From 0a4f6af142c57929bd743f3e95e25ada8642e9e4 Mon Sep 17 00:00:00 2001
From: Olivier Goffart <olivier.goffart@nokia.com>
Date: Wed, 6 Apr 2011 13:01:48 +0200
Subject: QStringBuilder: add operator += for QString and QByteArray

Optimize cases when we have.
string += someString + someOtherString
Avoid the allocation of one temporary string.

Behaviour change:
byteArray += someString + QByteArray("foo\0bar", 7)
before, the array would end at foo because of the conversion to string

Reviewed-by: hjk
---
 src/corelib/tools/qstring.h                  |  3 +++
 src/corelib/tools/qstringbuilder.h           | 29 ++++++++++++++++++++++++
 tests/auto/qstringbuilder1/stringbuilder.cpp | 33 ++++++++++++++++++++++++++++
 3 files changed, 65 insertions(+)

diff --git a/src/corelib/tools/qstring.h b/src/corelib/tools/qstring.h
index b54258f..002e516 100644
--- a/src/corelib/tools/qstring.h
+++ b/src/corelib/tools/qstring.h
@@ -485,6 +485,9 @@ public:
     const_iterator constEnd() const;
 
     // STL compatibility
+    typedef const QChar & const_reference;
+    typedef QChar & reference;
+    typedef QChar value_type;
     inline void push_back(QChar c) { append(c); }
     inline void push_back(const QString &s) { append(s); }
     inline void push_front(QChar c) { prepend(c); }
diff --git a/src/corelib/tools/qstringbuilder.h b/src/corelib/tools/qstringbuilder.h
index 260b574..2d3475f 100644
--- a/src/corelib/tools/qstringbuilder.h
+++ b/src/corelib/tools/qstringbuilder.h
@@ -419,6 +419,35 @@ operator+(const A &a, const B &b)
 }
 #endif
 
+template <typename A, typename B>
+QByteArray &operator+=(QByteArray &a, const QStringBuilder<A, B> &b)
+{
+#ifndef QT_NO_CAST_TO_ASCII
+    if (sizeof(typename QConcatenable< QStringBuilder<A, B> >::ConvertTo::value_type) == sizeof(QChar)) {
+        //it is not save to optimize as in utf8 it is not possible to compute the size
+        return a += QString(b);
+    }
+#endif
+    int len = a.size() + QConcatenable< QStringBuilder<A, B> >::size(b);
+    a.reserve(len);
+    char *it = a.data() + a.size();
+    QConcatenable< QStringBuilder<A, B> >::appendTo(b, it);
+    a.resize(len); //we need to resize after the appendTo for the case str+=foo+str
+    return a;
+}
+
+template <typename A, typename B>
+QString &operator+=(QString &a, const QStringBuilder<A, B> &b)
+{
+    int len = a.size() + QConcatenable< QStringBuilder<A, B> >::size(b);
+    a.reserve(len);
+    QChar *it = a.data() + a.size();
+    QConcatenable< QStringBuilder<A, B> >::appendTo(b, it);
+    a.resize(it - a.constData()); //may be smaller than len if there was conversion from utf8
+    return a;
+}
+
+
 QT_END_NAMESPACE
 
 QT_END_HEADER
diff --git a/tests/auto/qstringbuilder1/stringbuilder.cpp b/tests/auto/qstringbuilder1/stringbuilder.cpp
index 3c8ddc2..035a1f4 100644
--- a/tests/auto/qstringbuilder1/stringbuilder.cpp
+++ b/tests/auto/qstringbuilder1/stringbuilder.cpp
@@ -163,4 +163,37 @@ void runScenario()
         QCOMPARE(r, r2);
     }
 
+    //operator QString  +=
+    {
+        QString str = QString::fromUtf8(UTF8_LITERAL);
+        str +=  QLatin1String(LITERAL) P str;
+        QCOMPARE(str, QString::fromUtf8(UTF8_LITERAL LITERAL UTF8_LITERAL));
+#ifndef QT_NO_CAST_FROM_ASCII
+        str = (QString::fromUtf8(UTF8_LITERAL) += QLatin1String(LITERAL) P UTF8_LITERAL);
+        QCOMPARE(str, QString::fromUtf8(UTF8_LITERAL LITERAL UTF8_LITERAL));
+#endif
+    }
+
+    //operator QByteArray  +=
+    {
+        QByteArray ba = UTF8_LITERAL;
+        ba +=  QByteArray(LITERAL) P UTF8_LITERAL;
+        QCOMPARE(ba, QByteArray(UTF8_LITERAL LITERAL UTF8_LITERAL));
+        ba += LITERAL P QByteArray::fromRawData(UTF8_LITERAL_EXTRA, UTF8_LITERAL_LEN);
+        QCOMPARE(ba, QByteArray(UTF8_LITERAL LITERAL UTF8_LITERAL LITERAL UTF8_LITERAL));
+        QByteArray withZero = QByteArray(LITERAL "\0" LITERAL, LITERAL_LEN*2+1);
+        QByteArray ba2 = withZero;
+        ba2 += ba2 P withZero;
+        QCOMPARE(ba2, QByteArray(withZero + withZero + withZero));
+#ifndef QT_NO_CAST_TO_ASCII
+        ba = UTF8_LITERAL;
+        ba2 = (ba += QLatin1String(LITERAL) + QString::fromUtf8(UTF8_LITERAL));
+        QCOMPARE(ba2, ba);
+        QCOMPARE(ba, QByteArray(UTF8_LITERAL LITERAL UTF8_LITERAL));
+        ba = UTF8_LITERAL;
+        ba += QLatin1String(LITERAL) P withZero;
+        QCOMPARE(ba, QByteArray(UTF8_LITERAL LITERAL + withZero));
+#endif
+    }
+
 }
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