Reduce allocations by using reserve()

Change-Id: If34fa53402985f6b3c5e7217bce4a1177af835b6
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>

src/corelib/codecs/qicucodec.cpp

@@ -417,6 +417,7 @@ QList<QByteArray> QIcuCodec::availableCodecs()
 QList<int> QIcuCodec::availableMibs()
 {
     QList<int> mibs;
+    mibs.reserve(mibToNameSize + 1);
     for (int i = 0; i < mibToNameSize; ++i)
         mibs += mibToName[i].mib;
 

src/corelib/itemmodels/qstringlistmodel.cpp

@@ -276,7 +276,9 @@ void QStringListModel::sort(int, Qt::SortOrder order)
 
     QModelIndexList oldList = persistentIndexList();
     QModelIndexList newList;
-    for (int i = 0; i < oldList.count(); ++i)
+    const int numOldIndexes = oldList.count();
+    newList.reserve(numOldIndexes);
+    for (int i = 0; i < numOldIndexes; ++i)
         newList.append(index(forwarding.at(oldList.at(i).row()), 0));
     changePersistentIndexList(oldList, newList);
 

src/gui/image/qimagereader.cpp

@@ -1623,6 +1623,7 @@ void supportedImageHandlerMimeTypes(QFactoryLoader *loader,
 QList<QByteArray> QImageReader::supportedImageFormats()
 {
     QList<QByteArray> formats;
+    formats.reserve(_qt_NumFormats);
     for (int i = 0; i < _qt_NumFormats; ++i)
         formats << _qt_BuiltInFormats[i].extension;
 
@@ -1647,6 +1648,7 @@ QList<QByteArray> QImageReader::supportedImageFormats()
 QList<QByteArray> QImageReader::supportedMimeTypes()
 {
     QList<QByteArray> mimeTypes;
+    mimeTypes.reserve(_qt_NumFormats);
     for (int i = 0; i < _qt_NumFormats; ++i)
         mimeTypes << _qt_BuiltInFormats[i].mimeType;
 

src/gui/painting/qpdf.cpp

@@ -1003,7 +1003,8 @@ void QPdfEngine::drawHyperlink(const QRectF &r, const QUrl &url)
     const uint annot = d->addXrefEntry(-1);
     const QByteArray urlascii = url.toEncoded();
     int len = urlascii.size();
-    QVarLengthArray<char> url_esc(0);
+    QVarLengthArray<char> url_esc;
+    url_esc.reserve(len + 1);
     for (int j = 0; j < len; j++) {
         if (urlascii[j] == '(' || urlascii[j] == ')' || urlascii[j] == '\\')
             url_esc.append('\\');
@@ -2007,10 +2008,11 @@ int QPdfEnginePrivate::createShadingFunction(const QGradient *gradient, int from
     }
 
     QVector<QGradientBound> gradientBounds;
+    gradientBounds.reserve((to - from) * (numStops - 1));
 
     for (int step = from; step < to; ++step) {
         if (reflect && step % 2) {
-            for (int i = stops.size() - 1; i > 0; --i) {
+            for (int i = numStops - 1; i > 0; --i) {
                 QGradientBound b;
                 b.start = step + 1 - qBound(qreal(0.), stops.at(i).first, qreal(1.));
                 b.stop = step + 1 - qBound(qreal(0.), stops.at(i - 1).first, qreal(1.));
@@ -2019,7 +2021,7 @@ int QPdfEnginePrivate::createShadingFunction(const QGradient *gradient, int from
                 gradientBounds << b;
             }
         } else {
-            for (int i = 0; i < stops.size() - 1; ++i) {
+            for (int i = 0; i < numStops - 1; ++i) {
                 QGradientBound b;
                 b.start = step + qBound(qreal(0.), stops.at(i).first, qreal(1.));
                 b.stop = step + qBound(qreal(0.), stops.at(i + 1).first, qreal(1.));

src/gui/text/qfontdatabase.cpp

@@ -691,7 +691,9 @@ static QStringList familyList(const QFontDef &req)
         return family_list;
 
     QStringList list = req.family.split(QLatin1Char(','));
-    for (int i = 0; i < list.size(); ++i) {
+    const int numFamilies = list.size();
+    family_list.reserve(numFamilies);
+    for (int i = 0; i < numFamilies; ++i) {
         QString str = list.at(i).trimmed();
         if ((str.startsWith(QLatin1Char('"')) && str.endsWith(QLatin1Char('"')))
             || (str.startsWith(QLatin1Char('\'')) && str.endsWith(QLatin1Char('\''))))
@@ -1607,6 +1609,7 @@ QStringList QFontDatabase::styles(const QString &family) const
         }
     }
 
+    l.reserve(allStyles.count);
     for (int i = 0; i < allStyles.count; i++) {
         l.append(allStyles.styles[i]->styleName.isEmpty() ?
                  styleStringHelper(allStyles.styles[i]->key.weight,

src/gui/text/qfontsubset.cpp

@@ -1159,7 +1159,6 @@ QByteArray QFontSubset::toTruetype() const
 
     qreal ppem = fontEngine->fontDef.pixelSize;
 #define TO_TTF(x) qRound(x * 2048. / ppem)
-    QVector<QTtfGlyph> glyphs;
 
     QFontEngine::Properties properties = fontEngine->properties();
     // initialize some stuff needed in createWidthArray
@@ -1194,12 +1193,13 @@ QByteArray QFontSubset::toTruetype() const
     font.maxp.maxCompositeContours = 0;
     font.maxp.maxComponentElements = 0;
     font.maxp.maxComponentDepth = 0;
-    font.maxp.numGlyphs = nGlyphs();
+    const int numGlyphs = nGlyphs();
-
+    font.maxp.numGlyphs = numGlyphs;
-
+    QVector<QTtfGlyph> glyphs;
+    glyphs.reserve(numGlyphs);
 
     uint sumAdvances = 0;
-    for (int i = 0; i < nGlyphs(); ++i) {
+    for (int i = 0; i < numGlyphs; ++i) {
         glyph_t g = glyph_indices.at(i);
         QPainterPath path;
         glyph_metrics_t metric;

src/plugins/platforms/xcb/qxcbintegration.cpp

@@ -174,9 +174,11 @@ QXcbIntegration::QXcbIntegration(const QStringList &parameters, int &argc, char
     if (canNotGrabEnv)
         m_canGrab = false;
 
+    const int numParameters = parameters.size();
+    m_connections.reserve(1 + numParameters / 2);
     m_connections << new QXcbConnection(m_nativeInterface.data(), m_canGrab, m_defaultVisualId, displayName);
 
-    for (int i = 0; i < parameters.size() - 1; i += 2) {
+    for (int i = 0; i < numParameters - 1; i += 2) {
         qCDebug(lcQpaScreen) << "connecting to additional display: " << parameters.at(i) << parameters.at(i+1);
         QString display = parameters.at(i) + QLatin1Char(':') + parameters.at(i+1);
         m_connections << new QXcbConnection(m_nativeInterface.data(), m_canGrab, m_defaultVisualId, display.toLatin1().constData());

src/testlib/qtestcase.cpp

@@ -1563,7 +1563,9 @@ static void qPrintDataTags(FILE *stream)
             member.resize(qstrlen(slot) + qstrlen("_data()") + 1);
             qsnprintf(member.data(), member.size(), "%s_data()", slot);
             invokeMethod(QTest::currentTestObject, member.constData());
-            for (int j = 0; j < table.dataCount(); ++j)
+            const int dataCount = table.dataCount();
+            localTags.reserve(dataCount);
+            for (int j = 0; j < dataCount; ++j)
                 localTags << QLatin1String(table.testData(j)->dataTag());
 
             // Print all tag combinations:

src/tools/qdbuscpp2xml/qdbuscpp2xml.cpp

@@ -396,6 +396,7 @@ static void parseCmdLine(QStringList &arguments)
 int main(int argc, char **argv)
 {
     QStringList args;
+    args.reserve(argc - 1);
     for (int n = 1; n < argc; ++n)
         args.append(QString::fromLocal8Bit(argv[n]));
     parseCmdLine(args);

src/tools/qdbusxml2cpp/qdbusxml2cpp.cpp

@@ -389,7 +389,10 @@ static QStringList makeArgNames(const QDBusIntrospection::Arguments &inputArgs,
                                 QDBusIntrospection::Arguments())
 {
     QStringList retval;
-    for (int i = 0; i < inputArgs.count(); ++i) {
+    const int numInputArgs = inputArgs.count();
+    const int numOutputArgs = outputArgs.count();
+    retval.reserve(numInputArgs + numOutputArgs);
+    for (int i = 0; i < numInputArgs; ++i) {
         const QDBusIntrospection::Argument &arg = inputArgs.at(i);
         QString name = arg.name;
         if (name.isEmpty())
@@ -400,7 +403,7 @@ static QStringList makeArgNames(const QDBusIntrospection::Arguments &inputArgs,
             name += QLatin1String("_");
         retval << name;
     }
-    for (int i = 0; i < outputArgs.count(); ++i) {
+    for (int i = 0; i < numOutputArgs; ++i) {
         const QDBusIntrospection::Argument &arg = outputArgs.at(i);
         QString name = arg.name;
         if (name.isEmpty())
@@ -1145,7 +1148,7 @@ static void writeAdaptor(const QString &filename, const QDBusIntrospection::Inte
 int main(int argc, char **argv)
 {
     QStringList arguments;
-
+    arguments.reserve(argc);
     for (int i = 0; i < argc; ++i) {
         arguments.append(QString::fromLocal8Bit(argv[i]));
     }

src/tools/uic/cpp/cppwriteinitialization.cpp

@@ -2200,8 +2200,10 @@ QList<WriteInitialization::Item *> WriteInitialization::initializeTreeWidgetItem
 {
     // items
     QList<Item *> items;
+    const int numDomItems = domItems.size();
+    items.reserve(numDomItems);
 
-    for (int i = 0; i < domItems.size(); ++i) {
+    for (int i = 0; i < numDomItems; ++i) {
         const DomItem *domItem = domItems.at(i);
 
         Item *item = new Item(QLatin1String("QTreeWidgetItem"), m_indent, m_output, m_refreshOut, m_driver);

src/widgets/dialogs/qsidebar.cpp

@@ -460,6 +460,7 @@ void QSidebar::removeEntry()
     QList<QModelIndex> idxs = selectionModel()->selectedIndexes();
     QList<QPersistentModelIndex> indexes;
     const int numIndexes = idxs.count();
+    indexes.reserve(numIndexes);
     for (int i = 0; i < numIndexes; i++)
         indexes.append(idxs.at(i));
 

src/widgets/kernel/qwidgetbackingstore.cpp

@@ -1242,13 +1242,15 @@ void QWidgetBackingStore::doSync()
         // OpenGL content changes. Check if we have such widgets in the special
         // dirty list.
         QVarLengthArray<QWidget *, 16> paintPending;
-        for (int i = 0; i < dirtyRenderToTextureWidgets.count(); ++i) {
+        const int numPaintPending = dirtyRenderToTextureWidgets.count();
+        paintPending.reserve(numPaintPending);
+        for (int i = 0; i < numPaintPending; ++i) {
             QWidget *w = dirtyRenderToTextureWidgets.at(i);
             paintPending << w;
             resetWidget(w);
         }
         dirtyRenderToTextureWidgets.clear();
-        for (int i = 0; i < paintPending.count(); ++i) {
+        for (int i = 0; i < numPaintPending; ++i) {
             QWidget *w = paintPending[i];
             w->d_func()->sendPaintEvent(w->rect());
             if (w != tlw) {

src/widgets/widgets/qdockarealayout.cpp

@@ -3350,8 +3350,9 @@ QSet<QTabBar*> QDockAreaLayout::usedTabBars() const
 QSet<QWidget*> QDockAreaLayout::usedSeparatorWidgets() const
 {
     QSet<QWidget*> result;
-
+    const int numSeparators = separatorWidgets.count();
-    for (int i = 0; i < separatorWidgets.count(); ++i)
+    result.reserve(numSeparators);
+    for (int i = 0; i < numSeparators; ++i)
         result << separatorWidgets.at(i);
     for (int i = 0; i < QInternal::DockCount; ++i) {
         const QDockAreaLayoutInfo &dock = docks[i];