Introduce std::string conversion to QByteArray

Add conversion methods similar to those in QString to QByteArray. This
is often more useful than the QString version since std::string like
QByteArray are byte arrays.

[ChangeLog][QtCore][QByteArray] Added convenience methods to convert
directly to and from std::string.

Change-Id: I92c29d4bb1d9e06a667dd9cdd936970e2d272006
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>

src/corelib/tools/qbytearray.cpp

@@ -4189,6 +4189,27 @@ QByteArray QByteArray::fromPercentEncoding(const QByteArray &input, char percent
     return tmp;
 }
 
+/*! \fn QByteArray QByteArray::fromStdString(const std::string &str)
+    \since 5.4
+
+    Returns a copy of the \a str string as a QByteArray.
+
+    \sa toStdString(), QString::fromStdString()
+*/
+
+/*!
+    \fn std::string QByteArray::toStdString() const
+    \since 5.4
+
+    Returns a std::string object with the data contained in this
+    QByteArray.
+
+    This operator is mostly useful to pass a QByteArray to a function
+    that accepts a std::string object.
+
+    \sa fromStdString(), QString::toStdString()
+*/
+
 /*! \fn QByteArray QByteArray::fromCFData(CFDataRef data)
     \since 5.3
 

src/corelib/tools/qbytearray.h

@@ -50,6 +50,8 @@
 #include <string.h>
 #include <stdarg.h>
 
+#include <string>
+
 #ifdef truncate
 #error qbytearray.h must be included before any header file that defines truncate
 #endif
@@ -397,6 +399,9 @@ public:
     void push_front(const char *c);
     void push_front(const QByteArray &a);
 
+    static inline QByteArray fromStdString(const std::string &s);
+    inline std::string toStdString() const;
+
     inline int count() const { return d->size; }
     int length() const { return d->size; }
     bool isNull() const;
@@ -620,6 +625,11 @@ inline QByteArray &QByteArray::setNum(uint n, int base)
 inline QByteArray &QByteArray::setNum(float n, char f, int prec)
 { return setNum(double(n),f,prec); }
 
+inline std::string QByteArray::toStdString() const
+{ return std::string(constData(), length()); }
+
+inline QByteArray QByteArray::fromStdString(const std::string &s)
+{ return QByteArray(s.data(), int(s.size())); }
 
 #if !defined(QT_NO_DATASTREAM) || (defined(QT_BOOTSTRAPPED) && !defined(QT_BUILD_QMAKE))
 Q_CORE_EXPORT QDataStream &operator<<(QDataStream &, const QByteArray &);

src/corelib/tools/qstring.cpp

@@ -1330,7 +1330,7 @@ const QString::Null QString::null = { };
     This constructor is only available if Qt is configured with STL
     compatibility enabled.
 
-    \sa fromLatin1(), fromLocal8Bit(), fromUtf8()
+    \sa fromLatin1(), fromLocal8Bit(), fromUtf8(), QByteArray::fromStdString()
 */
 
 /*! \fn QString QString::fromStdWString(const std::wstring &str)
@@ -7748,7 +7748,7 @@ bool QString::isRightToLeft() const
     If the QString contains non-Latin1 Unicode characters, using this
     can lead to loss of information.
 
-    \sa toLatin1(), toUtf8(), toLocal8Bit()
+    \sa toLatin1(), toUtf8(), toLocal8Bit(), QByteArray::toStdString()
 */
 
 /*!

src/corelib/tools/qstring.h

@@ -1222,7 +1222,7 @@ inline QT_ASCII_CAST_WARN const QString operator+(const QString &s, const QByteA
 #endif // QT_USE_QSTRINGBUILDER
 
 inline std::string QString::toStdString() const
-{ const QByteArray asc = toUtf8(); return std::string(asc.constData(), asc.length()); }
+{ return toUtf8().toStdString(); }
 
 inline QString QString::fromStdString(const std::string &s)
 { return fromUtf8(s.data(), int(s.size())); }

tests/auto/corelib/tools/qbytearray/tst_qbytearray.cpp

@@ -153,6 +153,8 @@ private slots:
 #endif
 
     void macTypes();
+
+    void stdString();
 };
 
 static const struct StaticByteArrays {
@@ -2007,6 +2009,23 @@ void tst_QByteArray::macTypes()
 #endif
 }
 
+void tst_QByteArray::stdString()
+{
+    std::string stdstr( "QByteArray" );
+
+    const QByteArray stlqt = QByteArray::fromStdString(stdstr);
+    QCOMPARE(stlqt.length(), int(stdstr.length()));
+    QCOMPARE(stlqt.data(), stdstr.c_str());
+    QCOMPARE(stlqt.toStdString(), stdstr);
+
+    std::string utf8str( "Nøt æscii" );
+    const QByteArray u8 = QByteArray::fromStdString(utf8str);
+    const QByteArray l1 = QString::fromUtf8(u8).toLatin1();
+    std::string l1str = l1.toStdString();
+    QVERIFY(l1str.length() < utf8str.length());
+}
+
+
 const char globalChar = '1';
 
 QTEST_MAIN(tst_QByteArray)