5.15.14 - original headers

5.15.14/qtbase/src/corelib/global/qduplicatetracker_p.h

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+/****************************************************************************
+**
+** Copyright (C) 2020 Klarälvdalens Datakonsult AB, a KDAB Group company, info@kdab.com, author Marc Mutz <marc.mutz@kdab.com>
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the QtCore module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:COMM$
+**
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** $QT_END_LICENSE$
+**
+**
+**
+**
+**
+**
+**
+**
+**
+**
+**
+**
+**
+**
+**
+**
+**
+**
+**
+****************************************************************************/
+#ifndef QDUPLICATETRACKER_P_H
+#define QDUPLICATETRACKER_P_H
+
+//
+//  W A R N I N G
+//  -------------
+//
+// This file is not part of the Qt API.  It exists purely as an
+// implementation detail.  This header file may change from version to
+// version without notice, or even be removed.
+//
+// We mean it.
+//
+
+#include <qglobal.h>
+
+#if QT_HAS_INCLUDE(<memory_resource>) && __cplusplus > 201402L
+#  include <unordered_set>
+#  include <memory_resource>
+#else
+#  include <qset.h>
+#endif
+
+QT_BEGIN_NAMESPACE
+
+template <typename T, size_t Prealloc = 32>
+class QDuplicateTracker {
+#ifdef __cpp_lib_memory_resource
+    struct node_guesstimate { void *next; size_t hash; T value; };
+    static constexpr size_t bufferSize(size_t N) {
+        return N * sizeof(void*) // bucket list
+                + N * sizeof(node_guesstimate); // nodes
+    }
+
+    char buffer[bufferSize(Prealloc)];
+    std::pmr::monotonic_buffer_resource res{buffer, sizeof buffer};
+    std::pmr::unordered_set<T> set{Prealloc, &res};
+#else
+    static QSet<T> makeQSet() { QSet<T> r; r.reserve(Prealloc); return r; }
+    QSet<T> set = makeQSet();
+    int setSize = 0;
+#endif
+    Q_DISABLE_COPY_MOVE(QDuplicateTracker);
+public:
+    QDuplicateTracker() = default;
+    void reserve(int n) { set.reserve(n); }
+    Q_REQUIRED_RESULT bool hasSeen(const T &s)
+    {
+        bool inserted;
+#ifdef __cpp_lib_memory_resource
+        inserted = set.insert(s).second;
+#else
+        set.insert(s);
+        const int n = set.size();
+        inserted = qExchange(setSize, n) != n;
+#endif
+        return !inserted;
+    }
+};
+
+QT_END_NAMESPACE
+
+#endif /* QDUPLICATETRACKER_P_H */