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/*
* Copyright (C) 2021 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 <atomic>
#include <wtf/Forward.h>
#include <wtf/HashTraits.h>
#include <wtf/RawPtrTraits.h>
#if ASSERT_ENABLED
#include <wtf/Threading.h>
#endif
namespace WTF {
template<typename T, typename PtrTraits>
class CheckedRef {
WTF_MAKE_FAST_ALLOCATED;
public:
~CheckedRef()
{
unpoison(*this);
if (auto* ptr = PtrTraits::exchange(m_ptr, nullptr))
PtrTraits::unwrap(ptr)->decrementPtrCount();
}
CheckedRef(T& object)
: m_ptr(&object)
{
PtrTraits::unwrap(m_ptr)->incrementPtrCount();
}
ALWAYS_INLINE CheckedRef(const CheckedRef& other)
: m_ptr { PtrTraits::unwrap(other.m_ptr) }
{
PtrTraits::unwrap(m_ptr)->incrementPtrCount();
}
template<typename OtherType, typename OtherPtrTraits>
CheckedRef(const CheckedRef<OtherType, OtherPtrTraits>& other)
: m_ptr { PtrTraits::unwrap(other.m_ptr) }
{
PtrTraits::unwrap(m_ptr)->incrementPtrCount();
}
ALWAYS_INLINE CheckedRef(CheckedRef&& other)
: m_ptr { other.releasePtr() }
{
ASSERT(m_ptr);
}
template<typename OtherType, typename OtherPtrTraits>
CheckedRef(CheckedRef<OtherType, OtherPtrTraits>&& other)
: m_ptr { other.releasePtr() }
{
ASSERT(m_ptr);
}
CheckedRef(HashTableDeletedValueType) : m_ptr(PtrTraits::hashTableDeletedValue()) { }
bool isHashTableDeletedValue() const { return PtrTraits::isHashTableDeletedValue(m_ptr); }
CheckedRef(HashTableEmptyValueType) : m_ptr(hashTableEmptyValue()) { }
bool isHashTableEmptyValue() const { return m_ptr == hashTableEmptyValue(); }
static T* hashTableEmptyValue() { return nullptr; }
const T* ptrAllowingHashTableEmptyValue() const { ASSERT(m_ptr || isHashTableEmptyValue()); return PtrTraits::unwrap(m_ptr); }
T* ptrAllowingHashTableEmptyValue() { ASSERT(m_ptr || isHashTableEmptyValue()); return PtrTraits::unwrap(m_ptr); }
ALWAYS_INLINE const T* ptr() const { return PtrTraits::unwrap(m_ptr); }
ALWAYS_INLINE T* ptr() { return PtrTraits::unwrap(m_ptr); }
ALWAYS_INLINE const T& get() const { ASSERT(ptr()); return *ptr(); }
ALWAYS_INLINE T& get() { ASSERT(ptr()); return *ptr(); }
ALWAYS_INLINE const T* operator->() const { return ptr(); }
ALWAYS_INLINE T* operator->() { return ptr(); }
ALWAYS_INLINE operator const T&() const { return get(); }
ALWAYS_INLINE operator T&() { return get(); }
ALWAYS_INLINE bool operator!() const { return !get(); }
CheckedRef& operator=(T& reference)
{
unpoison(*this);
CheckedRef copy { reference };
PtrTraits::swap(m_ptr, copy.m_ptr);
return *this;
}
CheckedRef& operator=(const CheckedRef& other)
{
unpoison(*this);
CheckedRef copy { other };
PtrTraits::swap(m_ptr, copy.m_ptr);
return *this;
}
template<typename OtherType, typename OtherPtrTraits> CheckedRef& operator=(const CheckedRef<OtherType, OtherPtrTraits>& other)
{
unpoison(*this);
CheckedRef copy { other };
PtrTraits::swap(m_ptr, copy.m_ptr);
return *this;
}
CheckedRef& operator=(CheckedRef&& other)
{
unpoison(*this);
CheckedRef moved { WTFMove(other) };
PtrTraits::swap(m_ptr, moved.m_ptr);
return *this;
}
template<typename OtherType, typename OtherPtrTraits> CheckedRef& operator=(CheckedRef<OtherType, OtherPtrTraits>&& other)
{
unpoison(*this);
CheckedRef moved { WTFMove(other) };
PtrTraits::swap(m_ptr, moved.m_ptr);
return *this;
}
private:
template<typename OtherType, typename OtherPtrTraits> friend class CheckedRef;
template<typename OtherType, typename OtherPtrTraits> friend class CheckedPtr;
T* releasePtr()
{
T* ptr = PtrTraits::exchange(m_ptr, nullptr);
poison(*this);
return ptr;
}
#if ASAN_ENABLED
template <typename ObjectType>
void poison(ObjectType& object)
{
__asan_poison_memory_region(&object, sizeof(ObjectType));
}
template <typename ObjectType>
void unpoison(ObjectType& object)
{
if (__asan_address_is_poisoned(&object))
__asan_unpoison_memory_region(&object, sizeof(ObjectType));
}
#else
template <typename ObjectType> void poison(ObjectType&) { }
template <typename ObjectType> void unpoison(ObjectType&) { }
#endif
typename PtrTraits::StorageType m_ptr;
};
template <typename T, typename PtrTraits>
struct GetPtrHelper<CheckedRef<T, PtrTraits>> {
typedef T* PtrType;
static T* getPtr(const CheckedRef<T, PtrTraits>& p) { return const_cast<T*>(p.ptr()); }
};
template <typename T, typename U>
struct IsSmartPtr<CheckedRef<T, U>> {
static constexpr bool value = true;
};
template<typename ExpectedType, typename ArgType, typename ArgPtrTraits>
inline bool is(CheckedRef<ArgType, ArgPtrTraits>& source)
{
return is<ExpectedType>(source.get());
}
template<typename ExpectedType, typename ArgType, typename ArgPtrTraits>
inline bool is(const CheckedRef<ArgType, ArgPtrTraits>& source)
{
return is<ExpectedType>(source.get());
}
template<typename P> struct CheckedRefHashTraits : SimpleClassHashTraits<CheckedRef<P>> {
static constexpr bool emptyValueIsZero = true;
static CheckedRef<P> emptyValue() { return HashTableEmptyValue; }
template <typename>
static void constructEmptyValue(CheckedRef<P>& slot)
{
new (NotNull, std::addressof(slot)) CheckedRef<P>(HashTableEmptyValue);
}
static constexpr bool hasIsEmptyValueFunction = true;
static bool isEmptyValue(const CheckedRef<P>& value) { return value.isHashTableEmptyValue(); }
using PeekType = P*;
static PeekType peek(const CheckedRef<P>& value) { return const_cast<PeekType>(value.ptrAllowingHashTableEmptyValue()); }
static PeekType peek(P* value) { return value; }
using TakeType = CheckedPtr<P>;
static TakeType take(CheckedRef<P>&& value) { return isEmptyValue(value) ? nullptr : CheckedPtr<P>(WTFMove(value)); }
};
template<typename P> struct HashTraits<CheckedRef<P>> : CheckedRefHashTraits<P> { };
template<typename P> struct PtrHash<CheckedRef<P>> : PtrHashBase<CheckedRef<P>, IsSmartPtr<CheckedRef<P>>::value> {
static constexpr bool safeToCompareToEmptyOrDeleted = false;
};
template<typename P> struct DefaultHash<CheckedRef<P>> : PtrHash<CheckedRef<P>> { };
template <typename StorageType, typename PtrCounterType> class CanMakeCheckedPtrBase {
public:
~CanMakeCheckedPtrBase() { RELEASE_ASSERT(!m_count); }
PtrCounterType ptrCount() const { return m_count; }
void incrementPtrCount() const { ++m_count; }
void decrementPtrCount() const { ASSERT(m_count); --m_count; }
private:
mutable StorageType m_count { 0 };
};
template <typename IntegralType>
class SingleThreadIntegralWrapper {
public:
SingleThreadIntegralWrapper(IntegralType);
operator IntegralType() const;
bool operator!() const;
SingleThreadIntegralWrapper& operator++();
SingleThreadIntegralWrapper& operator--();
private:
#if ASSERT_ENABLED && !USE(WEB_THREAD)
void assertThread() const { ASSERT(m_thread.ptr() == &Thread::current()); }
#else
constexpr void assertThread() const { }
#endif
IntegralType m_value;
#if ASSERT_ENABLED && !USE(WEB_THREAD)
Ref<Thread> m_thread;
#endif
};
template <typename IntegralType>
inline SingleThreadIntegralWrapper<IntegralType>::SingleThreadIntegralWrapper(IntegralType value)
: m_value { value }
#if ASSERT_ENABLED && !USE(WEB_THREAD)
, m_thread { Thread::current() }
#endif
{ }
template <typename IntegralType>
inline SingleThreadIntegralWrapper<IntegralType>::operator IntegralType() const
{
assertThread();
return m_value;
}
template <typename IntegralType>
inline bool SingleThreadIntegralWrapper<IntegralType>::operator!() const
{
assertThread();
return !m_value;
}
template <typename IntegralType>
inline SingleThreadIntegralWrapper<IntegralType>& SingleThreadIntegralWrapper<IntegralType>::operator++()
{
assertThread();
m_value++;
return *this;
}
template <typename IntegralType>
inline SingleThreadIntegralWrapper<IntegralType>& SingleThreadIntegralWrapper<IntegralType>::operator--()
{
assertThread();
m_value--;
return *this;
}
using CanMakeCheckedPtr = CanMakeCheckedPtrBase<SingleThreadIntegralWrapper<uint32_t>, uint32_t>;
using CanMakeThreadSafeCheckedPtr = CanMakeCheckedPtrBase<std::atomic<uint32_t>, uint32_t>;
} // namespace WTF
using WTF::CanMakeCheckedPtr;
using WTF::CanMakeThreadSafeCheckedPtr;
using WTF::CheckedRef;