corelib/tools: add qMakeArray() API

This function can be used to create std::array without the need
to explicitly provide the size of array. It also has a specialization
that allow to generate sorted array at compile time. Sorted array can
be beneficial for example in binary search.

Change-Id: Ifc7e06e451812fce2ab94293959db5e9cc038793
Reviewed-by: Gatis Paeglis <gatis.paeglis@qt.io>

3 files changed, 108 insertions, 0 deletions

diff --git a/tests/auto/corelib/tools/qmakearray/qmakearray.pro b/tests/auto/corelib/tools/qmakearray/qmakearray.pro
new file mode 100644
index 0000000000..abb3d9fdbc
--- /dev/null
+++ b/tests/auto/corelib/tools/qmakearray/qmakearray.pro
@@ -0,0 +1,4 @@
+CONFIG += testcase
+TARGET = tst_qmakearray
+QT = core testlib core-private
+SOURCES = $$PWD/tst_qmakearray.cpp
diff --git a/tests/auto/corelib/tools/qmakearray/tst_qmakearray.cpp b/tests/auto/corelib/tools/qmakearray/tst_qmakearray.cpp
new file mode 100644
index 0000000000..e0d3f52719
--- /dev/null
+++ b/tests/auto/corelib/tools/qmakearray/tst_qmakearray.cpp
@@ -0,0 +1,103 @@
+/****************************************************************************
+**
+** Copyright (C) 2018 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the test suite of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:GPL-EXCEPT$
+** 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.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3 as published by the Free Software
+** Foundation with exceptions as appearing in the file LICENSE.GPL3-EXCEPT
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include <QtTest/QtTest>
+
+#include <private/qmakearray_p.h>
+
+
+class tst_QMakeArray : public QObject
+{
+    Q_OBJECT
+
+private slots:
+    void quicksort();
+};
+
+struct Pair {
+    unsigned int key;
+    unsigned int val;
+
+    constexpr bool operator <=(const Pair &that) const noexcept
+    {
+        return key <= that.key;
+    }
+
+    constexpr bool operator<(const Pair &that) const noexcept
+    {
+        return key < that.key;
+    }
+
+    constexpr bool operator==(const Pair &that) const noexcept
+    {
+        return key == that.key;
+    }
+};
+
+template<std::size_t Key, std::size_t Val>
+struct PairQuickSortElem
+{
+    using Type = Pair;
+    static constexpr Type data() noexcept { return Type{Key, Val}; }
+};
+
+void tst_QMakeArray::quicksort()
+{
+    constexpr const auto sorted_array = qMakeArray(
+        QSortedData<
+            PairQuickSortElem<10, 0>,
+            PairQuickSortElem<5, 0>,
+            PairQuickSortElem<7, 0>,
+            PairQuickSortElem<1, 0>,
+            PairQuickSortElem<8, 0>,
+            PairQuickSortElem<6, 0>,
+            PairQuickSortElem<4, 0>,
+            PairQuickSortElem<3, 0>,
+            PairQuickSortElem<1, 0>,
+            PairQuickSortElem<2, 0>,
+            PairQuickSortElem<10, 0>,
+            PairQuickSortElem<5, 0>
+        >::Data{});
+    static_assert(sorted_array.size() == 12, "sorted_array.size() != 12");
+    QCOMPARE(sorted_array[0].key, 1u);
+    QCOMPARE(sorted_array[1].key, 1u);
+    QCOMPARE(sorted_array[2].key, 2u);
+    QCOMPARE(sorted_array[3].key, 3u);
+    QCOMPARE(sorted_array[4].key, 4u);
+    QCOMPARE(sorted_array[5].key, 5u);
+    QCOMPARE(sorted_array[6].key, 5u);
+    QCOMPARE(sorted_array[7].key, 6u);
+    QCOMPARE(sorted_array[8].key, 7u);
+    QCOMPARE(sorted_array[9].key, 8u);
+    QCOMPARE(sorted_array[10].key, 10u);
+    QCOMPARE(sorted_array[11].key, 10u);
+}
+
+
+QTEST_APPLESS_MAIN(tst_QMakeArray)
+#include "tst_qmakearray.moc"
diff --git a/tests/auto/corelib/tools/tools.pro b/tests/auto/corelib/tools/tools.pro
index f35ed026ac..f28cf21b8b 100644
--- a/tests/auto/corelib/tools/tools.pro
+++ b/tests/auto/corelib/tools/tools.pro
@@ -30,6 +30,7 @@ SUBDIRS=\
     qlist \
     qlist_strictiterators \
     qlocale \
+    qmakearray \
     qmap \
     qmap_strictiterators \
     qmargins \