path: root/src/corelib/io/qfsfileengine.cpp

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#include "qfsfileengine_p.h"
#include "qfsfileengine_iterator_p.h"
#include "qdatetime.h"
#include "qdiriterator.h"
#include "qset.h"
#include <QtCore/qdebug.h>

#ifndef QT_NO_FSFILEENGINE

#if !defined(Q_OS_WINCE)
#include <errno.h>
#endif
#if defined(Q_OS_UNIX)
#include "private/qcore_unix_p.h"
#endif
#include <stdio.h>
#include <stdlib.h>
#if defined(Q_OS_MAC)
# include <private/qcore_mac_p.h>
#endif

QT_BEGIN_NAMESPACE

#ifdef Q_OS_WIN
#  ifndef S_ISREG
#    define S_ISREG(x)   (((x) & S_IFMT) == S_IFREG)
#  endif
#  ifndef S_ISCHR
#    define S_ISCHR(x)   (((x) & S_IFMT) == S_IFCHR)
#  endif
#  ifndef S_ISFIFO
#    define S_ISFIFO(x) false
#  endif
#  ifndef S_ISSOCK
#    define S_ISSOCK(x) false
#  endif
#  ifndef INVALID_FILE_ATTRIBUTES
#    define INVALID_FILE_ATTRIBUTES (DWORD (-1))
#  endif
#endif

/*! \class QFSFileEngine
    \brief The QFSFileEngine class implements Qt's default file engine.
    \since 4.1

    This class is part of the file engine framework in Qt. If you only want to
    access files or directories, use QFile, QFileInfo or QDir instead.

    QFSFileEngine is the default file engine for accessing regular files. It
    is provided for convenience; by subclassing this class, you can alter its
    behavior slightly, without having to write a complete QAbstractFileEngine
    subclass. To install your custom file engine, you must also subclass
    QAbstractFileEngineHandler and create an instance of your handler.

    It can also be useful to create a QFSFileEngine object directly if you
    need to use the local file system inside QAbstractFileEngine::create(), in
    order to avoid recursion (as higher-level classes tend to call
    QAbstractFileEngine::create()).
*/

//**************** QFSFileEnginePrivate
QFSFileEnginePrivate::QFSFileEnginePrivate() : QAbstractFileEnginePrivate()
{
    init();
}

/*!
    \internal
*/
void QFSFileEnginePrivate::init()
{
    is_sequential = 0;
    tried_stat = 0;
#if !defined(Q_OS_WINCE)
    need_lstat = 1;
    is_link = 0;
#endif
    openMode = QIODevice::NotOpen;
    fd = -1;
    fh = 0;
    lastIOCommand = IOFlushCommand;
    lastFlushFailed = false;
    closeFileHandle = false;
#ifdef Q_OS_WIN
    fileAttrib = INVALID_FILE_ATTRIBUTES;
    fileHandle = INVALID_HANDLE_VALUE;
    mapHandle = INVALID_HANDLE_VALUE;
#ifndef Q_OS_WINCE
    cachedFd = -1;
#endif
#endif
}

/*!
    \internal

    Returns the canonicalized form of \a path (i.e., with all symlinks
    resolved, and all redundant path elements removed.
*/
QString QFSFileEnginePrivate::canonicalized(const QString &path)
{
    if (path.isEmpty())
        return path;

    // FIXME let's see if this stuff works, then we might be able to remove some of the other code.
#if defined(Q_OS_UNIX) && !defined(Q_OS_SYMBIAN)
    if (path.size() == 1 && path.at(0) == QLatin1Char('/'))
        return path;
#endif
#if defined(Q_OS_LINUX) || defined(Q_OS_SYMBIAN) || defined(Q_OS_MAC)
    // ... but Linux with uClibc does not have it
#if !defined(__UCLIBC__)
    char *ret = 0;
#if defined(Q_OS_MAC)
    // Mac OS X 10.5.x doesn't support the realpath(X,0) extension we use here.
    if (QSysInfo::MacintoshVersion >= QSysInfo::MV_10_6) {
        ret = realpath(path.toLocal8Bit().constData(), (char*)0);
    } else {
        // on 10.5 we can use FSRef to resolve the file path.
        FSRef fsref;
        if (FSPathMakeRef((const UInt8 *)QDir::cleanPath(path).toUtf8().data(), &fsref, 0) == noErr) {
            CFURLRef urlref = CFURLCreateFromFSRef(NULL, &fsref);
            CFStringRef canonicalPath = CFURLCopyFileSystemPath(urlref, kCFURLPOSIXPathStyle);
            QString ret = QCFString::toQString(canonicalPath);
            CFRelease(canonicalPath);
            CFRelease(urlref);
            return ret;
        }
    }
#else
    ret = realpath(path.toLocal8Bit().constData(), (char*)0);
#endif
    if (ret) {
        QString canonicalPath = QDir::cleanPath(QString::fromLocal8Bit(ret));
        free(ret);
        return canonicalPath;
    }
#endif
#endif

    QFileInfo fi;
    const QChar slash(QLatin1Char('/'));
    QString tmpPath = path;
    int separatorPos = 0;
    QSet<QString> nonSymlinks;
    QSet<QString> known;

    known.insert(path);
    do {
#ifdef Q_OS_WIN
        if (separatorPos == 0) {
            if (tmpPath.size() >= 2 && tmpPath.at(0) == slash && tmpPath.at(1) == slash) {
                // UNC, skip past the first two elements
                separatorPos = tmpPath.indexOf(slash, 2);
            } else if (tmpPath.size() >= 3 && tmpPath.at(1) == QLatin1Char(':') && tmpPath.at(2) == slash) {
                // volume root, skip since it can not be a symlink
                separatorPos = 2;
            }
        }
        if (separatorPos != -1)
#endif
        separatorPos = tmpPath.indexOf(slash, separatorPos + 1);
        QString prefix = separatorPos == -1 ? tmpPath : tmpPath.left(separatorPos);
        if (
#ifdef Q_OS_SYMBIAN
            // Symbian doesn't support directory symlinks, so do not check for link unless we
            // are handling the last path element. This not only slightly improves performance,
            // but also saves us from lot of unnecessary platform security check failures
            // when dealing with files under *:/private directories.
            separatorPos == -1 &&
#endif
            !nonSymlinks.contains(prefix)) {
            fi.setFile(prefix);
            if (fi.isSymLink()) {
                QString target = fi.symLinkTarget();
                if(QFileInfo(target).isRelative())
                    target = fi.absolutePath() + slash + target;
                if (separatorPos != -1) {
                    if (fi.isDir() && !target.endsWith(slash))
                        target.append(slash);
                    target.append(tmpPath.mid(separatorPos));
                }
                tmpPath = QDir::cleanPath(target);
                separatorPos = 0;

                if (known.contains(tmpPath))
                    return QString();
                known.insert(tmpPath);
            } else {
                nonSymlinks.insert(prefix);
            }
        }
    } while (separatorPos != -1);

    return QDir::cleanPath(tmpPath);
}

/*!
    Constructs a QFSFileEngine for the file name \a file.
*/
QFSFileEngine::QFSFileEngine(const QString &file) : QAbstractFileEngine(*new QFSFileEnginePrivate)
{
    Q_D(QFSFileEngine);
    d->filePath = QDir::fromNativeSeparators(file);
    d->nativeInitFileName();
}

/*!
    Constructs a QFSFileEngine.
*/
QFSFileEngine::QFSFileEngine() : QAbstractFileEngine(*new QFSFileEnginePrivate)
{
}

/*!
    \internal
*/
QFSFileEngine::QFSFileEngine(QFSFileEnginePrivate &dd)
    : QAbstractFileEngine(dd)
{
}

/*!
    Destructs the QFSFileEngine.
*/
QFSFileEngine::~QFSFileEngine()
{
    Q_D(QFSFileEngine);
    if (d->closeFileHandle) {
        if (d->fh) {
            int ret;
            do {
                ret = fclose(d->fh);
            } while (ret == EOF && errno == EINTR);
        } else if (d->fd != -1) {
            int ret;
            do {
                ret = QT_CLOSE(d->fd);
            } while (ret == -1 && errno == EINTR);
        }
    }
    QList<uchar*> keys = d->maps.keys();
    for (int i = 0; i < keys.count(); ++i)
        unmap(keys.at(i));
}

/*!
    \reimp
*/
void QFSFileEngine::setFileName(const QString &file)
{
    Q_D(QFSFileEngine);
    d->init();
    d->filePath = QDir::fromNativeSeparators(file);
    d->nativeInitFileName();
}

/*!
    \reimp
*/
bool QFSFileEngine::open(QIODevice::OpenMode openMode)
{
    Q_D(QFSFileEngine);
    if (d->filePath.isEmpty()) {
        qWarning("QFSFileEngine::open: No file name specified");
        setError(QFile::OpenError, QLatin1String("No file name specified"));
        return false;
    }

    // Append implies WriteOnly.
    if (openMode & QFile::Append)
        openMode |= QFile::WriteOnly;

    // WriteOnly implies Truncate if neither ReadOnly nor Append are sent.
    if ((openMode & QFile::WriteOnly) && !(openMode & (QFile::ReadOnly | QFile::Append)))
        openMode |= QFile::Truncate;

    d->openMode = openMode;
    d->lastFlushFailed = false;
    d->tried_stat = 0;
    d->fh = 0;
    d->fd = -1;

    return d->nativeOpen(openMode);
}

/*!
    Opens the file handle \a fh in \a openMode mode. Returns true on
    success; otherwise returns false.
*/
bool QFSFileEngine::open(QIODevice::OpenMode openMode, FILE *fh)
{
    Q_D(QFSFileEngine);

    // Append implies WriteOnly.
    if (openMode & QFile::Append)
        openMode |= QFile::WriteOnly;

    // WriteOnly implies Truncate if neither ReadOnly nor Append are sent.
    if ((openMode & QFile::WriteOnly) && !(openMode & (QFile::ReadOnly | QFile::Append)))
        openMode |= QFile::Truncate;

    d->openMode = openMode;
    d->lastFlushFailed = false;
    d->closeFileHandle = false;
    d->nativeFilePath.clear();
    d->filePath.clear();
    d->tried_stat = 0;
    d->fd = -1;

    return d->openFh(openMode, fh);
}

/*!
    Opens the file handle \a fh using the open mode \a flags.
*/
bool QFSFileEnginePrivate::openFh(QIODevice::OpenMode openMode, FILE *fh)
{
    Q_Q(QFSFileEngine);
    this->fh = fh;
    fd = -1;

    // Seek to the end when in Append mode.
    if (openMode & QIODevice::Append) {
        int ret;
        do {
            ret = QT_FSEEK(fh, 0, SEEK_END);
        } while (ret != 0 && errno == EINTR);

        if (ret != 0) {
            q->setError(errno == EMFILE ? QFile::ResourceError : QFile::OpenError,
                        qt_error_string(int(errno)));

            this->openMode = QIODevice::NotOpen;
            this->fh = 0;

            return false;
        }
    }

    return true;
}

/*!
    Opens the file descriptor \a fd in \a openMode mode. Returns true
    on success; otherwise returns false.
*/
bool QFSFileEngine::open(QIODevice::OpenMode openMode, int fd)
{
    Q_D(QFSFileEngine);

    // Append implies WriteOnly.
    if (openMode & QFile::Append)
        openMode |= QFile::WriteOnly;

    // WriteOnly implies Truncate if neither ReadOnly nor Append are sent.
    if ((openMode & QFile::WriteOnly) && !(openMode & (QFile::ReadOnly | QFile::Append)))
        openMode |= QFile::Truncate;

    d->openMode = openMode;
    d->lastFlushFailed = false;
    d->closeFileHandle = false;
    d->nativeFilePath.clear();
    d->filePath.clear();
    d->fh = 0;
    d->fd = -1;
    d->tried_stat = 0;

    return d->openFd(openMode, fd);
}


/*!
    Opens the file descriptor \a fd to the file engine, using the open mode \a
    flags.
*/
bool QFSFileEnginePrivate::openFd(QIODevice::OpenMode openMode, int fd)
{
    Q_Q(QFSFileEngine);
    this->fd = fd;
    fh = 0;

    // Seek to the end when in Append mode.
    if (openMode & QFile::Append) {
        int ret;
        do {
            ret = QT_LSEEK(fd, 0, SEEK_END);
        } while (ret == -1 && errno == EINTR);

        if (ret == -1) {
            q->setError(errno == EMFILE ? QFile::ResourceError : QFile::OpenError,
                        qt_error_string(int(errno)));

            this->openMode = QIODevice::NotOpen;
            this->fd = -1;

            return false;
        }
    }

    return true;
}

/*!
    \reimp
*/
bool QFSFileEngine::close()
{
    Q_D(QFSFileEngine);
    d->openMode = QIODevice::NotOpen;
    return d->nativeClose();
}

/*!
    \internal
*/
bool QFSFileEnginePrivate::closeFdFh()
{
    Q_Q(QFSFileEngine);
    if (fd == -1 && !fh)
        return false;

    // Flush the file if it's buffered, and if the last flush didn't fail.
    bool flushed = !fh || (!lastFlushFailed && q->flush());
    bool closed = true;
    tried_stat = 0;

    // Close the file if we created the handle.
    if (closeFileHandle) {
        int ret;
        do {
            if (fh) {
                // Close buffered file.
                ret = fclose(fh) != 0 ? -1 : 0;
            } else {
                // Close unbuffered file.
                ret = QT_CLOSE(fd);
            }
        } while (ret == -1 && errno == EINTR);

        // We must reset these guys regardless; calling close again after a
        // failed close causes crashes on some systems.
        fh = 0;
        fd = -1;
        closed = (ret == 0);
    }

    // Report errors.
    if (!flushed || !closed) {
        if (flushed) {
            // If not flushed, we want the flush error to fall through.
            q->setError(QFile::UnspecifiedError, qt_error_string(errno));
        }
        return false;
    }

    return true;
}

/*!
    \reimp
*/
bool QFSFileEngine::flush()
{
    Q_D(QFSFileEngine);
    if ((d->openMode & QIODevice::WriteOnly) == 0) {
        // Nothing in the write buffers, so flush succeeds in doing
        // nothing.
        return true;
    }
    return d->nativeFlush();
}

/*!
    \internal
*/
bool QFSFileEnginePrivate::flushFh()
{
    Q_Q(QFSFileEngine);

    // Never try to flush again if the last flush failed. Otherwise you can
    // get crashes on some systems (AIX).
    if (lastFlushFailed)
        return false;

    int ret = fflush(fh);

    lastFlushFailed = (ret != 0);
    lastIOCommand = QFSFileEnginePrivate::IOFlushCommand;

    if (ret != 0) {
        q->setError(errno == ENOSPC ? QFile::ResourceError : QFile::WriteError,
                    qt_error_string(errno));
        return false;
    }
    return true;
}

/*!
    \reimp
*/
qint64 QFSFileEngine::size() const
{
    Q_D(const QFSFileEngine);
    return d->nativeSize();
}

/*!
    \internal
*/
qint64 QFSFileEnginePrivate::sizeFdFh() const
{
    Q_Q(const QFSFileEngine);
    // ### Fix this function, it should not stat unless the file is closed.
    QT_STATBUF st;
    int ret = 0;
    const_cast<QFSFileEngine *>(q)->flush();
    if (fh && nativeFilePath.isEmpty()) {
        // Buffered stdlib mode.
        // ### This should really be an ftell
        ret = QT_FSTAT(QT_FILENO(fh), &st);
    } else if (fd == -1) {
        // Stateless stat.
        ret = QT_STAT(nativeFilePath.constData(), &st);
    } else {
        // Unbuffered stdio mode.
        ret = QT_FSTAT(fd, &st);
    }
    if (ret == -1)
        return 0;
    return st.st_size;
}

/*!
    \reimp
*/
qint64 QFSFileEngine::pos() const
{
    Q_D(const QFSFileEngine);
    return d->nativePos();
}

/*!
    \internal
*/
qint64 QFSFileEnginePrivate::posFdFh() const
{
    if (fh)
        return qint64(QT_FTELL(fh));
    return QT_LSEEK(fd, 0, SEEK_CUR);
}

/*!
    \reimp
*/
bool QFSFileEngine::seek(qint64 pos)
{
    Q_D(QFSFileEngine);
    return d->nativeSeek(pos);
}

/*!
    \internal
*/
bool QFSFileEnginePrivate::seekFdFh(qint64 pos)
{
    Q_Q(QFSFileEngine);

    // On Windows' stdlib implementation, the results of calling fread and
    // fwrite are undefined if not called either in sequence, or if preceded
    // with a call to fflush().
    if (lastIOCommand != QFSFileEnginePrivate::IOFlushCommand && !q->flush())
        return false;

    if (pos < 0 || pos != qint64(QT_OFF_T(pos)))
        return false;

    if (fh) {
        // Buffered stdlib mode.
        int ret;
        do {
            ret = QT_FSEEK(fh, QT_OFF_T(pos), SEEK_SET);
        } while (ret != 0 && errno == EINTR);

        if (ret != 0) {
            q->setError(QFile::ReadError, qt_error_string(int(errno)));
            return false;
        }
    } else {
        // Unbuffered stdio mode.
        if (QT_LSEEK(fd, QT_OFF_T(pos), SEEK_SET) == -1) {
            qWarning() << "QFile::at: Cannot set file position" << pos;
            q->setError(QFile::PositionError, qt_error_string(errno));
            return false;
        }
    }
    return true;
}

/*!
    \reimp
*/
int QFSFileEngine::handle() const
{
    Q_D(const QFSFileEngine);
    return d->nativeHandle();
}

/*!
    \reimp
*/
qint64 QFSFileEngine::read(char *data, qint64 maxlen)
{
    Q_D(QFSFileEngine);

    // On Windows' stdlib implementation, the results of calling fread and
    // fwrite are undefined if not called either in sequence, or if preceded
    // with a call to fflush().
    if (d->lastIOCommand != QFSFileEnginePrivate::IOReadCommand) {
        flush();
        d->lastIOCommand = QFSFileEnginePrivate::IOReadCommand;
    }

    return d->nativeRead(data, maxlen);
}

/*!
    \internal
*/
qint64 QFSFileEnginePrivate::readFdFh(char *data, qint64 len)
{
    Q_Q(QFSFileEngine);

    if (len < 0 || len != qint64(size_t(len))) {
        q->setError(QFile::ReadError, qt_error_string(EINVAL));
        return -1;
    }

    qint64 readBytes = 0;
    bool eof = false;

    if (fh) {
        // Buffered stdlib mode.

        size_t result;
        bool retry = true;
        do {
            result = fread(data + readBytes, 1, size_t(len - readBytes), fh);
            eof = feof(fh);
            if (retry && eof && result == 0) {
                // On Mac OS, this is needed, e.g., if a file was written to
                // through another stream since our last read. See test
                // tst_QFile::appendAndRead
                QT_FSEEK(fh, QT_FTELL(fh), SEEK_SET); // re-sync stream.
                retry = false;
                continue;
            }
            readBytes += result;
        } while (!eof && (result == 0 ? errno == EINTR : readBytes < len));

    } else if (fd != -1) {
        // Unbuffered stdio mode.

#ifdef Q_OS_WIN
        int result;
#else
        ssize_t result;
#endif
        do {
            result = QT_READ(fd, data + readBytes, size_t(len - readBytes));
        } while ((result == -1 && errno == EINTR)
                || (result > 0 && (readBytes += result) < len));

        eof = !(result == -1);
    }

    if (!eof && readBytes == 0) {
        readBytes = -1;
        q->setError(QFile::ReadError, qt_error_string(errno));
    }

    return readBytes;
}

/*!
    \reimp
*/
qint64 QFSFileEngine::readLine(char *data, qint64 maxlen)
{
    Q_D(QFSFileEngine);

    // On Windows' stdlib implementation, the results of calling fread and
    // fwrite are undefined if not called either in sequence, or if preceded
    // with a call to fflush().
    if (d->lastIOCommand != QFSFileEnginePrivate::IOReadCommand) {
        flush();
        d->lastIOCommand = QFSFileEnginePrivate::IOReadCommand;
    }

    return d->nativeReadLine(data, maxlen);
}

/*!
    \internal
*/
qint64 QFSFileEnginePrivate::readLineFdFh(char *data, qint64 maxlen)
{
    Q_Q(QFSFileEngine);
    if (!fh)
        return q->QAbstractFileEngine::readLine(data, maxlen);

    QT_OFF_T oldPos = 0;
#ifdef Q_OS_WIN
    bool seq = q->isSequential();
    if (!seq)
#endif
        oldPos = QT_FTELL(fh);

    // QIODevice::readLine() passes maxlen - 1 to QFile::readLineData()
    // because it has made space for the '\0' at the end of data.  But fgets
    // does the same, so we'd get two '\0' at the end - passing maxlen + 1
    // solves this.
    if (!fgets(data, int(maxlen + 1), fh)) {
        if (!feof(fh))
            q->setError(QFile::ReadError, qt_error_string(int(errno)));
        return -1;              // error
    }

#ifdef Q_OS_WIN
    if (seq)
        return qstrlen(data);
#endif

    qint64 lineLength = QT_FTELL(fh) - oldPos;
    return lineLength > 0 ? lineLength : qstrlen(data);
}

/*!
    \reimp
*/
qint64 QFSFileEngine::write(const char *data, qint64 len)
{
    Q_D(QFSFileEngine);

    // On Windows' stdlib implementation, the results of calling fread and
    // fwrite are undefined if not called either in sequence, or if preceded
    // with a call to fflush().
    if (d->lastIOCommand != QFSFileEnginePrivate::IOWriteCommand) {
        flush();
        d->lastIOCommand = QFSFileEnginePrivate::IOWriteCommand;
    }

    return d->nativeWrite(data, len);
}

/*!
    \internal
*/
qint64 QFSFileEnginePrivate::writeFdFh(const char *data, qint64 len)
{
    Q_Q(QFSFileEngine);

    if (len < 0 || len != qint64(size_t(len))) {
        q->setError(QFile::WriteError, qt_error_string(EINVAL));
        return -1;
    }

    qint64 writtenBytes = 0;

    if (fh) {
        // Buffered stdlib mode.

        size_t result;
        do {
            result = fwrite(data + writtenBytes, 1, size_t(len - writtenBytes), fh);
            writtenBytes += result;
        } while (result == 0 ? errno == EINTR : writtenBytes < len);

    } else if (fd != -1) {
        // Unbuffered stdio mode.

#ifdef Q_OS_WIN
        int result;
#else
        ssize_t result;
#endif
        do {
            result = QT_WRITE(fd, data + writtenBytes, size_t(len - writtenBytes));
        } while ((result == -1 && errno == EINTR)
                || (result > 0 && (writtenBytes += result) < len));
    }

    if (len &&  writtenBytes == 0) {
        writtenBytes = -1;
        q->setError(errno == ENOSPC ? QFile::ResourceError : QFile::WriteError, qt_error_string(errno));
    }

    return writtenBytes;
}

/*!
    \internal
*/
QAbstractFileEngine::Iterator *QFSFileEngine::beginEntryList(QDir::Filters filters, const QStringList &filterNames)
{
    return new QFSFileEngineIterator(filters, filterNames);
}

/*!
    \internal
*/
QAbstractFileEngine::Iterator *QFSFileEngine::endEntryList()
{
    return 0;
}

/*!
    \internal
*/
QStringList QFSFileEngine::entryList(QDir::Filters filters, const QStringList &filterNames) const
{
    return QAbstractFileEngine::entryList(filters, filterNames);
}

/*!
    \reimp
*/
bool QFSFileEngine::isSequential() const
{
    Q_D(const QFSFileEngine);
    if (d->is_sequential == 0)
        d->is_sequential = d->nativeIsSequential() ? 1 : 2;
    return d->is_sequential == 1;
}

/*!
    \internal
*/
bool QFSFileEnginePrivate::isSequentialFdFh() const
{
    if (!tried_stat)
        doStat();
    if (could_stat) {
#ifdef Q_OS_UNIX
        return (st.st_mode & S_IFMT) != S_IFREG;
        // ### WINDOWS!
#endif
    }
    return true;
}

/*!
    \reimp
*/
bool QFSFileEngine::extension(Extension extension, const ExtensionOption *option, ExtensionReturn *output)
{
    Q_D(QFSFileEngine);
    if (extension == AtEndExtension && d->fh && isSequential())
        return feof(d->fh);

    if (extension == MapExtension) {
        const MapExtensionOption *options = (MapExtensionOption*)(option);
        MapExtensionReturn *returnValue = static_cast<MapExtensionReturn*>(output);
        returnValue->address = d->map(options->offset, options->size, options->flags);
        return (returnValue->address != 0);
    }
    if (extension == UnMapExtension) {
        UnMapExtensionOption *options = (UnMapExtensionOption*)option;
        return d->unmap(options->address);
    }

    return false;
}

/*!
    \reimp
*/
bool QFSFileEngine::supportsExtension(Extension extension) const
{
    Q_D(const QFSFileEngine);
    if (extension == AtEndExtension && d->fh && isSequential())
        return true;
    if (extension == FastReadLineExtension && d->fh)
        return true;
    if (extension == FastReadLineExtension && d->fd != -1 && isSequential())
        return true;
    if (extension == UnMapExtension || extension == MapExtension)
        return true;
    return false;
}

/*! \fn bool QFSFileEngine::caseSensitive() const
  Returns true for Windows, false for Unix.
*/

/*! \fn bool QFSFileEngine::copy(const QString &copyName)

  For windows, copy the file to file \a copyName.

  Not implemented for Unix.
*/

/*! \fn QString QFSFileEngine::currentPath(const QString &fileName)
  For Unix, returns the current working directory for the file
  engine.

  For Windows, returns the canonicalized form of the current path used
  by the file engine for the drive specified by \a fileName.  On
  Windows, each drive has its own current directory, so a different
  path is returned for file names that include different drive names
  (e.g. A: or C:).

  \sa setCurrentPath()
*/

/*! \fn QFileInfoList QFSFileEngine::drives()
  For Windows, returns the list of drives in the file system as a list
  of QFileInfo objects. On unix, Mac OS X and Windows CE, only the
  root path is returned.  On Windows, this function returns all drives
  (A:\, C:\, D:\, etc.).

  For Unix, the list contains just the root path "/".
*/

/*! \fn QString QFSFileEngine::fileName(FileName file) const
  \reimp
*/

/*! \fn QDateTime QFSFileEngine::fileTime(FileTime time) const
  \reimp
*/

/*! \fn QString QFSFileEngine::homePath()
  Returns the home path of the current user.

  \sa rootPath()
*/

/*! \fn bool QFSFileEngine::isRelativePath() const
  \reimp
*/

/*! \fn bool QFSFileEngine::link(const QString &newName)

  Creates a link from the file currently specified by fileName() to
  \a newName. What a link is depends on the underlying filesystem
  (be it a shortcut on Windows or a symbolic link on Unix). Returns
  true if successful; otherwise returns false.
*/

/*! \fn bool QFSFileEngine::mkdir(const QString &name, bool createParentDirectories) const
  \reimp
*/

/*! \fn uint QFSFileEngine::ownerId(FileOwner own) const
  In Unix, if stat() is successful, the \c uid is returned if
  \a own is the owner. Otherwise the \c gid is returned. If stat()
  is unsuccessful, -2 is reuturned.

  For Windows, -2 is always returned.
*/

/*! \fn QString QFSFileEngine::owner(FileOwner own) const
  \reimp
*/

/*! \fn bool QFSFileEngine::remove()
  \reimp
*/

/*! \fn bool QFSFileEngine::rename(const QString &newName)
  \reimp
*/

/*! \fn bool QFSFileEngine::rmdir(const QString &name, bool recurseParentDirectories) const
  \reimp
*/

/*! \fn QString QFSFileEngine::rootPath()
  Returns the root path.

  \sa homePath()
*/

/*! \fn bool QFSFileEngine::setCurrentPath(const QString &path)
  Sets the current path (e.g., for QDir), to \a path. Returns true if the
  new path exists; otherwise this function does nothing, and returns false.

  \sa currentPath()
*/

/*! \fn bool QFSFileEngine::setPermissions(uint perms)
  \reimp
*/

/*! \fn bool QFSFileEngine::setSize(qint64 size)
  \reimp
*/

/*! \fn QString QFSFileEngine::tempPath()
  Returns the temporary path (i.e., a path in which it is safe
  to store temporary files).
*/

/*! \fn QAbstractFileEngine::FileFlags QFSFileEnginePrivate::getPermissions(QAbstractFileEngine::FileFlags type) const
    \internal
*/

QT_END_NAMESPACE

#endif // QT_NO_FSFILEENGINE