qfile.cpp

QT 开发环境里面一个很重要的文件

}

/*!
    \fn void QFile::setEncodingFunction(EncoderFn function)

    \nonreentrant

    Sets the \a function for encoding Unicode file names. The
    default encodes in the locale-specific 8-bit encoding.

    \sa encodeName(), setDecodingFunction()
*/

void
QFile::setEncodingFunction(EncoderFn f)
{
    if (!f)
        f = locale_encode;
    QFilePrivate::encoder = f;
}

/*!
    \typedef QFile::DecoderFn

    This is a typedef for a pointer to a function with the following
    signature:

    \code
        QString myDecoderFunc(const QByteArray &localFileName);
    \endcode

    \sa setDecodingFunction()
*/

/*!
    \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[1024];
                while (!in.atEnd()) {
                    qint64 read = in.read(block, 1024);
                    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.

    \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;
    }
    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 {
                QTemporaryFile out;
                if(!out.open()) {
                    close();
                    error = true;
                    d->setError(QFile::CopyError, QLatin1String("Cannot open for output"));
                } else {
                    char block[1024];
                    while(!atEnd()) {
                        qint64 in = read(block, 1024);
                        if(in == -1)
                            break;
                        if(in != out.write(block, in)) {
                            d->setError(QFile::CopyError, QLatin1String("Failure to write block"));
                            error = true;
                            break;
                        }
                    }
                    if(!error && !out.rename(newName)) {
                        error = true;
                        QString errorMessage = QLatin1String("Cannot create %1 for output");
                        d->setError(QFile::CopyError, errorMessage.arg(newName));
                    }
                }
            }
            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.

    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.

    \sa QIODevice::OpenMode
*/
bool QFile::open(OpenMode mode)
{
    Q_D(QFile);
    if (isOpen()) {
        qWarning("QFile::open: File already open");
        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*)