Implement QAudioDeviceInfo operator==/!=

Compares some of the useful parts, but perhaps should be made more
tolerant.

Also refactored the auto test to properly skip if there are no
(output) devices, rather than manually skip.

Task-number: QTBUG-13723
Change-Id: I3b83f87a440a83f4237fa119a23009bc99e7626a
Reviewed-by: Jonas Rabbe <jonas.rabbe@nokia.com>
Reviewed-by: Dmytro Poplavskiy <dmytro.poplavskiy@nokia.com>

src/multimedia/audio/qaudiodeviceinfo.cpp

@@ -186,7 +186,31 @@ QAudioDeviceInfo& QAudioDeviceInfo::operator=(const QAudioDeviceInfo &other)
 }
 
 /*!
-    Returns whether this QAudioDeviceInfo object holds a device definition.
+    Returns true if this QAudioDeviceInfo class represents the
+    same audio device as \a other.
+*/
+bool QAudioDeviceInfo::operator ==(const QAudioDeviceInfo &other) const
+{
+    if (d == other.d)
+        return true;
+    if (d->realm == other.d->realm
+            && d->mode == other.d->mode
+            && d->handle == other.d->handle
+            && deviceName() == other.deviceName())
+        return true;
+}
+
+/*!
+    Returns true if this QAudioDeviceInfo class represents a
+    different audio device than \a other
+*/
+bool QAudioDeviceInfo::operator !=(const QAudioDeviceInfo &other) const
+{
+    return !operator==(other);
+}
+
+/*!
+    Returns whether this QAudioDeviceInfo object holds a valid device definition.
 */
 bool QAudioDeviceInfo::isNull() const
 {

src/multimedia/audio/qaudiodeviceinfo.h

@@ -76,6 +76,9 @@ public:
 
     QAudioDeviceInfo& operator=(const QAudioDeviceInfo& other);
 
+    bool operator==(const QAudioDeviceInfo &other) const;
+    bool operator!=(const QAudioDeviceInfo &other) const;
+
     bool isNull() const;
 
     QString deviceName() const;