prototype.h

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// Copyright 2014 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_PROTOTYPE_H_
#define V8_OBJECTS_PROTOTYPE_H_
 
#include "src/execution/isolate.h"
#include "src/objects/objects.h"
 
namespace v8 {
namespace internal {
 
class PrototypeIterator {
 public:
  enum WhereToEnd { END_AT_NULL, END_AT_NON_HIDDEN };
 
  inline PrototypeIterator(Isolate* isolate, DirectHandle<JSReceiver> receiver,
                           WhereToStart where_to_start = kStartAtPrototype,
                           WhereToEnd where_to_end = END_AT_NULL);
 
  inline PrototypeIterator(Isolate* isolate, Tagged<JSReceiver> receiver,
                           WhereToStart where_to_start = kStartAtPrototype,
                           WhereToEnd where_to_end = END_AT_NULL);
 
  inline explicit PrototypeIterator(Isolate* isolate, Tagged<Map> receiver_map,
                                    WhereToEnd where_to_end = END_AT_NULL);
 
  inline explicit PrototypeIterator(Isolate* isolate,
                                    DirectHandle<Map> receiver_map,
                                    WhereToEnd where_to_end = END_AT_NULL);
 
  ~PrototypeIterator() = default;
  PrototypeIterator(const PrototypeIterator&) = delete;
  PrototypeIterator& operator=(const PrototypeIterator&) = delete;
 
  inline bool HasAccess() const;
 
  template <typename T = JSPrototype>
  Tagged<T> GetCurrent() const {
    DCHECK(handle_.is_null());
    return Cast<T>(object_);
  }
 
  template <typename T = JSPrototype>
  static DirectHandle<T> GetCurrent(const PrototypeIterator& iterator) {
    DCHECK(!iterator.handle_.is_null());
    DCHECK_EQ(iterator.object_, Tagged<HeapObject>());
    return Cast<T>(iterator.handle_);
  }
 
  inline void Advance();
 
  inline void AdvanceIgnoringProxies();
 
  // Returns false iff a call to JSProxy::GetPrototype throws.
  V8_WARN_UNUSED_RESULT inline bool AdvanceFollowingProxies();
 
  V8_WARN_UNUSED_RESULT inline bool
  AdvanceFollowingProxiesIgnoringAccessChecks();
 
  bool IsAtEnd() const { return is_at_end_; }
  Isolate* isolate() const { return isolate_; }
 
 private:
  Isolate* isolate_;
  Tagged<JSPrototype> object_ = {};
  // TODO(372390038): This handle cannot be migrated to a direct one, because
  // the PrototypeIterator is used as a field in DebugPropertyIterator, which
  // can be heap allocated.
  IndirectHandle<JSPrototype> handle_;
  WhereToEnd where_to_end_;
  bool is_at_end_;
  int seen_proxies_;
};
 
}  // namespace internal
 
}  // namespace v8
 
#endif  // V8_OBJECTS_PROTOTYPE_H_