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/*
* Copyright (C) 2008-2024 Apple Inc. All rights reserved.
* Copyright (C) 2024 Samuel Weinig <sam@webkit.org>
* Copyright (C) 2013 Patrick Gansterer <paroga@paroga.com>
*
* 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 "Compiler.h"
#include "Platform.h"
#include <bit>
#include <cstdint>
#include <wtf/text/ASCIILiteral.h>
namespace WTF {
// A small mixin to quickly check downcasts in debug builds.
// MAKE_VALIDATED_REINTERPRET_CAST must be the first mixin included in the classs.
// Use VALIDATED_REINTERPRET_CAST to perform the downcast.
// A string (fqn) is provided to identify the class, that way downcasts
// do not need to depend on the definiton of the subclass.
template<typename T, typename U>
constexpr inline T* validatedReinterpretCast(U* v, uint64_t magic)
{
// We don't want to require the definition of T to do this cast.
ASSERT_UNUSED(magic, !v || std::bit_cast<uint64_t*>(v)[0] == magic);
return static_cast<T*>(v);
}
#if ASSERT_ENABLED
#define MAKE_VALIDATED_REINTERPRET_CAST \
constexpr inline static uint64_t expectedMagicValue(); \
const uint64_t magicValue = expectedMagicValue();
#define MAKE_VALIDATED_REINTERPRET_CAST_IMPL(fqn, T) \
constexpr inline uint64_t T::expectedMagicValue() \
{ \
static_assert(!OBJECT_OFFSETOF(T, magicValue)); \
return ASCIILiteral(fqn).hash(); \
}
#else
#define MAKE_VALIDATED_REINTERPRET_CAST
#define MAKE_VALIDATED_REINTERPRET_CAST_IMPL(fqn, T)
#endif
#define VALIDATED_REINTERPRET_CAST(fqn, T, v) \
WTF::validatedReinterpretCast<T>(v, ASCIILiteral(fqn).hash())
template<typename T, typename U>
ALWAYS_INLINE T* validatedReinterpretCast(U* u)
{
T* casted = static_cast<T*>(u);
ASSERT(casted->magicValue == T::MAGIC_VALUE);
return casted;
}
} // namespace WTF
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