qtbase/src/corelib/io/qtemporaryfile.cpp

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#include "qtemporaryfile.h"

#ifndef QT_NO_TEMPORARYFILE

#include "qplatformdefs.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"
#endif

QT_BEGIN_NAMESPACE

#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

/*
 * Copyright (c) 1987, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

/*!
    \internal

    Generates a unique file path and returns a native handle to the open file.
    \a path is used as a template when generating unique paths, \a pos
    identifies the position of the first character that will be replaced in the
    template and \a length the number of characters that may be substituted.

    Returns an open handle to the newly created file if successful, an invalid
    handle otherwise. In both cases, the string in \a path will be changed and
    contain the generated path name.
*/
static bool createFileFromTemplate(NativeFileHandle &file,
        QFileSystemEntry::NativePath &path, size_t pos, size_t length,
        QSystemError &error)
{
    Q_ASSERT(length != 0);
    Q_ASSERT(pos < size_t(path.length()));
    Q_ASSERT(length <= size_t(path.length()) - pos);

    Char *const placeholderStart = (Char *)path.data() + pos;
    Char *const placeholderEnd = placeholderStart + length;

    // Initialize placeholder with random chars + PID.
    {
        Char *rIter = placeholderEnd;

#if defined(QT_BUILD_CORE_LIB)
        quint64 pid = quint64(QCoreApplication::applicationPid());
        do {
            *--rIter = Latin1Char((pid % 10) + '0');
            pid /= 10;
        } while (rIter != placeholderStart && pid != 0);
#endif

        while (rIter != placeholderStart) {
            char ch = char((qrand() & 0xffff) % (26 + 26));
            if (ch < 26)
                *--rIter = Latin1Char(ch + 'A');
            else
                *--rIter = Latin1Char(ch - 26 + 'a');
        }
    }

    for (;;) {
        // Atomically create file and obtain handle
#if defined(Q_OS_WIN)
#  ifndef Q_OS_WINRT
        file = CreateFile((const wchar_t *)path.constData(),
                GENERIC_READ | GENERIC_WRITE,
                FILE_SHARE_READ | FILE_SHARE_WRITE, NULL, CREATE_NEW,
                FILE_ATTRIBUTE_NORMAL, NULL);
#  else // !Q_OS_WINRT
        file = CreateFile2((const wchar_t *)path.constData(),
                GENERIC_READ | GENERIC_WRITE,
                FILE_SHARE_READ | FILE_SHARE_WRITE, CREATE_NEW,
                NULL);
#  endif // Q_OS_WINRT

        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
        file = QT_OPEN(path.constData(),
                QT_OPEN_CREAT | O_EXCL | QT_OPEN_RDWR | QT_OPEN_LARGEFILE,
                0600);

        if (file != -1)
            return true;

        int err = errno;
        if (err != EEXIST) {
            error = QSystemError(err, QSystemError::NativeError);
            return false;
        }
#endif

        /* tricky little algorwwithm for backward compatibility */
        for (Char *iter = placeholderStart;;) {
            // Character progression: [0-9] => 'a' ... 'z' => 'A' .. 'Z'
            // String progression: "ZZaiC" => "aabiC"
            switch (char(*iter)) {
                case 'Z':
                    // Rollover, advance next character
                    *iter = Latin1Char('a');
                    if (++iter == placeholderEnd) {
                        // Out of alternatives. Return file exists error, previously set.
                        error = QSystemError(err, QSystemError::NativeError);
                        return false;
                    }

                    continue;

                case '0': case '1': case '2': case '3': case '4':
                case '5': case '6': case '7': case '8': case '9':
                    *iter = Latin1Char('a');
                    break;

                case 'z':
                    // increment 'z' to 'A'
                    *iter = Latin1Char('A');
                    break;

                default:
                    ++*iter;
                    break;
            }
            break;
        }
    }

    Q_ASSERT(false);
}

//************* QTemporaryFileEngine
QTemporaryFileEngine::~QTemporaryFileEngine()
{
    QFSFileEngine::close();
}

bool QTemporaryFileEngine::isReallyOpen()
{
    Q_D(QFSFileEngine);

    if (!((0 == 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);
}

void QTemporaryFileEngine::setFileTemplate(const QString &fileTemplate)
{
    Q_D(QFSFileEngine);
    if (filePathIsTemplate)
        d->fileEntry = QFileSystemEntry(fileTemplate);
}

bool QTemporaryFileEngine::open(QIODevice::OpenMode openMode)
{
    Q_D(QFSFileEngine);
    Q_ASSERT(!isReallyOpen());

    openMode |= QIODevice::ReadWrite;

    if (!filePathIsTemplate)
        return QFSFileEngine::open(openMode);

    QString qfilename = d->fileEntry.filePath();

    // Ensure there is a placeholder mask
    uint phPos = qfilename.length();
    uint phLength = 0;

    while (phPos != 0) {
        --phPos;

        if (qfilename[phPos] == QLatin1Char('X')) {
            ++phLength;
            continue;
        }

        if (phLength >= 6
                || qfilename[phPos] == QLatin1Char('/')) {
            ++phPos;
            break;
        }

        // start over
        phLength = 0;
    }

    if (phLength < 6)
        qfilename.append(QLatin1String(".XXXXXX"));

    // "Nativify" :-)
    QFileSystemEntry::NativePath filename = QFileSystemEngine::absoluteName(
            QFileSystemEntry(qfilename, QFileSystemEntry::FromInternalPath()))
        .nativeFilePath();

    // Find mask in native path
    phPos = filename.length();
    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);

    QSystemError error;
#if defined(Q_OS_WIN)
    NativeFileHandle &file = d->fileHandle;
#else // POSIX
    NativeFileHandle &file = d->fd;
#endif

    if (!createFileFromTemplate(file, filename, phPos, phLength, error)) {
        setError(QFile::OpenError, error.toString());
        return false;
    }

    d->fileEntry = QFileSystemEntry(filename, QFileSystemEntry::FromNativePath());

#if !defined(Q_OS_WIN) || defined(Q_OS_WINRT)
    d->closeFileHandle = true;
#endif

    filePathIsTemplate = false;

    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.
    QFSFileEngine::close();
    if (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)
{
    QFSFileEngine::close();
    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.
    seek(0);
    setError(QFile::UnspecifiedError, QString());
    return true;
}

//************* QTemporaryFilePrivate

QTemporaryFilePrivate::QTemporaryFilePrivate() : autoRemove(true)
{
}

QTemporaryFilePrivate::~QTemporaryFilePrivate()
{
}

QAbstractFileEngine *QTemporaryFilePrivate::engine() const
{
    if (!fileEngine) {
        if (fileName.isEmpty())
            fileEngine = new QTemporaryFileEngine(templateName);
        else
            fileEngine = new QTemporaryFileEngine(fileName, false);
    }
    return fileEngine;
}

QString QTemporaryFilePrivate::defaultTemplateName()
{
    QString baseName;
#if defined(QT_BUILD_CORE_LIB)
    baseName = QCoreApplication::applicationName();
    if (baseName.isEmpty())
#endif
        baseName = QLatin1String("qt_temp");

    return QDir::tempPath() + QLatin1Char('/') + baseName + QLatin1String(".XXXXXX");
}

//************* 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.

    Specified filenames can contain the following template \c XXXXXX
    (six upper case "X" characters), which will be replaced by the
    auto-generated portion of the filename. Note that the template is
    case sensitive. If the template is not present in the filename,
    QTemporaryFile appends the generated part to the filename given.

    \sa QDir::tempPath(), QFile
*/

#ifdef QT_NO_QOBJECT
QTemporaryFile::QTemporaryFile()
    : QFile(*new QTemporaryFilePrivate)
{
    Q_D(QTemporaryFile);
    d->templateName = QTemporaryFilePrivate::defaultTemplateName();
}

QTemporaryFile::QTemporaryFile(const QString &templateName)
    : QFile(*new QTemporaryFilePrivate)
{
    Q_D(QTemporaryFile);
    d->templateName = templateName;
}

#else
/*!
    Constructs a QTemporaryFile using as file template
    the application name returned by QCoreApplication::applicationName()
    (otherwise \c qt_temp) followed by ".XXXXXX".
    The file is stored in the system's temporary directory, QDir::tempPath().

    \sa setFileTemplate(), QDir::tempPath()
*/
QTemporaryFile::QTemporaryFile()
    : QFile(*new QTemporaryFilePrivate, 0)
{
    Q_D(QTemporaryFile);
    d->templateName = QTemporaryFilePrivate::defaultTemplateName();
}

/*!
    Constructs a QTemporaryFile with a template filename of \a
    templateName. Upon opening the temporary file this will be used to create
    a unique filename.

    If the \a templateName does not contain XXXXXX it will automatically be
    appended and used as the dynamic portion of the filename.

    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.

    \sa open(), fileTemplate()
*/
QTemporaryFile::QTemporaryFile(const QString &templateName)
    : QFile(*new QTemporaryFilePrivate, 0)
{
    Q_D(QTemporaryFile);
    d->templateName = templateName;
}

/*!
    Constructs a QTemporaryFile (with the given \a parent)
    using as file template the application name returned by QCoreApplication::applicationName()
    (otherwise \c qt_temp) followed by ".XXXXXX".
    The file is stored in the system's temporary directory, QDir::tempPath().

    \sa setFileTemplate()
*/
QTemporaryFile::QTemporaryFile(QObject *parent)
    : QFile(*new QTemporaryFilePrivate, parent)
{
    Q_D(QTemporaryFile);
    d->templateName = QTemporaryFilePrivate::defaultTemplateName();
}

/*!
    Constructs a QTemporaryFile with a template filename of \a
    templateName and the specified \a parent.
    Upon opening the temporary file this will be used to
    create a unique filename.

    If the \a templateName does not contain XXXXXX it will automatically be
    appended and used as the dynamic portion of the filename.

    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.

    \sa open(), fileTemplate()
*/
QTemporaryFile::QTemporaryFile(const QString &templateName, QObject *parent)
    : QFile(*new QTemporaryFilePrivate, parent)
{
    Q_D(QTemporaryFile);
    d->templateName = templateName;
}
#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()
*/

/*!
   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 true.

    Auto-remove is on by default.

    \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.

   \sa fileTemplate()
*/

QString QTemporaryFile::fileName() const
{
    Q_D(const QTemporaryFile);
    if(d->fileName.isEmpty())
        return QString();
    return d->engine()->fileName(QAbstractFileEngine::DefaultName);
}

/*!
  Returns the set file template. The default file template will be
  called qcoreappname.XXXXXX and be placed in QDir::tempPath().

  \sa setFileTemplate()
*/
QString QTemporaryFile::fileTemplate() const
{
    Q_D(const QTemporaryFile);
    return d->templateName;
}

/*!
   Sets the static portion of the file name to \a name. If the file
   template ends in XXXXXX that will automatically be replaced with
   the unique part of the filename, otherwise a filename will be
   determined automatically based on the static portion specified.

    If \a name contains a relative file path, the path will be relative to the
    current working directory. You can use QDir::tempPath() to construct \a
    name if you want use the system's temporary directory.

   \sa fileTemplate()
*/
void QTemporaryFile::setFileTemplate(const QString &name)
{
    Q_D(QTemporaryFile);
    d->templateName = name;
    if (d->fileEngine)
        static_cast<QTemporaryFileEngine*>(d->fileEngine)->setFileTemplate(name);
}

/*!
  \fn QTemporaryFile *QTemporaryFile::createLocalFile(const QString &fileName)
  \overload
  \obsolete

  Use QTemporaryFile::createNativeFile(const QString &fileName) instead.
*/

/*!
  \fn QTemporaryFile *QTemporaryFile::createLocalFile(QFile &file)
  \obsolete

  Use QTemporaryFile::createNativeFile(QFile &file) instead.
*/

/*!
  \fn QTemporaryFile *QTemporaryFile::createNativeFile(const QString &fileName)
  \overload

  Works on the given \a fileName rather than an existing QFile
  object.
*/


/*!
  If \a file is not already a native file then a QTemporaryFile is created
  in the tempPath() and \a file is copied into the temporary file, then a
  pointer to the temporary file is returned. If \a file is already a native
  file, a QTemporaryFile is not created, no copy is made and 0 is returned.

  For example:

  QFile f(":/resources/file.txt");
  QTemporaryFile::createNativeFile(f); // Returns a pointer to a temporary file

  QFile f("/users/qt/file.txt");
  QTemporaryFile::createNativeFile(f); // Returns 0

  \sa QFileInfo::isNativePath()
*/

QTemporaryFile *QTemporaryFile::createNativeFile(QFile &file)
{
    if (QAbstractFileEngine *engine = file.d_func()->engine()) {
        if(engine->fileFlags(QAbstractFileEngine::FlagsMask) & QAbstractFileEngine::LocalDiskFlag)
            return 0; //native already
        //cache
        bool wasOpen = file.isOpen();
        qint64 old_off = 0;
        if(wasOpen)
            old_off = file.pos();
        else
            file.open(QIODevice::ReadOnly);
        //dump data
        QTemporaryFile *ret = new QTemporaryFile;
        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);
        //restore
        if(wasOpen)
            file.seek(old_off);
        else
            file.close();
        //done
        return ret;
    }
    return 0;
}

/*!
   \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);
    if (!d->fileName.isEmpty()) {
        if (static_cast<QTemporaryFileEngine*>(d->engine())->isReallyOpen()) {
            setOpenMode(flags);
            return true;
        }
    }

    if (QFile::open(flags)) {
        d->fileName = d->fileEngine->fileName(QAbstractFileEngine::DefaultName);
        return true;
    }
    return false;
}

QT_END_NAMESPACE

#endif // QT_NO_TEMPORARYFILE