QtCore: use QStringRef in more places

Apart from removing some unwanted allocations, also reduces
text size by ~800B on Linux AMD64 GCC 4.9 release builds.

Change-Id: Ibcd1d8264f54f2b165b69bee8aa50ff7f4ad3a10
Reviewed-by: Olivier Goffart (Woboq GmbH) <ogoffart@woboq.com>

src/corelib/io/qfilesystemengine.cpp

@@ -152,7 +152,7 @@ static bool _q_resolveEntryAndCreateLegacyEngine_recursive(QFileSystemEntry &ent
 
             const QStringList &paths = QDir::searchPaths(filePath.left(prefixSeparator));
             for (int i = 0; i < paths.count(); i++) {
-                entry = QFileSystemEntry(QDir::cleanPath(paths.at(i) % QLatin1Char('/') % filePath.mid(prefixSeparator + 1)));
+                entry = QFileSystemEntry(QDir::cleanPath(paths.at(i) % QLatin1Char('/') % filePath.midRef(prefixSeparator + 1)));
                 // Recurse!
                 if (_q_resolveEntryAndCreateLegacyEngine_recursive(entry, data, engine, true))
                     return true;

src/corelib/io/qfilesystementry.cpp

@@ -53,8 +53,7 @@ static bool isUncRoot(const QString &server)
     if (idx == -1 || idx + 1 == localPath.length())
         return true;
 
-    localPath = localPath.right(localPath.length() - idx - 1).trimmed();
+    return localPath.rightRef(localPath.length() - idx - 1).trimmed().isEmpty();
-    return localPath.isEmpty();
 }
 
 static inline QString fixIfRelativeUncPath(const QString &path)

src/corelib/io/qfilesystemwatcher.cpp

@@ -296,7 +296,9 @@ QStringList QFileSystemWatcher::addPaths(const QStringList &paths)
 
     QFileSystemWatcherEngine *engine = 0;
 
-    if(!objectName().startsWith(QLatin1String("_qt_autotest_force_engine_"))) {
+    const QString on = objectName();
+
+    if (!on.startsWith(QLatin1String("_qt_autotest_force_engine_"))) {
         // Normal runtime case - search intelligently for best engine
         if(d->native) {
             engine = d->native;
@@ -307,7 +309,7 @@ QStringList QFileSystemWatcher::addPaths(const QStringList &paths)
 
     } else {
         // Autotest override case - use the explicitly selected engine only
-        QString forceName = objectName().mid(26);
+        const QStringRef forceName = on.midRef(26);
         if(forceName == QLatin1String("poller")) {
             qDebug() << "QFileSystemWatcher: skipping native engine, using only polling engine";
             d_func()->initPollerEngine();

src/corelib/io/qresource.cpp

@@ -800,8 +800,8 @@ bool QResourceRoot::mappingRootSubdir(const QString &path, QString *match) const
 {
     const QString root = mappingRoot();
     if(!root.isEmpty()) {
-        const QStringList root_segments = root.split(QLatin1Char('/'), QString::SkipEmptyParts),
+        const QVector<QStringRef> root_segments = root.splitRef(QLatin1Char('/'), QString::SkipEmptyParts),
-                          path_segments = path.split(QLatin1Char('/'), QString::SkipEmptyParts);
+                                  path_segments = path.splitRef(QLatin1Char('/'), QString::SkipEmptyParts);
         if(path_segments.size() <= root_segments.size()) {
             int matched = 0;
             for(int i = 0; i < path_segments.size(); ++i) {
@@ -811,7 +811,7 @@ bool QResourceRoot::mappingRootSubdir(const QString &path, QString *match) const
             }
             if(matched == path_segments.size()) {
                 if(match && root_segments.size() > matched)
-                    *match = root_segments.at(matched);
+                    *match = root_segments.at(matched).toString();
                 return true;
             }
         }

src/corelib/io/qsettings.cpp

@@ -488,7 +488,7 @@ QVariant QSettingsPrivate::stringToVariant(const QString &s)
     if (s.startsWith(QLatin1Char('@'))) {
         if (s.endsWith(QLatin1Char(')'))) {
             if (s.startsWith(QLatin1String("@ByteArray("))) {
-                return QVariant(s.toLatin1().mid(11, s.size() - 12));
+                return QVariant(s.midRef(11, s.size() - 12).toLatin1());
             } else if (s.startsWith(QLatin1String("@Variant("))
                        || s.startsWith(QLatin1String("@DateTime("))) {
 #ifndef QT_NO_DATASTREAM
@@ -501,7 +501,7 @@ QVariant QSettingsPrivate::stringToVariant(const QString &s)
                     version = QDataStream::Qt_4_0;
                     offset = 9;
                 }
-                QByteArray a(s.toLatin1().mid(offset));
+                QByteArray a = s.midRef(offset).toLatin1();
                 QDataStream stream(&a, QIODevice::ReadOnly);
                 stream.setVersion(version);
                 QVariant result;

src/corelib/io/qsettings_mac.cpp

@@ -403,11 +403,11 @@ QMacSettingsPrivate::QMacSettingsPrivate(QSettings::Scope scope, const QString &
     }
 
     while ((nextDot = domainName.indexOf(QLatin1Char('.'), curPos)) != -1) {
-        javaPackageName.prepend(domainName.mid(curPos, nextDot - curPos));
+        javaPackageName.prepend(domainName.midRef(curPos, nextDot - curPos));
         javaPackageName.prepend(QLatin1Char('.'));
         curPos = nextDot + 1;
     }
-    javaPackageName.prepend(domainName.mid(curPos));
+    javaPackageName.prepend(domainName.midRef(curPos));
     javaPackageName = javaPackageName.toLower();
     if (curPos == 0)
         javaPackageName.prepend(QLatin1String("com."));

src/corelib/plugin/qpluginloader.cpp

@@ -286,9 +286,9 @@ static QString locatePlugin(const QString& fileName)
     suffixes.prepend(QString());
 
     // Split up "subdir/filename"
-    const int slash = fileName.lastIndexOf('/');
+    const int slash = fileName.lastIndexOf(QLatin1Char('/'));
-    const QString baseName = fileName.mid(slash + 1);
+    const QStringRef baseName = fileName.midRef(slash + 1);
-    const QString basePath = isAbsolute ? QString() : fileName.left(slash + 1); // keep the '/'
+    const QStringRef basePath = isAbsolute ? QStringRef() : fileName.leftRef(slash + 1); // keep the '/'
 
     const bool debug = qt_debug_component();