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QMinimalFlatSet: support custom comparators 

Add a template argument a la std::set and a ctor taking a Compare
object (thus supporting stateful comparators, too), and storing it in
QtPrivate::CompactStorage. Rewrite lookup() to use the stored
comparator instead of std::less, carefully avoiding a copy to match
what std::map implementations do, even though key_comp() itself is
specified to return by value.

Change-Id: I4f74aaf5eda0a4ed276e99f73f407042c2767828
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
bb10
Marc Mutz 2024-02-13 16:18:53 +01:00
parent 3092f367f0
commit 7a8e7213e4
1 changed files with 14 additions and 7 deletions
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21
src/corelib/tools/qminimalflatset_p.h
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@ -16,6 +16,7 @@
//
#include <QtCore/qcontainerfwd.h>
#include <QtCore/qfunctionaltools_impl.h> // CompactStorage
#include <QtCore/private/qglobal_p.h>
//#define QMINIMAL_FLAT_SET_DEBUG
@ -29,7 +30,7 @@
#endif
#include <algorithm> // for std::lower_bound
#include <functional> // for std::less
#include <functional> // for std::less, std::ref
QT_BEGIN_NAMESPACE
@ -43,20 +44,26 @@ QT_BEGIN_NAMESPACE
bit, we can consider moving it as QFlatSet alongside QFlatMap.
*/
template <typename T, typename Container = QList<T>>
class QMinimalFlatSet
template <typename T, typename Container = QList<T>, typename Compare = std::less<T>>
class QMinimalFlatSet : QtPrivate::CompactStorage<Compare>
{
Container c;
using CompareStorage = QtPrivate::CompactStorage<Compare>;
public:
// compiler-generated default ctor is ok!
// compiler-generated copy/move ctor/assignment operators are ok!
// compiler-generated dtor is ok!
QMinimalFlatSet() = default;
explicit QMinimalFlatSet(const Compare &cmp) : CompareStorage{cmp} {}
// Rule Of Zero applies
using const_iterator = typename Container::const_iterator;
using iterator = const_iterator;
using const_reverse_iterator = typename Container::const_reverse_iterator;
using reverse_iterator = const_reverse_iterator;
using value_type = T;
using key_compare = Compare;
using value_compare = Compare;
key_compare key_comp() const { return this->object(); }
value_compare value_comp() const { return key_comp(); }
iterator begin() const { return c.cbegin(); }
iterator end() const { return c.cend(); }
@ -121,7 +128,7 @@ private:
bool exists;
};
auto cmp = std::less<value_type>{};
auto cmp = std::ref(this->object()); // don't let std::lower_bound copy it
const auto it = std::lower_bound(c.cbegin(), c.cend(), v, cmp);
return R{it, it != c.cend() && !cmp(v, *it)};