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/*
* Copyright (C) 2023 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. ``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 <type_traits>
#include <wtf/StdLibExtras.h>
#include <wtf/Vector.h>
WTF_ALLOW_UNSAFE_BUFFER_USAGE_BEGIN
namespace WTF {
// ButterflyArray offers the feature trailing and leading array in the derived class.
// We can allocate a memory like the following layout.
//
// [ Leading Array ][ DerivedClass ][ Trailing Array ]
template<typename Derived, typename LeadingType, typename TrailingType>
class ButterflyArray {
WTF_MAKE_NONCOPYABLE(ButterflyArray);
friend class JSC::LLIntOffsetsExtractor;
protected:
explicit ButterflyArray(unsigned leadingSize, unsigned trailingSize)
: m_leadingSize(leadingSize)
, m_trailingSize(trailingSize)
{
static_assert(std::is_final_v<Derived>);
auto leadingSpan = this->leadingSpan();
VectorTypeOperations<LeadingType>::initializeIfNonPOD(leadingSpan.data(), leadingSpan.data() + leadingSpan.size());
auto trailingSpan = this->trailingSpan();
VectorTypeOperations<TrailingType>::initializeIfNonPOD(trailingSpan.data(), trailingSpan.data() + trailingSpan.size());
}
template<typename... Args>
static Derived* createImpl(unsigned leadingSize, unsigned trailingSize, Args&&... args)
{
uint8_t* memory = std::bit_cast<uint8_t*>(fastMalloc(allocationSize(leadingSize, trailingSize)));
return new (NotNull, memory + memoryOffsetForDerived(leadingSize)) Derived(leadingSize, trailingSize, std::forward<Args>(args)...);
}
public:
static constexpr size_t allocationSize(unsigned leadingSize, unsigned trailingSize)
{
return memoryOffsetForDerived(leadingSize) + offsetOfTrailingData() + trailingSize * sizeof(TrailingType);
}
static constexpr ptrdiff_t offsetOfLeadingSize() { return OBJECT_OFFSETOF(Derived, m_leadingSize); }
static constexpr ptrdiff_t offsetOfTrailingSize() { return OBJECT_OFFSETOF(Derived, m_trailingSize); }
static constexpr ptrdiff_t offsetOfTrailingData()
{
return WTF::roundUpToMultipleOf<alignof(TrailingType)>(sizeof(Derived));
}
static constexpr ptrdiff_t memoryOffsetForDerived(unsigned leadingSize)
{
return WTF::roundUpToMultipleOf<alignof(Derived)>(sizeof(LeadingType) * leadingSize);
}
std::span<LeadingType> leadingSpan()
{
return std::span { leadingData(), m_leadingSize };
}
std::span<const LeadingType> leadingSpan() const
{
return std::span { leadingData(), m_leadingSize };
}
std::span<TrailingType> trailingSpan()
{
return std::span { trailingData(), m_trailingSize };
}
std::span<const TrailingType> trailingSpan() const
{
return std::span { trailingData(), m_trailingSize };
}
void operator delete(ButterflyArray* base, std::destroying_delete_t)
{
unsigned leadingSize = base->m_leadingSize;
std::destroy_at(static_cast<Derived*>(base));
fastFree(std::bit_cast<uint8_t*>(static_cast<Derived*>(base)) - memoryOffsetForDerived(leadingSize));
}
~ButterflyArray()
{
auto leadingSpan = this->leadingSpan();
VectorTypeOperations<LeadingType>::destruct(leadingSpan.data(), leadingSpan.data() + leadingSpan.size());
auto trailingSpan = this->trailingSpan();
VectorTypeOperations<TrailingType>::destruct(trailingSpan.data(), trailingSpan.data() + trailingSpan.size());
}
protected:
LeadingType* leadingData()
{
return std::bit_cast<LeadingType*>(static_cast<Derived*>(this)) - m_leadingSize;
}
const LeadingType leadingData() const
{
return std::bit_cast<const LeadingType*>(static_cast<const Derived*>(this)) - m_leadingSize;
}
TrailingType* trailingData()
{
return std::bit_cast<TrailingType*>(std::bit_cast<uint8_t*>(static_cast<Derived*>(this)) + offsetOfTrailingData());
}
const TrailingType* trailingData() const
{
return std::bit_cast<const TrailingType*>(std::bit_cast<const uint8_t*>(static_cast<const Derived*>(this)) + offsetOfTrailingData());
}
unsigned m_leadingSize { 0 };
unsigned m_trailingSize { 0 };
};
} // namespace WTF
using WTF::ButterflyArray;
WTF_ALLOW_UNSAFE_BUFFER_USAGE_END
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