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/*
* Copyright (C) 2013-2025 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. AND ITS CONTRIBUTORS ``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 ITS 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 <JavaScriptCore/JSCConfig.h>
#include <JavaScriptCore/MarkedBlock.h>
#include <compare>
#include <wtf/HashTraits.h>
#include <wtf/StdIntExtras.h>
namespace JSC {
class Structure;
#if CPU(ADDRESS64)
#if defined(STRUCTURE_HEAP_ADDRESS_SIZE_IN_MB) && STRUCTURE_HEAP_ADDRESS_SIZE_IN_MB > 0
constexpr uintptr_t structureHeapAddressSize = STRUCTURE_HEAP_ADDRESS_SIZE_IN_MB * MB;
#elif PLATFORM(PLAYSTATION) || OS(QNX)
constexpr uintptr_t structureHeapAddressSize = 128 * MB;
#elif (PLATFORM(IOS_FAMILY) && !CPU(ARM64E)) || PLATFORM(WATCHOS) || PLATFORM(APPLETV)
constexpr uintptr_t structureHeapAddressSize = 512 * MB;
#elif PLATFORM(IOS_FAMILY)
constexpr uintptr_t structureHeapAddressSize = 2 * GB;
#else
constexpr uintptr_t structureHeapAddressSize = 4 * GB;
#endif
#endif // CPU(ADDRESS64)
class StructureID {
public:
static constexpr uint32_t nukedStructureIDBit = 1;
#if CPU(ADDRESS64)
static constexpr uintptr_t structureIDMask = static_cast<uintptr_t>(UINT_MAX);
static_assert(structureHeapAddressSize - 1 <= structureIDMask, "StructureID relies on only the lower 32 bits of Structure addresses varying");
#endif
constexpr StructureID() = default;
constexpr StructureID(StructureID const&) = default;
constexpr StructureID& operator=(StructureID const&) = default;
StructureID nuke() const { return StructureID(m_bits | nukedStructureIDBit); }
bool isNuked() const { return m_bits & nukedStructureIDBit; }
StructureID decontaminate() const { return StructureID(m_bits & ~nukedStructureIDBit); }
inline Structure* decode() const;
inline Structure* tryDecode() const;
static StructureID encode(const Structure*);
explicit operator bool() const { return !!m_bits; }
friend auto operator<=>(const StructureID&, const StructureID&) = default;
constexpr uint32_t bits() const { return m_bits; }
constexpr StructureID(WTF::HashTableDeletedValueType) : m_bits(nukedStructureIDBit) { }
bool isHashTableDeletedValue() const { return *this == StructureID(WTF::HashTableDeletedValue); }
private:
explicit constexpr StructureID(uint32_t bits) : m_bits(bits) { }
uint32_t m_bits { 0 };
};
static_assert(sizeof(StructureID) == sizeof(uint32_t));
#if CPU(ADDRESS64)
ALWAYS_INLINE Structure* StructureID::decode() const
{
// Take care to only use the bits from m_bits in the structure's address reservation.
ASSERT(decontaminate());
return reinterpret_cast<Structure*>(static_cast<uintptr_t>(decontaminate().m_bits) + structureIDBase());
}
ALWAYS_INLINE Structure* StructureID::tryDecode() const
{
// Take care to only use the bits from m_bits in the structure's address reservation.
SUPPRESS_UNRETAINED_LOCAL Structure* structure = decode();
uintptr_t offset = std::bit_cast<uintptr_t>(structure) - startOfStructureHeap();
if (offset < MarkedBlock::blockSize || offset >= g_jscConfig.sizeOfStructureHeap)
return nullptr;
return structure;
}
ALWAYS_INLINE StructureID StructureID::encode(const Structure* structure)
{
ASSERT(structure);
ASSERT(startOfStructureHeap() <= reinterpret_cast<uintptr_t>(structure) && reinterpret_cast<uintptr_t>(structure) < startOfStructureHeap() + structureHeapAddressSize);
auto result = StructureID(reinterpret_cast<uintptr_t>(structure));
ASSERT(result.decode() == structure);
return result;
}
#else // CPU(ADDRESS64)
ALWAYS_INLINE Structure* StructureID::decode() const
{
ASSERT(decontaminate());
return reinterpret_cast<Structure*>(decontaminate().m_bits);
}
ALWAYS_INLINE Structure* StructureID::tryDecode() const
{
return reinterpret_cast<Structure*>(decontaminate().m_bits);
}
ALWAYS_INLINE StructureID StructureID::encode(const Structure* structure)
{
ASSERT(structure);
return StructureID(reinterpret_cast<uint32_t>(structure));
}
#endif
struct StructureIDHash {
static unsigned hash(const StructureID& key) { return key.bits(); }
static bool equal(const StructureID& a, const StructureID& b) { return a == b; }
static constexpr bool safeToCompareToEmptyOrDeleted = true;
};
} // namespace JSC
namespace WTF {
template<typename T> struct DefaultHash;
template<> struct DefaultHash<JSC::StructureID> : JSC::StructureIDHash { };
template<typename T> struct HashTraits;
template<> struct HashTraits<JSC::StructureID> : SimpleClassHashTraits<JSC::StructureID> {
static constexpr bool emptyValueIsZero = true;
};
}
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