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qtemporaryfile.cpp
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qtemporaryfile.cpp
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// Copyright (C) 2016 The Qt Company Ltd.
// Copyright (C) 2017 Intel Corporation.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
#include "qtemporaryfile.h"
#include "qplatformdefs.h"
#include "qrandom.h"
#include "private/qtemporaryfile_p.h"
#include "private/qfile_p.h"
#include "private/qsystemerror_p.h"
#if !defined(Q_OS_WIN)
#include "private/qcore_unix_p.h" // overrides QT_OPEN
#include <errno.h>
#endif
#if defined(QT_BUILD_CORE_LIB)
#include "qcoreapplication.h"
#else
#define tr(X) QString::fromLatin1(X)
#endif
QT_BEGIN_NAMESPACE
using namespace Qt::StringLiterals;
#if defined(Q_OS_WIN)
typedef ushort Char;
static inline Char Latin1Char(char ch)
{
return ushort(uchar(ch));
}
typedef HANDLE NativeFileHandle;
#else // POSIX
typedef char Char;
typedef char Latin1Char;
typedef int NativeFileHandle;
#endif
QTemporaryFileName::QTemporaryFileName(const QString &templateName)
{
// Ensure there is a placeholder mask
QString qfilename = QDir::fromNativeSeparators(templateName);
qsizetype phPos = qfilename.size();
qsizetype phLength = 0;
while (phPos != 0) {
--phPos;
if (qfilename[phPos] == u'X') {
++phLength;
continue;
}
if (phLength >= 6
|| qfilename[phPos] == u'/') {
++phPos;
break;
}
// start over
phLength = 0;
}
if (phLength < 6)
qfilename.append(".XXXXXX"_L1);
// "Nativify" :-)
QFileSystemEntry::NativePath filename =
QFileSystemEntry(QDir::cleanPath(qfilename)).nativeFilePath();
// Find mask in native path
phPos = filename.size();
phLength = 0;
while (phPos != 0) {
--phPos;
if (filename[phPos] == Latin1Char('X')) {
++phLength;
continue;
}
if (phLength >= 6) {
++phPos;
break;
}
// start over
phLength = 0;
}
Q_ASSERT(phLength >= 6);
path = filename;
pos = phPos;
length = phLength;
}
/*!
\internal
Generates a unique file path from the template \a templ and returns it.
The path in \c templ.path is modified.
*/
QFileSystemEntry::NativePath QTemporaryFileName::generateNext()
{
Q_ASSERT(length != 0);
Q_ASSERT(pos < path.size());
Q_ASSERT(length <= path.size() - pos);
Char *const placeholderStart = (Char *)path.data() + pos;
Char *const placeholderEnd = placeholderStart + length;
// Replace placeholder with random chars.
{
// Since our dictionary is 26+26 characters, it would seem we only need
// a random number from 0 to 63 to select a character. However, due to
// the limited range, that would mean 12 (64-52) characters have double
// the probability of the others: 1 in 32 instead of 1 in 64.
//
// To overcome this limitation, we use more bits per character. With 10
// bits, there are 16 characters with probability 19/1024 and the rest
// at 20/1024 (i.e, less than .1% difference). This allows us to do 3
// characters per 32-bit random number, which is also half the typical
// placeholder length.
enum { BitsPerCharacter = 10 };
Char *rIter = placeholderEnd;
while (rIter != placeholderStart) {
quint32 rnd = QRandomGenerator::global()->generate();
auto applyOne = [&]() {
quint32 v = rnd & ((1 << BitsPerCharacter) - 1);
rnd >>= BitsPerCharacter;
char ch = char((26 + 26) * v / (1 << BitsPerCharacter));
if (ch < 26)
*--rIter = Latin1Char(ch + 'A');
else
*--rIter = Latin1Char(ch - 26 + 'a');
};
applyOne();
if (rIter == placeholderStart)
break;
applyOne();
if (rIter == placeholderStart)
break;
applyOne();
}
}
return path;
}
#if QT_CONFIG(temporaryfile)
/*!
\internal
Generates a unique file path from the template \a templ and creates a new
file based on those parameters: the \c templ.length characters in \c
templ.path starting at \c templ.pos will be replaced by a random sequence of
characters. \a mode specifies the file mode bits (not used on Windows).
Returns true on success and sets the file handle on \a file. On error,
returns false, sets an invalid handle on \a handle and sets the error
condition in \a error. In both cases, the string in \a templ will be
changed and contain the generated path name.
*/
static bool createFileFromTemplate(NativeFileHandle &file, QTemporaryFileName &templ,
quint32 mode, int flags, QSystemError &error)
{
const int maxAttempts = 16;
for (int attempt = 0; attempt < maxAttempts; ++attempt) {
// Atomically create file and obtain handle
const QFileSystemEntry::NativePath &path = templ.generateNext();
#if defined(Q_OS_WIN)
Q_UNUSED(mode);
const DWORD shareMode = (flags & QTemporaryFileEngine::Win32NonShared)
? 0u : (FILE_SHARE_READ | FILE_SHARE_WRITE);
const DWORD extraAccessFlags = (flags & QTemporaryFileEngine::Win32NonShared) ? DELETE : 0;
file = CreateFile((const wchar_t *)path.constData(),
GENERIC_READ | GENERIC_WRITE | extraAccessFlags,
shareMode, NULL, CREATE_NEW,
FILE_ATTRIBUTE_NORMAL, NULL);
if (file != INVALID_HANDLE_VALUE)
return true;
DWORD err = GetLastError();
if (err == ERROR_ACCESS_DENIED) {
WIN32_FILE_ATTRIBUTE_DATA attributes;
if (!GetFileAttributesEx((const wchar_t *)path.constData(),
GetFileExInfoStandard, &attributes)
|| attributes.dwFileAttributes == INVALID_FILE_ATTRIBUTES) {
// Potential write error (read-only parent directory, etc.).
error = QSystemError(err, QSystemError::NativeError);
return false;
} // else file already exists as a directory.
} else if (err != ERROR_FILE_EXISTS) {
error = QSystemError(err, QSystemError::NativeError);
return false;
}
#else // POSIX
Q_UNUSED(flags);
file = QT_OPEN(path.constData(),
QT_OPEN_CREAT | QT_OPEN_EXCL | QT_OPEN_RDWR | QT_OPEN_LARGEFILE,
static_cast<mode_t>(mode));
if (file != -1)
return true;
int err = errno;
if (err != EEXIST) {
error = QSystemError(err, QSystemError::NativeError);
return false;
}
#endif
}
return false;
}
enum class CreateUnnamedFileStatus {
Success = 0,
NotSupported,
OtherError
};
static CreateUnnamedFileStatus
createUnnamedFile(NativeFileHandle &file, QTemporaryFileName &tfn, quint32 mode, QSystemError *error)
{
#ifdef LINUX_UNNAMED_TMPFILE
// first, check if we have /proc, otherwise can't make the file exist later
// (no error message set, as caller will try regular temporary file)
if (!qt_haveLinuxProcfs())
return CreateUnnamedFileStatus::NotSupported;
const char *p = ".";
QByteArray::size_type lastSlash = tfn.path.lastIndexOf('/');
if (lastSlash >= 0) {
if (lastSlash == 0)
lastSlash = 1;
tfn.path[lastSlash] = '\0';
p = tfn.path.data();
}
file = QT_OPEN(p, O_TMPFILE | QT_OPEN_RDWR | QT_OPEN_LARGEFILE,
static_cast<mode_t>(mode));
if (file != -1)
return CreateUnnamedFileStatus::Success;
if (errno == EOPNOTSUPP || errno == EISDIR) {
// fs or kernel doesn't support O_TMPFILE, so
// put the slash back so we may try a regular file
if (lastSlash != -1)
tfn.path[lastSlash] = '/';
return CreateUnnamedFileStatus::NotSupported;
}
// real error
*error = QSystemError(errno, QSystemError::NativeError);
return CreateUnnamedFileStatus::OtherError;
#else
Q_UNUSED(file);
Q_UNUSED(tfn);
Q_UNUSED(mode);
Q_UNUSED(error);
return CreateUnnamedFileStatus::NotSupported;
#endif
}
//************* QTemporaryFileEngine
QTemporaryFileEngine::~QTemporaryFileEngine()
{
Q_D(QFSFileEngine);
d->unmapAll();
QFSFileEngine::close();
}
bool QTemporaryFileEngine::isReallyOpen() const
{
Q_D(const QFSFileEngine);
if (!((nullptr == d->fh) && (-1 == d->fd)
#if defined Q_OS_WIN
&& (INVALID_HANDLE_VALUE == d->fileHandle)
#endif
))
return true;
return false;
}
void QTemporaryFileEngine::setFileName(const QString &file)
{
// Really close the file, so we don't leak
QFSFileEngine::close();
QFSFileEngine::setFileName(file);
}
bool QTemporaryFileEngine::open(QIODevice::OpenMode openMode,
std::optional<QFile::Permissions> permissions)
{
Q_D(QFSFileEngine);
Q_ASSERT(!isReallyOpen());
openMode |= QIODevice::ReadWrite;
if (!filePathIsTemplate)
return QFSFileEngine::open(openMode, permissions);
QTemporaryFileName tfn(templateName);
QSystemError error;
#if defined(Q_OS_WIN)
NativeFileHandle &file = d->fileHandle;
#else // POSIX
NativeFileHandle &file = d->fd;
#endif
CreateUnnamedFileStatus st = createUnnamedFile(file, tfn, fileMode, &error);
if (st == CreateUnnamedFileStatus::Success) {
unnamedFile = true;
d->fileEntry.clear();
} else if (st == CreateUnnamedFileStatus::NotSupported &&
createFileFromTemplate(file, tfn, fileMode, flags, error)) {
filePathIsTemplate = false;
unnamedFile = false;
d->fileEntry = QFileSystemEntry(tfn.path, QFileSystemEntry::FromNativePath());
} else {
setError(QFile::OpenError, error.toString());
return false;
}
#if !defined(Q_OS_WIN)
d->closeFileHandle = true;
#endif
d->openMode = openMode;
d->lastFlushFailed = false;
d->tried_stat = 0;
return true;
}
bool QTemporaryFileEngine::remove()
{
Q_D(QFSFileEngine);
// Since the QTemporaryFileEngine::close() does not really close the file,
// we must explicitly call QFSFileEngine::close() before we remove it.
d->unmapAll();
QFSFileEngine::close();
if (isUnnamedFile())
return true;
if (!filePathIsTemplate && QFSFileEngine::remove()) {
d->fileEntry.clear();
// If a QTemporaryFile is constructed using a template file path, the path
// is generated in QTemporaryFileEngine::open() and then filePathIsTemplate
// is set to false. If remove() and then open() are called on the same
// QTemporaryFile, the path is not regenerated. Here we ensure that if the
// file path was generated, it will be generated again in the scenario above.
filePathIsTemplate = filePathWasTemplate;
return true;
}
return false;
}
bool QTemporaryFileEngine::rename(const QString &newName)
{
if (isUnnamedFile()) {
bool ok = materializeUnnamedFile(newName, DontOverwrite);
QFSFileEngine::close();
return ok;
}
QFSFileEngine::close();
return QFSFileEngine::rename(newName);
}
bool QTemporaryFileEngine::renameOverwrite(const QString &newName)
{
if (isUnnamedFile()) {
bool ok = materializeUnnamedFile(newName, Overwrite);
QFSFileEngine::close();
return ok;
}
#ifdef Q_OS_WIN
if (flags & Win32NonShared) {
QFileSystemEntry newEntry(newName, QFileSystemEntry::FromInternalPath());
bool ok = d_func()->nativeRenameOverwrite(newEntry);
QFSFileEngine::close();
if (ok) {
// Match what QFSFileEngine::renameOverwrite() does
setFileEntry(std::move(newEntry));
}
return ok;
}
#endif
QFSFileEngine::close();
return QFSFileEngine::renameOverwrite(newName);
}
bool QTemporaryFileEngine::close()
{
// Don't close the file, just seek to the front.
seek(0);
setError(QFile::UnspecifiedError, QString());
return true;
}
QString QTemporaryFileEngine::fileName(QAbstractFileEngine::FileName file) const
{
if (isUnnamedFile()) {
if (file == AbsoluteLinkTarget || file == RawLinkPath) {
// we know our file isn't (won't be) a symlink
return QString();
}
// for all other cases, materialize the file
const_cast<QTemporaryFileEngine *>(this)->materializeUnnamedFile(templateName, NameIsTemplate);
}
return QFSFileEngine::fileName(file);
}
bool QTemporaryFileEngine::materializeUnnamedFile(const QString &newName, QTemporaryFileEngine::MaterializationMode mode)
{
Q_ASSERT(isUnnamedFile());
#ifdef LINUX_UNNAMED_TMPFILE
Q_D(QFSFileEngine);
const QByteArray src = "/proc/self/fd/" + QByteArray::number(d->fd);
auto materializeAt = [=](const QFileSystemEntry &dst) {
return ::linkat(AT_FDCWD, src, AT_FDCWD, dst.nativeFilePath(), AT_SYMLINK_FOLLOW) == 0;
};
#else
auto materializeAt = [](const QFileSystemEntry &) { return false; };
#endif
auto success = [this](const QFileSystemEntry &entry) {
filePathIsTemplate = false;
unnamedFile = false;
d_func()->fileEntry = entry;
return true;
};
auto materializeAsTemplate = [=](const QString &newName) {
QTemporaryFileName tfn(newName);
static const int maxAttempts = 16;
for (int attempt = 0; attempt < maxAttempts; ++attempt) {
tfn.generateNext();
QFileSystemEntry entry(tfn.path, QFileSystemEntry::FromNativePath());
if (materializeAt(entry))
return success(entry);
}
return false;
};
if (mode == NameIsTemplate) {
if (materializeAsTemplate(newName))
return true;
} else {
// Use linkat to materialize the file
QFileSystemEntry dst(newName);
if (materializeAt(dst))
return success(dst);
if (errno == EEXIST && mode == Overwrite) {
// retry by first creating a temporary file in the right dir
if (!materializeAsTemplate(templateName))
return false;
// then rename the materialized file to target (same as renameOverwrite)
QFSFileEngine::close();
return QFSFileEngine::renameOverwrite(newName);
}
}
// failed
setError(QFile::RenameError, QSystemError(errno, QSystemError::NativeError).toString());
return false;
}
bool QTemporaryFileEngine::isUnnamedFile() const
{
#ifdef LINUX_UNNAMED_TMPFILE
if (unnamedFile) {
Q_ASSERT(d_func()->fileEntry.isEmpty());
Q_ASSERT(filePathIsTemplate);
}
return unnamedFile;
#else
return false;
#endif
}
//************* QTemporaryFilePrivate
QTemporaryFilePrivate::QTemporaryFilePrivate()
{
}
QTemporaryFilePrivate::QTemporaryFilePrivate(const QString &templateNameIn)
: templateName(templateNameIn)
{
}
QTemporaryFilePrivate::~QTemporaryFilePrivate()
{
}
QAbstractFileEngine *QTemporaryFilePrivate::engine() const
{
if (!fileEngine) {
fileEngine.reset(new QTemporaryFileEngine(&templateName));
resetFileEngine();
}
return fileEngine.get();
}
void QTemporaryFilePrivate::resetFileEngine() const
{
if (!fileEngine)
return;
QTemporaryFileEngine *tef = static_cast<QTemporaryFileEngine *>(fileEngine.get());
if (fileName.isEmpty())
tef->initialize(templateName, 0600);
else
tef->initialize(fileName, 0600, false);
}
void QTemporaryFilePrivate::materializeUnnamedFile()
{
#ifdef LINUX_UNNAMED_TMPFILE
if (!fileName.isEmpty() || !fileEngine)
return;
auto *tef = static_cast<QTemporaryFileEngine *>(fileEngine.get());
fileName = tef->fileName(QAbstractFileEngine::DefaultName);
#endif
}
QString QTemporaryFilePrivate::defaultTemplateName()
{
QString baseName;
#if defined(QT_BUILD_CORE_LIB)
baseName = QCoreApplication::applicationName();
if (baseName.isEmpty())
#endif
baseName = "qt_temp"_L1;
return QDir::tempPath() + u'/' + baseName + ".XXXXXX"_L1;
}
//************* QTemporaryFile
/*!
\class QTemporaryFile
\inmodule QtCore
\reentrant
\brief The QTemporaryFile class is an I/O device that operates on temporary files.
\ingroup io
QTemporaryFile is used to create unique temporary files safely.
The file itself is created by calling open(). The name of the
temporary file is guaranteed to be unique (i.e., you are
guaranteed to not overwrite an existing file), and the file will
subsequently be removed upon destruction of the QTemporaryFile
object. This is an important technique that avoids data
corruption for applications that store data in temporary files.
The file name is either auto-generated, or created based on a
template, which is passed to QTemporaryFile's constructor.
Example:
\snippet code/src_corelib_io_qtemporaryfile.cpp 0
Reopening a QTemporaryFile after calling close() is safe. For as long as
the QTemporaryFile object itself is not destroyed, the unique temporary
file will exist and be kept open internally by QTemporaryFile.
The file name of the temporary file can be found by calling fileName().
Note that this is only defined after the file is first opened; the function
returns an empty string before this.
A temporary file will have some static part of the name and some
part that is calculated to be unique. The default filename will be
determined from QCoreApplication::applicationName() (otherwise \c qt_temp) and will
be placed into the temporary path as returned by QDir::tempPath().
If you specify your own filename, a relative file path will not be placed in the
temporary directory by default, but be relative to the current working directory.
//! [note-about-rename-method]
It is important to specify the correct directory if the rename() function will be
called, as QTemporaryFile can only rename files within the same volume / filesystem
as the temporary file itself was created on.
//! [note-about-rename-method]
The file name (the part after the last directory path separator in the
specified file template) can contain the special sequence \c {"XXXXXX"}
(at least six upper case \c "X" characters), which will be replaced with
the auto-generated portion of the file name. If the file name doesn't
contain \c {"XXXXXX"}, QTemporaryFile will append the generated part to the
file name. Only the first occurrence of \c {"XXXXXX"} will be considered.
\note On Linux, QTemporaryFile will attempt to create unnamed temporary
files. If that succeeds, open() will return true but exists() will be
false. If you call fileName() or any function that calls it,
QTemporaryFile will give the file a name, so most applications will
not see a difference.
\sa QDir::tempPath(), QFile
*/
#ifdef QT_NO_QOBJECT
QTemporaryFile::QTemporaryFile()
: QFile(*new QTemporaryFilePrivate)
{
}
QTemporaryFile::QTemporaryFile(const QString &templateName)
: QFile(*new QTemporaryFilePrivate(templateName))
{
}
#else
/*!
Constructs a QTemporaryFile.
//! [default-file-name-template]
\keyword Default File Name Template
The default file name template is determined from the application name as
returned by QCoreApplication::applicationName() (or \c {"qt_temp"} if the
application name is empty), followed by \c {".XXXXXX"}. The file is stored
in the system's temporary directory, as returned by QDir::tempPath().
//! [default-file-name-template]
\sa setFileTemplate(), fileTemplate(), fileName(), QDir::tempPath()
*/
QTemporaryFile::QTemporaryFile()
: QTemporaryFile(nullptr)
{
}
/*!
\fn QTemporaryFile::QTemporaryFile(const std::filesystem::path &templateName, QObject *parent)
\overload
\since 6.7
*/
/*!
Constructs a QTemporaryFile with \a templateName as the file name template.
//! [file-created-on-open]
Upon opening the temporary file, \a templateName will be used to create
a unique filename.
//! [file-created-on-open]
//! [dynamic-part-of-filename]
If the file name (the part after the last directory path separator in
\a templateName) doesn't contain \c {"XXXXXX"}, it will be added
automatically.
\c {"XXXXXX"} will be replaced with the dynamic part of the file name,
which is calculated to be unique.
//! [dynamic-part-of-filename]
//! [filename-relative-or-absolute-path]
If \a templateName is a relative path, the path will be relative to the
current working directory. You can use QDir::tempPath() to construct \a
templateName if you want use the system's temporary directory.
//! [filename-relative-or-absolute-path]
\include qtemporaryfile.cpp note-about-rename-method
\sa open(), fileTemplate()
*/
QTemporaryFile::QTemporaryFile(const QString &templateName)
: QTemporaryFile(templateName, nullptr)
{
}
/*!
Constructs a QTemporaryFile with the given \a parent.
\include qtemporaryfile.cpp default-file-name-template
\sa setFileTemplate()
*/
QTemporaryFile::QTemporaryFile(QObject *parent)
: QFile(*new QTemporaryFilePrivate, parent)
{
}
/*!
Constructs a QTemporaryFile with the specified \a parent, and
\a templateName as the file name template.
\include qtemporaryfile.cpp file-created-on-open
\include qtemporaryfile.cpp dynamic-part-of-filename
\include qtemporaryfile.cpp filename-relative-or-absolute-path
\include qtemporaryfile.cpp note-about-rename-method
\sa open(), fileTemplate()
*/
QTemporaryFile::QTemporaryFile(const QString &templateName, QObject *parent)
: QFile(*new QTemporaryFilePrivate(templateName), parent)
{
}
#endif
/*!
Destroys the temporary file object, the file is automatically
closed if necessary and if in auto remove mode it will
automatically delete the file.
\sa autoRemove()
*/
QTemporaryFile::~QTemporaryFile()
{
Q_D(QTemporaryFile);
close();
if (!d->fileName.isEmpty() && d->autoRemove)
remove();
}
/*!
\fn bool QTemporaryFile::open()
A QTemporaryFile will always be opened in QIODevice::ReadWrite mode,
this allows easy access to the data in the file. This function will
return true upon success and will set the fileName() to the unique
filename used.
\sa fileName(), QT_USE_NODISCARD_FILE_OPEN
*/
/*!
Returns \c true if the QTemporaryFile is in auto remove
mode. Auto-remove mode will automatically delete the filename from
disk upon destruction. This makes it very easy to create your
QTemporaryFile object on the stack, fill it with data, read from
it, and finally on function return it will automatically clean up
after itself.
Auto-remove is on by default.
\sa setAutoRemove(), remove()
*/
bool QTemporaryFile::autoRemove() const
{
Q_D(const QTemporaryFile);
return d->autoRemove;
}
/*!
Sets the QTemporaryFile into auto-remove mode if \a b is \c true.
Auto-remove is on by default.
If you set this property to \c false, ensure the application provides a way
to remove the file once it is no longer needed, including passing the
responsibility on to another process. Always use the fileName() function to
obtain the name and never try to guess the name that QTemporaryFile has
generated.
On some systems, if fileName() is not called before closing the file, the
temporary file may be removed regardless of the state of this property.
This behavior should not be relied upon, so application code should either
call fileName() or leave the auto removal functionality enabled.
\sa autoRemove(), remove()
*/
void QTemporaryFile::setAutoRemove(bool b)
{
Q_D(QTemporaryFile);
d->autoRemove = b;
}
/*!
Returns the complete unique filename backing the QTemporaryFile
object. This string is null before the QTemporaryFile is opened,
afterwards it will contain the fileTemplate() plus
additional characters to make it unique.
The file name returned by this method is relative or absolute depending on
the file name template used to construct this object (or passed to
setFileTemplate()) being relative or absolute, respectively.
\sa fileTemplate()
*/
QString QTemporaryFile::fileName() const
{
Q_D(const QTemporaryFile);
auto tef = static_cast<QTemporaryFileEngine *>(d->fileEngine.get());
if (tef && tef->isReallyOpen())
const_cast<QTemporaryFilePrivate *>(d)->materializeUnnamedFile();
if (d->fileName.isEmpty())
return QString();
return d->engine()->fileName(QAbstractFileEngine::DefaultName);
}
/*!
Returns the file name template.
The file name template returned by this method, will be relative or
absolute depending on the file name template used to construct this object
(or passed to setFileTemplate()) being relative or absolute, respectively.
\sa setFileTemplate(), fileName(), {Default File Name Template}
*/
QString QTemporaryFile::fileTemplate() const
{
Q_D(const QTemporaryFile);
return d->templateName;
}
/*!
\fn void QTemporaryFile::setFileTemplate(const std::filesystem::path &name)
\overload
\since 6.7
*/
/*!
\fn void QTemporaryFile::setFileTemplate(const QString &templateName)
Sets the file name template to \a templateName.
\include qtemporaryfile.cpp dynamic-part-of-filename
\include qtemporaryfile.cpp filename-relative-or-absolute-path
\include qtemporaryfile.cpp note-about-rename-method
\sa fileTemplate(), fileName()
*/
void QTemporaryFile::setFileTemplate(const QString &name)
{
Q_D(QTemporaryFile);
d->templateName = name;
}
/*!
\fn bool QTemporaryFile::rename(const std::filesystem::path &newName)
\overload
\since 6.7
*/
/*!
Renames the current temporary file to \a newName and returns true if it
succeeded.
This function has an important difference compared to QFile::rename(): it
will not perform a copy+delete if the low-level system call to rename the
file fails, something that could happen if \a newName specifies a file in a
different volume or filesystem than the temporary file was created on. In
other words, QTemporaryFile only supports atomic file renaming.
This functionality is intended to support materializing the destination
file with all contents already present, so another process cannot see an
incomplete file in the process of being written. The \l QSaveFile class can
be used for a similar purpose too, particularly if the destination file is
not temporary.
\sa QSaveFile, QSaveFile::commit(), QFile::rename()
*/
bool QTemporaryFile::rename(const QString &newName)
{
Q_D(QTemporaryFile);
auto tef = static_cast<QTemporaryFileEngine *>(d->fileEngine.get());
if (!tef || !tef->isReallyOpen() || !tef->filePathWasTemplate)
return QFile::rename(newName);
unsetError();
close();
if (error() == QFile::NoError) {
if (tef->rename(newName)) {
unsetError();
// engine was able to handle the new name so we just reset it
d->fileName = newName;
return true;
}
d->setError(QFile::RenameError, tef->errorString());
}
return false;
}
/*!
\fn QTemporaryFile *QTemporaryFile::createNativeFile(const QString &fileName)
\overload
Works on the given \a fileName rather than an existing QFile
object.
*/
/*!
\fn QTemporaryFile *QTemporaryFile::createNativeFile(const std::filesystem::path &fileName)
\overload
\since 6.7
*/
/*!
If \a file is not already a native file, then a QTemporaryFile is created
in QDir::tempPath(), the contents of \a file is copied into it, and a pointer
to the temporary file is returned. Does nothing and returns \c 0 if \a file
is already a native file.
For example:
\snippet code/src_corelib_io_qtemporaryfile.cpp 1
\sa QFileInfo::isNativePath()
*/
QTemporaryFile *QTemporaryFile::createNativeFile(QFile &file)
{
if (QAbstractFileEngine *engine = file.d_func()->engine()) {
if (engine->fileFlags(QAbstractFileEngine::FlagsMask) & QAbstractFileEngine::LocalDiskFlag)
return nullptr; // native already
//cache
bool wasOpen = file.isOpen();
qint64 old_off = 0;
if (wasOpen)
old_off = file.pos();
else if (!file.open(QIODevice::ReadOnly))
return nullptr;
//dump data
QTemporaryFile *ret = new QTemporaryFile;
if (ret->open()) {
file.seek(0);
char buffer[1024];
while (true) {
qint64 len = file.read(buffer, 1024);
if (len < 1)
break;
ret->write(buffer, len);
}
ret->seek(0);
} else {
delete ret;
ret = nullptr;
}
//restore
if (wasOpen)
file.seek(old_off);
else
file.close();
//done
return ret;
}
return nullptr;
}
/*!
\reimp
Creates a unique file name for the temporary file, and opens it. You can
get the unique name later by calling fileName(). The file is guaranteed to
have been created by this function (i.e., it has never existed before).
*/
bool QTemporaryFile::open(OpenMode flags)
{
Q_D(QTemporaryFile);
auto tef = static_cast<QTemporaryFileEngine *>(d->fileEngine.get());
if (tef && tef->isReallyOpen()) {
setOpenMode(flags);
return true;
}
// reset the engine state so it creates a new, unique file name from the template;
// equivalent to:
// delete d->fileEngine;
// d->fileEngine = 0;
// d->engine();
d->resetFileEngine();
if (QFile::open(flags)) {
tef = static_cast<QTemporaryFileEngine *>(d->fileEngine.get());
if (tef->isUnnamedFile())
d->fileName.clear();
else
d->fileName = tef->fileName(QAbstractFileEngine::DefaultName);
return true;
}
return false;
}
#endif // QT_CONFIG(temporaryfile)