    switch (kind) {
      case Snapshot::kCore:
      case Snapshot::kScript:
      case Snapshot::kAppWithJIT:
        return reinterpret_cast<RawObject**>(&ptr()->guarded_list_length_);
      case Snapshot::kAppNoJIT:
        return reinterpret_cast<RawObject**>(&ptr()->initializer_);
      case Snapshot::kMessage:
      case Snapshot::kNone:
      case Snapshot::kInvalid:
        break;
    }
    UNREACHABLE();
    return NULL;
  }

  TokenPosition token_pos_;
  classid_t guarded_cid_;
  classid_t is_nullable_;  // kNullCid if field can contain null value and
                           // any other value otherwise.
  // Offset to the guarded length field inside an instance of class matching
  // guarded_cid_. Stored corrected by -kHeapObjectTag to simplify code
  // generated on platforms with weak addressing modes (ARM, MIPS).
  int8_t guarded_list_length_in_object_offset_;

  uint8_t kind_bits_;  // static, final, const, has initializer....
};


class RawLiteralToken : public RawObject {
  RAW_HEAP_OBJECT_IMPLEMENTATION(LiteralToken);

  RawObject** from() {
    return reinterpret_cast<RawObject**>(&ptr()->literal_);
  }
  RawString* literal_;  // Literal characters as they appear in source text.
  RawObject* value_;  // The actual object corresponding to the token.
  RawObject** to() {
    return reinterpret_cast<RawObject**>(&ptr()->value_);
  }
  Token::Kind kind_;  // The literal kind (string, integer, double).

  friend class SnapshotReader;
};


class RawTokenStream : public RawObject {
  RAW_HEAP_OBJECT_IMPLEMENTATION(TokenStream);

  RawObject** from() {
    return reinterpret_cast<RawObject**>(&ptr()->private_key_);
  }
  RawString* private_key_;  // Key used for private identifiers.
  RawGrowableObjectArray* token_objects_;
  RawExternalTypedData* stream_;
  RawObject** to() {
    return reinterpret_cast<RawObject**>(&ptr()->stream_);
  }

  friend class SnapshotReader;
};


class RawScript : public RawObject {
 public:
  enum Kind {
    kScriptTag = 0,
    kLibraryTag,
    kSourceTag,
    kPatchTag,
    kEvaluateTag,
  };

 private:
  RAW_HEAP_OBJECT_IMPLEMENTATION(Script);

  RawObject** from() { return reinterpret_cast<RawObject**>(&ptr()->url_); }
  RawString* url_;
  RawTokenStream* tokens_;
  RawString* source_;
  RawObject** to() { return reinterpret_cast<RawObject**>(&ptr()->source_); }
  RawObject** to_snapshot(Snapshot::Kind kind) {
    switch (kind) {
      case Snapshot::kAppNoJIT:
        return reinterpret_cast<RawObject**>(&ptr()->url_);
      case Snapshot::kCore:
      case Snapshot::kAppWithJIT:
      case Snapshot::kScript:
        return reinterpret_cast<RawObject**>(&ptr()->tokens_);
      case Snapshot::kMessage:
      case Snapshot::kNone:
      case Snapshot::kInvalid:
        break;
    }
    UNREACHABLE();
    return NULL;
  }

  int32_t line_offset_;
  int32_t col_offset_;
  int8_t kind_;  // Of type Kind.
  int64_t load_timestamp_;
};


class RawLibrary : public RawObject {
  enum LibraryState {
    kAllocated,       // Initial state.
    kLoadRequested,   // Compiler or script requested load of library.
    kLoadInProgress,  // Library is in the process of being loaded.
    kLoaded,          // Library is loaded.
    kLoadError,       // Error occurred during load of the Library.
  };

  RAW_HEAP_OBJECT_IMPLEMENTATION(Library);

  RawObject** from() { return reinterpret_cast<RawObject**>(&ptr()->name_); }
  RawString* name_;
  RawString* url_;
  RawString* private_key_;
  RawArray* dictionary_;         // Top-level names in this library.
  RawGrowableObjectArray* metadata_;  // Metadata on classes, methods etc.
  RawClass* toplevel_class_;     // Class containing top-level elements.
  RawGrowableObjectArray* patch_classes_;
  RawArray* imports_;            // List of Namespaces imported without prefix.
  RawArray* exports_;            // List of re-exported Namespaces.
  RawInstance* load_error_;      // Error iff load_state_ == kLoadError.
  RawObject** to_snapshot() {
    return reinterpret_cast<RawObject**>(&ptr()->load_error_);
  }
  RawArray* resolved_names_;     // Cache of resolved names in library scope.
  RawArray* exported_names_;     // Cache of exported names by library.
  RawArray* loaded_scripts_;     // Array of scripts loaded in this library.
  RawObject** to() {
    return reinterpret_cast<RawObject**>(&ptr()->loaded_scripts_);
  }

  Dart_NativeEntryResolver native_entry_resolver_;  // Resolves natives.
  Dart_NativeEntrySymbol native_entry_symbol_resolver_;
  classid_t index_;              // Library id number.
  uint16_t num_imports_;         // Number of entries in imports_.
  int8_t load_state_;            // Of type LibraryState.
  bool corelib_imported_;
  bool is_dart_scheme_;
  bool debuggable_;              // True if debugger can stop in library.
  bool is_in_fullsnapshot_;      // True if library is in a full snapshot.

  friend class Class;
  friend class Isolate;
};


class RawNamespace : public RawObject {
  RAW_HEAP_OBJECT_IMPLEMENTATION(Namespace);

  RawObject** from() {
    return reinterpret_cast<RawObject**>(&ptr()->library_);
  }
  RawLibrary* library_;          // library with name dictionary.
  RawArray* show_names_;         // list of names that are exported.
  RawArray* hide_names_;         // blacklist of names that are not exported.
  RawField* metadata_field_;     // remembers the token pos of metadata if any,
                                 // and the metadata values if computed.
  RawObject** to() {
    return reinterpret_cast<RawObject**>(&ptr()->metadata_field_);
  }
};


class RawCode : public RawObject {
  enum InlinedMetadataIndex {
    kInlinedIntervalsIndex = 0,
    kInlinedIdToFunctionIndex = 1,
    kInlinedCallerIdMapIndex = 2,
    kInlinedIdToTokenPosIndex = 3,
    kInlinedMetadataSize = 4,
  };

  RAW_HEAP_OBJECT_IMPLEMENTATION(Code);

  uword entry_point_;

  RawObject** from() {
    return reinterpret_cast<RawObject**>(&ptr()->active_instructions_);
  }
  RawInstructions* active_instructions_;
  RawInstructions* instructions_;
  RawObjectPool* object_pool_;
  // If owner_ is Function::null() the owner is a regular stub.
  // If owner_ is a Class the owner is the allocation stub for that class.
  // Else, owner_ is a regular Dart Function.
  RawObject* owner_;  // Function, Null, or a Class.
  RawExceptionHandlers* exception_handlers_;
  RawPcDescriptors* pc_descriptors_;
  RawArray* stackmaps_;
  RawArray* deopt_info_array_;
  RawArray* static_calls_target_table_;  // (code-offset, function, code).
  RawLocalVarDescriptors* var_descriptors_;
  RawArray* inlined_metadata_;
  RawCodeSourceMap* code_source_map_;
  RawArray* comments_;
  // If return_address_metadata_ is a Smi, it is the offset to the prologue.
  // Else, return_address_metadata_ is null.
  RawObject* return_address_metadata_;
  RawObject** to() {
    return reinterpret_cast<RawObject**>(&ptr()->return_address_metadata_);
  }

  // Compilation timestamp.
  int64_t compile_timestamp_;

  // state_bits_ is a bitfield with three fields:
  // The optimized bit, the alive bit, and a count of the number of pointer
  // offsets.
  // Alive: If true, the embedded object pointers will be visited during GC.
  int32_t state_bits_;

  // PC offsets for code patching.
  int32_t lazy_deopt_pc_offset_;

  // Variable length data follows here.
  int32_t* data() { OPEN_ARRAY_START(int32_t, int32_t); }
  const int32_t* data() const { OPEN_ARRAY_START(int32_t, int32_t); }

  static bool ContainsPC(RawObject* raw_obj, uword pc);

  friend class Function;
  template<bool> friend class MarkingVisitorBase;
  friend class SkippedCodeFunctions;
  friend class StackFrame;
  friend class Profiler;
};


class RawObjectPool : public RawObject {
  RAW_HEAP_OBJECT_IMPLEMENTATION(ObjectPool);

  intptr_t length_;
  RawTypedData* info_array_;

  struct Entry {
    union {
      RawObject* raw_obj_;
      uword raw_value_;
    };
  };
  Entry* data() { OPEN_ARRAY_START(Entry, Entry); }
  Entry const* data() const { OPEN_ARRAY_START(Entry, Entry); }

  Entry* first_entry() { return &ptr()->data()[0]; }

  friend class Object;
  friend class SnapshotReader;
};


class RawInstructions : public RawObject {
  RAW_HEAP_OBJECT_IMPLEMENTATION(Instructions);

  int32_t size_;

  // Variable length data follows here.
  uint8_t* data() { OPEN_ARRAY_START(uint8_t, uint8_t); }

  // Private helper function used while visiting stack frames. The
  // code which iterates over dart frames is also called during GC and
  // is not allowed to create handles.
  static bool ContainsPC(RawInstructions* raw_instr, uword pc);

  friend class RawCode;
  friend class RawFunction;
  friend class Code;
  friend class StackFrame;
  template<bool> friend class MarkingVisitorBase;
  friend class SkippedCodeFunctions;
  friend class Function;
  friend class InstructionsReader;
  friend class InstructionsWriter;
};


class RawPcDescriptors : public RawObject {
 public:
  enum Kind {
    kDeopt           = 1,  // Deoptimization continuation point.
    kIcCall          = kDeopt << 1,  // IC call.
    kUnoptStaticCall = kIcCall << 1,  // Call to a known target via stub.
    kRuntimeCall     = kUnoptStaticCall << 1,  // Runtime call.
    kOsrEntry        = kRuntimeCall << 1,  // OSR entry point in unopt. code.
    kOther           = kOsrEntry << 1,
    kLastKind        = kOther,
    kAnyKind         = -1
  };

  class MergedKindTry {
   public:
    // Most of the time try_index will be small and merged field will fit into
    // one byte.
    static intptr_t Encode(intptr_t kind, intptr_t try_index) {
      intptr_t kind_shift = Utils::ShiftForPowerOfTwo(kind);
      ASSERT(Utils::IsUint(kKindShiftSize, kind_shift));
      ASSERT(Utils::IsInt(kTryIndexSize, try_index));
      return (try_index << kTryIndexPos) | (kind_shift << kKindShiftPos);
    }

    static intptr_t DecodeKind(intptr_t merged_kind_try) {
      const intptr_t kKindShiftMask = (1 << kKindShiftSize) - 1;
      return 1 << (merged_kind_try & kKindShiftMask);
    }

    static intptr_t DecodeTryIndex(intptr_t merged_kind_try) {
      // Arithmetic shift.
      return merged_kind_try >> kTryIndexPos;
    }

   private:
    static const intptr_t kKindShiftPos = 0;
    static const intptr_t kKindShiftSize = 3;
    // Is kKindShiftSize enough bits?
    COMPILE_ASSERT(kLastKind <= 1 << ((1 << kKindShiftSize) - 1));

    static const intptr_t kTryIndexPos = kKindShiftSize;
    static const intptr_t kTryIndexSize = kBitsPerWord - kKindShiftSize;
  };

 private:
  RAW_HEAP_OBJECT_IMPLEMENTATION(PcDescriptors);

  int32_t length_;  // Number of descriptors.

  // Variable length data follows here.
  uint8_t* data() { OPEN_ARRAY_START(uint8_t, intptr_t); }
  const uint8_t* data() const { OPEN_ARRAY_START(uint8_t, intptr_t); }

  friend class Object;
  friend class SnapshotReader;
};


// CodeSourceMap stores a mapping between code PC ranges and source token
// positions.
class RawCodeSourceMap : public RawObject {
 private:
  RAW_HEAP_OBJECT_IMPLEMENTATION(CodeSourceMap);

  int32_t length_;  // Number of entries.

  // Variable length data follows here.
  uint8_t* data() { OPEN_ARRAY_START(uint8_t, intptr_t); }
  const uint8_t* data() const { OPEN_ARRAY_START(uint8_t, intptr_t); }

  friend class Object;
  friend class SnapshotReader;
};


// Stackmap is an immutable representation of the layout of the stack at a
// PC. The stack map representation consists of a bit map which marks each
// live object index starting from the base of the frame.
//
// The bit map representation is optimized for dense and small bit maps, without
// any upper bound.
class RawStackmap : public RawObject {
  RAW_HEAP_OBJECT_IMPLEMENTATION(Stackmap);

  // Regarding changing this to a bitfield: ARM64 requires register_bit_count_
  // to be as large as 96, meaning 7 bits, leaving 25 bits for the length, or
  // as large as ~33 million entries. If that is sufficient, then these two
  // fields can be merged into a BitField.
  int32_t length_;  // Length of payload, in bits.
  int32_t slow_path_bit_count_;  // Slow path live values, included in length_.

  // Offset from code entry point corresponding to this stack map
  // representation.
  uint32_t pc_offset_;

  // Variable length data follows here (bitmap of the stack layout).
  uint8_t* data() { OPEN_ARRAY_START(uint8_t, uint8_t); }
  const uint8_t* data() const { OPEN_ARRAY_START(uint8_t, uint8_t); }

  friend class SnapshotReader;
};


class RawLocalVarDescriptors : public RawObject {
 public:
  enum VarInfoKind {
    kStackVar = 1,
    kContextVar,
    kContextLevel,
    kSavedCurrentContext,
  };

  enum {
    kKindPos = 0,
    kKindSize = 8,
    kIndexPos = kKindPos + kKindSize,
    // Since there are 24 bits for the stack slot index, Functions can have
    // only ~16.7 million stack slots.
    kPayloadSize = sizeof(int32_t) * kBitsPerByte,
    kIndexSize = kPayloadSize - kIndexPos,
    kIndexBias = 1 << (kIndexSize - 1),
    kMaxIndex = (1 << (kIndexSize - 1)) - 1,
  };

  class IndexBits : public BitField<int32_t, int32_t, kIndexPos, kIndexSize> {};
  class KindBits : public BitField<int32_t, int8_t, kKindPos, kKindSize>{};

  struct VarInfo {
    int32_t index_kind;  // Bitfield for slot index on stack or in context,
                         // and Entry kind of type VarInfoKind.
    TokenPosition begin_pos;   // Token position of scope start.
    TokenPosition end_pos;     // Token position of scope end.
    int16_t scope_id;    // Scope to which the variable belongs.

    VarInfoKind kind() const {
      return static_cast<VarInfoKind>(KindBits::decode(index_kind));
    }
    void set_kind(VarInfoKind kind) {
      index_kind = KindBits::update(kind, index_kind);
    }
    int32_t index() const {
      return IndexBits::decode(index_kind) - kIndexBias;
    }
    void set_index(int32_t index) {
      index_kind = IndexBits::update(index + kIndexBias, index_kind);
    }
  };

 private:
  RAW_HEAP_OBJECT_IMPLEMENTATION(LocalVarDescriptors);
  int32_t num_entries_;  // Number of descriptors.

  RawObject** from() {
    return reinterpret_cast<RawObject**>(&ptr()->names()[0]);
  }
  RawString** names() {
    // Array of [num_entries_] variable names.
    OPEN_ARRAY_START(RawString*, RawString*);
  }
  RawString** nameAddrAt(intptr_t i) {
    return &(ptr()->names()[i]);
  }

  RawObject** to(intptr_t num_entries) {
    return reinterpret_cast<RawObject**>(nameAddrAt(num_entries - 1));
  }

  // Variable info with [num_entries_] entries.
  VarInfo* data() {
    return reinterpret_cast<VarInfo*>(nameAddrAt(ptr()->num_entries_));
  }

  friend class Object;
  friend class SnapshotReader;
};


class RawExceptionHandlers : public RawObject {
 public:
  // The index into the ExceptionHandlers table corresponds to
  // the try_index of the handler.
  struct HandlerInfo {
    uint32_t handler_pc_offset;  // PC offset value of handler.
    int16_t outer_try_index;   // Try block index of enclosing try block.
    int8_t needs_stacktrace;   // True if a stacktrace is needed.
    int8_t has_catch_all;      // Catches all exceptions.
  };

 private:
  RAW_HEAP_OBJECT_IMPLEMENTATION(ExceptionHandlers);

  // Number of exception handler entries.
  int32_t num_entries_;

  // Array with [num_entries_] entries. Each entry is an array of all handled
  // exception types.
  RawArray* handled_types_data_;

  // Exception handler info of length [num_entries_].
  const HandlerInfo* data() const { OPEN_ARRAY_START(HandlerInfo, intptr_t); }
  HandlerInfo* data() { OPEN_ARRAY_START(HandlerInfo, intptr_t); }

  friend class Object;
  friend class SnapshotReader;
};


class RawContext : public RawObject {
  RAW_HEAP_OBJECT_IMPLEMENTATION(Context);

  int32_t num_variables_;

  RawObject** from() { return reinterpret_cast<RawObject**>(&ptr()->parent_); }
  RawContext* parent_;

  // Variable length data follows here.
  RawObject** data() { OPEN_ARRAY_START(RawObject*, RawObject*); }
  RawObject* const* data() const {
      OPEN_ARRAY_START(RawObject*, RawObject*);
  }
  RawObject** to(intptr_t num_vars) {
    return reinterpret_cast<RawObject**>(&ptr()->data()[num_vars - 1]);
  }

  friend class SnapshotReader;
};


class RawContextScope : public RawObject {
  RAW_HEAP_OBJECT_IMPLEMENTATION(ContextScope);

  // TODO(iposva): Switch to conventional enum offset based structure to avoid
  // alignment mishaps.
  struct VariableDesc {
    RawSmi* token_pos;
    RawString* name;
    RawBool* is_final;
    RawBool* is_const;
    union {
      RawAbstractType* type;
      RawInstance* value;  // iff is_const is true
    };
    RawSmi* context_index;
    RawSmi* context_level;
  };

  int32_t num_variables_;
  bool is_implicit_;  // true, if this context scope is for an implicit closure.

  RawObject** from() {
    VariableDesc* begin = const_cast<VariableDesc*>(ptr()->VariableDescAddr(0));
    return reinterpret_cast<RawObject**>(begin);
  }
  // Variable length data follows here.
  RawObject* const* data() const { OPEN_ARRAY_START(RawObject*, RawObject*); }
  const VariableDesc* VariableDescAddr(intptr_t index) const {
    ASSERT((index >= 0) && (index < num_variables_ + 1));
    // data() points to the first component of the first descriptor.
    return &(reinterpret_cast<const VariableDesc*>(data())[index]);
  }
  RawObject** to(intptr_t num_vars) {
    uword end = reinterpret_cast<uword>(ptr()->VariableDescAddr(num_vars));
    // 'end' is the address just beyond the last descriptor, so step back.
    return reinterpret_cast<RawObject**>(end - kWordSize);
  }

  friend class Object;
  friend class RawClosureData;
  friend class SnapshotReader;
};


class RawICData : public RawObject {
  RAW_HEAP_OBJECT_IMPLEMENTATION(ICData);

  RawObject** from() {
    return reinterpret_cast<RawObject**>(&ptr()->ic_data_);
  }
  RawArray* ic_data_;  // Contains class-ids, target and count.
  RawString* target_name_;  // Name of target function.
  RawArray* args_descriptor_;  // Arguments descriptor.
  RawObject* owner_;  // Parent/calling function or original IC of cloned IC.
  RawObject** to() {
    return reinterpret_cast<RawObject**>(&ptr()->owner_);
  }
  RawObject** to_snapshot(Snapshot::Kind kind) {
    switch (kind) {
      case Snapshot::kAppNoJIT:
        return reinterpret_cast<RawObject**>(&ptr()->args_descriptor_);
      case Snapshot::kCore:
      case Snapshot::kScript:
      case Snapshot::kAppWithJIT:
        return to();
      case Snapshot::kMessage:
      case Snapshot::kNone:
      case Snapshot::kInvalid:
        break;
    }
    UNREACHABLE();
    return NULL;
  }
  int32_t deopt_id_;     // Deoptimization id corresponding to this IC.
  uint32_t state_bits_;  // Number of arguments tested in IC, deopt reasons,
                         // range feedback.
#if defined(TAG_IC_DATA)
  intptr_t tag_;  // Debugging, verifying that the icdata is assigned to the
                  // same instruction again. Store -1 or Instruction::Tag.
#endif
};


class RawMegamorphicCache : public RawObject {
  RAW_HEAP_OBJECT_IMPLEMENTATION(MegamorphicCache);

  RawObject** from() {
    return reinterpret_cast<RawObject**>(&ptr()->buckets_);
  }
  RawArray* buckets_;
  RawSmi* mask_;
  RawString* target_name_;     // Name of target function.
  RawArray* args_descriptor_;  // Arguments descriptor.
  RawObject** to() {
    return reinterpret_cast<RawObject**>(&ptr()->args_descriptor_);
  }

  int32_t filled_entry_count_;
};


class RawSubtypeTestCache : public RawObject {
  RAW_HEAP_OBJECT_IMPLEMENTATION(SubtypeTestCache);
  RawArray* cache_;
};


class RawError : public RawObject {
  RAW_HEAP_OBJECT_IMPLEMENTATION(Error);
};


class RawApiError : public RawError {
  RAW_HEAP_OBJECT_IMPLEMENTATION(ApiError);

  RawObject** from() {
    return reinterpret_cast<RawObject**>(&ptr()->message_);
  }
  RawString* message_;
  RawObject** to() {
    return reinterpret_cast<RawObject**>(&ptr()->message_);
  }
};


class RawLanguageError : public RawError {
  RAW_HEAP_OBJECT_IMPLEMENTATION(LanguageError);

  RawObject** from() {
    return reinterpret_cast<RawObject**>(&ptr()->previous_error_);
  }
  RawError* previous_error_;  // May be null.
  RawScript* script_;
  RawString* message_;
  RawString* formatted_message_;  // Incl. previous error's formatted message.
  RawObject** to() {
    return reinterpret_cast<RawObject**>(&ptr()->formatted_message_);
  }
  TokenPosition token_pos_;  // Source position in script_.
  bool report_after_token_;  // Report message at or after the token.
  int8_t kind_;  // Of type LanguageError::Kind.
};


class RawUnhandledException : public RawError {
  RAW_HEAP_OBJECT_IMPLEMENTATION(UnhandledException);

  RawObject** from() {
    return reinterpret_cast<RawObject**>(&ptr()->exception_);
  }
  RawInstance* exception_;
  RawInstance* stacktrace_;
  RawObject** to() {
    return reinterpret_cast<RawObject**>(&ptr()->stacktrace_);
  }
};


class RawUnwindError : public RawError {
  RAW_HEAP_OBJECT_IMPLEMENTATION(UnwindError);

  RawObject** from() {
    return reinterpret_cast<RawObject**>(&ptr()->message_);
  }
  RawString* message_;
  RawObject** to() {
    return reinterpret_cast<RawObject**>(&ptr()->message_);
  }
  bool is_user_initiated_;
  bool is_vm_restart_;
};


class RawInstance : public RawObject {
  RAW_HEAP_OBJECT_IMPLEMENTATION(Instance);
};


class RawLibraryPrefix : public RawInstance {
  RAW_HEAP_OBJECT_IMPLEMENTATION(LibraryPrefix);

  RawObject** from() { return reinterpret_cast<RawObject**>(&ptr()->name_); }
  RawString* name_;               // Library prefix name.
  RawLibrary* importer_;          // Library which declares this prefix.
  RawArray* imports_;             // Libraries imported with this prefix.
  RawArray* dependent_code_;      // Code that refers to deferred, unloaded
                                  // library prefix.
  RawObject** to() {
    return reinterpret_cast<RawObject**>(&ptr()->dependent_code_);
  }
  RawObject** to_snapshot(Snapshot::Kind kind) {
    switch (kind) {
      case Snapshot::kCore:
      case Snapshot::kScript:
      case Snapshot::kAppWithJIT:
        return reinterpret_cast<RawObject**>(&ptr()->imports_);
      case Snapshot::kAppNoJIT:
        return reinterpret_cast<RawObject**>(&ptr()->importer_);
      case Snapshot::kMessage:
      case Snapshot::kNone:
      case Snapshot::kInvalid:
        break;
    }
    UNREACHABLE();
    return NULL;
  }
  uint16_t num_imports_;          // Number of library entries in libraries_.
  bool is_deferred_load_;
  bool is_loaded_;
};


class RawAbstractType : public RawInstance {
 protected:
  enum TypeState {
    kAllocated,  // Initial state.
    kResolved,  // Type class and type arguments resolved.
    kBeingFinalized,  // In the process of being finalized.
    kFinalizedInstantiated,  // Instantiated type ready for use.
    kFinalizedUninstantiated,  // Uninstantiated type ready for use.
  };

 private:
  RAW_HEAP_OBJECT_IMPLEMENTATION(AbstractType);

  friend class ObjectStore;
};


class RawType : public RawAbstractType {
 private:
  RAW_HEAP_OBJECT_IMPLEMENTATION(Type);

  RawObject** from() {
    return reinterpret_cast<RawObject**>(&ptr()->type_class_id_);
  }
  // Either the id of the resolved class as a Smi or an UnresolvedClass.
  RawObject* type_class_id_;
  RawTypeArguments* arguments_;
  RawSmi* hash_;
  // This type object represents a function type if its signature field is a
  // non-null function object.
  // If this type is malformed or malbounded, the signature field gets
  // overwritten by the error object in order to save space. If the type is a
  // function type, its signature is lost, but the message in the error object
  // can describe the issue without needing the signature.
  union {
    RawFunction* signature_;  // If not null, this type is a function type.
    RawLanguageError* error_;  // If not null, type is malformed or malbounded.
  } sig_or_err_;
  RawObject** to() {
    return reinterpret_cast<RawObject**>(&ptr()->sig_or_err_.error_);
  }
  TokenPosition token_pos_;
  int8_t type_state_;
};


class RawTypeRef : public RawAbstractType {
 private:
  RAW_HEAP_OBJECT_IMPLEMENTATION(TypeRef);

  RawObject** from() {
    return reinterpret_cast<RawObject**>(&ptr()->type_);
  }
  RawAbstractType* type_;  // The referenced type.
  RawObject** to() {
    return reinterpret_cast<RawObject**>(&ptr()->type_);
  }
};


class RawTypeParameter : public RawAbstractType {
 private:
  RAW_HEAP_OBJECT_IMPLEMENTATION(TypeParameter);

  RawObject** from() {
    return reinterpret_cast<RawObject**>(&ptr()->name_);
  }
  RawString* name_;
  RawSmi* hash_;
  RawAbstractType* bound_;  // ObjectType if no explicit bound specified.
  RawObject** to() { return reinterpret_cast<RawObject**>(&ptr()->bound_); }
  classid_t parameterized_class_id_;
  TokenPosition token_pos_;
  int16_t index_;
  int8_t type_state_;
};


class RawBoundedType : public RawAbstractType {
 private:
  RAW_HEAP_OBJECT_IMPLEMENTATION(BoundedType);

  RawObject** from() {
    return reinterpret_cast<RawObject**>(&ptr()->type_);
  }
  RawAbstractType* type_;
  RawAbstractType* bound_;
  RawSmi* hash_;
  RawTypeParameter* type_parameter_;  // For more detailed error reporting.
  RawObject** to() {
    return reinterpret_cast<RawObject**>(&ptr()->type_parameter_);
  }
};


class RawMixinAppType : public RawAbstractType {
 private:
  RAW_HEAP_OBJECT_IMPLEMENTATION(MixinAppType);

  RawObject** from() {
    return reinterpret_cast<RawObject**>(&ptr()->super_type_);
  }
  RawAbstractType* super_type_;
  RawSmi* hash_;
  RawArray* mixin_types_;  // Array of AbstractType.
  RawObject** to() {
    return reinterpret_cast<RawObject**>(&ptr()->mixin_types_);
  }
};


class RawClosure : public RawInstance {
 private:
  RAW_HEAP_OBJECT_IMPLEMENTATION(Closure);

  RawObject** from() {
    return reinterpret_cast<RawObject**>(&ptr()->type_arguments_);
  }

  RawTypeArguments* type_arguments_;
  RawFunction* function_;
  RawContext* context_;

  RawObject** to() {
    return reinterpret_cast<RawObject**>(&ptr()->context_);
  }
};


class RawNumber : public RawInstance {
  RAW_OBJECT_IMPLEMENTATION(Number);
};


class RawInteger : public RawNumber {
  RAW_OBJECT_IMPLEMENTATION(Integer);
};


class RawSmi : public RawInteger {
  RAW_OBJECT_IMPLEMENTATION(Smi);
};


class RawMint : public RawInteger {
  RAW_HEAP_OBJECT_IMPLEMENTATION(Mint);

  ALIGN8 int64_t value_;

  friend class Api;
  friend class SnapshotReader;
};
COMPILE_ASSERT(sizeof(RawMint) == 16);


class RawBigint : public RawInteger {
  RAW_HEAP_OBJECT_IMPLEMENTATION(Bigint);

  RawObject** from() { return reinterpret_cast<RawObject**>(&ptr()->neg_); }
  RawBool* neg_;
  RawSmi* used_;
  RawTypedData* digits_;
  RawObject** to() { return reinterpret_cast<RawObject**>(&ptr()->digits_); }
};


class RawDouble : public RawNumber {
  RAW_HEAP_OBJECT_IMPLEMENTATION(Double);

  ALIGN8 double value_;

  friend class Api;
  friend class SnapshotReader;
};
COMPILE_ASSERT(sizeof(RawDouble) == 16);


class RawString : public RawInstance {
  RAW_HEAP_OBJECT_IMPLEMENTATION(String);

 protected:
  RawObject** from() { return reinterpret_cast<RawObject**>(&ptr()->length_); }
  RawSmi* length_;
  RawSmi* hash_;
  RawObject** to() { return reinterpret_cast<RawObject**>(&ptr()->hash_); }

  friend class Library;
};


class RawOneByteString : public RawString {
  RAW_HEAP_OBJECT_IMPLEMENTATION(OneByteString);

  // Variable length data follows here.
  uint8_t* data() { OPEN_ARRAY_START(uint8_t, uint8_t); }
  const uint8_t* data() const { OPEN_ARRAY_START(uint8_t, uint8_t); }

  friend class ApiMessageReader;
  friend class SnapshotReader;
};


class RawTwoByteString : public RawString {
  RAW_HEAP_OBJECT_IMPLEMENTATION(TwoByteString);

  // Variable length data follows here.
  uint16_t* data() { OPEN_ARRAY_START(uint16_t, uint16_t); }
  const uint16_t* data() const { OPEN_ARRAY_START(uint16_t, uint16_t); }

  friend class SnapshotReader;
};


template<typename T>
class ExternalStringData {
 public:
  ExternalStringData(const T* data, void* peer, Dart_PeerFinalizer callback) :
      data_(data), peer_(peer), callback_(callback) {
  }
  ~ExternalStringData() {
    if (callback_ != NULL) (*callback_)(peer_);
  }

  const T* data() {
    return data_;
  }
  void* peer() {
    return peer_;
  }

  static intptr_t data_offset() {
    return OFFSET_OF(ExternalStringData<T>, data_);
  }

 private:
  const T* data_;
  void* peer_;
  Dart_PeerFinalizer callback_;
};


class RawExternalOneByteString : public RawString {
  RAW_HEAP_OBJECT_IMPLEMENTATION(ExternalOneByteString);
 public:
  typedef ExternalStringData<uint8_t> ExternalData;

 private:
  ExternalData* external_data_;
  friend class Api;
};


class RawExternalTwoByteString : public RawString {
  RAW_HEAP_OBJECT_IMPLEMENTATION(ExternalTwoByteString);
 public:
  typedef ExternalStringData<uint16_t> ExternalData;

 private:
  ExternalData* external_data_;
  friend class Api;
};


class RawBool : public RawInstance {
  RAW_HEAP_OBJECT_IMPLEMENTATION(Bool);

  bool value_;
};


class RawArray : public RawInstance {
  RAW_HEAP_OBJECT_IMPLEMENTATION(Array);

  RawObject** from() {
    return reinterpret_cast<RawObject**>(&ptr()->type_arguments_);
  }
  RawTypeArguments* type_arguments_;
  RawSmi* length_;
  // Variable length data follows here.
  RawObject** data() { OPEN_ARRAY_START(RawObject*, RawObject*); }
  RawObject* const* data() const { OPEN_ARRAY_START(RawObject*, RawObject*); }
  RawObject** to(intptr_t length) {
    return reinterpret_cast<RawObject**>(&ptr()->data()[length - 1]);
  }

  friend class RawCode;
  friend class RawImmutableArray;
  friend class SnapshotReader;
  friend class GrowableObjectArray;
  friend class LinkedHashMap;
  friend class RawLinkedHashMap;
  friend class Object;
  friend class ICData;  // For high performance access.
  friend class SubtypeTestCache;  // For high performance access.
};


class RawImmutableArray : public RawArray {
  RAW_HEAP_OBJECT_IMPLEMENTATION(ImmutableArray);

  friend class SnapshotReader;
};


class RawGrowableObjectArray : public RawInstance {
  RAW_HEAP_OBJECT_IMPLEMENTATION(GrowableObjectArray);

  RawObject** from() {
    return reinterpret_cast<RawObject**>(&ptr()->type_arguments_);
  }
  RawTypeArguments* type_arguments_;
  RawSmi* length_;
  RawArray* data_;
  RawObject** to() {
    return reinterpret_cast<RawObject**>(&ptr()->data_);
  }

  friend class SnapshotReader;
};


class RawLinkedHashMap : public RawInstance {
  RAW_HEAP_OBJECT_IMPLEMENTATION(LinkedHashMap);

  RawObject** from() {
    return reinterpret_cast<RawObject**>(&ptr()->type_arguments_);
  }
  RawTypeArguments* type_arguments_;
  RawTypedData* index_;
  RawSmi* hash_mask_;
  RawArray* data_;
  RawSmi* used_data_;
  RawSmi* deleted_keys_;
  RawObject** to() {
    return reinterpret_cast<RawObject**>(&ptr()->deleted_keys_);
  }


  friend class SnapshotReader;
};


class RawFloat32x4 : public RawInstance {
  RAW_HEAP_OBJECT_IMPLEMENTATION(Float32x4);

  float value_[4];

  friend class SnapshotReader;
 public:
  float x() const { return value_[0]; }
  float y() const { return value_[1]; }
  float z() const { return value_[2]; }
  float w() const { return value_[3]; }
};


class RawInt32x4 : public RawInstance {
  RAW_HEAP_OBJECT_IMPLEMENTATION(Int32x4);

  int32_t value_[4];

  friend class SnapshotReader;
 public:
  int32_t x() const { return value_[0]; }
  int32_t y() const { return value_[1]; }
  int32_t z() const { return value_[2]; }
  int32_t w() const { return value_[3]; }
};


class RawFloat64x2 : public RawInstance {
  RAW_HEAP_OBJECT_IMPLEMENTATION(Float64x2);

  double value_[2];

  friend class SnapshotReader;
 public:
  double x() const { return value_[0]; }
  double y() const { return value_[1]; }
};


// Define an aliases for intptr_t.
#if defined(ARCH_IS_32_BIT)
#define kIntPtrCid kTypedDataInt32ArrayCid
#define SetIntPtr SetInt32
#elif defined(ARCH_IS_64_BIT)
#define kIntPtrCid kTypedDataInt64ArrayCid
#define SetIntPtr SetInt64
#else
#error Architecture is not 32-bit or 64-bit.
#endif  // ARCH_IS_32_BIT


class RawTypedData : public RawInstance {
  RAW_HEAP_OBJECT_IMPLEMENTATION(TypedData);

 protected:
  RawObject** from() { return reinterpret_cast<RawObject**>(&ptr()->length_); }
  RawSmi* length_;
  // Variable length data follows here.
  uint8_t* data() { OPEN_ARRAY_START(uint8_t, uint8_t); }
  const uint8_t* data() const { OPEN_ARRAY_START(uint8_t, uint8_t); }
  RawObject** to() { return reinterpret_cast<RawObject**>(&ptr()->length_); }

  friend class Api;
  friend class Object;
  friend class Instance;
  friend class SnapshotReader;
  friend class ObjectPool;
  friend class RawObjectPool;
};


class RawExternalTypedData : public RawInstance {
  RAW_HEAP_OBJECT_IMPLEMENTATION(ExternalTypedData);

 protected:
  RawObject** from() { return reinterpret_cast<RawObject**>(&ptr()->length_); }
  RawSmi* length_;
  RawObject** to() { return reinterpret_cast<RawObject**>(&ptr()->length_); }

  uint8_t* data_;

  friend class TokenStream;
  friend class RawTokenStream;
};

// VM implementations of the basic types in the isolate.
class RawCapability : public RawInstance {
  RAW_HEAP_OBJECT_IMPLEMENTATION(Capability);
  uint64_t id_;
};


class RawSendPort : public RawInstance {
  RAW_HEAP_OBJECT_IMPLEMENTATION(SendPort);
  Dart_Port id_;
  Dart_Port origin_id_;

  friend class ReceivePort;
};


class RawReceivePort : public RawInstance {
  RAW_HEAP_OBJECT_IMPLEMENTATION(ReceivePort);

  RawObject** from() {
    return reinterpret_cast<RawObject**>(&ptr()->send_port_);
  }
  RawSendPort* send_port_;
  RawInstance* handler_;
  RawObject** to() {
    return reinterpret_cast<RawObject**>(&ptr()->handler_);
  }
};


// VM type for capturing stacktraces when exceptions are thrown,
// Currently we don't have any interface that this object is supposed
// to implement so we just support the 'toString' method which
// converts the stack trace into a string.
class RawStacktrace : public RawInstance {
  RAW_HEAP_OBJECT_IMPLEMENTATION(Stacktrace);

  RawObject** from() {
    return reinterpret_cast<RawObject**>(&ptr()->code_array_);
  }
  RawArray* code_array_;  // Code object for each frame in the stack trace.
  RawArray* pc_offset_array_;  // Offset of PC for each frame.
  RawObject** to() {
    return reinterpret_cast<RawObject**>(&ptr()->pc_offset_array_);
  }
  // False for pre-allocated stack trace (used in OOM and Stack overflow).
  bool expand_inlined_;
};


// VM type for capturing JS regular expressions.
class RawRegExp : public RawInstance {
  RAW_HEAP_OBJECT_IMPLEMENTATION(RegExp);

  RawObject** from() {
    return reinterpret_cast<RawObject**>(&ptr()->num_bracket_expressions_);
  }
  RawSmi* num_bracket_expressions_;
  RawString* pattern_;  // Pattern to be used for matching.
  RawFunction* one_byte_function_;
  RawFunction* two_byte_function_;
  RawFunction* external_one_byte_function_;
  RawFunction* external_two_byte_function_;
  RawTypedData* one_byte_bytecode_;
  RawTypedData* two_byte_bytecode_;
  RawObject** to() {
    return reinterpret_cast<RawObject**>(&ptr()->two_byte_bytecode_);
  }

  intptr_t num_registers_;

  // A bitfield with two fields:
  // type: Uninitialized, simple or complex.
  // flags: Represents global/local, case insensitive, multiline.
  int8_t type_flags_;
};


class RawWeakProperty : public RawInstance {
  RAW_HEAP_OBJECT_IMPLEMENTATION(WeakProperty);

  RawObject** from() {
    return reinterpret_cast<RawObject**>(&ptr()->key_);
  }
  RawObject* key_;
  RawObject* value_;
  RawObject** to() {
    return reinterpret_cast<RawObject**>(&ptr()->value_);
  }

  // Linked list is chaining all pending weak properties.
  // Untyped to make it clear that it is not to be visited by GC.
  uword next_;

  friend class GCMarker;
  template<bool> friend class MarkingVisitorBase;
  friend class Scavenger;
  friend class ScavengerVisitor;
};

// MirrorReferences are used by mirrors to hold reflectees that are VM
// internal objects, such as libraries, classes, functions or types.
class RawMirrorReference : public RawInstance {
  RAW_HEAP_OBJECT_IMPLEMENTATION(MirrorReference);

  RawObject** from() {
    return reinterpret_cast<RawObject**>(&ptr()->referent_);
  }
  RawObject* referent_;
  RawObject** to() {
    return reinterpret_cast<RawObject**>(&ptr()->referent_);
  }
};


// UserTag are used by the profiler to track Dart script state.
class RawUserTag : public RawInstance {
  RAW_HEAP_OBJECT_IMPLEMENTATION(UserTag);

  RawObject** from() {
    return reinterpret_cast<RawObject**>(&ptr()->label_);
  }

  RawString* label_;

  RawObject** to() {
    return reinterpret_cast<RawObject**>(&ptr()->label_);
  }

  // Isolate unique tag.
  uword tag_;

  friend class SnapshotReader;
  friend class Object;

 public:
  uword tag() const { return tag_; }
};

// Class Id predicates.

inline bool RawObject::IsErrorClassId(intptr_t index) {
  // Make sure this function is updated when new Error types are added.
  COMPILE_ASSERT(kApiErrorCid == kErrorCid + 1 &&
                 kLanguageErrorCid == kErrorCid + 2 &&
                 kUnhandledExceptionCid == kErrorCid + 3 &&
                 kUnwindErrorCid == kErrorCid + 4 &&
                 kInstanceCid == kErrorCid + 5);
  return (index >= kErrorCid && index < kInstanceCid);
}


inline bool RawObject::IsNumberClassId(intptr_t index) {
  // Make sure this function is updated when new Number types are added.
  COMPILE_ASSERT(kIntegerCid == kNumberCid + 1 &&
                 kSmiCid == kNumberCid + 2 &&
                 kMintCid == kNumberCid + 3 &&
                 kBigintCid == kNumberCid + 4 &&
                 kDoubleCid == kNumberCid + 5);
  return (index >= kNumberCid && index < kBoolCid);
}


inline bool RawObject::IsIntegerClassId(intptr_t index) {
  // Make sure this function is updated when new Integer types are added.
  COMPILE_ASSERT(kSmiCid == kIntegerCid + 1 &&
                 kMintCid == kIntegerCid + 2 &&
                 kBigintCid == kIntegerCid + 3 &&
                 kDoubleCid == kIntegerCid + 4);
  return (index >= kIntegerCid && index < kDoubleCid);
}


inline bool RawObject::IsStringClassId(intptr_t index) {
  // Make sure this function is updated when new StringCid types are added.
  COMPILE_ASSERT(kOneByteStringCid == kStringCid + 1 &&
                 kTwoByteStringCid == kStringCid + 2 &&
                 kExternalOneByteStringCid == kStringCid + 3 &&
                 kExternalTwoByteStringCid == kStringCid + 4);
  return (index >= kStringCid && index <= kExternalTwoByteStringCid);
}


inline bool RawObject::IsOneByteStringClassId(intptr_t index) {
  // Make sure this function is updated when new StringCid types are added.
  COMPILE_ASSERT(kOneByteStringCid == kStringCid + 1 &&
                 kTwoByteStringCid == kStringCid + 2 &&
                 kExternalOneByteStringCid == kStringCid + 3 &&
                 kExternalTwoByteStringCid == kStringCid + 4);
  return (index == kOneByteStringCid || index == kExternalOneByteStringCid);
}


inline bool RawObject::IsTwoByteStringClassId(intptr_t index) {
  // Make sure this function is updated when new StringCid types are added.
  COMPILE_ASSERT(kOneByteStringCid == kStringCid + 1 &&
                 kTwoByteStringCid == kStringCid + 2 &&
                 kExternalOneByteStringCid == kStringCid + 3 &&
                 kExternalTwoByteStringCid == kStringCid + 4);
  return (index == kOneByteStringCid ||
          index == kTwoByteStringCid ||
          index == kExternalOneByteStringCid ||
          index == kExternalTwoByteStringCid);
}


inline bool RawObject::IsExternalStringClassId(intptr_t index) {
  // Make sure this function is updated when new StringCid types are added.
  COMPILE_ASSERT(kOneByteStringCid == kStringCid + 1 &&
                 kTwoByteStringCid == kStringCid + 2 &&
                 kExternalOneByteStringCid == kStringCid + 3 &&
                 kExternalTwoByteStringCid == kStringCid + 4);
  return (index == kExternalOneByteStringCid ||
          index == kExternalTwoByteStringCid);
}


inline bool RawObject::IsBuiltinListClassId(intptr_t index) {
  // Make sure this function is updated when new builtin List types are added.
  COMPILE_ASSERT(kImmutableArrayCid == kArrayCid + 1);
  return ((index >= kArrayCid && index <= kImmutableArrayCid) ||
          (index == kGrowableObjectArrayCid) ||
          IsTypedDataClassId(index) ||
          IsTypedDataViewClassId(index) ||
          IsExternalTypedDataClassId(index) ||
          (index == kByteBufferCid));
}


inline bool RawObject::IsTypedDataClassId(intptr_t index) {
  // Make sure this is updated when new TypedData types are added.
  COMPILE_ASSERT(kTypedDataUint8ArrayCid == kTypedDataInt8ArrayCid + 1 &&
                 kTypedDataUint8ClampedArrayCid == kTypedDataInt8ArrayCid + 2 &&
                 kTypedDataInt16ArrayCid == kTypedDataInt8ArrayCid + 3 &&
                 kTypedDataUint16ArrayCid == kTypedDataInt8ArrayCid + 4 &&
                 kTypedDataInt32ArrayCid == kTypedDataInt8ArrayCid + 5 &&
                 kTypedDataUint32ArrayCid == kTypedDataInt8ArrayCid + 6 &&
                 kTypedDataInt64ArrayCid == kTypedDataInt8ArrayCid + 7 &&
                 kTypedDataUint64ArrayCid == kTypedDataInt8ArrayCid + 8 &&
                 kTypedDataFloat32ArrayCid == kTypedDataInt8ArrayCid + 9 &&
                 kTypedDataFloat64ArrayCid == kTypedDataInt8ArrayCid + 10 &&
                 kTypedDataFloat32x4ArrayCid == kTypedDataInt8ArrayCid + 11 &&
                 kTypedDataInt32x4ArrayCid == kTypedDataInt8ArrayCid + 12 &&
                 kTypedDataFloat64x2ArrayCid == kTypedDataInt8ArrayCid + 13 &&
                 kTypedDataInt8ArrayViewCid == kTypedDataInt8ArrayCid + 14);
  return (index >= kTypedDataInt8ArrayCid &&
          index <= kTypedDataFloat64x2ArrayCid);
}


inline bool RawObject::IsTypedDataViewClassId(intptr_t index) {
  // Make sure this is updated when new TypedData types are added.
  COMPILE_ASSERT(
      kTypedDataUint8ArrayViewCid == kTypedDataInt8ArrayViewCid + 1 &&
      kTypedDataUint8ClampedArrayViewCid == kTypedDataInt8ArrayViewCid + 2 &&
      kTypedDataInt16ArrayViewCid == kTypedDataInt8ArrayViewCid + 3 &&
      kTypedDataUint16ArrayViewCid == kTypedDataInt8ArrayViewCid + 4 &&
      kTypedDataInt32ArrayViewCid == kTypedDataInt8ArrayViewCid + 5 &&
      kTypedDataUint32ArrayViewCid == kTypedDataInt8ArrayViewCid + 6 &&
      kTypedDataInt64ArrayViewCid == kTypedDataInt8ArrayViewCid + 7 &&
      kTypedDataUint64ArrayViewCid == kTypedDataInt8ArrayViewCid + 8 &&
      kTypedDataFloat32ArrayViewCid == kTypedDataInt8ArrayViewCid + 9 &&
      kTypedDataFloat64ArrayViewCid == kTypedDataInt8ArrayViewCid + 10 &&
      kTypedDataFloat32x4ArrayViewCid == kTypedDataInt8ArrayViewCid + 11 &&
      kTypedDataInt32x4ArrayViewCid == kTypedDataInt8ArrayViewCid + 12 &&
      kTypedDataFloat64x2ArrayViewCid == kTypedDataInt8ArrayViewCid + 13 &&
      kByteDataViewCid == kTypedDataInt8ArrayViewCid + 14 &&
      kExternalTypedDataInt8ArrayCid == kTypedDataInt8ArrayViewCid + 15);
  return (index >= kTypedDataInt8ArrayViewCid &&
          index <= kByteDataViewCid);
}


inline bool RawObject::IsExternalTypedDataClassId(intptr_t index) {
  // Make sure this is updated when new ExternalTypedData types are added.
  COMPILE_ASSERT(
      (kExternalTypedDataUint8ArrayCid ==
       kExternalTypedDataInt8ArrayCid + 1) &&
      (kExternalTypedDataUint8ClampedArrayCid ==
       kExternalTypedDataInt8ArrayCid + 2) &&
      (kExternalTypedDataInt16ArrayCid ==
       kExternalTypedDataInt8ArrayCid + 3) &&
      (kExternalTypedDataUint16ArrayCid ==
       kExternalTypedDataInt8ArrayCid + 4) &&
      (kExternalTypedDataInt32ArrayCid ==
       kExternalTypedDataInt8ArrayCid + 5) &&
      (kExternalTypedDataUint32ArrayCid ==
       kExternalTypedDataInt8ArrayCid + 6) &&
      (kExternalTypedDataInt64ArrayCid ==
       kExternalTypedDataInt8ArrayCid + 7) &&
      (kExternalTypedDataUint64ArrayCid ==
       kExternalTypedDataInt8ArrayCid + 8) &&
      (kExternalTypedDataFloat32ArrayCid ==
       kExternalTypedDataInt8ArrayCid + 9) &&
      (kExternalTypedDataFloat64ArrayCid ==
       kExternalTypedDataInt8ArrayCid + 10) &&
      (kExternalTypedDataFloat32x4ArrayCid ==
       kExternalTypedDataInt8ArrayCid + 11) &&
      (kExternalTypedDataInt32x4ArrayCid ==
       kExternalTypedDataInt8ArrayCid + 12) &&
      (kExternalTypedDataFloat64x2ArrayCid ==
       kExternalTypedDataInt8ArrayCid + 13) &&
      (kByteBufferCid == kExternalTypedDataInt8ArrayCid + 14));
  return (index >= kExternalTypedDataInt8ArrayCid &&
          index <= kExternalTypedDataFloat64x2ArrayCid);
}


inline bool RawObject::IsInternalVMdefinedClassId(intptr_t index) {
  return ((index < kNumPredefinedCids) &&
          !RawObject::IsImplicitFieldClassId(index));
}


inline bool RawObject::IsVariableSizeClassId(intptr_t index) {
  return (index == kArrayCid) ||
         (index == kImmutableArrayCid) ||
         RawObject::IsOneByteStringClassId(index) ||
         RawObject::IsTwoByteStringClassId(index) ||
         RawObject::IsTypedDataClassId(index) ||
         (index == kContextCid) ||
         (index == kTypeArgumentsCid) ||
         (index == kInstructionsCid) ||
         (index == kObjectPoolCid) ||
         (index == kPcDescriptorsCid) ||
         (index == kCodeSourceMapCid) ||
         (index == kStackmapCid) ||
         (index == kLocalVarDescriptorsCid) ||
         (index == kExceptionHandlersCid) ||
         (index == kCodeCid) ||
         (index == kContextScopeCid) ||
         (index == kInstanceCid) ||
         (index == kRegExpCid);
}


// This is a set of classes that are not Dart classes whose representation
// is defined by the VM but are used in the VM code by computing the
// implicit field offsets of the various fields in the dart object.
inline bool RawObject::IsImplicitFieldClassId(intptr_t index) {
  return (IsTypedDataViewClassId(index) || index == kByteBufferCid);
}


inline intptr_t RawObject::NumberOfTypedDataClasses() {
  // Make sure this is updated when new TypedData types are added.
  COMPILE_ASSERT(kTypedDataInt8ArrayViewCid == kTypedDataInt8ArrayCid + 14);
  COMPILE_ASSERT(kExternalTypedDataInt8ArrayCid ==
                 kTypedDataInt8ArrayViewCid + 15);
  COMPILE_ASSERT(kByteBufferCid == kExternalTypedDataInt8ArrayCid + 14);
  COMPILE_ASSERT(kNullCid == kByteBufferCid + 1);
  return (kNullCid - kTypedDataInt8ArrayCid);
}

}  // namespace dart

#endif  // VM_RAW_OBJECT_H_