1 files changed, 5 insertions, 19 deletions
diff --git a/src/corelib/tools/qstringbuilder.cpp b/src/corelib/tools/qstringbuilder.cpp
index eba939a413..de12de19cb 100644
--- a/src/corelib/tools/qstringbuilder.cpp
+++ b/src/corelib/tools/qstringbuilder.cpp
@@ -39,6 +39,7 @@
 
 #include "qstringbuilder.h"
 #include <QtCore/qtextcodec.h>
+#include <private/qutfcodec_p.h>
 
 QT_BEGIN_NAMESPACE
 
@@ -107,29 +108,14 @@ QT_BEGIN_NAMESPACE
 /*!
     \internal
  */
-void QAbstractConcatenable::convertFromAscii(const char *a, int len, QChar *&out)
+void QAbstractConcatenable::convertFromAscii(const char *a, int len, QChar *&out) Q_DECL_NOTHROW
 {
-    if (len == -1) {
+    if (Q_UNLIKELY(len == -1)) {
         if (!a)
             return;
-        while (*a && uchar(*a) < 0x80U)
-            *out++ = QLatin1Char(*a++);
-        if (!*a)
-            return;
-    } else {
-        int i;
-        for (i = 0; i < len && uchar(a[i]) < 0x80U; ++i)
-            *out++ = QLatin1Char(a[i]);
-        if (i == len)
-            return;
-        a += i;
-        len -= i;
+        len = int(strlen(a));
     }
-
-    // we need to complement with UTF-8 appending
-    QString tmp = QString::fromUtf8(a, len);
-    memcpy(out, reinterpret_cast<const char *>(tmp.constData()), sizeof(QChar) * tmp.size());
-    out += tmp.size();
+    out = QUtf8::convertToUnicode(out, a, len);
 }
 
 QT_END_NAMESPACE