DBus: 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.

Add overloaded functions with QStringRef arg
in QDBusUtil:
- isValidUniqueConnectionName()
- isValidMemberName()
- isValidPartOfObjectPath()

Change-Id: I4a24a298702728ba7d3a65c39e25c3a9c759e07f
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>

5 files changed, 60 insertions, 39 deletions

diff --git a/src/dbus/qdbusconnection.cpp b/src/dbus/qdbusconnection.cpp
index ea8c2b0311..cddb7dfb95 100644
--- a/src/dbus/qdbusconnection.cpp
+++ b/src/dbus/qdbusconnection.cpp
@@ -44,6 +44,7 @@
 #include <qdebug.h>
 #include <qcoreapplication.h>
 #include <qstringlist.h>
+#include <qvector.h>
 #include <qtimer.h>
 #include <qthread.h>
 
@@ -909,8 +910,8 @@ bool QDBusConnection::registerObject(const QString &path, const QString &interfa
     if (!d || !d->connection || !object || !options || !QDBusUtil::isValidObjectPath(path))
         return false;
 
-    QStringList pathComponents = path.split(QLatin1Char('/'));
-    if (pathComponents.last().isEmpty())
+    auto pathComponents = path.splitRef(QLatin1Char('/'));
+    if (pathComponents.constLast().isEmpty())
         pathComponents.removeLast();
     QDBusWriteLocker locker(RegisterObjectAction, d);
 
@@ -965,7 +966,7 @@ bool QDBusConnection::registerObject(const QString &path, const QString &interfa
             }
         } else {
             // add entry
-            node = node->children.insert(it, pathComponents.at(i));
+            node = node->children.insert(it, pathComponents.at(i).toString());
         }
 
         // iterate
@@ -1017,8 +1018,8 @@ QObject *QDBusConnection::objectRegisteredAt(const QString &path) const
     if (!d || !d->connection || !QDBusUtil::isValidObjectPath(path))
         return 0;
 
-    QStringList pathComponents = path.split(QLatin1Char('/'));
-    if (pathComponents.last().isEmpty())
+    auto pathComponents = path.splitRef(QLatin1Char('/'));
+    if (pathComponents.constLast().isEmpty())
         pathComponents.removeLast();
 
     // lower-bound search for where this object should enter in the tree
diff --git a/src/dbus/qdbusintegrator.cpp b/src/dbus/qdbusintegrator.cpp
index 6d4a27cdb5..cc3080e6db 100644
--- a/src/dbus/qdbusintegrator.cpp
+++ b/src/dbus/qdbusintegrator.cpp
@@ -586,7 +586,7 @@ static void huntAndDestroy(QObject *needle, QDBusConnectionPrivate::ObjectTreeNo
     }
 }
 
-static void huntAndUnregister(const QStringList &pathComponents, int i, QDBusConnection::UnregisterMode mode,
+static void huntAndUnregister(const QVector<QStringRef> &pathComponents, int i, QDBusConnection::UnregisterMode mode,
                               QDBusConnectionPrivate::ObjectTreeNode *node)
 {
     if (pathComponents.count() == i) {
@@ -2335,12 +2335,12 @@ void QDBusConnectionPrivate::registerObject(const ObjectTreeNode *node)
 void QDBusConnectionPrivate::unregisterObject(const QString &path, QDBusConnection::UnregisterMode mode)
 {
     QDBusConnectionPrivate::ObjectTreeNode *node = &rootNode;
-    QStringList pathComponents;
+    QVector<QStringRef> pathComponents;
     int i;
     if (path == QLatin1String("/")) {
         i = 0;
     } else {
-        pathComponents = path.split(QLatin1Char('/'));
+        pathComponents = path.splitRef(QLatin1Char('/'));
         i = 1;
     }
 
diff --git a/src/dbus/qdbusmisc.cpp b/src/dbus/qdbusmisc.cpp
index 6ecd66f3e7..0502bea0ac 100644
--- a/src/dbus/qdbusmisc.cpp
+++ b/src/dbus/qdbusmisc.cpp
@@ -94,14 +94,15 @@ QString qDBusInterfaceFromMetaObject(const QMetaObject *mo)
             interface.prepend(QLatin1String("local."));
          } else {
             interface.prepend(QLatin1Char('.')).prepend(QCoreApplication::instance()->applicationName());
-            QStringList domainName =
-                QCoreApplication::instance()->organizationDomain().split(QLatin1Char('.'),
-                                                                         QString::SkipEmptyParts);
-            if (domainName.isEmpty())
+            const QString organizationDomain = QCoreApplication::instance()->organizationDomain();
+            const auto domainName = organizationDomain.splitRef(QLatin1Char('.'), QString::SkipEmptyParts);
+            if (domainName.isEmpty()) {
                  interface.prepend(QLatin1String("local."));
-            else
-                for (int i = 0; i < domainName.count(); ++i)
-                    interface.prepend(QLatin1Char('.')).prepend(domainName.at(i));
+            } else {
+                interface.reserve(interface.size() + organizationDomain.size());
+                for (const QStringRef &x : domainName)
+                    interface.prepend(QLatin1Char('.')).prepend(x);
+            }
          }
      }
 
diff --git a/src/dbus/qdbusutil.cpp b/src/dbus/qdbusutil.cpp
index aababd12e9..28341a71a8 100644
--- a/src/dbus/qdbusutil.cpp
+++ b/src/dbus/qdbusutil.cpp
@@ -42,6 +42,7 @@
 #include "qdbus_symbols_p.h"
 
 #include <QtCore/qstringlist.h>
+#include <QtCore/qvector.h>
 
 #include "qdbusargument.h"
 #include "qdbusunixfiledescriptor.h"
@@ -330,10 +331,10 @@ namespace QDBusUtil
 
     /*!
         \internal
-        \fn bool QDBusUtil::isValidPartOfObjectPath(const QString &part)
+        \fn bool QDBusUtil::isValidPartOfObjectPath(const QStringRef &part)
         See QDBusUtil::isValidObjectPath
     */
-    bool isValidPartOfObjectPath(const QString &part)
+    bool isValidPartOfObjectPath(const QStringRef &part)
     {
         if (part.isEmpty())
             return false;       // can't be valid if it's empty
@@ -347,6 +348,13 @@ namespace QDBusUtil
     }
 
     /*!
+        \internal
+        \fn bool QDBusUtil::isValidPartOfObjectPath(const QString &part)
+
+        \overload
+    */
+
+    /*!
         \fn bool QDBusUtil::isValidInterfaceName(const QString &ifaceName)
         Returns \c true if this is \a ifaceName is a valid interface name.
 
@@ -364,36 +372,35 @@ namespace QDBusUtil
         if (ifaceName.isEmpty() || ifaceName.length() > DBUS_MAXIMUM_NAME_LENGTH)
             return false;
 
-        QStringList parts = ifaceName.split(QLatin1Char('.'));
+        const auto parts = ifaceName.splitRef(QLatin1Char('.'));
         if (parts.count() < 2)
             return false;           // at least two parts
 
-        for (int i = 0; i < parts.count(); ++i)
-            if (!isValidMemberName(parts.at(i)))
+        for (const QStringRef &part : parts)
+            if (!isValidMemberName(part))
                 return false;
 
         return true;
     }
 
     /*!
-        \fn bool QDBusUtil::isValidUniqueConnectionName(const QString &connName)
+        \fn bool QDBusUtil::isValidUniqueConnectionName(const QStringRef &connName)
         Returns \c true if \a connName is a valid unique connection name.
 
         Unique connection names start with a colon (":") and are followed by a list of dot-separated
         components composed of ASCII letters, digits, the hyphen or the underscore ("_") character.
     */
-    bool isValidUniqueConnectionName(const QString &connName)
+    bool isValidUniqueConnectionName(const QStringRef &connName)
     {
         if (connName.isEmpty() || connName.length() > DBUS_MAXIMUM_NAME_LENGTH ||
             !connName.startsWith(QLatin1Char(':')))
             return false;
 
-        QStringList parts = connName.mid(1).split(QLatin1Char('.'));
+        const auto parts = connName.mid(1).split(QLatin1Char('.'));
         if (parts.count() < 1)
             return false;
 
-        for (int i = 0; i < parts.count(); ++i) {
-            const QString &part = parts.at(i);
+        for (const QStringRef &part : parts) {
             if (part.isEmpty())
                  return false;
 
@@ -407,6 +414,12 @@ namespace QDBusUtil
     }
 
     /*!
+        \fn bool QDBusUtil::isValidUniqueConnectionName(const QString &connName)
+
+        \overload
+    */
+
+    /*!
         \fn bool QDBusUtil::isValidBusName(const QString &busName)
         Returns \c true if \a busName is a valid bus name.
 
@@ -429,12 +442,11 @@ namespace QDBusUtil
         if (busName.startsWith(QLatin1Char(':')))
             return isValidUniqueConnectionName(busName);
 
-        QStringList parts = busName.split(QLatin1Char('.'));
+        const auto parts = busName.splitRef(QLatin1Char('.'));
         if (parts.count() < 1)
             return false;
 
-        for (int i = 0; i < parts.count(); ++i) {
-            const QString &part = parts.at(i);
+        for (const QStringRef &part : parts) {
             if (part.isEmpty())
                 return false;
 
@@ -450,12 +462,12 @@ namespace QDBusUtil
     }
 
     /*!
-        \fn bool QDBusUtil::isValidMemberName(const QString &memberName)
+        \fn bool QDBusUtil::isValidMemberName(const QStringRef &memberName)
         Returns \c true if \a memberName is a valid member name. A valid member name does not exceed
         255 characters in length, is not empty, is composed only of ASCII letters, digits and
         underscores, but does not start with a digit.
     */
-    bool isValidMemberName(const QString &memberName)
+    bool isValidMemberName(const QStringRef &memberName)
     {
         if (memberName.isEmpty() || memberName.length() > DBUS_MAXIMUM_NAME_LENGTH)
             return false;
@@ -470,6 +482,12 @@ namespace QDBusUtil
     }
 
     /*!
+        \fn bool QDBusUtil::isValidMemberName(const QString &memberName)
+
+        \overload
+    */
+
+    /*!
         \fn bool QDBusUtil::isValidErrorName(const QString &errorName)
         Returns \c true if \a errorName is a valid error name. Valid error names are valid interface
         names and vice-versa, so this function is actually an alias for isValidInterfaceName.
@@ -501,12 +519,10 @@ namespace QDBusUtil
             path.endsWith(QLatin1Char('/')))
             return false;
 
-        QStringList parts = path.split(QLatin1Char('/'));
-        Q_ASSERT(parts.count() >= 1);
-        parts.removeFirst();    // it starts with /, so we get an empty first part
-
-        for (int i = 0; i < parts.count(); ++i)
-            if (!isValidPartOfObjectPath(parts.at(i)))
+        // it starts with /, so we skip the empty first part
+        const auto parts = path.midRef(1).split(QLatin1Char('/'));
+        for (const QStringRef &part : parts)
+            if (!isValidPartOfObjectPath(part))
                 return false;
 
         return true;
diff --git a/src/dbus/qdbusutil_p.h b/src/dbus/qdbusutil_p.h
index 27b61ad7f2..e0ba92be2e 100644
--- a/src/dbus/qdbusutil_p.h
+++ b/src/dbus/qdbusutil_p.h
@@ -68,15 +68,18 @@ namespace QDBusUtil
 {
     Q_DBUS_EXPORT bool isValidInterfaceName(const QString &ifaceName);
 
-    Q_DBUS_EXPORT bool isValidUniqueConnectionName(const QString &busName);
+    Q_DBUS_EXPORT bool isValidUniqueConnectionName(const QStringRef &busName);
+    bool inline isValidUniqueConnectionName(const QString &busName) { return isValidUniqueConnectionName(QStringRef(&busName)); }
 
     Q_DBUS_EXPORT bool isValidBusName(const QString &busName);
 
-    Q_DBUS_EXPORT bool isValidMemberName(const QString &memberName);
+    Q_DBUS_EXPORT bool isValidMemberName(const QStringRef &memberName);
+    bool inline isValidMemberName(const QString &memberName) { return isValidMemberName(QStringRef(&memberName)); }
 
     Q_DBUS_EXPORT bool isValidErrorName(const QString &errorName);
 
-    Q_DBUS_EXPORT bool isValidPartOfObjectPath(const QString &path);
+    Q_DBUS_EXPORT bool isValidPartOfObjectPath(const QStringRef &path);
+    bool inline isValidPartOfObjectPath(const QString &path) { return isValidPartOfObjectPath(QStringRef(&path)); }
 
     Q_DBUS_EXPORT bool isValidObjectPath(const QString &path);