Add renameOverwrite() to QAbstractFileEngine.

QFSFileEngine::rename() on Windows doesn't overwrite the existing destination.
Keep that unchanged (it's the desired behavior in QFile::rename), and
provide cross-platform rename-overwrite behavior in the new method.

This is needed by QSaveFile.

Change-Id: I5e753d289d8a53692530a48a1783d62e26169cdc
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/io/qabstractfileengine.cpp

@@ -495,6 +495,24 @@ bool QAbstractFileEngine::rename(const QString &newName)
     return false;
 }
 
+/*!
+    \since 5.1
+
+    Requests that the file be renamed to \a newName in the file
+    system. If the new name already exists, it must be overwritten.
+    If the operation succeeds, returns true; otherwise returns
+    false.
+
+    This virtual function must be reimplemented by all subclasses.
+
+    \sa setFileName()
+ */
+bool QAbstractFileEngine::renameOverwrite(const QString &newName)
+{
+    Q_UNUSED(newName);
+    return false;
+}
+
 /*!
     Creates a link from the file currently specified by fileName() to
     \a newName. What a link is depends on the underlying filesystem

src/corelib/io/qabstractfileengine_p.h

@@ -131,6 +131,7 @@ public:
     virtual bool remove();
     virtual bool copy(const QString &newName);
     virtual bool rename(const QString &newName);
+    virtual bool renameOverwrite(const QString &newName);
     virtual bool link(const QString &newName);
     virtual bool mkdir(const QString &dirName, bool createParentDirectories) const;
     virtual bool rmdir(const QString &dirName, bool recurseParentDirectories) const;

src/corelib/io/qfsfileengine.cpp

@@ -908,6 +908,11 @@ bool QFSFileEngine::supportsExtension(Extension extension) const
   \reimp
 */
 
+
+/*! \fn bool QFSFileEngine::renameOverwrite(const QString &newName)
+  \reimp
+*/
+
 /*! \fn bool QFSFileEngine::rmdir(const QString &name, bool recurseParentDirectories) const
   \reimp
 */

src/corelib/io/qfsfileengine_p.h

@@ -88,6 +88,7 @@ public:
     bool remove();
     bool copy(const QString &newName);
     bool rename(const QString &newName);
+    bool renameOverwrite(const QString &newName);
     bool link(const QString &newName);
     bool mkdir(const QString &dirName, bool createParentDirectories) const;
     bool rmdir(const QString &dirName, bool recurseParentDirectories) const;

src/corelib/io/qfsfileengine_unix.cpp

@@ -388,6 +388,12 @@ bool QFSFileEngine::copy(const QString &newName)
     return ret;
 }
 
+bool QFSFileEngine::renameOverwrite(const QString &newName)
+{
+    // On Unix, rename() overwrites.
+    return rename(newName);
+}
+
 bool QFSFileEngine::rename(const QString &newName)
 {
     Q_D(QFSFileEngine);

src/corelib/io/qfsfileengine_win.cpp

@@ -507,6 +507,17 @@ bool QFSFileEngine::rename(const QString &newName)
     return ret;
 }
 
+bool QFSFileEngine::renameOverwrite(const QString &newName)
+{
+    Q_D(QFSFileEngine);
+    bool ret = ::MoveFileEx((wchar_t*)d->fileEntry.nativeFilePath().utf16(),
+                            (wchar_t*)QFileSystemEntry(newName).nativeFilePath().utf16(),
+                            MOVEFILE_REPLACE_EXISTING | MOVEFILE_COPY_ALLOWED) != 0;
+    if (!ret)
+        setError(QFile::RenameError, QSystemError(::GetLastError(), QSystemError::NativeError).toString());
+    return ret;
+}
+
 bool QFSFileEngine::mkdir(const QString &name, bool createParentDirectories) const
 {
     return QFileSystemEngine::createDirectory(QFileSystemEntry(name), createParentDirectories);

src/corelib/io/qtemporaryfile.cpp

@@ -242,6 +242,7 @@ public:
     bool open(QIODevice::OpenMode flags);
     bool remove();
     bool rename(const QString &newName);
+    bool renameOverwrite(const QString &newName);
     bool close();
 
     bool filePathIsTemplate;
@@ -398,6 +399,12 @@ bool QTemporaryFileEngine::rename(const QString &newName)
     return QFSFileEngine::rename(newName);
 }
 
+bool QTemporaryFileEngine::renameOverwrite(const QString &newName)
+{
+    QFSFileEngine::close();
+    return QFSFileEngine::renameOverwrite(newName);
+}
+
 bool QTemporaryFileEngine::close()
 {
     // Don't close the file, just seek to the front.