qfile.cpp

奇趣公司比较新的qt/emd版本

    \fn void QFile::setDecodingFunction(DecoderFn function)

    \nonreentrant

    Sets the \a function for decoding 8-bit file names. The
    default uses the locale-specific 8-bit encoding.

    \sa setEncodingFunction(), decodeName()
*/

void
QFile::setDecodingFunction(DecoderFn f)
{
    if (!f)
        f = locale_decode;
    QFilePrivate::decoder = f;
}

/*!
    \overload

    Returns true if the file specified by fileName() exists; otherwise
    returns false.

    \sa fileName(), setFileName()
*/

bool
QFile::exists() const
{
    // 0x1000000 = QAbstractFileEngine::Refresh, forcing an update
    return (fileEngine()->fileFlags(QAbstractFileEngine::FlagsMask
                                    | QAbstractFileEngine::FileFlag(0x1000000)) & QAbstractFileEngine::ExistsFlag);
}

/*!
    Returns true if the file specified by \a fileName exists; otherwise
    returns false.
*/

bool
QFile::exists(const QString &fileName)
{
    return QFileInfo(fileName).exists();
}

/*!
    \fn QString QFile::symLinkTarget() const
    \since 4.2
    \overload

    Returns the absolute path of the file or directory a symlink (or shortcut
    on Windows) points to, or a an empty string if the object isn't a symbolic
    link.

    This name may not represent an existing file; it is only a string.
    QFile::exists() returns true if the symlink points to an existing file.

    \sa fileName() setFileName()
*/

/*!
    \obsolete

    Use symLinkTarget() instead.
*/
QString
QFile::readLink() const
{
    return fileEngine()->fileName(QAbstractFileEngine::LinkName);
}

/*!
    \fn static QString QFile::symLinkTarget(const QString &fileName)
    \since 4.2

    Returns the absolute path of the file or directory referred to by the
    symlink (or shortcut on Windows) specified by \a fileName, or returns an
    empty string if the \a fileName does not correspond to a symbolic link.

    This name may not represent an existing file; it is only a string.
    QFile::exists() returns true if the symlink points to an existing file.
*/

/*!
    \obsolete

    Use symLinkTarget() instead.
*/
QString
QFile::readLink(const QString &fileName)
{
    return QFileInfo(fileName).readLink();
}

/*!
    Removes the file specified by fileName(). Returns true if successful;
    otherwise returns false.

    The file is closed before it is removed.

    \sa setFileName()
*/

bool
QFile::remove()
{
    Q_D(QFile);
    if (d->fileName.isEmpty()) {
        qWarning("QFile::remove: Empty or null file name");
        return false;
    }
    close();
    if(error() == QFile::NoError) {
        if(fileEngine()->remove()) {
            unsetError();
            return true;
        }
        d->setError(QFile::RemoveError, errno);
    }
    return false;
}

/*!
    \overload

    Removes the file specified by the \a fileName given.

    Returns true if successful; otherwise returns false.

    \sa remove()
*/

bool
QFile::remove(const QString &fileName)
{
    return QFile(fileName).remove();
}

/*!
    Renames the file currently specified by fileName() to \a newName.
    Returns true if successful; otherwise returns false.

    If a file with the name \a newName already exists, rename() returns false
    (i.e., QFile will not overwrite it).

    The file is closed before it is renamed.

    \sa setFileName()
*/

bool
QFile::rename(const QString &newName)
{
    Q_D(QFile);
    if (d->fileName.isEmpty()) {
        qWarning("QFile::rename: Empty or null file name");
        return false;
    }
    if (QFile(newName).exists()) {
        // ### Race condition. If a file is moved in after this, it /will/ be
        // overwritten. On Unix, the proper solution is to use hardlinks:
        // return ::link(old, new) && ::remove(old);
        d->setError(QFile::RenameError, QLatin1String("Destination file exists"));
        return false;
    }
    close();
    if(error() == QFile::NoError) {
        if (fileEngine()->rename(newName)) {
            unsetError();
            return true;
        }

        QFile in(fileName());
        QFile out(newName);
        if (in.open(QIODevice::ReadOnly)) {
            if (out.open(QIODevice::WriteOnly | QIODevice::Truncate)) {
                bool error = false;
                char block[4096];
                while (!in.atEnd()) {
                    qint64 read = in.read(block, sizeof(block));
                    if (read == -1) {
                        d->setError(QFile::RenameError, in.errorString());
                        error = true;
                        break;
                    }
                    if (read != out.write(block, read)) {
                        d->setError(QFile::RenameError, out.errorString());
                        error = true;
                        break;
                    }
                }
                if(!error)
                    in.remove();
                return !error;
            }
        }
        d->setError(QFile::RenameError, out.isOpen() ? in.errorString() : out.errorString());
    }
    return false;
}

/*!
    \overload

    Renames the file \a oldName to \a newName. Returns true if
    successful; otherwise returns false.

    If a file with the name \a newName already exists, rename() returns false
    (i.e., QFile will not overwrite it).

    \sa rename()
*/

bool
QFile::rename(const QString &oldName, const QString &newName)
{
    return QFile(oldName).rename(newName);
}

/*!

    Creates a link named \a linkName that points to the file currently specified by
    fileName().  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.

    This function will not overwrite an already existing entity in the file system;
    in this case, \c link() will return false and set \l{QFile::}{error()} to
    return \l{QFile::}{RenameError}.

    \note To create a valid link on Windows, \a linkName must have a \c{.lnk} file extension.

    \sa setFileName()
*/

bool
QFile::link(const QString &linkName)
{
    Q_D(QFile);
    if (d->fileName.isEmpty()) {
        qWarning("QFile::link: Empty or null file name");
        return false;
    }
    QFileInfo fi(linkName);
    if(fileEngine()->link(fi.absoluteFilePath())) {
        unsetError();
        return true;
    }
    d->setError(QFile::RenameError, errno);
    return false;
}

/*!
    \overload

    Creates a link named \a linkName that points to the file \a fileName. 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.

    \sa link()
*/

bool
QFile::link(const QString &fileName, const QString &linkName)
{
    return QFile(fileName).link(linkName);
}

/*!
    Copies the file currently specified by fileName() to a file called
    \a newName.  Returns true if successful; otherwise returns false.

    Note that if a file with the name \a newName already exists,
    copy() returns false (i.e. QFile will not overwrite it).

    The source file is closed before it is copied.

    \sa setFileName()
*/

bool
QFile::copy(const QString &newName)
{
    Q_D(QFile);
    if (d->fileName.isEmpty()) {
        qWarning("QFile::copy: Empty or null file name");
        return false;
    }
    if (QFile(newName).exists()) {
        // ### Race condition. If a file is moved in after this, it /will/ be
        // overwritten. On Unix, the proper solution is to use hardlinks:
        // return ::link(old, new) && ::remove(old); See also rename().
        d->setError(QFile::CopyError, QLatin1String("Destination file exists"));
        return false;
    }
    close();
    if(error() == QFile::NoError) {
        if(fileEngine()->copy(newName)) {
            unsetError();
            return true;
        } else {
            bool error = false;
            if(!open(QFile::ReadOnly)) {
                error = true;
                QString errorMessage = QLatin1String("Cannot open %1 for input");
                d->setError(QFile::CopyError, errorMessage.arg(d->fileName));
            } else {
                QString fileTemplate = QLatin1String("%1/qt_temp.XXXXXX");
#ifdef QT_NO_TEMPORARYFILE
                QFile out(fileTemplate.arg(QFileInfo(newName).path()));
                if (!out.open(QIODevice::ReadWrite))
                    error = true;
#else
                QTemporaryFile out(fileTemplate.arg(QFileInfo(newName).path()));
                if (!out.open()) {
                    out.setFileTemplate(fileTemplate.arg(QDir::tempPath()));
                    if (!out.open())
                        error = true;
                }
#endif
                if (error) {
                    out.close();
                    d->setError(QFile::CopyError, QLatin1String("Cannot open for output"));
                } else {
                    char block[4096];
                    qint64 totalRead = 0;
                    while(!atEnd()) {
                        qint64 in = read(block, sizeof(block));
                        if (in <= 0)
                            break;
                        totalRead += in;
                        if(in != out.write(block, in)) {
                            d->setError(QFile::CopyError, QLatin1String("Failure to write block"));
                            error = true;
                            break;
                        }
                    }

                    if (totalRead != size()) {
                        // Unable to read from the source. The error string is
                        // already set from read().
                        error = true;
                    }
                    if (!error && !out.rename(newName)) {
                        error = true;
                        QString errorMessage = QLatin1String("Cannot create %1 for output");
                        d->setError(QFile::CopyError, errorMessage.arg(newName));
                    }
#ifndef QT_NO_TEMPORARYFILE
                    if (!error)
                        out.setAutoRemove(false);
#endif
                }
            }
            if(!error) {
                QFile::setPermissions(newName, permissions());
                unsetError();
                return true;
            }
        }
    }
    return false;
}

/*!
    \overload

    Copies the file \a fileName to \a newName. Returns true if successful;
    otherwise returns false.

    If a file with the name \a newName already exists, copy() returns false
    (i.e., QFile will not overwrite it).

    \sa rename()
*/

bool
QFile::copy(const QString &fileName, const QString &newName)
{
    return QFile(fileName).copy(newName);
}

/*!
    Returns true if the file can only be manipulated sequentially;
    otherwise returns false.

    Most files support random-access, but some special files may not.

    \sa QIODevice::isSequential()
*/
bool QFile::isSequential() const
{
    Q_D(const QFile);
    return d->fileEngine && d->fileEngine->isSequential();
}

/*!
    Opens the file using OpenMode \a mode, returning true if successful;
    otherwise false.

    The \a mode must be QIODevice::ReadOnly, QIODevice::WriteOnly, or
    QIODevice::ReadWrite. It may also have additional flags, such as
    QIODevice::Text and QIODevice::Unbuffered.

    \note In \l{QIODevice::}{WriteOnly} or \l{QIODevice::}{ReadWrite}
    mode, if the relevant file does not already exist, this function
    will try to create a new file before opening it.

    \note Because of limitations in the native API, QFile ignores the
    Unbuffered flag on Windows.

    \sa QIODevice::OpenMode, setFileName()
*/
bool QFile::open(OpenMode mode)
{
    Q_D(QFile);
    if (isOpen()) {
        qWarning("QFile::open: File (%s) already open", qPrintable(fileName()));
        return false;
    }
    if (mode & Append)
        mode |= WriteOnly;

    unsetError();
    if ((mode & (ReadOnly | WriteOnly)) == 0) {
        qWarning("QIODevice::open: File access not specified");
        return false;
    }
    if (fileEngine()->open(mode)) {
        setOpenMode(mode);
        if (mode & Append)
            seek(size());
        return true;
    }
    QFile::FileError err = fileEngine()->error();
    if(err == QFile::UnspecifiedError)
        err = QFile::OpenError;
    d->setError(err, fileEngine()->errorString());
    return false;
}

/*! \fn QFile::open(OpenMode, FILE*)

    Use open(FILE *, OpenMode) instead.
*/

/*!
    \overload

    Opens the existing file handle \a fh in the given \a mode.
    Returns true if successful; otherwise returns false.

    Example:
    \code
        #include <stdio.h>

        void printError(const char* msg)
        {
            QFile file;
            file.open(stderr, QIODevice::WriteOnly);
            file.write(msg, qstrlen(msg));        // write to stderr
            file.close();
        }
    \endcode

    When a QFile is opened using this function, close() does not actually
    close the file, but only flushes it.

    \warning If \a fh is \c stdin, \c stdout, or \c stderr, you may not be
    able to seek(). See QIODevice::isSequentialAccess() for more
    information.

    \bold{Note:} On Windows, you need to enable support for console applications
    in order to use the stdin, stdout and stderr streams at the console. To do
    this, add the following declaration to your application's project file:

    \code
    CONFIG += console
    \endcode

    \note On Windows, \a fh must be opened in binary mode (i.e., the mode
    string must contain 'b', as in "rb" or "wb") when accessing files and
    other random-access devices. Qt will translate the end-of-line characters
    if you pass QIODevice::Text to \a mode. Sequential devices, such as stdin
    and stdout, are unaffected by this limitation.

    \sa close(), {qmake Variable Reference#CONFIG}{qmake Variable Reference}
*/
bool QFile::open(FILE *fh, OpenMode mode)
{
    Q_D(QFile);
    if (isOpen()) {
        qWarning("QFile::open: File (%s) already open", qPrintable(fileName()));
        return false;
    }
    if (mode & Append)
        mode |= WriteOnly;
    unsetError();
    if ((mode & (ReadOnly | WriteOnly)) == 0) {
        qWarning("QFile::open: File access not specified");
        return false;
    }
    if(d->openExternalFile(mode, fh)) {
        setOpenMode(mode);
        if (mode & Append) {
            seek(size());
        } else {
            long pos = ftell(fh);
            if (pos != -1)
                seek(pos);
        }