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/*
* Copyright (C) 2022 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 <memory>
#include <wtf/FastMalloc.h>
#include <wtf/Forward.h>
#include <wtf/FunctionTraits.h>
#include <wtf/Hasher.h>
#include <wtf/PtrTag.h>
WTF_ALLOW_UNSAFE_BUFFER_USAGE_BEGIN
namespace WTF {
// FunctionAttributes and FunctionCallConvention are only needed because x86 builds
// (especially for Windows) supports different calling conventions. We need to
// preserve these attributes so that when the function pointer is used in a
// call, the C/C++ compiler will be able to use the matching calling convention.
enum class FunctionAttributes {
None,
JITOperation, // JIT_OPERATION_ATTRIBUTES
JSCHostCall, // JSC_HOST_CALL_ATTRIBUTES
};
template<PtrTag tag, typename, FunctionAttributes = FunctionAttributes::None> class FunctionPtr;
template<FunctionAttributes, typename> struct FunctionCallConvention;
template<typename Out, typename... In>
struct FunctionCallConvention<FunctionAttributes::None, Out(In...)> {
using Type = Out(*)(In...);
};
template<typename Out, typename... In>
struct FunctionCallConvention<FunctionAttributes::JITOperation, Out(In...)> {
using Type = Out(JIT_OPERATION_ATTRIBUTES *)(In...);
};
template<typename Out, typename... In>
struct FunctionCallConvention<FunctionAttributes::JSCHostCall, Out(In...)> {
using Type = Out(JSC_HOST_CALL_ATTRIBUTES *)(In...);
};
class FunctionPtrBase {
public:
// We need to declare this in this non-template base. Otherwise, every use of
// AlreadyTaggedValueTag will require a specialized template qualification.
enum AlreadyTaggedValueTag { AlreadyTaggedValue };
friend bool operator==(FunctionPtrBase, FunctionPtrBase) = default;
};
template<PtrTag tag, typename Out, typename... In, FunctionAttributes attr>
class FunctionPtr<tag, Out(In...), attr> : public FunctionPtrBase {
public:
using Ptr = typename FunctionCallConvention<attr, Out(In...)>::Type;
constexpr FunctionPtr() : m_ptr(nullptr) { }
constexpr FunctionPtr(std::nullptr_t) : m_ptr(nullptr) { }
constexpr FunctionPtr(Out(*ptr)(In...))
: m_ptr(encode(ptr))
{ }
#if OS(WINDOWS)
constexpr FunctionPtr(Out(SYSV_ABI *ptr)(In...))
: m_ptr(encode(ptr))
{ }
#endif
// MSVC doesn't seem to treat functions with different calling conventions as
// different types; these methods already defined for fastcall, below.
#if CALLING_CONVENTION_IS_STDCALL && !OS(WINDOWS)
constexpr FunctionPtr(Out(CDECL *ptr)(In...))
: m_ptr(encode(ptr))
{ }
#endif
#if COMPILER_SUPPORTS(FASTCALL_CALLING_CONVENTION)
constexpr FunctionPtr(Out(FASTCALL *ptr)(In...))
: m_ptr(encode(ptr))
{ }
#endif
Out operator()(In... in) const
{
ASSERT(m_ptr);
return (*get())(std::forward<In>(in)...);
}
constexpr Ptr get() const { return decode(m_ptr); }
template<PtrTag otherTag>
FunctionPtr<otherTag, Out(In...), attr> retagged() const
{
static_assert(tag != otherTag);
return FunctionPtr<otherTag, Out(In...), attr>(AlreadyTaggedValue, retaggedPtr<otherTag>());
}
constexpr void* taggedPtr() const { return reinterpret_cast<void*>(m_ptr); }
template<PtrTag newTag>
void* retaggedPtr() const
{
static_assert(tag != newTag);
return retagCodePtr<void*, tag, newTag>(m_ptr);
}
void* untaggedPtr() const { return untagCodePtr<void*, tag>(m_ptr); }
explicit operator bool() const { return !!m_ptr; }
bool operator!() const { return !m_ptr; }
friend bool operator==(FunctionPtr, FunctionPtr) = default;
FunctionPtr& operator=(Ptr ptr)
{
m_ptr = encode(ptr);
return *this;
}
template<PtrTag otherTag>
FunctionPtr& operator=(const FunctionPtr<otherTag, Out(In...), attr>& other)
{
m_ptr = encode(other.get());
return *this;
}
FunctionPtr& operator=(std::nullptr_t)
{
m_ptr = nullptr;
return *this;
}
protected:
FunctionPtr(AlreadyTaggedValueTag, void* ptr)
: m_ptr(std::bit_cast<Ptr>(ptr))
{
assertIsNullOrTaggedWith<tag>(ptr);
}
ALWAYS_INLINE static constexpr Ptr encode(Ptr ptr)
{
// Note: we cannot do the assert before this check because it will disqualify
// this function for use in an constexpr context for some use cases.
if constexpr (tag == CFunctionPtrTag)
return ptr;
assertIsNullOrCFunctionPtr(ptr);
return retagCodePtr<CFunctionPtrTag, tag>(ptr);
}
ALWAYS_INLINE static constexpr Ptr decode(Ptr ptr)
{
if constexpr (tag == CFunctionPtrTag)
return ptr;
auto result = retagCodePtr<tag, CFunctionPtrTag>(ptr);
assertIsNullOrCFunctionPtr(result);
return result;
}
Ptr m_ptr;
template<PtrTag, typename, FunctionAttributes> friend class FunctionPtr;
};
static_assert(sizeof(FunctionPtr<CFunctionPtrTag, void()>) == sizeof(void*));
#if COMPILER_SUPPORTS(BUILTIN_IS_TRIVIALLY_COPYABLE)
static_assert(__is_trivially_copyable(FunctionPtr<CFunctionPtrTag, void()>));
#endif
template<PtrTag tag, typename Out, typename... In, FunctionAttributes attr>
struct FunctionTraits<FunctionPtr<tag, Out(In...), attr>> : public FunctionTraits<Out(In...)> {
};
template<PtrTag tag, typename Out, typename... In, FunctionAttributes attr>
void add(Hasher& hasher, const FunctionPtr<tag, Out(In...), attr>& ptr)
{
add(hasher, ptr.taggedPtr());
}
} // namespace WTF
using WTF::FunctionAttributes;
using WTF::FunctionPtr;
WTF_ALLOW_UNSAFE_BUFFER_USAGE_END
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