1 files changed, 16 insertions, 22 deletions

diff --git a/src/corelib/tools/qchar.cpp b/src/corelib/tools/qchar.cpp
index 88053d618..458a3830b 100644
--- a/src/corelib/tools/qchar.cpp
+++ b/src/corelib/tools/qchar.cpp
@@ -1421,16 +1421,15 @@ QDataStream &operator>>(QDataStream &in, QChar &chr)
 // ---------------------------------------------------------------------------
 
 
-static QString decomposeHelper
-    (const QString &str, bool canonical, QChar::UnicodeVersion version)
+static void decomposeHelper(QString *str, bool canonical, QChar::UnicodeVersion version, int from)
 {
     unsigned short buffer[3];
 
-    QString s = str;
+    QString &s = *str;
 
-    const unsigned short *utf16 = s.utf16();
+    const unsigned short *utf16 = reinterpret_cast<unsigned short *>(s.data());
     const unsigned short *uc = utf16 + s.length();
-    while (uc != utf16) {
+    while (uc != utf16 + from) {
         uint ucs4 = *(--uc);
         if (QChar(ucs4).isLowSurrogate() && uc != utf16) {
             ushort high = *(uc - 1);
@@ -1450,11 +1449,9 @@ static QString decomposeHelper
         s.replace(uc - utf16, ucs4 > 0x10000 ? 2 : 1, (const QChar *)d, length);
         // since the insert invalidates the pointers and we do decomposition recursive
         int pos = uc - utf16;
-        utf16 = s.utf16();
+        utf16 = reinterpret_cast<unsigned short *>(s.data());
         uc = utf16 + pos + length;
     }
-
-    return s;
 }
 
 
@@ -1489,21 +1486,21 @@ static ushort ligatureHelper(ushort u1, ushort u2)
     return 0;
 }
 
-static QString composeHelper(const QString &str)
+static void composeHelper(QString *str, int from)
 {
-    QString s = str;
+    QString &s = *str;
 
-    if (s.length() < 2)
-        return s;
+    if (s.length() - from < 2)
+        return;
 
     // the loop can partly ignore high Unicode as all ligatures are in the BMP
     int starter = 0;
     int lastCombining = 0;
-    int pos = 0;
+    int pos = from;
     while (pos < s.length()) {
-        uint uc = s.utf16()[pos];
+        uint uc = s.at(pos).unicode();
         if (QChar(uc).isHighSurrogate() && pos < s.length()-1) {
-            ushort low = s.utf16()[pos+1];
+            ushort low = s.at(pos+1).unicode();
             if (QChar(low).isLowSurrogate()) {
                 uc = QChar::surrogateToUcs4(uc, low);
                 ++pos;
@@ -1512,7 +1509,7 @@ static QString composeHelper(const QString &str)
         int combining = QChar::combiningClass(uc);
         if (starter == pos - 1 || combining > lastCombining) {
             // allowed to form ligature with S
-            QChar ligature = ligatureHelper(s.utf16()[starter], uc);
+            QChar ligature = ligatureHelper(s.at(starter).unicode(), uc);
             if (ligature.unicode()) {
                 s[starter] = ligature;
                 s.remove(pos, 1);
@@ -1524,16 +1521,14 @@ static QString composeHelper(const QString &str)
         lastCombining = combining;
         ++pos;
     }
-    return s;
 }
 
 
-static QString canonicalOrderHelper
-    (const QString &str, QChar::UnicodeVersion version)
+static void canonicalOrderHelper(QString *str, QChar::UnicodeVersion version, int from)
 {
-    QString s = str;
+    QString &s = *str;
     const int l = s.length()-1;
-    int pos = 0;
+    int pos = from;
     while (pos < l) {
         int p2 = pos+1;
         uint u1 = s.at(pos).unicode();
@@ -1593,7 +1588,6 @@ static QString canonicalOrderHelper
                 ++pos;
         }
     }
-    return s;
 }
 
 int QT_FASTCALL QUnicodeTables::script(unsigned int uc)