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Support Alternate Data Streams in QSaveFile

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We can't use MoveFile to do atomic commits on an ADS, so QSaveFile needs
to detect when the target name is ADS and then use the direct fallback
mode.

[ChangeLog][QtCore][QSaveFile] Saving to Alternate Data Streams on NTFS
on Windows is now possible, but requires setDirectWriteFallback(true).

Task-number: QTBUG-47379
Change-Id: I81480fdb578d4d43b3fcfffd14d4bc062ae1750d
Reviewed-by: Kai Koehne <kai.koehne@qt.io>
Reviewed-by: David Faure <david.faure@kdab.com>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@qt.io>
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
This commit is contained in:
Thiago Macieira 2017-07-25 18:08:30 -07:00
parent 9a3ce25f98
commit 66500b9d75
2 changed files with 92 additions and 5 deletions
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37
src/corelib/io/qsavefile.cpp
View File

@ -231,6 +231,37 @@ bool QSaveFile::open(OpenMode mode)
d->finalFileName = existingFile.filePath();
}
auto openDirectly = [&]() {
d->fileEngine = QAbstractFileEngine::create(d->finalFileName);
if (d->fileEngine->open(mode | QIODevice::Unbuffered)) {
d->useTemporaryFile = false;
QFileDevice::open(mode);
return true;
}
return false;
};
#ifdef Q_OS_WIN
// check if it is an Alternate Data Stream
if (d->finalFileName == d->fileName && d->fileName.indexOf(QLatin1Char(':'), 2) > 1) {
// yes, we can't rename onto it...
if (d->directWriteFallback) {
if (openDirectly())
return true;
d->setError(d->fileEngine->error(), d->fileEngine->errorString());
delete d->fileEngine;
d->fileEngine = 0;
} else {
QString msg =
QSaveFile::tr("QSaveFile cannot open '%1' without direct write fallback "
"enabled: path contains an Alternate Data Stream specifier")
.arg(QDir::toNativeSeparators(d->fileName));
d->setError(QFileDevice::OpenError, msg);
}
return false;
}
#endif
d->fileEngine = new QTemporaryFileEngine(&d->finalFileName);
// if the target file exists, we'll copy its permissions below,
// but until then, let's ensure the temporary file is not accessible
@ -243,12 +274,8 @@ bool QSaveFile::open(OpenMode mode)
#ifdef Q_OS_UNIX
if (d->directWriteFallback && err == QFileDevice::OpenError && errno == EACCES) {
delete d->fileEngine;
d->fileEngine = QAbstractFileEngine::create(d->finalFileName);
if (d->fileEngine->open(mode | QIODevice::Unbuffered)) {
d->useTemporaryFile = false;
QFileDevice::open(mode);
if (openDirectly())
return true;
}
err = d->fileEngine->error();
}
#endif

60
tests/auto/corelib/io/qsavefile/tst_qsavefile.cpp
View File

@ -82,6 +82,11 @@ private slots:
void transactionalWriteErrorRenaming();
void symlink();
void directory();
#ifdef Q_OS_WIN
void alternateDataStream_data();
void alternateDataStream();
#endif
};
static inline QByteArray msgCannotOpen(const QFileDevice &f)
@ -474,5 +479,60 @@ void tst_QSaveFile::directory()
#endif
}
#ifdef Q_OS_WIN
void tst_QSaveFile::alternateDataStream_data()
{
QTest::addColumn<bool>("directWriteFallback");
QTest::addColumn<bool>("success");
QTest::newRow("default") << false << false;
QTest::newRow("directWriteFallback") << true << true;
}
void tst_QSaveFile::alternateDataStream()
{
QFETCH(bool, directWriteFallback);
QFETCH(bool, success);
static const char newContent[] = "New content\r\n";
QTemporaryDir dir;
QVERIFY2(dir.isValid(), qPrintable(dir.errorString()));
QString baseName = dir.path() + QLatin1String("/base");
{
QFile baseFile(baseName);
QVERIFY2(baseFile.open(QIODevice::ReadWrite), qPrintable(baseFile.errorString()));
}
// First, create a file with old content
QString adsName = baseName + QLatin1String(":outfile");
{
QFile targetFile(adsName);
if (!targetFile.open(QIODevice::ReadWrite))
QSKIP("Failed to ceate ADS file (" + targetFile.errorString().toUtf8()
+ "). Temp dir is FAT?");
targetFile.write("Old content\r\n");
}
// And write to it again using QSaveFile; only works if directWriteFallback is enabled
QSaveFile file(adsName);
file.setDirectWriteFallback(directWriteFallback);
QCOMPARE(file.directWriteFallback(), directWriteFallback);
if (success) {
QVERIFY2(file.open(QIODevice::WriteOnly), qPrintable(file.errorString()));
file.write(newContent);
QVERIFY2(file.commit(), qPrintable(file.errorString()));
// check the contents
QFile targetFile(adsName);
QVERIFY2(targetFile.open(QIODevice::ReadOnly), qPrintable(targetFile.errorString()));
QByteArray contents = targetFile.readAll();
QCOMPARE(contents, QByteArray(newContent));
} else {
QVERIFY(!file.open(QIODevice::WriteOnly));
}
}
#endif
QTEST_MAIN(tst_QSaveFile)
#include "tst_qsavefile.moc"