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util: faster constexpr offsetof calc, at the cost of standards compliance
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1 changed files with 84 additions and 66 deletions
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@ -23,6 +23,10 @@ namespace ams::util {
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namespace impl {
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#define AMS_UTIL_OFFSET_OF_STANDARD_COMPLIANT 0
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#if AMS_UTIL_OFFSET_OF_STANDARD_COMPLIANT
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template<size_t MaxDepth>
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struct OffsetOfUnionHolder {
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template<typename ParentType, typename MemberType, size_t Offset>
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@ -101,6 +105,20 @@ namespace ams::util {
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}
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};
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#else
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template<typename ParentType, typename MemberType>
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struct OffsetOfCalculator {
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static constexpr std::ptrdiff_t OffsetOf(MemberType ParentType::*member) {
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constexpr TYPED_STORAGE(ParentType) Holder = {};
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const auto *parent = GetPointer(Holder);
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const auto *target = std::addressof(parent->*member);
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return static_cast<const uint8_t *>(static_cast<const void *>(target)) - static_cast<const uint8_t *>(static_cast<const void *>(parent));
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}
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};
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#endif
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template<typename T>
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struct GetMemberPointerTraits;
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