Removed QDirPrivate layer of indirection

Merged QDirPrivate with QDirPrivate::Data, as QDirPrivate served no
purpose by itself, only adding an additional layer of indirection to the
potentially shared private data, and an unnecessary allocation.

Now, QDir holds a QSharedDataPointer to its private data. Private data
will be shared among copied instances with COW semantics. Still, this
sharing is very limited as plenty of regular use cases will cause the
shared data to detach, such as refreshing the file lists.

As the use QSharedDataPointer breaks usage of the Q_DECLARE_PRIVATE
macro, we manually define the d_func'tions. Non-const d_func detaches on
shared data. A detach function was added to the public interface to
support this. (On a side note, QFileInfo already exposes a similar
detach function).

As much as possible, detach is handled implicitly inside the Q_D macro,
through the d_func() non-const overload.  On the other hand, implicit
creation of file engines through detach was made explicit with a call to
a new initFileEngine function.

Reviewed-by: Thomas Zander

2 files changed, 216 insertions, 229 deletions

diff --git a/src/corelib/io/qdir.cpp b/src/corelib/io/qdir.cpp
index 0644675..de95a40 100644
--- a/src/corelib/io/qdir.cpp
+++ b/src/corelib/io/qdir.cpp
@@ -82,117 +82,105 @@ static QString driveSpec(const QString &path)
 
 //************* QDirPrivate
 class QDirPrivate
+    : public QSharedData
 {
-    friend struct QScopedPointerDeleter<QDirPrivate>;
-
 public:
-    QDirPrivate(const QDir *copy = 0);
-    ~QDirPrivate();
-
-    struct Data {
-        inline Data()
-            : ref(1),
+    QDirPrivate()
+        : QSharedData()
 #ifdef QT3_SUPPORT
-            filterSepChar(0), matchAllDirs(false),
+        , filterSepChar(0)
+        , matchAllDirs(false)
 #endif
-            fileEngine(0), listsDirty(1)
-        {}
-        inline Data(const Data &copy)
-            : ref(1), path(copy.path), nameFilters(copy.nameFilters), sort(copy.sort),
-              filters(copy.filters),
+        , fileEngine(0)
+        , listsDirty(1)
+    {
+    }
+
+    QDirPrivate(const QDirPrivate &copy)
+        : QSharedData(copy)
+        , path(copy.path)
+        , nameFilters(copy.nameFilters)
+        , sort(copy.sort)
+        , filters(copy.filters)
 #ifdef QT3_SUPPORT
-              filterSepChar(copy.filterSepChar), matchAllDirs(copy.matchAllDirs),
+        , filterSepChar(copy.filterSepChar)
+        , matchAllDirs(copy.matchAllDirs)
 #endif
-              fileEngine(0), listsDirty(1)
-        {}
-        inline ~Data()
-        { delete fileEngine; }
-
-        void updateFileLists() const;
-        static void sortFileList(QDir::SortFlags, QFileInfoList &, QStringList *, QFileInfoList *);
-
-        static inline QChar getFilterSepChar(const QString &nameFilter)
-        {
-            QChar sep(QLatin1Char(';'));
-            int i = nameFilter.indexOf(sep, 0);
-            if (i == -1 && nameFilter.indexOf(QLatin1Char(' '), 0) != -1)
-                sep = QChar(QLatin1Char(' '));
-            return sep;
-        }
+        , fileEngine(0)
+        , listsDirty(1)
+    {
+    }
 
-        static inline QStringList splitFilters(const QString &nameFilter, QChar sep = 0)
-        {
-            if (sep == 0)
-                sep = getFilterSepChar(nameFilter);
-            QStringList ret = nameFilter.split(sep);
-            for (int i = 0; i < ret.count(); ++i)
-                ret[i] = ret[i].trimmed();
-            return ret;
-        }
+    ~QDirPrivate()
+    {
+        delete fileEngine;
+    }
 
-        static void detach(QDirPrivate::Data *&data, bool createFileEngine = true);
+    void initFileEngine();
+    void updateFileLists() const;
 
-        inline void setPath(QString p)
-        {
-            if ((p.endsWith(QLatin1Char('/')) || p.endsWith(QLatin1Char('\\')))
-                    && p.length() > 1) {
-#if defined(Q_OS_WIN) || defined(Q_OS_SYMBIAN)
-                if (!(p.length() == 3 && p.at(1) == QLatin1Char(':')))
-#endif
-                    p.truncate(p.length() - 1);
-            }
+    static void sortFileList(QDir::SortFlags, QFileInfoList &, QStringList *, QFileInfoList *);
 
-            delete fileEngine;
-            fileEngine = QAbstractFileEngine::create(p);
+    static inline QChar getFilterSepChar(const QString &nameFilter)
+    {
+        QChar sep(QLatin1Char(';'));
+        int i = nameFilter.indexOf(sep, 0);
+        if (i == -1 && nameFilter.indexOf(QLatin1Char(' '), 0) != -1)
+            sep = QChar(QLatin1Char(' '));
+        return sep;
+    }
 
-            // set the path to be the qt friendly version so then we can operate on it using just /
-            path = fileEngine->fileName(QAbstractFileEngine::DefaultName);
-            clear();
-        }
+    static inline QStringList splitFilters(const QString &nameFilter, QChar sep = 0)
+    {
+        if (sep == 0)
+            sep = getFilterSepChar(nameFilter);
+        QStringList ret = nameFilter.split(sep);
+        for (int i = 0; i < ret.count(); ++i)
+            ret[i] = ret[i].trimmed();
+        return ret;
+    }
 
-        inline void clear() {
-            listsDirty = 1;
-            files.clear();
-            fileInfos.clear();
+    inline void setPath(QString p)
+    {
+        if ((p.endsWith(QLatin1Char('/')) || p.endsWith(QLatin1Char('\\')))
+                && p.length() > 1) {
+#if defined(Q_OS_WIN) || defined(Q_OS_SYMBIAN)
+            if (!(p.length() == 3 && p.at(1) == QLatin1Char(':')))
+#endif
+                p.truncate(p.length() - 1);
         }
 
-        mutable QAtomicInt ref;
+        delete fileEngine;
+        fileEngine = QAbstractFileEngine::create(p);
+
+        // set the path to be the qt friendly version so then we can operate on it using just /
+        path = fileEngine->fileName(QAbstractFileEngine::DefaultName);
+        clear();
+    }
 
-        QString path;
-        QStringList nameFilters;
-        QDir::SortFlags sort;
-        QDir::Filters filters;
+    inline void clear() {
+        listsDirty = 1;
+        files.clear();
+        fileInfos.clear();
+    }
+
+    QString path;
+    QStringList nameFilters;
+    QDir::SortFlags sort;
+    QDir::Filters filters;
 
 #ifdef QT3_SUPPORT
-        QChar filterSepChar;
-        bool matchAllDirs;
+    QChar filterSepChar;
+    bool matchAllDirs;
 #endif
-        mutable QAbstractFileEngine *fileEngine;
 
-        mutable uint listsDirty : 1;
-        mutable QStringList files;
-        mutable QFileInfoList fileInfos;
-    } *data;
+    QAbstractFileEngine *fileEngine;
 
+    mutable uint listsDirty : 1;
+    mutable QStringList files;
+    mutable QFileInfoList fileInfos;
 };
 
-QDirPrivate::QDirPrivate(const QDir *copy)
-{
-    if (copy) {
-        copy->d_func()->data->ref.ref();
-        data = copy->d_func()->data;
-    } else {
-        data = new QDirPrivate::Data;
-    }
-}
-
-QDirPrivate::~QDirPrivate()
-{
-    if (!data->ref.deref())
-        delete data;
-    data = 0;
-}
-
 /* For sorting */
 struct QDirSortItem
 {
@@ -273,7 +261,7 @@ bool QDirSortItemComparator::operator()(const QDirSortItem &n1, const QDirSortIt
     return r < 0;
 }
 
-inline void QDirPrivate::Data::sortFileList(QDir::SortFlags sort, QFileInfoList &l,
+inline void QDirPrivate::sortFileList(QDir::SortFlags sort, QFileInfoList &l,
                                       QStringList *names, QFileInfoList *infos)
 {
     // names and infos are always empty lists or 0 here
@@ -304,7 +292,7 @@ inline void QDirPrivate::Data::sortFileList(QDir::SortFlags sort, QFileInfoList
     }
 }
 
-inline void QDirPrivate::Data::updateFileLists() const
+inline void QDirPrivate::updateFileLists() const
 {
     if (listsDirty) {
         QFileInfoList l;
@@ -318,14 +306,11 @@ inline void QDirPrivate::Data::updateFileLists() const
     }
 }
 
-void QDirPrivate::Data::detach(QDirPrivate::Data *&data, bool createFileEngine)
+void QDirPrivate::initFileEngine()
 {
-    qAtomicDetach(data);
-    if (createFileEngine) {
-        QAbstractFileEngine *newFileEngine = QAbstractFileEngine::create(data->path);
-        delete data->fileEngine;
-        data->fileEngine = newFileEngine;
-    }
+    QAbstractFileEngine *newFileEngine = QAbstractFileEngine::create(path);
+    delete fileEngine;
+    fileEngine = newFileEngine;
 }
 
 /*!
@@ -512,11 +497,10 @@ void QDirPrivate::Data::detach(QDirPrivate::Data *&data, bool createFileEngine)
 QDir::QDir(const QString &path) : d_ptr(new QDirPrivate)
 {
     Q_D(QDir);
-    QDirPrivate::Data::detach(d->data, false);
-    d->data->setPath(path.isEmpty() ? QString::fromLatin1(".") : path);
-    d->data->nameFilters = QStringList(QString::fromLatin1("*"));
-    d->data->filters = AllEntries;
-    d->data->sort = SortFlags(Name | IgnoreCase);
+    d->setPath(path.isEmpty() ? QString::fromLatin1(".") : path);
+    d->nameFilters = QStringList(QString::fromLatin1("*"));
+    d->filters = AllEntries;
+    d->sort = SortFlags(Name | IgnoreCase);
 }
 
 /*!
@@ -541,23 +525,22 @@ QDir::QDir(const QString &path, const QString &nameFilter,
            SortFlags sort, Filters filters) : d_ptr(new QDirPrivate)
 {
     Q_D(QDir);
-    QDirPrivate::Data::detach(d->data, false);
-    d->data->setPath(path.isEmpty() ? QString::fromLatin1(".") : path);
-    d->data->nameFilters = QDir::nameFiltersFromString(nameFilter);
-    bool empty = d->data->nameFilters.isEmpty();
+    d->setPath(path.isEmpty() ? QString::fromLatin1(".") : path);
+    d->nameFilters = QDir::nameFiltersFromString(nameFilter);
+    bool empty = d->nameFilters.isEmpty();
     if (!empty) {
         empty = true;
-        for (int i = 0; i < d->data->nameFilters.size(); ++i) {
-            if (!d->data->nameFilters.at(i).isEmpty()) {
+        for (int i = 0; i < d->nameFilters.size(); ++i) {
+            if (!d->nameFilters.at(i).isEmpty()) {
                 empty = false;
                 break;
             }
         }
     }
     if (empty)
-        d->data->nameFilters = QStringList(QString::fromLatin1("*"));
-    d->data->sort = sort;
-    d->data->filters = filters;
+        d->nameFilters = QStringList(QString::fromLatin1("*"));
+    d->sort = sort;
+    d->filters = filters;
 }
 
 /*!
@@ -566,7 +549,8 @@ QDir::QDir(const QString &path, const QString &nameFilter,
 
     \sa operator=()
 */
-QDir::QDir(const QDir &dir) : d_ptr(new QDirPrivate(&dir))
+QDir::QDir(const QDir &dir)
+    : d_ptr(dir.d_ptr)
 {
 }
 
@@ -578,6 +562,11 @@ QDir::~QDir()
 {
 }
 
+void QDir::detach()
+{
+    d_ptr.detach();
+}
+
 /*!
     Sets the path of the directory to \a path. The path is cleaned of
     redundant ".", ".." and of multiple separators. No check is made
@@ -596,9 +585,7 @@ QDir::~QDir()
 */
 void QDir::setPath(const QString &path)
 {
-    Q_D(QDir);
-    QDirPrivate::Data::detach(d->data, false);
-    d->data->setPath(path);
+    d_ptr->setPath(path);
 }
 
 /*!
@@ -614,7 +601,7 @@ void QDir::setPath(const QString &path)
 QString QDir::path() const
 {
     Q_D(const QDir);
-    return d->data->path;
+    return d->path;
 }
 
 /*!
@@ -628,7 +615,7 @@ QString QDir::path() const
 QString QDir::absolutePath() const
 {
     Q_D(const QDir);
-    QString ret = d->data->path;
+    QString ret = d->path;
     if (QDir::isRelativePath(ret))
         ret = absoluteFilePath(QString::fromLatin1(""));
     return cleanPath(ret);
@@ -654,9 +641,9 @@ QString QDir::canonicalPath() const
 {
     Q_D(const QDir);
 
-    if (!d->data->fileEngine)
+    if (!d->fileEngine)
         return QLatin1String("");
-    return cleanPath(d->data->fileEngine->fileName(QAbstractFileEngine::CanonicalName));
+    return cleanPath(d->fileEngine->fileName(QAbstractFileEngine::CanonicalName));
 }
 
 /*!
@@ -673,10 +660,10 @@ QString QDir::canonicalPath() const
 QString QDir::dirName() const
 {
     Q_D(const QDir);
-    int pos = d->data->path.lastIndexOf(QLatin1Char('/'));
+    int pos = d->path.lastIndexOf(QLatin1Char('/'));
     if (pos == -1)
-        return d->data->path;
-    return d->data->path.mid(pos + 1);
+        return d->path;
+    return d->path.mid(pos + 1);
 }
 
 /*!
@@ -694,7 +681,7 @@ QString QDir::filePath(const QString &fileName) const
     if (isAbsolutePath(fileName))
         return QString(fileName);
 
-    QString ret = d->data->path;
+    QString ret = d->path;
     if (!fileName.isEmpty()) {
         if (!ret.isEmpty() && ret[(int)ret.length()-1] != QLatin1Char('/') && fileName[0] != QLatin1Char('/'))
             ret += QLatin1Char('/');
@@ -716,18 +703,18 @@ QString QDir::absoluteFilePath(const QString &fileName) const
     Q_D(const QDir);
     if (isAbsolutePath(fileName))
         return fileName;
-    if (!d->data->fileEngine)
+    if (!d->fileEngine)
         return fileName;
 
     QString ret;
 #ifndef QT_NO_FSFILEENGINE
-    if (isRelativePath(d->data->path)) //get pwd
+    if (isRelativePath(d->path)) //get pwd
         ret = QFSFileEngine::currentPath(fileName);
 #endif
-    if (!d->data->path.isEmpty() && d->data->path != QLatin1String(".")) {
+    if (!d->path.isEmpty() && d->path != QLatin1String(".")) {
         if (!ret.isEmpty() && !ret.endsWith(QLatin1Char('/')))
             ret += QLatin1Char('/');
-        ret += d->data->path;
+        ret += d->path;
     }
     if (!fileName.isEmpty()) {
         if (!ret.isEmpty() && !ret.endsWith(QLatin1Char('/')))
@@ -875,11 +862,12 @@ QString QDir::fromNativeSeparators(const QString &pathName)
 */
 bool QDir::cd(const QString &dirName)
 {
-    Q_D(QDir);
+    // Don't detach just yet.
+    const QDirPrivate * const d = d_ptr.constData();
 
     if (dirName.isEmpty() || dirName == QLatin1String("."))
         return true;
-    QString newPath = d->data->path;
+    QString newPath = d->path;
     if (isAbsolutePath(dirName)) {
         newPath = cleanPath(dirName);
     } else {
@@ -892,7 +880,7 @@ bool QDir::cd(const QString &dirName)
 
         newPath += dirName;
         if (dirName.indexOf(QLatin1Char('/')) >= 0
-            || d->data->path == QLatin1String(".")
+            || d->path == QLatin1String(".")
             || dirName == QLatin1String("..")) {
             newPath = cleanPath(newPath);
             /*
@@ -939,8 +927,7 @@ bool QDir::cdUp()
 QStringList QDir::nameFilters() const
 {
     Q_D(const QDir);
-
-    return d->data->nameFilters;
+    return d->nameFilters;
 }
 
 /*!
@@ -961,10 +948,10 @@ QStringList QDir::nameFilters() const
 void QDir::setNameFilters(const QStringList &nameFilters)
 {
     Q_D(QDir);
+    d->initFileEngine();
+    d->clear();
 
-    QDirPrivate::Data::detach(d->data);
-    d->data->clear();
-    d->data->nameFilters = nameFilters;
+    d->nameFilters = nameFilters;
 }
 
 /*!
@@ -1068,8 +1055,7 @@ QStringList QDir::searchPaths(const QString &prefix)
 QDir::Filters QDir::filter() const
 {
     Q_D(const QDir);
-
-    return d->data->filters;
+    return d->filters;
 }
 
 /*!
@@ -1151,10 +1137,10 @@ QDir::Filters QDir::filter() const
 void QDir::setFilter(Filters filters)
 {
     Q_D(QDir);
+    d->initFileEngine();
+    d->clear();
 
-    QDirPrivate::Data::detach(d->data);
-    d->data->clear();
-    d->data->filters = filters;
+    d->filters = filters;
 }
 
 /*!
@@ -1165,8 +1151,7 @@ void QDir::setFilter(Filters filters)
 QDir::SortFlags QDir::sorting() const
 {
     Q_D(const QDir);
-
-    return d->data->sort;
+    return d->sort;
 }
 
 /*!
@@ -1210,10 +1195,10 @@ QDir::SortFlags QDir::sorting() const
 void QDir::setSorting(SortFlags sort)
 {
     Q_D(QDir);
+    d->initFileEngine();
+    d->clear();
 
-    QDirPrivate::Data::detach(d->data);
-    d->data->clear();
-    d->data->sort = sort;
+    d->sort = sort;
 }
 
 /*!
@@ -1226,9 +1211,8 @@ void QDir::setSorting(SortFlags sort)
 uint QDir::count() const
 {
     Q_D(const QDir);
-
-    d->data->updateFileLists();
-    return d->data->files.count();
+    d->updateFileLists();
+    return d->files.count();
 }
 
 /*!
@@ -1241,9 +1225,8 @@ uint QDir::count() const
 QString QDir::operator[](int pos) const
 {
     Q_D(const QDir);
-
-    d->data->updateFileLists();
-    return d->data->files[pos];
+    d->updateFileLists();
+    return d->files[pos];
 }
 
 /*!
@@ -1268,8 +1251,7 @@ QString QDir::operator[](int pos) const
 QStringList QDir::entryList(Filters filters, SortFlags sort) const
 {
     Q_D(const QDir);
-
-    return entryList(d->data->nameFilters, filters, sort);
+    return entryList(d->nameFilters, filters, sort);
 }
 
 
@@ -1292,8 +1274,7 @@ QStringList QDir::entryList(Filters filters, SortFlags sort) const
 QFileInfoList QDir::entryInfoList(Filters filters, SortFlags sort) const
 {
     Q_D(const QDir);
-
-    return entryInfoList(d->data->nameFilters, filters, sort);
+    return entryInfoList(d->nameFilters, filters, sort);
 }
 
 /*!
@@ -1318,27 +1299,27 @@ QStringList QDir::entryList(const QStringList &nameFilters, Filters filters,
     Q_D(const QDir);
 
     if (filters == NoFilter)
-        filters = d->data->filters;
+        filters = d->filters;
 #ifdef QT3_SUPPORT
-    if (d->data->matchAllDirs)
+    if (d->matchAllDirs)
         filters |= AllDirs;
 #endif
     if (sort == NoSort)
-        sort = d->data->sort;
+        sort = d->sort;
 
-    if (filters == d->data->filters && sort == d->data->sort && nameFilters == d->data->nameFilters) {
-        d->data->updateFileLists();
-        return d->data->files;
+    if (filters == d->filters && sort == d->sort && nameFilters == d->nameFilters) {
+        d->updateFileLists();
+        return d->files;
     }
 
     QFileInfoList l;
-    QDirIterator it(d->data->path, nameFilters, filters);
+    QDirIterator it(d->path, nameFilters, filters);
     while (it.hasNext()) {
         it.next();
         l.append(it.fileInfo());
     }
     QStringList ret;
-    d->data->sortFileList(sort, l, &ret, 0);
+    d->sortFileList(sort, l, &ret, 0);
     return ret;
 }
 
@@ -1364,27 +1345,27 @@ QFileInfoList QDir::entryInfoList(const QStringList &nameFilters, Filters filter
     Q_D(const QDir);
 
     if (filters == NoFilter)
-        filters = d->data->filters;
+        filters = d->filters;
 #ifdef QT3_SUPPORT
-    if (d->data->matchAllDirs)
+    if (d->matchAllDirs)
         filters |= AllDirs;
 #endif
     if (sort == NoSort)
-        sort = d->data->sort;
+        sort = d->sort;
 
-    if (filters == d->data->filters && sort == d->data->sort && nameFilters == d->data->nameFilters) {
-        d->data->updateFileLists();
-        return d->data->fileInfos;
+    if (filters == d->filters && sort == d->sort && nameFilters == d->nameFilters) {
+        d->updateFileLists();
+        return d->fileInfos;
     }
 
     QFileInfoList l;
-    QDirIterator it(d->data->path, nameFilters, filters);
+    QDirIterator it(d->path, nameFilters, filters);
     while (it.hasNext()) {
         it.next();
         l.append(it.fileInfo());
     }
     QFileInfoList ret;
-    d->data->sortFileList(sort, l, 0, &ret);
+    d->sortFileList(sort, l, 0, &ret);
     return ret;
 }
 
@@ -1403,11 +1384,11 @@ bool QDir::mkdir(const QString &dirName) const
         qWarning("QDir::mkdir: Empty or null file name(s)");
         return false;
     }
-    if (!d->data->fileEngine)
+    if (!d->fileEngine)
         return false;
 
     QString fn = filePath(dirName);
-    return d->data->fileEngine->mkdir(fn, false);
+    return d->fileEngine->mkdir(fn, false);
 }
 
 /*!
@@ -1427,11 +1408,11 @@ bool QDir::rmdir(const QString &dirName) const
         qWarning("QDir::rmdir: Empty or null file name(s)");
         return false;
     }
-    if (!d->data->fileEngine)
+    if (!d->fileEngine)
         return false;
 
     QString fn = filePath(dirName);
-    return d->data->fileEngine->rmdir(fn, false);
+    return d->fileEngine->rmdir(fn, false);
 }
 
 /*!
@@ -1452,11 +1433,11 @@ bool QDir::mkpath(const QString &dirPath) const
         qWarning("QDir::mkpath: Empty or null file name(s)");
         return false;
     }
-    if (!d->data->fileEngine)
+    if (!d->fileEngine)
         return false;
 
     QString fn = filePath(dirPath);
-    return d->data->fileEngine->mkdir(fn, true);
+    return d->fileEngine->mkdir(fn, true);
 }
 
 /*!
@@ -1478,11 +1459,11 @@ bool QDir::rmpath(const QString &dirPath) const
         qWarning("QDir::rmpath: Empty or null file name(s)");
         return false;
     }
-    if (!d->data->fileEngine)
+    if (!d->fileEngine)
         return false;
 
     QString fn = filePath(dirPath);
-    return d->data->fileEngine->rmdir(fn, true);
+    return d->fileEngine->rmdir(fn, true);
 }
 
 /*!
@@ -1498,10 +1479,10 @@ bool QDir::isReadable() const
 {
     Q_D(const QDir);
 
-    if (!d->data->fileEngine)
+    if (!d->fileEngine)
         return false;
     const QAbstractFileEngine::FileFlags info =
-        d->data->fileEngine->fileFlags(QAbstractFileEngine::DirectoryType
+        d->fileEngine->fileFlags(QAbstractFileEngine::DirectoryType
                                        | QAbstractFileEngine::PermsMask);
     if (!(info & QAbstractFileEngine::DirectoryType))
         return false;
@@ -1523,10 +1504,10 @@ bool QDir::exists() const
 {
     Q_D(const QDir);
 
-    if (!d->data->fileEngine)
+    if (!d->fileEngine)
         return false;
     const QAbstractFileEngine::FileFlags info =
-        d->data->fileEngine->fileFlags(QAbstractFileEngine::DirectoryType
+        d->fileEngine->fileFlags(QAbstractFileEngine::DirectoryType
                                        | QAbstractFileEngine::ExistsFlag
                                        | QAbstractFileEngine::Refresh);
     if (!(info & QAbstractFileEngine::DirectoryType))
@@ -1550,9 +1531,9 @@ bool QDir::isRoot() const
 {
     Q_D(const QDir);
 
-    if (!d->data->fileEngine)
+    if (!d->fileEngine)
         return true;
-    return d->data->fileEngine->fileFlags(QAbstractFileEngine::FlagsMask) & QAbstractFileEngine::RootFlag;
+    return d->fileEngine->fileFlags(QAbstractFileEngine::FlagsMask) & QAbstractFileEngine::RootFlag;
 }
 
 /*!
@@ -1584,9 +1565,9 @@ bool QDir::isRelative() const
 {
     Q_D(const QDir);
 
-    if (!d->data->fileEngine)
+    if (!d->fileEngine)
         return false;
-    return d->data->fileEngine->isRelativePath();
+    return d->fileEngine->isRelativePath();
 }
 
 
@@ -1599,17 +1580,19 @@ bool QDir::isRelative() const
 */
 bool QDir::makeAbsolute() // ### What do the return values signify?
 {
-    Q_D(QDir);
-
-    if (!d->data->fileEngine)
+    if (!d_ptr.constData()->fileEngine)
         return false;
-    QString absolutePath = d->data->fileEngine->fileName(QAbstractFileEngine::AbsoluteName);
+    QString absolutePath = d_ptr.constData()->fileEngine->fileName(QAbstractFileEngine::AbsoluteName);
     if (QDir::isRelativePath(absolutePath))
         return false;
-    QDirPrivate::Data::detach(d->data);
-    d->data->path = absolutePath;
-    d->data->fileEngine->setFileName(absolutePath);
-    if (!(d->data->fileEngine->fileFlags(QAbstractFileEngine::TypesMask) & QAbstractFileEngine::DirectoryType))
+
+    Q_D(QDir);
+
+    d->path = absolutePath;
+    d->initFileEngine();
+    d->clear();
+
+    if (!(d->fileEngine->fileFlags(QAbstractFileEngine::TypesMask) & QAbstractFileEngine::DirectoryType))
         return false;
     return true;
 }
@@ -1628,16 +1611,16 @@ bool QDir::operator==(const QDir &dir) const
     const QDirPrivate *d = d_func();
     const QDirPrivate *other = dir.d_func();
 
-    if (d->data == other->data)
+    if (d == other)
         return true;
-    Q_ASSERT(d->data->fileEngine && other->data->fileEngine);
-    if (d->data->fileEngine->caseSensitive() != other->data->fileEngine->caseSensitive())
+    Q_ASSERT(d->fileEngine && other->fileEngine);
+    if (d->fileEngine->caseSensitive() != other->fileEngine->caseSensitive())
         return false;
-    if (d->data->filters == other->data->filters
-       && d->data->sort == other->data->sort
-       && d->data->nameFilters == other->data->nameFilters) {
+    if (d->filters == other->filters
+       && d->sort == other->sort
+       && d->nameFilters == other->nameFilters) {
         QString dir1 = absolutePath(), dir2 = dir.absolutePath();
-        if (!other->data->fileEngine->caseSensitive())
+        if (!other->fileEngine->caseSensitive())
             return (dir1.toLower() == dir2.toLower());
 
         return (dir1 == dir2);
@@ -1655,8 +1638,7 @@ QDir &QDir::operator=(const QDir &dir)
     if (this == &dir)
         return *this;
 
-    Q_D(QDir);
-    qAtomicAssign(d->data, dir.d_func()->data);
+    d_ptr = dir.d_ptr;
     return *this;
 }
 
@@ -1670,10 +1652,7 @@ QDir &QDir::operator=(const QDir &dir)
 */
 QDir &QDir::operator=(const QString &path)
 {
-    Q_D(QDir);
-
-    QDirPrivate::Data::detach(d->data, false);
-    d->data->setPath(path);
+    d_ptr->setPath(path);
     return *this;
 }
 
@@ -1717,13 +1696,12 @@ bool QDir::remove(const QString &fileName)
 */
 bool QDir::rename(const QString &oldName, const QString &newName)
 {
-    Q_D(QDir);
-
     if (oldName.isEmpty() || newName.isEmpty()) {
         qWarning("QDir::rename: Empty or null file name(s)");
         return false;
     }
-    if (!d->data->fileEngine)
+
+    if (!d_ptr.constData()->fileEngine)
         return false;
 
     QFile file(filePath(oldName));
@@ -2162,10 +2140,9 @@ bool QDir::isRelativePath(const QString &path)
 */
 void QDir::refresh() const
 {
-    Q_D(const QDir);
-
-    QDirPrivate::Data::detach(const_cast<QDirPrivate *>(d)->data);
-    d->data->clear();
+    QDirPrivate *d = const_cast<QDir*>(this)->d_func();
+    d->initFileEngine();
+    d->clear();
 }
 
 /*!
@@ -2177,7 +2154,7 @@ void QDir::refresh() const
 */
 QStringList QDir::nameFiltersFromString(const QString &nameFilter)
 {
-    return QDirPrivate::Data::splitFilters(nameFilter);
+    return QDirPrivate::splitFilters(nameFilter);
 }
 
 /*!
@@ -2242,7 +2219,7 @@ QStringList QDir::nameFiltersFromString(const QString &nameFilter)
 bool QDir::matchAllDirs() const
 {
     Q_D(const QDir);
-    return d->data->matchAllDirs;
+    return d->matchAllDirs;
 }
 
 
@@ -2254,10 +2231,10 @@ bool QDir::matchAllDirs() const
 void QDir::setMatchAllDirs(bool on)
 {
     Q_D(QDir);
+    d->initFileEngine();
+    d->clear();
 
-    QDirPrivate::Data::detach(d->data);
-    d->data->clear();
-    d->data->matchAllDirs = on;
+    d->matchAllDirs = on;
 }
 
 /*!
@@ -2266,8 +2243,7 @@ void QDir::setMatchAllDirs(bool on)
 QString QDir::nameFilter() const
 {
     Q_D(const QDir);
-
-    return nameFilters().join(QString(d->data->filterSepChar));
+    return nameFilters().join(QString(d->filterSepChar));
 }
 
 /*!
@@ -2293,9 +2269,8 @@ QString QDir::nameFilter() const
 void QDir::setNameFilter(const QString &nameFilter)
 {
     Q_D(QDir);
-
-    d->data->filterSepChar = QDirPrivate::Data::getFilterSepChar(nameFilter);
-    setNameFilters(QDirPrivate::Data::splitFilters(nameFilter, d->data->filterSepChar));
+    d->filterSepChar = QDirPrivate::getFilterSepChar(nameFilter);
+    setNameFilters(QDirPrivate::splitFilters(nameFilter, d->filterSepChar));
 }
 
 /*!
diff --git a/src/corelib/io/qdir.h b/src/corelib/io/qdir.h
index 28da271..abfe387 100644
--- a/src/corelib/io/qdir.h
+++ b/src/corelib/io/qdir.h
@@ -45,7 +45,7 @@
 #include <QtCore/qstring.h>
 #include <QtCore/qfileinfo.h>
 #include <QtCore/qstringlist.h>
-#include <QtCore/qscopedpointer.h>
+#include <QtCore/qshareddata.h>
 
 QT_BEGIN_HEADER
 
@@ -58,9 +58,19 @@ class QDirPrivate;
 class Q_CORE_EXPORT QDir
 {
 protected:
-    QScopedPointer<QDirPrivate> d_ptr;
+    QSharedDataPointer<QDirPrivate> d_ptr;
 private:
-    Q_DECLARE_PRIVATE(QDir)
+    inline QDirPrivate* d_func()
+    {
+        detach();
+        return const_cast<QDirPrivate *>(d_ptr.constData());
+    }
+
+    inline const QDirPrivate* d_func() const
+    {
+        return d_ptr.constData();
+    }
+
 public:
     enum Filter { Dirs        = 0x001,
                   Files       = 0x002,
@@ -130,6 +140,8 @@ public:
     QDir &operator=(const QDir &);
     QDir &operator=(const QString &path);
 
+    void detach();
+
     void setPath(const QString &path);
     QString path() const;
     QString absolutePath() const;