Utils: Add sized array

Sometimes you need a very small array which has a size and max size.
QVarLengthArray is simular but has some size and run time overhead and it
has no max size. It will instead malloc. So this array is for very small
collections under 256 values which never allocate and have only a size
overhead of a byte.

Change-Id: Ia392c750d566c4accc6077c3dc4d9d4ae501e599
Reviewed-by: Eike Ziller <eike.ziller@theqtcompany.com>

src/libs/utils/sizedarray.h

+/****************************************************************************
+**
+** Copyright (C) 2016 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of Qt Creator.
+**
+** 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.
+**
+****************************************************************************/
+
+#pragma once
+
+#include <array>
+#include <cstdint>
+
+#pragma push_macro("constexpr")
+#ifndef __cpp_constexpr
+#define constexpr
+#endif
+
+namespace Utils {
+
+template <typename T, std::uint8_t MaxSize>
+class SizedArray : public std::array<T, MaxSize>
+{
+public:
+    using size_type = std::uint8_t;
+    using reference = typename std::array<T, MaxSize>::reference;
+    using const_reference = typename std::array<T, MaxSize>::const_reference;
+    using iterator = typename std::array<T, MaxSize>::iterator;
+    using const_iterator = typename std::array<T, MaxSize>::const_iterator;
+    using reverse_iterator = typename std::array<T, MaxSize>::reverse_iterator;
+    using const_reverse_iterator = typename std::array<T, MaxSize>::const_reverse_iterator;
+    using value_type = typename std::array<T, MaxSize>::value_type;
+    using pointer = typename std::array<T, MaxSize>::pointer;
+    using difference_type = typename std::array<T, MaxSize>::difference_type;
+
+    using std::array<T, MaxSize>::operator[];
+    using std::array<T, MaxSize>::begin;
+    using std::array<T, MaxSize>::cbegin;
+    using std::array<T, MaxSize>::rend;
+    using std::array<T, MaxSize>::crend;
+
+    constexpr size_type size() const
+    {
+        return m_size;
+    }
+
+    void push_back(const T &value)
+    {
+        operator[](m_size) = value;
+
+        ++m_size;
+    }
+
+    constexpr const_reference back() const
+    {
+        return operator[](m_size - 1);
+    }
+
+    iterator end()
+    {
+        return std::next(begin(), m_size);
+    }
+
+    const_iterator end() const
+    {
+        return std::next(begin(), m_size);
+    }
+
+    const_iterator cend() const
+    {
+        return std::next(cbegin(), m_size);
+    }
+
+    reverse_iterator rbegin()
+    {
+        return std::prev(rend(), m_size);
+    }
+
+    const_reverse_iterator rbegin() const
+    {
+        return std::prev(rend(), m_size);
+    }
+
+    const_reverse_iterator crbegin() const
+    {
+        return std::prev(crend(), m_size);
+    }
+
+    bool empty() const
+    {
+        return m_size == 0;
+    }
+
+private:
+    std::uint8_t m_size = 0;
+};
+
+}  // namespace Utils
+
+#pragma pop_macro("constexpr")

src/libs/utils/utils-lib.pri

@@ -217,7 +217,8 @@ HEADERS += \
     $$PWD/smallstringliteral.h \
     $$PWD/smallstringmemory.h \
     $$PWD/smallstringvector.h \
-    $$PWD/smallstringlayout.h
+    $$PWD/smallstringlayout.h \
+    $$PWD/sizedarray.h
 
 FORMS += $$PWD/filewizardpage.ui \
     $$PWD/projectintropage.ui \

src/libs/utils/utils.qbs

@@ -182,6 +182,7 @@ QtcLibrary {
         "shellcommand.h",
         "shellcommandpage.cpp",
         "shellcommandpage.h",
+        "sizedarray.h",
         "sleep.cpp",
         "sleep.h",
         "smallstring.h",

tests/unit/unittest/sizedarraytest.cpp

+/****************************************************************************
+**
+** Copyright (C) 2016 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of Qt Creator.
+**
+** 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.
+**
+****************************************************************************/
+
+#include "gtest/gtest.h"
+#include "gmock/gmock-matchers.h"
+#include "gtest-qt-printing.h"
+
+#include <utils/sizedarray.h>
+
+namespace {
+
+using Utils::SizedArray;
+
+TEST(SizedArray, EmptySize)
+{
+    SizedArray<char, 8> array;
+
+    ASSERT_THAT(array.size(), 0);
+}
+
+TEST(SizedArray, IsEmpty)
+{
+    SizedArray<char, 8> array;
+
+    ASSERT_TRUE(array.empty());
+}
+
+TEST(SizedArray, IsNotEmpty)
+{
+    SizedArray<char, 8> array;
+
+    array.push_back('x');
+
+    ASSERT_FALSE(array.empty());
+}
+
+TEST(SizedArray, SizeOneAfterPushBack)
+{
+    SizedArray<char, 8> array;
+
+    array.push_back('x');
+
+    ASSERT_THAT(array.size(), 1);
+}
+
+TEST(SizedArray, FirstValueAfterPushBack)
+{
+    SizedArray<char, 8> array;
+
+    array.push_back('x');
+
+    ASSERT_THAT(array.front(), 'x');
+}
+
+TEST(SizedArray, LastValueAfterPushBack)
+{
+    SizedArray<char, 8> array;
+
+    array.push_back('x');
+
+    ASSERT_THAT(array.back(), 'x');
+}
+
+TEST(SizedArray, EndIteratorIsEqualBeginForEmptyArray)
+{
+    SizedArray<char, 8> array;
+
+    ASSERT_THAT(array.begin(), array.end());
+}
+
+TEST(SizedArray, ConstEndIteratorIsEqualBeginForEmptyArray)
+{
+    const SizedArray<char, 8> array = {};
+
+    ASSERT_THAT(array.begin(), array.end());
+}
+
+TEST(SizedArray, EndIteratorIsOneAfterBeginForOneSizedArray)
+{
+    SizedArray<char, 8> array;
+
+    array.push_back('x');
+
+    ASSERT_THAT(std::next(array.begin(), 1), array.end());
+}
+
+TEST(SizedArray, CEndIteratorIsOneAfterBeginForOneSizedArray)
+{
+    SizedArray<char, 8> array = {};
+
+    array.push_back('x');
+
+    ASSERT_THAT(std::next(array.cbegin(), 1), array.cend());
+}
+
+TEST(SizedArray, REndIteratorIsEqualRBeginForEmptyArray)
+{
+    SizedArray<char, 8> array;
+
+    ASSERT_THAT(array.rbegin(), array.rend());
+}
+
+TEST(SizedArray, ConstREndIteratorIsEqualRBeginForEmptyArray)
+{
+    const SizedArray<char, 8> array = {};
+
+    ASSERT_THAT(array.rbegin(), array.rend());
+}
+
+TEST(SizedArray, REndIteratorIsOneAfterRBeginForOneSizedArray)
+{
+    SizedArray<char, 8> array;
+
+    array.push_back('x');
+
+    ASSERT_THAT(std::next(array.rbegin(), 1), array.rend());
+}
+
+TEST(SizedArray, ConstREndIteratorIsOneAfterRBeginForOneSizedArray)
+{
+    SizedArray<char, 8> array = {};
+
+    array.push_back('x');
+
+    ASSERT_THAT(std::next(array.crbegin(), 1), array.crend());
+}
+
+} // anonymous namespace

tests/unit/unittest/unittest.pro

@@ -67,7 +67,8 @@ SOURCES += \
     chunksreportedmonitor.cpp \
     unsavedfiletest.cpp \
     clangisdiagnosticrelatedtolocationtest.cpp \
-    smallstringtest.cpp
+    smallstringtest.cpp \
+    sizedarraytest.cpp
 
 exists($$GOOGLEBENCHMARK_DIR) {
 SOURCES += \