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Fix and extend key extraction for unique map/set containers #5050

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merged 4 commits into from
Oct 30, 2024
Merged

Fix and extend key extraction for unique map/set containers #5050

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2ca0ec0
Fix and extend key extraction for unique map containers
frederick-vs-ja Oct 28, 2024
039d895
Fix grammar and rewrap comment.
StephanTLavavej Oct 29, 2024
2af6750
`_Remove_cref_t` => `_Remove_const_ref_t`
StephanTLavavej Oct 29, 2024
16d24d3
Centralize `_Remove_const_ref_t` with alias templates.
StephanTLavavej Oct 29, 2024
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4 changes: 2 additions & 2 deletions stl/inc/xhash
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Original file line number Diff line number Diff line change
Expand Up @@ -590,7 +590,7 @@ public:
template <class... _Valtys>
conditional_t<_Multi, iterator, pair<iterator, bool>> emplace(_Valtys&&... _Vals) {
// try to insert value_type(_Vals...)
using _In_place_key_extractor = typename _Traits::template _In_place_key_extractor<_Remove_cvref_t<_Valtys>...>;
using _In_place_key_extractor = typename _Traits::template _In_place_key_extractor<_Valtys...>;
if constexpr (_Multi) {
_Check_max_size();
_List_node_emplace_op2<_Alnode> _Newnode(_List._Getal(), _STD forward<_Valtys>(_Vals)...);
Expand Down Expand Up @@ -642,7 +642,7 @@ public:

template <class... _Valtys>
iterator emplace_hint(const_iterator _Hint, _Valtys&&... _Vals) { // try to insert value_type(_Vals...)
using _In_place_key_extractor = typename _Traits::template _In_place_key_extractor<_Remove_cvref_t<_Valtys>...>;
using _In_place_key_extractor = typename _Traits::template _In_place_key_extractor<_Valtys...>;
if constexpr (_Multi) {
_Check_max_size();
_List_node_emplace_op2<_Alnode> _Newnode(_List._Getal(), _STD forward<_Valtys>(_Vals)...);
Expand Down
63 changes: 54 additions & 9 deletions stl/inc/xmemory
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Original file line number Diff line number Diff line change
Expand Up @@ -2088,31 +2088,41 @@ _CXX17_DEPRECATE_TEMPORARY_BUFFER void return_temporary_buffer(_Ty* _Pbuf) {
}
#endif // _HAS_DEPRECATED_TEMPORARY_BUFFER

// assumes _Args have already been _Remove_cvref_t'd
// The key_type of an (unordered) associative container is cv-unqualified, and we can't bind const Key& to a
// volatile glvalue. Also, Cpp17CopyInsertable and Cpp17MoveInsertable don't require value-preservation for
// the construction from a volatile glvalue, so generally we can't perform this optimization for them.
// See N4993 [container.alloc.reqmts]/2.3, /2.4.
template <class _Ty>
using _Remove_const_ref_t = remove_const_t<remove_reference_t<_Ty>>;

// assumes _Args have already been _Remove_const_ref_t'd
template <class _Key, class... _Args>
struct _In_place_key_extract_set {
struct _In_place_key_extract_set_impl {
// by default we can't extract the key in the emplace family and must construct a node we might not use
static constexpr bool _Extractable = false;
};

template <class _Key>
struct _In_place_key_extract_set<_Key, _Key> {
struct _In_place_key_extract_set_impl<_Key, _Key> {
// we can extract the key in emplace if the emplaced type is identical to the key type
static constexpr bool _Extractable = true;
static const _Key& _Extract(const _Key& _Val) noexcept {
return _Val;
}
};

// assumes _Args have already been _Remove_cvref_t'd
template <class... _Valtys>
using _In_place_key_extract_set = _In_place_key_extract_set_impl<_Remove_const_ref_t<_Valtys>...>;

// assumes _Args have already been _Remove_const_ref_t'd
template <class _Key, class... _Args>
struct _In_place_key_extract_map {
struct _In_place_key_extract_map_impl {
// by default we can't extract the key in the emplace family and must construct a node we might not use
static constexpr bool _Extractable = false;
};

template <class _Key, class _Second>
struct _In_place_key_extract_map<_Key, _Key, _Second> {
struct _In_place_key_extract_map_impl<_Key, _Key, _Second> {
// if we would call the pair(key, value) constructor family, we can use the first parameter as the key
static constexpr bool _Extractable = true;
static const _Key& _Extract(const _Key& _Val, const _Second&) noexcept {
Expand All @@ -2121,14 +2131,49 @@ struct _In_place_key_extract_map<_Key, _Key, _Second> {
};

template <class _Key, class _First, class _Second>
struct _In_place_key_extract_map<_Key, pair<_First, _Second>> {
struct _In_place_key_extract_map_impl<_Key, pair<_First, _Second>> {
// if we would call the pair(pair<other, other>) constructor family, we can use the pair.first member as the key
static constexpr bool _Extractable = is_same_v<_Key, _Remove_cvref_t<_First>>;
static const _Key& _Extract(const pair<_First, _Second>& _Val) {
static constexpr bool _Extractable = is_same_v<_Key, _Remove_const_ref_t<_First>>;
static const _Key& _Extract(const pair<_First, _Second>& _Val) noexcept {
return _Val.first;
}
};

#if _HAS_CXX23
// if we would call the pair(pair-like) constructor family and the argument is not a subrange,
// we can use get<0>(pair-like) as the key

template <class _Key, class _Elem>
struct _In_place_key_extract_map_impl<_Key, array<_Elem, 2>> {
static constexpr bool _Extractable = is_same_v<_Key, remove_const_t<_Elem>>;
static const _Key& _Extract(const array<_Elem, 2>& _Val) noexcept {
return _Val[0];
}
};

template <class _Key, class _First, class _Second>
struct _In_place_key_extract_map_impl<_Key, tuple<_First, _Second>> {
static constexpr bool _Extractable = is_same_v<_Key, _Remove_const_ref_t<_First>>;
static const _Key& _Extract(const tuple<_First, _Second>& _Val) noexcept {
return _STD get<0>(_Val);
}
};
#endif // _HAS_CXX23

template <class _Key, class _First, class... _RestTypes>
struct _In_place_key_extract_map_impl<_Key, piecewise_construct_t, tuple<_First>, tuple<_RestTypes...>> {
// if we would call the piecewise_construct_t constructor and the first argument is a 1-tuple,
// we can use get<0>(first_tuple) as the key
static constexpr bool _Extractable = is_same_v<_Key, _Remove_const_ref_t<_First>>;
static const _Key& _Extract(
const piecewise_construct_t&, const tuple<_First>& _Tup_val, const tuple<_RestTypes...>&) noexcept {
return _STD get<0>(_Tup_val);
}
};

template <class... _Valtys>
using _In_place_key_extract_map = _In_place_key_extract_map_impl<_Remove_const_ref_t<_Valtys>...>;

#pragma warning(push)
#pragma warning(disable : 4624) // '%s': destructor was implicitly defined as deleted
template <class _Ty>
Expand Down
4 changes: 2 additions & 2 deletions stl/inc/xtree
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Original file line number Diff line number Diff line change
Expand Up @@ -998,7 +998,7 @@ private:
protected:
template <class... _Valtys>
pair<_Nodeptr, bool> _Emplace(_Valtys&&... _Vals) {
using _In_place_key_extractor = typename _Traits::template _In_place_key_extractor<_Remove_cvref_t<_Valtys>...>;
using _In_place_key_extractor = typename _Traits::template _In_place_key_extractor<_Valtys...>;
const auto _Scary = _Get_scary();
_Tree_find_result<_Nodeptr> _Loc;
_Nodeptr _Inserted;
Expand Down Expand Up @@ -1042,7 +1042,7 @@ public:
protected:
template <class... _Valtys>
_Nodeptr _Emplace_hint(const _Nodeptr _Hint, _Valtys&&... _Vals) {
using _In_place_key_extractor = typename _Traits::template _In_place_key_extractor<_Remove_cvref_t<_Valtys>...>;
using _In_place_key_extractor = typename _Traits::template _In_place_key_extractor<_Valtys...>;
const auto _Scary = _Get_scary();
_Tree_find_hint_result<_Nodeptr> _Loc;
_Nodeptr _Inserted;
Expand Down
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