Add class QSaveFile.

This QIODevice uses a temporary file for writing, so that in case of
write errors, the writing operation is canceled, without losing any
existing file. It also avoids having a partially-written file visible
by other processes, at the final destination.

Change-Id: I9482df45751cb890b1b6f1382ec2eea3eb980627
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

3 files changed, 240 insertions, 0 deletions

diff --git a/tests/auto/corelib/io/io.pro b/tests/auto/corelib/io/io.pro
index 03b42a2cbb..948e9dec5f 100644
--- a/tests/auto/corelib/io/io.pro
+++ b/tests/auto/corelib/io/io.pro
@@ -20,6 +20,7 @@ SUBDIRS=\
     qprocessenvironment \
     qresourceengine \
     qsettings \
+    qsavefile \
     qstandardpaths \
     qtemporarydir \
     qtemporaryfile \
diff --git a/tests/auto/corelib/io/qsavefile/qsavefile.pro b/tests/auto/corelib/io/qsavefile/qsavefile.pro
new file mode 100644
index 0000000000..36db000fa7
--- /dev/null
+++ b/tests/auto/corelib/io/qsavefile/qsavefile.pro
@@ -0,0 +1,5 @@
+CONFIG += testcase parallel_test
+TARGET = tst_qsavefile
+QT = core testlib
+SOURCES = tst_qsavefile.cpp
+TESTDATA += tst_qsavefile.cpp
diff --git a/tests/auto/corelib/io/qsavefile/tst_qsavefile.cpp b/tests/auto/corelib/io/qsavefile/tst_qsavefile.cpp
new file mode 100644
index 0000000000..61fef80af7
--- /dev/null
+++ b/tests/auto/corelib/io/qsavefile/tst_qsavefile.cpp
@@ -0,0 +1,234 @@
+/****************************************************************************
+**
+** Copyright (C) 2012 David Faure <faure@kde.org>
+** Contact: http://www.qt-project.org/legal
+**
+** This file is part of the QtCore module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and Digia.  For licensing terms and
+** conditions see http://qt.digia.com/licensing.  For further information
+** use the contact form at http://qt.digia.com/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 2.1 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU Lesser General Public License version 2.1 requirements
+** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** In addition, as a special exception, Digia gives you certain additional
+** rights.  These rights are described in the Digia Qt LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3.0 as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU General Public License version 3.0 requirements will be
+** met: http://www.gnu.org/copyleft/gpl.html.
+**
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include <QtTest/QtTest>
+#include <qcoreapplication.h>
+#include <qstring.h>
+#include <qtemporaryfile.h>
+#include <qfile.h>
+#include <qdir.h>
+#include <qset.h>
+
+#if defined(Q_OS_UNIX)
+# include <unistd.h> // for geteuid
+# include <sys/types.h>
+#endif
+
+#if defined(Q_OS_WIN)
+# include <windows.h>
+#endif
+
+class tst_QSaveFile : public QObject
+{
+    Q_OBJECT
+public slots:
+
+private slots:
+    void transactionalWrite();
+    void textStreamManualFlush();
+    void textStreamAutoFlush();
+    void saveTwice();
+    void transactionalWriteNoPermissions();
+    void transactionalWriteCanceled();
+    void transactionalWriteErrorRenaming();
+};
+
+void tst_QSaveFile::transactionalWrite()
+{
+    QTemporaryDir dir;
+    const QString targetFile = dir.path() + QString::fromLatin1("/outfile");
+    QFile::remove(targetFile);
+    QSaveFile file(targetFile);
+    QVERIFY(file.open(QIODevice::WriteOnly));
+    QVERIFY(file.isOpen());
+    QCOMPARE(file.fileName(), targetFile);
+    QVERIFY(!QFile::exists(targetFile));
+
+    QCOMPARE(file.write("Hello"), Q_INT64_C(5));
+    QCOMPARE(file.error(), QFile::NoError);
+    QVERIFY(!QFile::exists(targetFile));
+
+    QVERIFY(file.commit());
+    QVERIFY(QFile::exists(targetFile));
+    QCOMPARE(file.fileName(), targetFile);
+
+    QFile reader(targetFile);
+    QVERIFY(reader.open(QIODevice::ReadOnly));
+    QCOMPARE(QString::fromLatin1(reader.readAll()), QString::fromLatin1("Hello"));
+}
+
+void tst_QSaveFile::saveTwice()
+{
+    // Check that we can reuse a QSaveFile object
+    // (and test the case of an existing target file)
+    QTemporaryDir dir;
+    const QString targetFile = dir.path() + QString::fromLatin1("/outfile");
+    QSaveFile file(targetFile);
+    QVERIFY(file.open(QIODevice::WriteOnly));
+    QCOMPARE(file.write("Hello"), Q_INT64_C(5));
+    QVERIFY2(file.commit(), qPrintable(file.errorString()));
+
+    QVERIFY(file.open(QIODevice::WriteOnly));
+    QCOMPARE(file.write("World"), Q_INT64_C(5));
+    QVERIFY2(file.commit(), qPrintable(file.errorString()));
+
+    QFile reader(targetFile);
+    QVERIFY(reader.open(QIODevice::ReadOnly));
+    QCOMPARE(QString::fromLatin1(reader.readAll()), QString::fromLatin1("World"));
+}
+
+void tst_QSaveFile::textStreamManualFlush()
+{
+    QTemporaryDir dir;
+    const QString targetFile = dir.path() + QString::fromLatin1("/outfile");
+    QSaveFile file(targetFile);
+    QVERIFY(file.open(QIODevice::WriteOnly));
+
+    QTextStream ts(&file);
+    ts << "Manual flush";
+    ts.flush();
+    QCOMPARE(file.error(), QFile::NoError);
+    QVERIFY(!QFile::exists(targetFile));
+
+    QVERIFY(file.commit());
+    QFile reader(targetFile);
+    QVERIFY(reader.open(QIODevice::ReadOnly));
+    QCOMPARE(QString::fromLatin1(reader.readAll().constData()), QString::fromLatin1("Manual flush"));
+    QFile::remove(targetFile);
+}
+
+void tst_QSaveFile::textStreamAutoFlush()
+{
+    QTemporaryDir dir;
+    const QString targetFile = dir.path() + QString::fromLatin1("/outfile");
+    QSaveFile file(targetFile);
+    QVERIFY(file.open(QIODevice::WriteOnly));
+
+    QTextStream ts(&file);
+    ts << "Auto-flush.";
+    // no flush
+    QVERIFY(file.commit()); // QIODevice::close will emit aboutToClose, which will flush the stream
+    QFile reader(targetFile);
+    QVERIFY(reader.open(QIODevice::ReadOnly));
+    QCOMPARE(QString::fromLatin1(reader.readAll().constData()), QString::fromLatin1("Auto-flush."));
+    QFile::remove(targetFile);
+}
+
+void tst_QSaveFile::transactionalWriteNoPermissions()
+{
+#ifdef Q_OS_UNIX
+    if (::geteuid() == 0)
+        QSKIP("not valid running this test as root");
+
+    // You can write into /dev/zero, but you can't create a /dev/zero.XXXXXX temp file.
+    QSaveFile file("/dev/zero");
+    if (!QDir("/dev").exists())
+        QSKIP("/dev doesn't exist on this system");
+
+    QVERIFY(!file.open(QIODevice::WriteOnly));
+    QCOMPARE((int)file.error(), (int)QFile::OpenError);
+    QVERIFY(!file.commit());
+#endif
+}
+
+void tst_QSaveFile::transactionalWriteCanceled()
+{
+    QTemporaryDir dir;
+    const QString targetFile = dir.path() + QString::fromLatin1("/outfile");
+    QFile::remove(targetFile);
+    QSaveFile file(targetFile);
+    QVERIFY(file.open(QIODevice::WriteOnly));
+
+    QTextStream ts(&file);
+    ts << "This writing operation will soon be canceled.\n";
+    ts.flush();
+    QCOMPARE(file.error(), QFile::NoError);
+    QVERIFY(!QFile::exists(targetFile));
+
+    // We change our mind, let's abort writing
+    file.cancelWriting();
+
+    QVERIFY(!file.commit());
+
+    QVERIFY(!QFile::exists(targetFile)); // temp file was discarded
+    QCOMPARE(file.fileName(), targetFile);
+}
+
+void tst_QSaveFile::transactionalWriteErrorRenaming()
+{
+    QTemporaryDir dir;
+    const QString targetFile = dir.path() + QString::fromLatin1("/outfile");
+    QSaveFile file(targetFile);
+    QVERIFY(file.open(QIODevice::WriteOnly));
+    QCOMPARE(file.write("Hello"), qint64(5));
+    QVERIFY(!QFile::exists(targetFile));
+
+#ifdef Q_OS_UNIX
+    // Make rename() fail for lack of permissions in the directory
+    QFile dirAsFile(dir.path()); // yay, I have to use QFile to change a dir's permissions...
+    QVERIFY(dirAsFile.setPermissions(QFile::Permissions(0))); // no permissions
+#else
+    // Windows: Make rename() fail for lack of permissions on an existing target file
+    QFile existingTargetFile(targetFile);
+    QVERIFY(existingTargetFile.open(QIODevice::WriteOnly));
+    QCOMPARE(file.write("Target"), qint64(6));
+    existingTargetFile.close();
+    QVERIFY(existingTargetFile.setPermissions(QFile::ReadOwner));
+#endif
+
+    // The saving should fail.
+    QVERIFY(!file.commit());
+#ifdef Q_OS_UNIX
+    QVERIFY(!QFile::exists(targetFile)); // renaming failed
+#endif
+    QCOMPARE(file.error(), QFile::RenameError);
+
+    // Restore permissions so that the cleanup can happen
+#ifdef Q_OS_UNIX
+    QVERIFY(dirAsFile.setPermissions(QFile::Permissions(QFile::ReadOwner | QFile::WriteOwner | QFile::ExeOwner)));
+#else
+    QVERIFY(existingTargetFile.setPermissions(QFile::WriteOwner));
+    QVERIFY(existingTargetFile.remove());
+#endif
+}
+
+QTEST_MAIN(tst_QSaveFile)
+#include "tst_qsavefile.moc"