src/prototype.h

// 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_PROTOTYPE_H_
#define V8_PROTOTYPE_H_

#include "src/isolate.h"
#include "src/objects.h"

namespace v8 {
namespace internal {

/**
 * A class to uniformly access the prototype of any Object and walk its
 * prototype chain.
 *
 * The PrototypeIterator can either start at the prototype (default), or
 * include the receiver itself. If a PrototypeIterator is constructed for a
 * Map, it will always start at the prototype.
 *
 * The PrototypeIterator can either run to the null_value(), the first
 * non-hidden prototype, or a given object.
 */

class PrototypeIterator {
 public:
  enum WhereToEnd { END_AT_NULL, END_AT_NON_HIDDEN };

  inline PrototypeIterator(Isolate* isolate, Handle<JSReceiver> receiver,
                           WhereToStart where_to_start = kStartAtPrototype,
                           WhereToEnd where_to_end = END_AT_NULL);

  inline PrototypeIterator(Isolate* isolate, JSReceiver receiver,
                           WhereToStart where_to_start = kStartAtPrototype,
                           WhereToEnd where_to_end = END_AT_NULL);

  inline explicit PrototypeIterator(Isolate* isolate, Map receiver_map,
                                    WhereToEnd where_to_end = END_AT_NULL);

  inline explicit PrototypeIterator(Isolate* isolate, Handle<Map> receiver_map,
                                    WhereToEnd where_to_end = END_AT_NULL);

  ~PrototypeIterator() = default;

  inline bool HasAccess() const;

  template <typename T = HeapObject>
  T GetCurrent() const {
    DCHECK(handle_.is_null());
    return T::cast(object_);
  }

  template <typename T = HeapObject>
  static Handle<T> GetCurrent(const PrototypeIterator& iterator) {
    DCHECK(!iterator.handle_.is_null());
    DCHECK_EQ(iterator.object_, Object());
    return Handle<T>::cast(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_;
  Object object_;
  Handle<HeapObject> handle_;
  WhereToEnd where_to_end_;
  bool is_at_end_;
  int seen_proxies_;

  DISALLOW_COPY_AND_ASSIGN(PrototypeIterator);
};


}  // namespace internal

}  // namespace v8

#endif  // V8_PROTOTYPE_H_