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/*
* Copyright (C) 2014 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 <type_traits>
namespace WTF {
template <typename ExpectedType, typename ArgType, bool isBaseType = std::is_base_of_v<ExpectedType, ArgType>>
struct TypeCastTraits {
static bool isOfType(ArgType&)
{
// If you're hitting this assertion, it is likely because you used
// is<>() or downcast<>() with a type that doesn't have the needed
// TypeCastTraits specialization. Please use the following macro
// to add that specialization:
// SPECIALIZE_TYPE_TRAITS_BEGIN() / SPECIALIZE_TYPE_TRAITS_END()
static_assert(std::is_void_v<ExpectedType>, "Missing TypeCastTraits specialization");
return false;
}
};
// Template specialization for the case where ExpectedType is a base of ArgType,
// so we can return return true unconditionally.
template <typename ExpectedType, typename ArgType>
struct TypeCastTraits<ExpectedType, ArgType, true /* isBaseType */> {
static bool isOfType(ArgType&) { return true; }
};
// Type checking function, to use before casting with downcast<>().
template <typename ExpectedType, typename ArgType>
inline bool is(const ArgType& source)
{
static_assert(std::is_base_of_v<ArgType, ExpectedType>, "Unnecessary type check");
return TypeCastTraits<const ExpectedType, const ArgType>::isOfType(source);
}
template <typename ExpectedType, typename ArgType>
inline bool is(ArgType* source)
{
static_assert(std::is_base_of_v<ArgType, ExpectedType>, "Unnecessary type check");
return source && TypeCastTraits<const ExpectedType, const ArgType>::isOfType(*source);
}
// Update T's constness to match Reference's.
template <typename Reference, typename T>
using match_constness_t =
typename std::conditional_t<std::is_const_v<Reference>, typename std::add_const_t<T>, typename std::remove_const_t<T>>;
template<typename Target, typename Source>
inline match_constness_t<Source, Target>& uncheckedDowncast(Source& source)
{
static_assert(!std::is_same_v<Source, Target>, "Unnecessary cast to same type");
static_assert(std::is_base_of_v<Source, Target>, "Should be a downcast");
ASSERT_WITH_SECURITY_IMPLICATION(is<Target>(source));
SUPPRESS_MEMORY_UNSAFE_CAST return static_cast<match_constness_t<Source, Target>&>(source);
}
template<typename Target, typename Source>
inline match_constness_t<Source, Target>* uncheckedDowncast(Source* source)
{
static_assert(!std::is_same_v<Source, Target>, "Unnecessary cast to same type");
static_assert(std::is_base_of_v<Source, Target>, "Should be a downcast");
ASSERT_WITH_SECURITY_IMPLICATION(!source || is<Target>(*source));
SUPPRESS_MEMORY_UNSAFE_CAST return static_cast<match_constness_t<Source, Target>*>(source);
}
template<typename Target, typename Source>
inline match_constness_t<Source, Target>& downcast(Source& source)
{
static_assert(!std::is_same_v<Source, Target>, "Unnecessary cast to same type");
static_assert(std::is_base_of_v<Source, Target>, "Should be a downcast");
RELEASE_ASSERT(is<Target>(source));
SUPPRESS_MEMORY_UNSAFE_CAST return static_cast<match_constness_t<Source, Target>&>(source);
}
template<typename Target, typename Source>
inline match_constness_t<Source, Target>* downcast(Source* source)
{
static_assert(!std::is_same_v<Source, Target>, "Unnecessary cast to same type");
static_assert(std::is_base_of_v<Source, Target>, "Should be a downcast");
RELEASE_ASSERT(!source || is<Target>(*source));
SUPPRESS_MEMORY_UNSAFE_CAST return static_cast<match_constness_t<Source, Target>*>(source);
}
template<typename Target, typename Source>
inline match_constness_t<Source, Target>* dynamicDowncast(Source& source)
{
static_assert(!std::is_same_v<Source, Target>, "Unnecessary cast to same type");
static_assert(std::is_base_of_v<Source, Target>, "Should be a downcast");
SUPPRESS_MEMORY_UNSAFE_CAST return is<Target>(source) ? &static_cast<match_constness_t<Source, Target>&>(source) : nullptr;
}
template<typename Target, typename Source>
inline match_constness_t<Source, Target>* dynamicDowncast(Source* source)
{
static_assert(!std::is_same_v<Source, Target>, "Unnecessary cast to same type");
static_assert(std::is_base_of_v<Source, Target>, "Should be a downcast");
SUPPRESS_MEMORY_UNSAFE_CAST return is<Target>(source) ? static_cast<match_constness_t<Source, Target>*>(source) : nullptr;
}
// Add support for type checking / casting using is<>() / downcast<>() helpers for a specific class.
#define SPECIALIZE_TYPE_TRAITS_BEGIN(ClassName) \
namespace WTF { \
template <typename ArgType> \
class TypeCastTraits<const ClassName, ArgType, false /* isBaseType */> { \
public: \
static bool isOfType(ArgType& source) { return isType(source); } \
private:
#define SPECIALIZE_TYPE_TRAITS_END() \
}; \
}
// Explicit specialization for C++ standard library types.
template<typename ExpectedType, typename ArgType, typename Deleter>
inline bool is(std::unique_ptr<ArgType, Deleter>& source)
{
return is<ExpectedType>(source.get());
}
template<typename ExpectedType, typename ArgType, typename Deleter>
inline bool is(const std::unique_ptr<ArgType, Deleter>& source)
{
return is<ExpectedType>(source.get());
}
} // namespace WTF
using WTF::TypeCastTraits;
using WTF::is;
using WTF::downcast;
using WTF::dynamicDowncast;
using WTF::uncheckedDowncast;
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