QImageReader/Writer: replace dubious use of QSet<QByteArray> with QList

The code populated QSets with some strings and went
on to copy the values to QLists. Since QSet is unordered_set, those
lists were not sorted, so the code did that manually.

Since QSet is a node-based container and not even an ordered one,
the code pays a hefty price just for ensuring uniqueness of values
prior to sorting.

The new code just crams everything into lists, duplicates and all,
then sorts the lists and only then removes duplicates using
std::unique.

Saves 3376B in text size on Linux AMD64 GCC 4.9-trunk release
stripped QtGui.

Change-Id: Ifee931102c01b7505c712cebf4effc37e94165b0
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>

src/gui/image/qimagereader.cpp

@@ -125,7 +125,6 @@
 #include <qimageiohandler.h>
 #include <qlist.h>
 #include <qrect.h>
-#include <qset.h>
 #include <qsize.h>
 #include <qcolor.h>
 #include <qvariant.h>
@@ -1444,11 +1443,11 @@ QByteArray QImageReader::imageFormat(QIODevice *device)
 #ifndef QT_NO_IMAGEFORMATPLUGIN
 void supportedImageHandlerFormats(QFactoryLoader *loader,
                                   QImageIOPlugin::Capability cap,
-                                  QSet<QByteArray> *result);
+                                  QList<QByteArray> *result);
 
 void supportedImageHandlerMimeTypes(QFactoryLoader *loader,
                                   QImageIOPlugin::Capability cap,
-                                  QSet<QByteArray> *result);
+                                  QList<QByteArray> *result);
 #endif
 
 /*!
@@ -1481,7 +1480,7 @@ void supportedImageHandlerMimeTypes(QFactoryLoader *loader,
 
 QList<QByteArray> QImageReader::supportedImageFormats()
 {
-    QSet<QByteArray> formats;
+    QList<QByteArray> formats;
     for (int i = 0; i < _qt_NumFormats; ++i)
         formats << _qt_BuiltInFormats[i].extension;
 
@@ -1489,12 +1488,9 @@ QList<QByteArray> QImageReader::supportedImageFormats()
     supportedImageHandlerFormats(loader(), QImageIOPlugin::CanRead, &formats);
 #endif // QT_NO_IMAGEFORMATPLUGIN
 
-    QList<QByteArray> sortedFormats;
+    std::sort(formats.begin(), formats.end());
-    for (QSet<QByteArray>::ConstIterator it = formats.constBegin(); it != formats.constEnd(); ++it)
+    formats.erase(std::unique(formats.begin(), formats.end()), formats.end());
-        sortedFormats << *it;
+    return formats;
-
-    std::sort(sortedFormats.begin(), sortedFormats.end());
-    return sortedFormats;
 }
 
 /*!
@@ -1508,7 +1504,7 @@ QList<QByteArray> QImageReader::supportedImageFormats()
 
 QList<QByteArray> QImageReader::supportedMimeTypes()
 {
-    QSet<QByteArray> mimeTypes;
+    QList<QByteArray> mimeTypes;
     for (int i = 0; i < _qt_NumFormats; ++i)
         mimeTypes << _qt_BuiltInFormats[i].mimeType;
 
@@ -1516,12 +1512,9 @@ QList<QByteArray> QImageReader::supportedMimeTypes()
     supportedImageHandlerMimeTypes(loader(), QImageIOPlugin::CanRead, &mimeTypes);
 #endif // QT_NO_IMAGEFORMATPLUGIN
 
-    QList<QByteArray> sortedMimeTypes;
+    std::sort(mimeTypes.begin(), mimeTypes.end());
-    for (QSet<QByteArray>::ConstIterator it = mimeTypes.constBegin(); it != mimeTypes.constEnd(); ++it)
+    mimeTypes.erase(std::unique(mimeTypes.begin(), mimeTypes.end()), mimeTypes.end());
-        sortedMimeTypes << *it;
+    return mimeTypes;
-
-    std::sort(sortedMimeTypes.begin(), sortedMimeTypes.end());
-    return sortedMimeTypes;
 }
 
 QT_END_NAMESPACE

src/gui/image/qimagewriter.cpp

@@ -678,7 +678,7 @@ bool QImageWriter::supportsOption(QImageIOHandler::ImageOption option) const
 #ifndef QT_NO_IMAGEFORMATPLUGIN
 void supportedImageHandlerFormats(QFactoryLoader *loader,
                                   QImageIOPlugin::Capability cap,
-                                  QSet<QByteArray> *result)
+                                  QList<QByteArray> *result)
 {
     typedef QMultiMap<int, QString> PluginKeyMap;
     typedef PluginKeyMap::const_iterator PluginKeyMapConstIterator;
@@ -687,6 +687,7 @@ void supportedImageHandlerFormats(QFactoryLoader *loader,
     const PluginKeyMapConstIterator cend = keyMap.constEnd();
     int i = -1;
     QImageIOPlugin *plugin = 0;
+    result->reserve(result->size() + keyMap.size());
     for (PluginKeyMapConstIterator it = keyMap.constBegin(); it != cend; ++it) {
         if (it.key() != i) {
             i = it.key();
@@ -694,13 +695,13 @@ void supportedImageHandlerFormats(QFactoryLoader *loader,
         }
         const QByteArray key = it.value().toLatin1();
         if (plugin && (plugin->capabilities(0, key) & cap) != 0)
-            result->insert(key);
+            result->append(key);
     }
 }
 
 void supportedImageHandlerMimeTypes(QFactoryLoader *loader,
                                     QImageIOPlugin::Capability cap,
-                                    QSet<QByteArray> *result)
+                                    QList<QByteArray> *result)
 {
     QList<QJsonObject> metaDataList = loader->metaData();
 
@@ -713,7 +714,7 @@ void supportedImageHandlerMimeTypes(QFactoryLoader *loader,
         const int keyCount = keys.size();
         for (int k = 0; k < keyCount; ++k) {
             if (plugin && (plugin->capabilities(0, keys.at(k).toString().toLatin1()) & cap) != 0)
-                result->insert(mimeTypes.at(k).toString().toLatin1());
+                result->append(mimeTypes.at(k).toString().toLatin1());
         }
     }
 }
@@ -746,7 +747,7 @@ void supportedImageHandlerMimeTypes(QFactoryLoader *loader,
 */
 QList<QByteArray> QImageWriter::supportedImageFormats()
 {
-    QSet<QByteArray> formats;
+    QList<QByteArray> formats;
 #ifndef QT_NO_IMAGEFORMAT_BMP
     formats << "bmp";
 #endif
@@ -770,12 +771,9 @@ QList<QByteArray> QImageWriter::supportedImageFormats()
     supportedImageHandlerFormats(loader(), QImageIOPlugin::CanWrite, &formats);
 #endif // QT_NO_IMAGEFORMATPLUGIN
 
-    QList<QByteArray> sortedFormats;
+    std::sort(formats.begin(), formats.end());
-    for (QSet<QByteArray>::ConstIterator it = formats.constBegin(); it != formats.constEnd(); ++it)
+    formats.erase(std::unique(formats.begin(), formats.end()), formats.end());
-        sortedFormats << *it;
+    return formats;
-
-    std::sort(sortedFormats.begin(), sortedFormats.end());
-    return sortedFormats;
 }
 
 /*!
@@ -788,7 +786,7 @@ QList<QByteArray> QImageWriter::supportedImageFormats()
 */
 QList<QByteArray> QImageWriter::supportedMimeTypes()
 {
-    QSet<QByteArray> mimeTypes;
+    QList<QByteArray> mimeTypes;
 #ifndef QT_NO_IMAGEFORMAT_BMP
     mimeTypes << "image/bmp";
 #endif
@@ -814,12 +812,9 @@ QList<QByteArray> QImageWriter::supportedMimeTypes()
     supportedImageHandlerMimeTypes(loader(), QImageIOPlugin::CanWrite, &mimeTypes);
 #endif // QT_NO_IMAGEFORMATPLUGIN
 
-    QList<QByteArray> sortedMimeTypes;
+    std::sort(mimeTypes.begin(), mimeTypes.end());
-    for (QSet<QByteArray>::ConstIterator it = mimeTypes.constBegin(); it != mimeTypes.constEnd(); ++it)
+    mimeTypes.erase(std::unique(mimeTypes.begin(), mimeTypes.end()), mimeTypes.end());
-        sortedMimeTypes << *it;
+    return mimeTypes;
-
-    std::sort(sortedMimeTypes.begin(), sortedMimeTypes.end());
-    return sortedMimeTypes;
 }
 
 QT_END_NAMESPACE