descriptor-array.h | Explore in Territory

// Copyright 2017 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_DESCRIPTOR_ARRAY_H_
#define V8_OBJECTS_DESCRIPTOR_ARRAY_H_

#include "src/common/globals.h"
#include "src/objects/fixed-array.h"
// TODO(jkummerow): Consider forward-declaring instead.
#include "src/base/bit-field.h"
#include "src/objects/internal-index.h"
#include "src/objects/objects.h"
#include "src/objects/struct.h"
#include "src/utils/utils.h"

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

namespace v8 {
namespace internal {

class StructBodyDescriptor;

#include "torque-generated/src/objects/descriptor-array-tq.inc"

// An EnumCache is a pair used to hold keys and indices caches.
class EnumCache : public TorqueGeneratedEnumCache<EnumCache, Struct> { … };

// A DescriptorArray is a custom array that holds instance descriptors.
// It has the following layout:
//   Header:
//     [16:0  bits]: number_of_all_descriptors (including slack)
//     [32:16 bits]: number_of_descriptors
//     [64:32 bits]: raw_gc_state (used by GC)
//     [kEnumCacheOffset]: enum cache
//   Elements:
//     [kHeaderSize + 0]: first key (and internalized String)
//     [kHeaderSize + 1]: first descriptor details (see PropertyDetails)
//     [kHeaderSize + 2]: first value for constants / Tagged<Smi>(1) when not
//     used
//   Slack:
//     [kHeaderSize + number of descriptors * 3]: start of slack
// The "value" fields store either values or field types. A field type is either
// FieldType::None(), FieldType::Any() or a weak reference to a Map. All other
// references are strong.
class DescriptorArray
    : public TorqueGeneratedDescriptorArray<DescriptorArray, HeapObject> { … };

// Custom DescriptorArray marking state for visitors that are allowed to write
// into the heap. The marking state uses DescriptorArray::raw_gc_state() as
// storage.
//
// The state essentially keeps track of 3 fields:
// 1. The collector epoch: The rest of the state is only valid if the epoch
//    matches. If the epoch doesn't match, the other fields should be considered
//    invalid. The epoch is necessary, as not all DescriptorArray objects are
//    eventually trimmed in the atomic pause and thus available for resetting
//    the state.
// 2. Number of already marked descriptors.
// 3. Delta of to be marked descriptors in this cycle. This must be 0 after
//    marking is done.
class DescriptorArrayMarkingState final { … };

}  // namespace internal
}  // namespace v8

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

#endif  // V8_OBJECTS_DESCRIPTOR_ARRAY_H_
chromium/v8/src/objects/descriptor-array.h
