1 files changed, 54 insertions, 0 deletions
diff --git a/src/corelib/global/q20iterator.h b/src/corelib/global/q20iterator.h
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+++ b/src/corelib/global/q20iterator.h
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+// Copyright (C) 2021 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
+#ifndef Q20ITERATOR_H
+#define Q20ITERATOR_H
+
+#include <QtCore/qglobal.h>
+
+#include <iterator>
+
+//
+//  W A R N I N G
+//  -------------
+//
+// This file is not part of the Qt API. Types and functions defined in this
+// file can reliably be replaced by their std counterparts, once available.
+// You may use these definitions in your own code, but be aware that we
+// will remove them once Qt depends on the C++ version that supports
+// them in namespace std. There will be NO deprecation warning, the
+// definitions will JUST go away.
+//
+// If you can't agree to these terms, don't use these definitions!
+//
+// We mean it.
+//
+
+QT_BEGIN_NAMESPACE
+
+// like std::ssize
+namespace q20 {
+#ifdef __cpp_lib_ssize
+    using std::ssize;
+#else
+    template<class C> constexpr auto ssize(const C &c)
+      -> std::common_type_t<std::ptrdiff_t, std::make_signed_t<decltype(c.size())>>
+    { return static_cast<std::common_type_t<std::ptrdiff_t, std::make_signed_t<decltype(c.size())>>>(c.size()); }
+
+    template<class T, std::ptrdiff_t N> constexpr std::ptrdiff_t ssize(const T (&)[N]) noexcept
+    { return N; }
+#endif
+} // namespace q20
+
+// like q20::iter_reference_t
+namespace q20 {
+#ifdef __cpp_lib_ranges
+    using std::iter_reference_t;
+#else
+    template <typename Dereferencable> // unconstrained (constraint requires concepts)
+    using iter_reference_t = decltype(*std::declval<Dereferencable&>());
+#endif // __cpp_lib_ranges
+} // namespace q20
+
+QT_END_NAMESPACE
+
+#endif /* Q20ITERATOR_H */