chromium/v8/src/objects/keys.h

// Copyright 2012 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_KEYS_H_
#define V8_OBJECTS_KEYS_H_

#include "include/v8-object.h"
#include "src/objects/hash-table.h"
#include "src/objects/js-objects.h"
#include "src/objects/objects.h"

namespace v8 {
namespace internal {

class AccessCheckInfo;
class FastKeyAccumulator;
class JSProxy;

enum AddKeyConversion { … };

enum class GetKeysConversion { … };

enum class KeyCollectionMode { … };

// This is a helper class for JSReceiver::GetKeys which collects and sorts keys.
// GetKeys needs to sort keys per prototype level, first showing the integer
// indices from elements then the strings from the properties. However, this
// does not apply to proxies which are in full control of how the keys are
// sorted.
//
// For performance reasons the KeyAccumulator internally separates integer keys
// in |elements_| into sorted lists per prototype level. String keys are
// collected in |string_properties_|, a single OrderedHashSet (similar for
// Symbols in |symbol_properties_|. To separate the keys per level later when
// assembling the final list, |levelLengths_| keeps track of the number of
// String and Symbol keys per level.
//
// Only unique keys are kept by the KeyAccumulator, strings are stored in a
// HashSet for inexpensive lookups. Integer keys are kept in sorted lists which
// are more compact and allow for reasonably fast includes check.
class KeyAccumulator final { … };

// The FastKeyAccumulator handles the cases where there are no elements on the
// prototype chain and forwards the complex/slow cases to the normal
// KeyAccumulator. This significantly speeds up the cases where the OWN_ONLY
// case where we do not have to walk the prototype chain.
class FastKeyAccumulator { … };

}  // namespace internal
}  // namespace v8

#endif  // V8_OBJECTS_KEYS_H_