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/*
* Copyright (C) 2020 Apple Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#pragma once
#include "JSCJSValue.h"
namespace WTF {
class PrintStream;
class UniquedStringImpl;
} // namespace WTF
using WTF::PrintStream;
using WTF::UniquedStringImpl;
namespace JSC {
class Identifier;
class JSCell;
class SlotVisitor;
class CacheableIdentifier {
public:
CacheableIdentifier() = default;
inline CacheableIdentifier(const Identifier&);
inline CacheableIdentifier(JSCell* identifier);
CacheableIdentifier(const CacheableIdentifier&) = default;
CacheableIdentifier(CacheableIdentifier&&) = default;
CacheableIdentifier(std::nullptr_t)
: m_bits(0)
{ }
bool isUid() const { return m_bits & s_uidTag; }
bool isCell() const { return !isUid(); }
inline bool isSymbolCell() const;
inline bool isStringCell() const;
bool isSymbol() const { return m_bits && uid()->isSymbol(); }
inline JSCell* cell() const;
UniquedStringImpl* uid() const;
explicit operator bool() const { return m_bits; }
CacheableIdentifier& operator=(const CacheableIdentifier&) = default;
CacheableIdentifier& operator=(CacheableIdentifier&&) = default;
bool operator==(const CacheableIdentifier& other) const;
bool operator!=(const CacheableIdentifier& other) const;
bool operator==(const Identifier& other) const;
static inline bool isCacheableIdentifierCell(JSCell*);
static inline bool isCacheableIdentifierCell(JSValue);
inline void visitAggregate(SlotVisitor&) const;
JS_EXPORT_PRIVATE void dump(PrintStream&) const;
private:
inline void setCellBits(JSCell*);
inline void setUidBits(UniquedStringImpl*);
// CacheableIdentifier can either hold a cell pointer or a uid. To discern which
// it is holding, we tag the low bit if we have a uid. We choose to tag the uid
// instead of the cell because this keeps the bits of the cell pointer form
// unpolluted, and therefore, it can be scanned by our conservative GC to keep the
// cell alive when the CacheableIdentifier is on the stack.
static constexpr uintptr_t s_uidTag = 1;
uintptr_t m_bits;
};
} // namespace JSC