Use QStringRef to optimize memory allocation

Replace substring functions that return QString with
corresponding functions that return QStringRef where
it's possible.

Create QString from QStringRef only where necessary.

While touching the code, also port loops to C++11 style.

Change-Id: I04c99b24ea6afd3715e3edf9ea00bfab838fd53c
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>
Reviewed-by: Simon Hausmann <simon.hausmann@theqtcompany.com>
Reviewed-by: Frank Meerkoetter <frank.meerkoetter@basyskom.com>
Reviewed-by: Shawn Rutledge <shawn.rutledge@theqtcompany.com>
Reviewed-by: Robin Burchell <robin.burchell@viroteck.net>

9 files changed, 40 insertions, 34 deletions

diff --git a/src/qml/compiler/qqmlirbuilder.cpp b/src/qml/compiler/qqmlirbuilder.cpp
index 065e91109b..eaf0e72296 100644
--- a/src/qml/compiler/qqmlirbuilder.cpp
+++ b/src/qml/compiler/qqmlirbuilder.cpp
@@ -250,8 +250,8 @@ void Document::collectTypeReferences()
 
 void Document::removeScriptPragmas(QString &script)
 {
-    const QString pragma(QLatin1String("pragma"));
-    const QString library(QLatin1String("library"));
+    const QLatin1String pragma("pragma");
+    const QLatin1String library("library");
 
     QQmlJS::Lexer l(0);
     l.setCode(script, 0);
@@ -269,7 +269,7 @@ void Document::removeScriptPragmas(QString &script)
 
         if (token != QQmlJSGrammar::T_PRAGMA ||
             l.tokenStartLine() != startLine ||
-            script.mid(l.tokenOffset(), l.tokenLength()) != pragma)
+            script.midRef(l.tokenOffset(), l.tokenLength()) != pragma)
             return;
 
         token = l.lex();
@@ -278,7 +278,7 @@ void Document::removeScriptPragmas(QString &script)
             l.tokenStartLine() != startLine)
             return;
 
-        QString pragmaValue = script.mid(l.tokenOffset(), l.tokenLength());
+        const QStringRef pragmaValue = script.midRef(l.tokenOffset(), l.tokenLength());
         int endOffset = l.tokenLength() + l.tokenOffset();
 
         token = l.lex();
diff --git a/src/qml/compiler/qqmltypecompiler.cpp b/src/qml/compiler/qqmltypecompiler.cpp
index a71793f2b6..da00496cb2 100644
--- a/src/qml/compiler/qqmltypecompiler.cpp
+++ b/src/qml/compiler/qqmltypecompiler.cpp
@@ -179,16 +179,16 @@ bool QQmlTypeCompiler::compile()
     for (int scriptIndex = 0; scriptIndex < scripts.count(); ++scriptIndex) {
         const QQmlTypeData::ScriptReference &script = scripts.at(scriptIndex);
 
-        QString qualifier = script.qualifier;
+        QStringRef qualifier(&script.qualifier);
         QString enclosingNamespace;
 
         const int lastDotIndex = qualifier.lastIndexOf(QLatin1Char('.'));
         if (lastDotIndex != -1) {
-            enclosingNamespace = qualifier.left(lastDotIndex);
+            enclosingNamespace = qualifier.left(lastDotIndex).toString();
             qualifier = qualifier.mid(lastDotIndex+1);
         }
 
-        compiledData->importCache->add(qualifier, scriptIndex, enclosingNamespace);
+        compiledData->importCache->add(qualifier.toString(), scriptIndex, enclosingNamespace);
         QQmlScriptData *scriptData = script.script->scriptData();
         scriptData->addref();
         compiledData->scripts << scriptData;
@@ -624,7 +624,7 @@ bool QQmlPropertyCacheCreator::createMetaObject(int objectIndex, const QmlIR::Ob
         QString path = compiler->url().path();
         int lastSlash = path.lastIndexOf(QLatin1Char('/'));
         if (lastSlash > -1) {
-            QString nameBase = path.mid(lastSlash + 1, path.length()-lastSlash-5);
+            const QStringRef nameBase = path.midRef(lastSlash + 1, path.length() - lastSlash - 5);
             if (!nameBase.isEmpty() && nameBase.at(0).isUpper())
                 newClassName = nameBase.toUtf8() + "_QMLTYPE_" +
                                QByteArray::number(classIndexCounter.fetchAndAddRelaxed(1));
@@ -1163,10 +1163,10 @@ struct StaticQtMetaObject : public QObject
         { return &staticQtMetaObject; }
 };
 
-bool QQmlEnumTypeResolver::assignEnumToBinding(QmlIR::Binding *binding, const QString &enumName, int enumValue, bool isQtObject)
+bool QQmlEnumTypeResolver::assignEnumToBinding(QmlIR::Binding *binding, const QStringRef &enumName, int enumValue, bool isQtObject)
 {
     if (enumName.length() > 0 && enumName[0].isLower() && !isQtObject) {
-        COMPILE_EXCEPTION(binding, tr("Invalid property assignment: Enum value \"%1\" cannot start with a lowercase letter").arg(enumName));
+        COMPILE_EXCEPTION(binding, tr("Invalid property assignment: Enum value \"%1\" cannot start with a lowercase letter").arg(enumName.toString()));
     }
     binding->type = QV4::CompiledData::Binding::Type_Number;
     binding->value.d = (double)enumValue;
@@ -1197,7 +1197,7 @@ bool QQmlEnumTypeResolver::tryQualifiedEnumAssignment(const QmlIR::Object *obj,
 
     QHashedStringRef typeName(string.constData(), dot);
     const bool isQtObject = (typeName == QLatin1String("Qt"));
-    QString enumValue = string.mid(dot+1);
+    const QStringRef enumValue = string.midRef(dot + 1);
 
     if (isIntProp) {
         // Allow enum assignment to ints.
diff --git a/src/qml/compiler/qqmltypecompiler_p.h b/src/qml/compiler/qqmltypecompiler_p.h
index 240f591f91..273ba01a88 100644
--- a/src/qml/compiler/qqmltypecompiler_p.h
+++ b/src/qml/compiler/qqmltypecompiler_p.h
@@ -196,7 +196,11 @@ public:
     bool resolveEnumBindings();
 
 private:
-    bool assignEnumToBinding(QmlIR::Binding *binding, const QString &enumName, int enumValue, bool isQtObject);
+    bool assignEnumToBinding(QmlIR::Binding *binding, const QStringRef &enumName, int enumValue, bool isQtObject);
+    bool assignEnumToBinding(QmlIR::Binding *binding, const QString &enumName, int enumValue, bool isQtObject)
+    {
+        return assignEnumToBinding(binding, QStringRef(&enumName), enumValue, isQtObject);
+    }
     bool tryQualifiedEnumAssignment(const QmlIR::Object *obj, const QQmlPropertyCache *propertyCache,
                                     const QQmlPropertyData *prop,
                                     QmlIR::Binding *binding);
diff --git a/src/qml/compiler/qv4compileddata.cpp b/src/qml/compiler/qv4compileddata.cpp
index 4d0361302e..a63f35152a 100644
--- a/src/qml/compiler/qv4compileddata.cpp
+++ b/src/qml/compiler/qv4compileddata.cpp
@@ -221,8 +221,8 @@ QString Binding::valueAsString(const Unit *unit) const
         // This code must match that in the qsTr() implementation
         const QString &path = unit->stringAt(unit->sourceFileIndex);
         int lastSlash = path.lastIndexOf(QLatin1Char('/'));
-        QString context = (lastSlash > -1) ? path.mid(lastSlash + 1, path.length()-lastSlash-5) :
-                                             QString();
+        QStringRef context = (lastSlash > -1) ? path.midRef(lastSlash + 1, path.length() - lastSlash - 5)
+                                              : QStringRef();
         QByteArray contextUtf8 = context.toUtf8();
         QByteArray comment = unit->stringAt(value.translationData.commentIndex).toUtf8();
         QByteArray text = unit->stringAt(stringIndex).toUtf8();
diff --git a/src/qml/qml/qqmlerror.cpp b/src/qml/qml/qqmlerror.cpp
index 47c85c907c..74ceeabeb4 100644
--- a/src/qml/qml/qqmlerror.cpp
+++ b/src/qml/qml/qqmlerror.cpp
@@ -43,6 +43,7 @@
 #include <QtCore/qdebug.h>
 #include <QtCore/qfile.h>
 #include <QtCore/qstringlist.h>
+#include <QtCore/qvector.h>
 
 #include <private/qv4errorobject_p.h>
 
@@ -288,11 +289,11 @@ QDebug operator<<(QDebug debug, const QQmlError &error)
             stream.setCodec("UTF-8");
 #endif
             const QString code = stream.readAll();
-            const QStringList lines = code.split(QLatin1Char('\n'));
+            const auto lines = code.splitRef(QLatin1Char('\n'));
 
             if (lines.count() >= error.line()) {
-                const QString &line = lines.at(error.line() - 1);
-                debug << "\n    " << qPrintable(line);
+                const QStringRef &line = lines.at(error.line() - 1);
+                debug << "\n    " << line.toLocal8Bit().constData();
 
                 if(error.column() > 0) {
                     int column = qMax(0, error.column() - 1);
diff --git a/src/qml/qml/qqmlfile.cpp b/src/qml/qml/qqmlfile.cpp
index ea4e9a1013..5fe3cba5c3 100644
--- a/src/qml/qml/qqmlfile.cpp
+++ b/src/qml/qml/qqmlfile.cpp
@@ -583,7 +583,7 @@ QString QQmlFile::urlToLocalFileOrQrc(const QString& url)
 {
     if (url.startsWith(QLatin1String("qrc:"), Qt::CaseInsensitive)) {
         if (url.length() > 4)
-            return QLatin1Char(':') + url.mid(4);
+            return QLatin1Char(':') + url.midRef(4);
         return QString();
     }
 
diff --git a/src/qml/qml/qqmlimport.cpp b/src/qml/qml/qqmlimport.cpp
index ec29e600ed..2a1717f190 100644
--- a/src/qml/qml/qqmlimport.cpp
+++ b/src/qml/qml/qqmlimport.cpp
@@ -85,12 +85,11 @@ QString resolveLocalUrl(const QString &url, const QString &relative)
     } else if (relative.at(0) == Slash || !url.contains(Slash)) {
         return relative;
     } else {
-        QString base(url.left(url.lastIndexOf(Slash) + 1));
-
+        const QStringRef baseRef = url.leftRef(url.lastIndexOf(Slash) + 1);
         if (relative == QLatin1String("."))
-            return base;
+            return baseRef.toString();
 
-        base.append(relative);
+        QString base = baseRef + relative;
 
         // Remove any relative directory elements in the path
         int length = base.length();
@@ -815,11 +814,11 @@ bool QQmlImportNamespace::resolveType(QQmlTypeLoader *typeLoader, const QHashedS
                             QString u1 = import->url;
                             QString u2 = import2->url;
                             if (base) {
-                                QString b = *base;
+                                QStringRef b(base);
                                 int dot = b.lastIndexOf(Dot);
                                 if (dot >= 0) {
                                     b = b.left(dot+1);
-                                    QString l = b.left(dot);
+                                    QStringRef l = b.left(dot);
                                     if (u1.startsWith(b))
                                         u1 = u1.mid(b.count());
                                     else if (u1 == l)
@@ -1173,11 +1172,11 @@ bool QQmlImportsPrivate::locateQmldir(const QString &uri, int vmaj, int vmin, QQ
         QString absoluteFilePath = typeLoader.absoluteFilePath(qmldirPath);
         if (!absoluteFilePath.isEmpty()) {
             QString url;
-            QString absolutePath = absoluteFilePath.left(absoluteFilePath.lastIndexOf(Slash)+1);
+            const QStringRef absolutePath = absoluteFilePath.leftRef(absoluteFilePath.lastIndexOf(Slash) + 1);
             if (absolutePath.at(0) == Colon)
                 url = QLatin1String("qrc://") + absolutePath.mid(1);
             else
-                url = QUrl::fromLocalFile(absolutePath).toString();
+                url = QUrl::fromLocalFile(absolutePath.toString()).toString();
 
             QQmlImportDatabase::QmldirCache *cache = new QQmlImportDatabase::QmldirCache;
             cache->versionMajor = vmaj;
diff --git a/src/qml/qml/qqmlproperty.cpp b/src/qml/qml/qqmlproperty.cpp
index 22de5e1ae9..df2ff05de1 100644
--- a/src/qml/qml/qqmlproperty.cpp
+++ b/src/qml/qml/qqmlproperty.cpp
@@ -58,6 +58,7 @@
 #include <private/qv4functionobject_p.h>
 
 #include <QStringList>
+#include <QVector>
 #include <private/qmetaobject_p.h>
 #include <private/qqmlvaluetypewrapper_p.h>
 #include <QtCore/qdebug.h>
@@ -240,14 +241,14 @@ void QQmlPropertyPrivate::initProperty(QObject *obj, const QString &name)
 
     QQmlTypeNameCache *typeNameCache = context?context->imports:0;
 
-    QStringList path = name.split(QLatin1Char('.'));
+    const auto path = name.splitRef(QLatin1Char('.'));
     if (path.isEmpty()) return;
 
     QObject *currentObject = obj;
 
     // Everything up to the last property must be an "object type" property
     for (int ii = 0; ii < path.count() - 1; ++ii) {
-        const QString &pathName = path.at(ii);
+        const QStringRef &pathName = path.at(ii);
 
         if (typeNameCache) {
             QQmlTypeNameCache::Result r = typeNameCache->query(pathName);
@@ -284,7 +285,7 @@ void QQmlPropertyPrivate::initProperty(QObject *obj, const QString &name)
 
         QQmlPropertyData local;
         QQmlPropertyData *property =
-            QQmlPropertyCache::property(engine, currentObject, pathName, context, local);
+            QQmlPropertyCache::property(engine, currentObject, pathName.toString(), context, local);
 
         if (!property) return; // Not a property
         if (property->isFunction())
@@ -324,14 +325,14 @@ void QQmlPropertyPrivate::initProperty(QObject *obj, const QString &name)
 
     }
 
-    const QString &terminal = path.last();
+    const QStringRef &terminal = path.last();
 
     if (terminal.count() >= 3 &&
         terminal.at(0) == QLatin1Char('o') &&
         terminal.at(1) == QLatin1Char('n') &&
         terminal.at(2).isUpper()) {
 
-        QString signalName = terminal.mid(2);
+        QString signalName = terminal.mid(2).toString();
         signalName[0] = signalName.at(0).toLower();
 
         // XXX - this code treats methods as signals
@@ -376,13 +377,14 @@ void QQmlPropertyPrivate::initProperty(QObject *obj, const QString &name)
     }
 
     // Property
+    const QString terminalString = terminal.toString();
     QQmlPropertyData local;
     QQmlPropertyData *property =
-        QQmlPropertyCache::property(engine, currentObject, terminal, context, local);
+        QQmlPropertyCache::property(engine, currentObject, terminalString, context, local);
     if (property && !property->isFunction()) {
         object = currentObject;
         core = *property;
-        nameCache = terminal;
+        nameCache = terminalString;
         isNameCached = true;
     }
 }
diff --git a/src/qml/types/qqmldelegatemodel.cpp b/src/qml/types/qqmldelegatemodel.cpp
index 527b8aad55..0e7b0c1b14 100644
--- a/src/qml/types/qqmldelegatemodel.cpp
+++ b/src/qml/types/qqmldelegatemodel.cpp
@@ -1042,7 +1042,7 @@ QString QQmlDelegateModelPrivate::stringValue(Compositor::Group group, int index
                 return QString();
             int from = dot+1;
             dot = name.indexOf(QLatin1Char('.'), from);
-            value = obj->property(name.mid(from, dot-from).toUtf8());
+            value = obj->property(name.midRef(from, dot - from).toUtf8());
         }
         return value.toString();
     }