Add a QHostAddress::toIPv4Address overload taking a bool *ok

This allows one to check whether the conversion is successful without
checking for the return result, as the value of 0 represents the valid
IPv4 address 0.0.0.0.

Change-Id: I637fe55583f2255c85b0d955e5886b61494e0c7c
Reviewed-by: Richard J. Moore <rich@kde.org>

src/network/kernel/qhostaddress.cpp

@@ -633,8 +633,32 @@ void QHostAddress::setAddress(const struct sockaddr *sockaddr)
     \sa toString()
 */
 quint32 QHostAddress::toIPv4Address() const
+{
+    return toIPv4Address(Q_NULLPTR);
+}
+
+/*!
+    Returns the IPv4 address as a number.
+
+    For example, if the address is 127.0.0.1, the returned value is
+    2130706433 (i.e. 0x7f000001).
+
+    This value is valid if the protocol() is
+    \l{QAbstractSocket::}{IPv4Protocol},
+    or if the protocol is
+    \l{QAbstractSocket::}{IPv6Protocol},
+    and the IPv6 address is an IPv4 mapped address. (RFC4291). In those
+    cases, \a ok will be set to true. Otherwise, it will be set to false.
+
+    \sa toString()
+*/
+quint32 QHostAddress::toIPv4Address(bool *ok) const
 {
     QT_ENSURE_PARSED(this);
+    quint32 dummy;
+    if (ok)
+        *ok = d->protocol == QAbstractSocket::IPv4Protocol || d->protocol == QAbstractSocket::AnyIPProtocol
+              || (d->protocol == QAbstractSocket::IPv6Protocol && convertToIpv4(dummy, d->a6));
     return d->a;
 }
 

src/network/kernel/qhostaddress.h

@@ -93,7 +93,8 @@ public:
     bool setAddress(const QString &address);
 
     QAbstractSocket::NetworkLayerProtocol protocol() const;
-    quint32 toIPv4Address() const;
+    quint32 toIPv4Address() const; // ### Qt6: merge with next overload
+    quint32 toIPv4Address(bool *ok) const;
     Q_IPV6ADDR toIPv6Address() const;
 
     QString toString() const;

tests/auto/network/kernel/qhostaddress/tst_qhostaddress.cpp

@@ -83,6 +83,8 @@ private slots:
     void isInSubnet();
     void isLoopback_data();
     void isLoopback();
+    void convertv4v6_data();
+    void convertv4v6();
 };
 
 QT_BEGIN_NAMESPACE
@@ -662,5 +664,51 @@ void tst_QHostAddress::isLoopback()
     QCOMPARE(address.isLoopback(), result);
 }
 
+void tst_QHostAddress::convertv4v6_data()
+{
+    QTest::addColumn<QHostAddress>("source");
+    QTest::addColumn<int>("protocol");
+    QTest::addColumn<QHostAddress>("result");
+
+    QTest::newRow("any-to-v4") << QHostAddress(QHostAddress::Any) << 4 << QHostAddress(QHostAddress::AnyIPv4);
+    QTest::newRow("any-to-v6") << QHostAddress(QHostAddress::Any) << 6 << QHostAddress(QHostAddress::AnyIPv6);
+    QTest::newRow("anyv4-to-v6") << QHostAddress(QHostAddress::AnyIPv4) << 6 << QHostAddress(QHostAddress::AnyIPv6);
+    QTest::newRow("anyv6-to-v4") << QHostAddress(QHostAddress::AnyIPv6) << 4 << QHostAddress(QHostAddress::AnyIPv4);
+
+    QTest::newRow("v4mapped-to-v4") << QHostAddress("::ffff:192.0.2.1") << 4 << QHostAddress("192.0.2.1");
+    QTest::newRow("v4-to-v4mapped") << QHostAddress("192.0.2.1") << 6 << QHostAddress("::ffff:192.0.2.1");
+
+    // we won't convert 127.0.0.1 to ::1 or vice-versa:
+    // you can connect to a v4 server socket with ::ffff:127.0.0.1, but not with ::1
+    QTest::newRow("localhost-to-v4mapped") << QHostAddress(QHostAddress::LocalHost) << 6 << QHostAddress("::ffff:127.0.0.1");
+    QTest::newRow("v4mapped-to-localhost") << QHostAddress("::ffff:127.0.0.1") << 4 << QHostAddress(QHostAddress::LocalHost);
+
+    // in turn, that means localhost6 doesn't convert to v4
+    QTest::newRow("localhost6-to-v4") << QHostAddress(QHostAddress::LocalHostIPv6) << 4 << QHostAddress();
+
+    // some other v6 addresses that won't convert to v4
+    QTest::newRow("v4compat-to-v4") << QHostAddress("::192.0.2.1") << 4 << QHostAddress();
+    QTest::newRow("localhostv4compat-to-v4") << QHostAddress("::127.0.0.1") << 4 << QHostAddress();
+    QTest::newRow("v6global-to-v4") << QHostAddress("2001:db8::1") << 4 << QHostAddress();
+    QTest::newRow("v6multicast-to-v4") << QHostAddress("ff02::1") << 4 << QHostAddress();
+}
+
+void tst_QHostAddress::convertv4v6()
+{
+    QFETCH(QHostAddress, source);
+    QFETCH(int, protocol);
+    QFETCH(QHostAddress, result);
+
+    if (protocol == 4) {
+        bool ok;
+        quint32 v4 = source.toIPv4Address(&ok);
+        QCOMPARE(ok, result.protocol() == QAbstractSocket::IPv4Protocol);
+        if (ok)
+            QCOMPARE(QHostAddress(v4), result);
+    } else if (protocol == 6) {
+        QCOMPARE(QHostAddress(source.toIPv6Address()), result);
+    }
+}
+
 QTEST_MAIN(tst_QHostAddress)
 #include "tst_qhostaddress.moc"