Implements the parts of layout_left that don't depend on any of the
other layouts.
libstdc++/ChangeLog:
* include/std/mdspan (layout_left): New class.
Signed-off-by: Luc Grosheintz <luc.groshei...@gmail.com>
---
libstdc++-v3/include/std/mdspan | 179 ++++++++++++++++++++++++++++++++
1 file changed, 179 insertions(+)
diff --git a/libstdc++-v3/include/std/mdspan b/libstdc++-v3/include/std/mdspan
index 39ced1d6301..e05048a5b93 100644
--- a/libstdc++-v3/include/std/mdspan
+++ b/libstdc++-v3/include/std/mdspan
@@ -286,6 +286,26 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
namespace __mdspan
{
+ template<typename _Extents>
+ constexpr typename _Extents::index_type
+ __fwd_prod(const _Extents& __exts, size_t __r) noexcept
+ {
+ typename _Extents::index_type __fwd = 1;
+ for(size_t __i = 0; __i < __r; ++__i)
+ __fwd *= __exts.extent(__i);
+ return __fwd;
+ }
+
+ template<typename _Extents>
+ constexpr typename _Extents::index_type
+ __rev_prod(const _Extents& __exts, size_t __r) noexcept
+ {
+ typename _Extents::index_type __rev = 1;
+ for(size_t __i = __r + 1; __i < __exts.rank(); ++__i)
+ __rev *= __exts.extent(__i);
+ return __rev;
+ }
+
template<typename _IndexType, size_t... _Counts>
auto __build_dextents_type(integer_sequence<size_t, _Counts...>)
-> extents<_IndexType, ((void) _Counts, dynamic_extent)...>;
@@ -304,6 +324,165 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
explicit extents(_Integrals...) ->
extents<size_t, __mdspan::__dynamic_extent<_Integrals>()...>;
+ struct layout_left
+ {
+ template<typename _Extents>
+ class mapping;
+ };
+
+ namespace __mdspan
+ {
+ template<typename _Tp>
+ constexpr bool __is_extents = false;
+
+ template<typename _IndexType, size_t... _Extents>
+ constexpr bool __is_extents<extents<_IndexType, _Extents...>> = true;
+
+ template<size_t _Count>
+ struct _LinearIndexLeft
+ {
+ template<typename _Extents, typename... _Indices>
+ static constexpr typename _Extents::index_type
+ _S_value(const _Extents& __exts, typename _Extents::index_type __idx,
+ _Indices... __indices) noexcept
+ {
+ return __idx + __exts.extent(_Count)
+ * _LinearIndexLeft<_Count + 1>::_S_value(__exts, __indices...);
+ }
+
+ template<typename _Extents>
+ static constexpr typename _Extents::index_type
+ _S_value(const _Extents&) noexcept
+ { return 0; }
+ };
+
+ template<typename _Extents, typename... _Indices>
+ constexpr typename _Extents::index_type
+ __linear_index_left(const _Extents& __exts, _Indices... __indices)
+ {
+ return _LinearIndexLeft<0>::_S_value(__exts, __indices...);
+ }
+
+ template<typename _IndexType, typename _Tp, size_t _Nm>
+ consteval bool
+ __is_representable_product(array<_Tp, _Nm> __factors)
+ {
+ size_t __rest = numeric_limits<_IndexType>::max();
+ for(size_t __i = 0; __i < _Nm; ++__i)
+ {
+ if (__factors[__i] == 0)
+ return true;
+ __rest /= _IndexType(__factors[__i]);
+ }
+ return __rest > 0;
+ }
+
+ template<typename _Extents>
+ consteval array<typename _Extents::index_type, _Extents::rank()>
+ __static_extents_array()
+ {
+ array<typename _Extents::index_type, _Extents::rank()> __exts;
+ for(size_t __i = 0; __i < _Extents::rank(); ++__i)
+ __exts[__i] = _Extents::static_extent(__i);
+ return __exts;
+ }
+
+ template<typename _Extents, typename _IndexType>
+ concept __representable_size = _Extents::rank_dynamic() != 0
+ || __is_representable_product<_IndexType>(
+ __static_extents_array<_Extents>());
+
+ template<typename _Extents>
+ concept __layout_extent = __representable_size<
+ _Extents, typename _Extents::index_type>;
+ }
+
+ template<typename _Extents>
+ class layout_left::mapping
+ {
+ static_assert(__mdspan::__layout_extent<_Extents>,
+ "The size of extents_type is not representable as index_type.");
+ public:
+ using extents_type = _Extents;
+ using index_type = typename extents_type::index_type;
+ using size_type = typename extents_type::size_type;
+ using rank_type = typename extents_type::rank_type;
+ using layout_type = layout_left;
+
+ constexpr
+ mapping() noexcept = default;
+
+ constexpr
+ mapping(const mapping&) noexcept = default;
+
+ constexpr
+ mapping(const extents_type& __extents) noexcept
+ : _M_extents(__extents)
+ { }
+
+ template<typename _OExtents>
+ requires (is_constructible_v<extents_type, _OExtents>)
+ constexpr explicit(!is_convertible_v<_OExtents, extents_type>)
+ mapping(const mapping<_OExtents>& __other) noexcept
+ : _M_extents(__other.extents())
+ { }
+
+ constexpr mapping&
+ operator=(const mapping&) noexcept = default;
+
+ constexpr const extents_type&
+ extents() const noexcept { return _M_extents; }
+
+ constexpr index_type
+ required_span_size() const noexcept
+ { return __mdspan::__fwd_prod(_M_extents, _M_extents.rank()); }
+
+ template<__mdspan::__valid_index_type<index_type>... _Indices>
+ requires (sizeof...(_Indices) == extents_type::rank())
+ constexpr index_type
+ operator()(_Indices... __indices) const noexcept
+ {
+ return __mdspan::__linear_index_left(
+ _M_extents, static_cast<index_type>(__indices)...);
+ }
+
+ static constexpr bool
+ is_always_unique() noexcept { return true; }
+
+ static constexpr bool
+ is_always_exhaustive() noexcept { return true; }
+
+ static constexpr bool
+ is_always_strided() noexcept { return true; }
+
+ static constexpr bool
+ is_unique() noexcept { return true; }
+
+ static constexpr bool
+ is_exhaustive() noexcept { return true; }
+
+ static constexpr bool
+ is_strided() noexcept { return true; }
+
+ constexpr index_type
+ stride(rank_type __i) const noexcept
+ requires (extents_type::rank() > 0)
+ {
+ __glibcxx_assert(__i < extents_type::rank());
+ return __mdspan::__fwd_prod(_M_extents, __i);
+ }
+
+ template<typename _OExtents>
+ requires (extents_type::rank() == _OExtents::rank())
+ friend constexpr bool
+ operator==(const mapping& __self, const mapping<_OExtents>& __other)
+ noexcept
+ { return __self.extents() == __other.extents(); }
+
+ private:
+ [[no_unique_address]] extents_type _M_extents;
+ };
+
_GLIBCXX_END_NAMESPACE_VERSION
}
#endif
--
2.49.0
