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

5 files changed, 7 insertions, 6 deletions

diff --git a/src/corelib/io/qprocess_unix.cpp b/src/corelib/io/qprocess_unix.cpp
index 0bf7d3f..5119ec0 100644
--- a/src/corelib/io/qprocess_unix.cpp
+++ b/src/corelib/io/qprocess_unix.cpp
@@ -783,7 +783,7 @@ bool QProcessPrivate::processStarted()
 
     // did we read an error message?
     if (i > 0)
-        q_func()->setErrorString(QString::fromUtf16(buf, i / sizeof(QChar)));
+        q_func()->setErrorString(QString((const QChar *)buf, i / sizeof(QChar)));
 
     return i <= 0;
 }
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));
diff --git a/src/corelib/tools/qstring.cpp b/src/corelib/tools/qstring.cpp
index 44e4d16..3388500 100644
--- a/src/corelib/tools/qstring.cpp
+++ b/src/corelib/tools/qstring.cpp
@@ -885,7 +885,7 @@ int QString::grow(int size)
 QString QString::fromWCharArray(const wchar_t *string, int size)
 {
     if (sizeof(wchar_t) == sizeof(QChar)) {
-        return fromUtf16((ushort *)string, size);
+        return QString((const QChar *)string, size);
     } else {
         return fromUcs4((uint *)string, size);
     }
@@ -7751,7 +7751,7 @@ QString QStringRef::toString() const {
         return QString();
     if (m_size && m_position == 0 && m_size == m_string->size())
         return *m_string;
-    return QString::fromUtf16(reinterpret_cast<const ushort*>(m_string->unicode() + m_position), m_size);
+    return QString(m_string->unicode() + m_position, m_size);
 }