Speed up interceptor

Using QStringLiterals and explicit QByteArray ctors makes it possible
for the compiler to skip the more expensive QString ctors and use very
cheap ones. This should give the interceptor a nice speedup.

src/plasmaquick/autotests/packageurlinterceptortest.cpp

@@ -30,7 +30,7 @@ QTEST_MAIN(PackageUrlInterceptorTest)
 
 void PackageUrlInterceptorTest::loadAccessManager()
 {
-    Plasma::Package pkg = Plasma::Package();
+    const Plasma::Package &pkg = Plasma::Package();
     QQmlNetworkAccessManagerFactory* pui = PackageUrlInterceptor::createPackageAccessManagerFactory(pkg);
     QVERIFY(pui != 0);
     delete pui;

src/plasmaquick/packageurlinterceptor.cpp

@@ -67,13 +67,13 @@ QUrl PackageUrlInterceptor::intercept(const QUrl &path, QQmlAbstractUrlIntercept
             //should never happen
             Q_ASSERT(!relativePath.isEmpty());
 
-            QStringList components = relativePath.split("/");
+            QStringList components = relativePath.split(QLatin1Char('/'));
             //a path with less than 2 items should ever happen
             Q_ASSERT(components.count() >= 2);
 
             components.pop_front();
             //obtain a string in the form foo/bar/baz.qml: ui/ gets discarded
-            QString filename = components.join("/");
+            const QString &filename = components.join("/");
 
             //qDebug() << "Returning" << QUrl::fromLocalFile(m_package.filePath(prefixForType(type, filename), filename));
             return QUrl::fromLocalFile(m_package.filePath(prefixForType(type, filename), filename));
@@ -91,8 +91,8 @@ QUrl PackageUrlInterceptor::intercept(const QUrl &path, QQmlAbstractUrlIntercept
                         qDebug() << "Trying" << platform;
 
                         //search for a platformqml/ path sibling of this import path
-                        QString platformPath = import+QStringLiteral("/../platformqml/")+platform+path.path().mid(import.length());
-                        QFile f(platformPath);
+                        const QString &platformPath = import+QStringLiteral("/../platformqml/")+platform+path.path().mid(import.length());
+                        const QFile f(platformPath);
 
                         qDebug() << "Found a platform specific file:" << QUrl::fromLocalFile(platformPath)<<f.exists();
                         if (f.exists()) {

src/plasmaquick/packageurlinterceptor.h

@@ -44,28 +44,28 @@ public:
     {
         switch (type) {
         case QQmlAbstractUrlInterceptor::QmlFile:
-            return "ui";
+            return QByteArray("ui");
         case QQmlAbstractUrlInterceptor::JavaScriptFile:
-            return "scripts";
+            return QByteArray("scripts");
         default:
             break;
         }
 
         //failed by type, let's try by extension
-        const QString extension = fileName.mid(fileName.lastIndexOf(".") + 1).toLower();
+        const QString extension = fileName.mid(fileName.lastIndexOf(QLatin1Char('.')) + 1).toLower();
 
-        if (extension == "svg" || extension == "svgz" ||
-            extension == "png" || extension == "gif" ||
-            extension == "jpg" || extension == "jpeg") {
-            return "images";
+        if (extension == QStringLiteral("svg") || extension == QStringLiteral("svgz") ||
+            extension == QStringLiteral("png") || extension == QStringLiteral("gif") ||
+            extension == QStringLiteral("jpg") || extension == QStringLiteral("jpeg")) {
+            return QByteArray("images");
         //FIXME: are those necessary? are they *always* catched by type?
-        } else if (extension == "js") {
-            return "scripts";
-        } else if (extension == "qml") {
-            return "ui";
+        } else if (extension == QStringLiteral("js")) {
+            return QByteArray("scripts");
+        } else if (extension == QStringLiteral("qml")) {
+            return QByteArray("ui");
         //everything else, throw it in "data"
         } else {
-            return "data";
+            return QByteArray("data");
         }
     }