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// Copyright 2018 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_EMBEDDER_DATA_SLOT_H_
#define V8_OBJECTS_EMBEDDER_DATA_SLOT_H_
#include <utility>
#include "src/assert-scope.h"
#include "src/globals.h"
#include "src/objects/slots.h"
// Has to be the last include (doesn't have include guards):
#include "src/objects/object-macros.h"
namespace v8 {
namespace internal {
class EmbedderDataArray;
class JSObject;
class Object;
// An EmbedderDataSlot instance describes a kEmbedderDataSlotSize field ("slot")
// holding an embedder data which may contain raw aligned pointer or a tagged
// pointer (smi or heap object).
// Its address() is the address of the slot.
// The slot's contents can be read and written using respective load_XX() and
// store_XX() methods.
// Storing heap object through this slot may require triggering write barriers
// so this operation must be done via static store_tagged() methods.
class EmbedderDataSlot
: public SlotBase<EmbedderDataSlot, Address, kEmbedderDataSlotSize> {
public:
EmbedderDataSlot() : SlotBase(kNullAddress) {}
V8_INLINE EmbedderDataSlot(EmbedderDataArray array, int entry_index);
V8_INLINE EmbedderDataSlot(JSObject object, int embedder_field_index);
// TODO(ishell): these offsets are currently little-endian specific.
// The less significant part contains tagged value and the other part
// contains the raw value.
static constexpr int kTaggedPayloadOffset = 0;
#ifdef V8_COMPRESS_POINTERS
static constexpr int kRawPayloadOffset = kTaggedSize;
#endif
static constexpr int kRequiredPtrAlignment = kSmiTagSize;
// Opaque type used for storing raw embedder data.
struct RawData {
const Address data_[kEmbedderDataSlotSizeInTaggedSlots];
};
V8_INLINE Object load_tagged() const;
V8_INLINE void store_smi(Smi value);
// Setting an arbitrary tagged value requires triggering a write barrier
// which requires separate object and offset values, therefore these static
// functions a
static V8_INLINE void store_tagged(EmbedderDataArray array, int entry_index,
Object value);
static V8_INLINE void store_tagged(JSObject object, int embedder_field_index,
Object value);
// Tries reinterpret the value as an aligned pointer and on success sets
// *out_result to the pointer-like value and returns true. Note, that some
// Smis could still look like an aligned pointers.
// Returns false otherwise.
V8_INLINE bool ToAlignedPointer(void** out_result) const;
// Returns true if the pointer was successfully stored or false it the pointer
// was improperly aligned.
V8_INLINE V8_WARN_UNUSED_RESULT bool store_aligned_pointer(void* ptr);
V8_INLINE RawData load_raw(const DisallowHeapAllocation& no_gc) const;
V8_INLINE void store_raw(const RawData& data,
const DisallowHeapAllocation& no_gc);
};
} // namespace internal
} // namespace v8
#include "src/objects/object-macros-undef.h"
#endif // V8_OBJECTS_EMBEDDER_DATA_SLOT_H_
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