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[span] Make span standard_layout #877

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merged 10 commits into from
Jun 24, 2020
Merged

[span] Make span standard_layout #877

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a5e7b32
[span] Make span standard_layout
miscco Jun 3, 2020
e3ed3f5
using _Span_extent_type<_Ty, _Extent>::size;
CaseyCarter Jun 3, 2020
87edb67
Update tests/std/tests/P0122R7_span/test.cpp
CaseyCarter Jun 3, 2020
6cec43b
Adress review comments
miscco Jun 3, 2020
649c9ef
Implement sugestion of STL to use static _Mysize
miscco Jun 3, 2020
b8e5786
Inherit privately
miscco Jun 4, 2020
8b9843a
Supress spurious warnings
miscco Jun 4, 2020
778b410
Address Review comments
miscco Jun 5, 2020
6c51f38
Merge branch 'master' into span_standard_layout
StephanTLavavej Jun 23, 2020
908dab2
Reverse _Span_extent_type ctor parameters.
StephanTLavavej Jun 23, 2020
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69 changes: 32 additions & 37 deletions stl/inc/span
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Original file line number Diff line number Diff line change
Expand Up @@ -234,12 +234,9 @@ struct _Span_extent_type {

constexpr explicit _Span_extent_type(size_t, const pointer _Data) noexcept : _Mydata{_Data} {}
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_NODISCARD constexpr size_t size() const noexcept {
return _Extent;
}

protected:
pointer _Mydata{nullptr};
static constexpr size_t _Mysize = _Extent;
};

template <class _Ty>
Expand All @@ -249,15 +246,11 @@ struct _Span_extent_type<_Ty, dynamic_extent> {
constexpr _Span_extent_type() noexcept = default;

constexpr explicit _Span_extent_type(const size_t _Size, const pointer _Data) noexcept
: _Mysize(_Size), _Mydata{_Data} {}

_NODISCARD constexpr size_t size() const noexcept {
return _Mysize;
}
: _Mydata{_Data}, _Mysize{_Size} {}

protected:
size_t _Mysize{0};
pointer _Mydata{nullptr};
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size_t _Mysize{0};
};

template <class _Ty, size_t _Size>
Expand Down Expand Up @@ -356,6 +349,10 @@ inline constexpr bool _Is_span_compatible_range = conjunction_v<
// CLASS TEMPLATE span
template <class _Ty, size_t _Extent = dynamic_extent>
class span : public _Span_extent_type<_Ty, _Extent> {
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using _Mybase = _Span_extent_type<_Ty, _Extent>;
using _Mybase::_Mydata;
using _Mybase::_Mysize;

public:
using element_type = _Ty;
using value_type = remove_cv_t<_Ty>;
Expand Down Expand Up @@ -529,7 +526,7 @@ public:
}
#if _CONTAINER_DEBUG_LEVEL > 0
else {
_STL_VERIFY(_Count <= size(), "Count out of range in span::first()");
_STL_VERIFY(_Count <= _Mysize, "Count out of range in span::first()");
}
#endif // _CONTAINER_DEBUG_LEVEL > 0
return span<element_type, _Count>{_Mydata, _Count};
Expand All @@ -538,7 +535,7 @@ public:
_NODISCARD constexpr auto first(const size_type _Count) const noexcept
/* strengthened */ {
#if _CONTAINER_DEBUG_LEVEL > 0
_STL_VERIFY(_Count <= size(), "Count out of range in span::first(count)");
_STL_VERIFY(_Count <= _Mysize, "Count out of range in span::first(count)");
#endif // _CONTAINER_DEBUG_LEVEL > 0
return span<element_type, dynamic_extent>{_Mydata, _Count};
}
Expand All @@ -550,17 +547,17 @@ public:
}
#if _CONTAINER_DEBUG_LEVEL > 0
else {
_STL_VERIFY(_Count <= size(), "Count out of range in span::last()");
_STL_VERIFY(_Count <= _Mysize, "Count out of range in span::last()");
}
#endif // _CONTAINER_DEBUG_LEVEL > 0
return span<element_type, _Count>{_Mydata + (size() - _Count), _Count};
return span<element_type, _Count>{_Mydata + (_Mysize - _Count), _Count};
}

_NODISCARD constexpr auto last(const size_type _Count) const noexcept /* strengthened */ {
#if _CONTAINER_DEBUG_LEVEL > 0
_STL_VERIFY(_Count <= size(), "Count out of range in span::last(count)");
_STL_VERIFY(_Count <= _Mysize, "Count out of range in span::last(count)");
#endif // _CONTAINER_DEBUG_LEVEL > 0
return span<element_type, dynamic_extent>{_Mydata + (size() - _Count), _Count};
return span<element_type, dynamic_extent>{_Mydata + (_Mysize - _Count), _Count};
}

template <size_t _Offset, size_t _Count = dynamic_extent>
Expand All @@ -572,64 +569,66 @@ public:
}
#if _CONTAINER_DEBUG_LEVEL > 0
else {
_STL_VERIFY(_Offset <= size(), "Offset out of range in span::subspan()");
_STL_VERIFY(_Offset <= _Mysize, "Offset out of range in span::subspan()");

if constexpr (_Count != dynamic_extent) {
_STL_VERIFY(_Count <= size() - _Offset, "Count out of range in span::subspan()");
_STL_VERIFY(_Count <= _Mysize - _Offset, "Count out of range in span::subspan()");
}
}
#endif // _CONTAINER_DEBUG_LEVEL > 0
using _ReturnType = span<element_type,
_Count != dynamic_extent ? _Count : (_Extent != dynamic_extent ? _Extent - _Offset : dynamic_extent)>;
return _ReturnType{_Mydata + _Offset, _Count == dynamic_extent ? size() - _Offset : _Count};
return _ReturnType{_Mydata + _Offset, _Count == dynamic_extent ? _Mysize - _Offset : _Count};
}

_NODISCARD constexpr auto subspan(const size_type _Offset, const size_type _Count = dynamic_extent) const noexcept
/* strengthened */ {
#if _CONTAINER_DEBUG_LEVEL > 0
_STL_VERIFY(_Offset <= size(), "Offset out of range in span::subspan(offset, count)");
_STL_VERIFY(_Count == dynamic_extent || _Count <= size() - _Offset,
_STL_VERIFY(_Offset <= _Mysize, "Offset out of range in span::subspan(offset, count)");
_STL_VERIFY(_Count == dynamic_extent || _Count <= _Mysize - _Offset,
"Count out of range in span::subspan(offset, count)");
#endif // _CONTAINER_DEBUG_LEVEL > 0
using _ReturnType = span<element_type, dynamic_extent>;
return _ReturnType{_Mydata + _Offset, _Count == dynamic_extent ? size() - _Offset : _Count};
return _ReturnType{_Mydata + _Offset, _Count == dynamic_extent ? _Mysize - _Offset : _Count};
}

// [span.obs] Observers
using _Span_extent_type<_Ty, _Extent>::size;
_NODISCARD constexpr size_t size() const noexcept {
return _Mysize;
}

_NODISCARD constexpr size_type size_bytes() const noexcept {
#if _CONTAINER_DEBUG_LEVEL > 0
_STL_VERIFY(size() <= dynamic_extent / sizeof(element_type),
_STL_VERIFY(_Mysize <= dynamic_extent / sizeof(element_type),
"size of span in bytes exceeds std::numeric_limits<size_t>::max()");
#endif // _CONTAINER_DEBUG_LEVEL > 0
return size() * sizeof(element_type);
return _Mysize * sizeof(element_type);
}

_NODISCARD constexpr bool empty() const noexcept {
return size() == 0;
return _Mysize == 0;
}

// [span.elem] Element access
_NODISCARD constexpr reference operator[](const size_type _Off) const noexcept /* strengthened */ {
#if _CONTAINER_DEBUG_LEVEL > 0
_STL_VERIFY(_Off < size(), "span index out of range");
_STL_VERIFY(_Off < _Mysize, "span index out of range");
#endif // _CONTAINER_DEBUG_LEVEL > 0
return _Mydata[_Off];
}

_NODISCARD constexpr reference front() const noexcept /* strengthened */ {
#if _CONTAINER_DEBUG_LEVEL > 0
_STL_VERIFY(size() > 0, "front of empty span");
_STL_VERIFY(_Mysize > 0, "front of empty span");
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#endif // _CONTAINER_DEBUG_LEVEL > 0
return _Mydata[0];
}

_NODISCARD constexpr reference back() const noexcept /* strengthened */ {
#if _CONTAINER_DEBUG_LEVEL > 0
_STL_VERIFY(size() > 0, "back of empty span");
_STL_VERIFY(_Mysize > 0, "back of empty span");
#endif // _CONTAINER_DEBUG_LEVEL > 0
return _Mydata[size() - 1];
return _Mydata[_Mysize - 1];
}

_NODISCARD constexpr pointer data() const noexcept {
Expand All @@ -639,14 +638,14 @@ public:
// [span.iterators] Iterator support
_NODISCARD constexpr iterator begin() const noexcept {
#if _ITERATOR_DEBUG_LEVEL >= 1
return {_Mydata, _Mydata, _Mydata + size()};
return {_Mydata, _Mydata, _Mydata + _Mysize};
#else // ^^^ _ITERATOR_DEBUG_LEVEL >= 1 ^^^ // vvv _ITERATOR_DEBUG_LEVEL == 0 vvv
return {_Mydata};
#endif // _ITERATOR_DEBUG_LEVEL
}

_NODISCARD constexpr iterator end() const noexcept {
const auto _End = _Mydata + size();
const auto _End = _Mydata + _Mysize;
#if _ITERATOR_DEBUG_LEVEL >= 1
return {_End, _Mydata, _End};
#else // ^^^ _ITERATOR_DEBUG_LEVEL >= 1 ^^^ // vvv _ITERATOR_DEBUG_LEVEL == 0 vvv
Expand All @@ -667,12 +666,8 @@ public:
}

_NODISCARD constexpr pointer _Unchecked_end() const noexcept {
return _Mydata + size();
return _Mydata + _Mysize;
}

private:
using _Mybase = _Span_extent_type<_Ty, _Extent>;
using _Mybase::_Mydata;
};

// DEDUCTION GUIDES
Expand Down