optimization: get rid of QString::fromUtf16() usage

QString::fromUtf16() is slow - it does a BOM check and optionally byte
swapping, which is utterly pointless when converting internal data
structures which are raw utf16 in host byte order anyway. so replace
it with QString::fromRawData() (for short-lived strings) or
QString(const QChar *, int) (otherwise) if possible.

Reviewed-by: axis
Reviewed-by: mariusSO
Reviewed-by: Bill King

3 files changed, 4 insertions, 3 deletions

diff --git a/src/corelib/kernel/qcore_symbian_p.cpp b/src/corelib/kernel/qcore_symbian_p.cpp
index 5d2a6a5..0257ac4 100644
--- a/src/corelib/kernel/qcore_symbian_p.cpp
+++ b/src/corelib/kernel/qcore_symbian_p.cpp
@@ -71,7 +71,7 @@ Q_CORE_EXPORT QString qt_TDesC2QString(const TDesC& aDescriptor)
 #ifdef QT_NO_UNICODE
     return QString::fromLocal8Bit(aDescriptor.Ptr(), aDescriptor.Length());
 #else
-    return QString::fromUtf16(aDescriptor.Ptr(), aDescriptor.Length());
+    return QString(reinterpret_cast<const QChar *>(aDescriptor.Ptr()), aDescriptor.Length());
 #endif
 }
 
diff --git a/src/corelib/kernel/qcoreapplication.cpp b/src/corelib/kernel/qcoreapplication.cpp
index 005dedc..5c65416 100644
--- a/src/corelib/kernel/qcoreapplication.cpp
+++ b/src/corelib/kernel/qcoreapplication.cpp
@@ -2219,7 +2219,8 @@ QStringList QCoreApplication::libraryPaths()
             TFindFile finder(fs);
             TInt err = finder.FindByDir(tempPathPtr, tempPathPtr);
             while (err == KErrNone) {
-                QString foundDir = QString::fromUtf16(finder.File().Ptr(), finder.File().Length());
+                QString foundDir(reinterpret_cast<const QChar *>(finder.File().Ptr()),
+                                 finder.File().Length());
                 foundDir = QDir(foundDir).canonicalPath();
                 if (!app_libpaths->contains(foundDir))
                     app_libpaths->append(foundDir);
diff --git a/src/corelib/kernel/qtranslator.cpp b/src/corelib/kernel/qtranslator.cpp
index b7e6ea0..7d1e1d3 100644
--- a/src/corelib/kernel/qtranslator.cpp
+++ b/src/corelib/kernel/qtranslator.cpp
@@ -633,7 +633,7 @@ static QString getMessage(const uchar *m, const uchar *end, const char *context,
 end:
     if (!tn)
         return QString();
-    QString str = QString::fromUtf16((const ushort *)tn, tn_length/2);
+    QString str = QString((const QChar *)tn, tn_length/2);
     if (QSysInfo::ByteOrder == QSysInfo::LittleEndian) {
         for (int i = 0; i < str.length(); ++i)
             str[i] = QChar((str.at(i).unicode() >> 8) + ((str.at(i).unicode() << 8) & 0xff00));