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

4 files changed, 6 insertions, 5 deletions

diff --git a/src/gui/itemviews/qitemdelegate.cpp b/src/gui/itemviews/qitemdelegate.cpp
index 6fd26a7..9069ce4 100644
--- a/src/gui/itemviews/qitemdelegate.cpp
+++ b/src/gui/itemviews/qitemdelegate.cpp
@@ -1033,7 +1033,7 @@ static QString qPixmapSerial(quint64 i, bool enabled)
         i >>= 4;
     }
 
-    return QString::fromUtf16(ptr, int(&arr[sizeof(arr) / sizeof(ushort)] - ptr));
+    return QString((const QChar *)ptr, int(&arr[sizeof(arr) / sizeof(ushort)] - ptr));
 }
 
 /*!
diff --git a/src/gui/kernel/qclipboard_s60.cpp b/src/gui/kernel/qclipboard_s60.cpp
index 71c355b..f07e066 100644
--- a/src/gui/kernel/qclipboard_s60.cpp
+++ b/src/gui/kernel/qclipboard_s60.cpp
@@ -164,7 +164,8 @@ void readFromStreamLX(QMimeData* aData,RReadStream& aStream)
         TCardinality mimeTypeSize;
         aStream >> mimeTypeSize;
         HBufC* mimeTypeBuf = HBufC::NewLC(aStream,mimeTypeSize);
-        QString mimeType = QString::fromUtf16(mimeTypeBuf->Des().Ptr(),mimeTypeBuf->Length());
+        QString mimeType = QString(reinterpret_cast<const QChar *>(mimeTypeBuf->Des().Ptr()),
+                                   mimeTypeBuf->Length());
         CleanupStack::PopAndDestroy(mimeTypeBuf);
         // mime data
         TCardinality dataSize;
diff --git a/src/gui/kernel/qdnd_x11.cpp b/src/gui/kernel/qdnd_x11.cpp
index edab6a0..33968bd 100644
--- a/src/gui/kernel/qdnd_x11.cpp
+++ b/src/gui/kernel/qdnd_x11.cpp
@@ -617,7 +617,7 @@ QVariant QX11Data::xdndMimeConvertToFormat(Atom a, const QByteArray &data, const
             // so it should be safe to check that the second char is 0
             // to verify that it is utf16
             if (data.size() > 1 && data.at(1) == 0)
-                return QString::fromUtf16(reinterpret_cast<const ushort *>(data.constData()),
+                return QString::fromRawData((const QChar *)data.constData(),
                                 data.size() / 2).split(QLatin1Char('\n')).first().toLatin1();
         }
     }
diff --git a/src/gui/kernel/qmime_mac.cpp b/src/gui/kernel/qmime_mac.cpp
index 0431f2f..071f80d 100644
--- a/src/gui/kernel/qmime_mac.cpp
+++ b/src/gui/kernel/qmime_mac.cpp
@@ -431,8 +431,8 @@ QVariant QMacPasteboardMimeUnicodeText::convertToMime(const QString &mimetype, Q
                                              firstData.size(), CFStringGetSystemEncoding(), false));
         ret = QString(str);
     } else if (flavor == QLatin1String("public.utf16-plain-text")) {
-        ret = QString::fromUtf16(reinterpret_cast<const ushort *>(firstData.constData()),
-                                 firstData.size() / sizeof(ushort));
+        ret = QString(reinterpret_cast<const QChar *>(firstData.constData()),
+                      firstData.size() / sizeof(QChar));
     } else {
         qWarning("QMime::convertToMime: unhandled mimetype: %s", qPrintable(mimetype));
     }