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Please review the following information to ** ensure the GNU General Public License version 3.0 requirements will be ** met: http://www.gnu.org/copyleft/gpl.html. ** ** ** $QT_END_LICENSE$ ** ****************************************************************************/ #include "qsocketnotifier.h" #include "qplatformdefs.h" #include "qabstracteventdispatcher.h" #include "qcoreapplication.h" #include "qobject_p.h" #include QT_BEGIN_NAMESPACE /*! \class QSocketNotifier \brief The QSocketNotifier class provides support for monitoring activity on a file descriptor. \ingroup network \ingroup io The QSocketNotifier makes it possible to integrate Qt's event loop with other event loops based on file descriptors. For example, the \l{CORBA Framework} uses it to process CORBA events. File descriptor action is detected in Qt's main event loop (QCoreApplication::exec()). \target write notifiers Once you have opened a device using a low-level (usually platform-specific) API, you can create a socket notifier to monitor the file descriptor. The socket notifier is enabled by default, i.e. it emits the activated() signal whenever a socket event corresponding to its type occurs. Connect the activated() signal to the slot you want to be called when an event corresponding to your socket notifier's type occurs. There are three types of socket notifiers: read, write, and exception. The type is described by the \l Type enum, and must be specified when constructing the socket notifier. After construction it can be determined using the type() function. Note that if you need to monitor both reads and writes for the same file descriptor, you must create two socket notifiers. Note also that it is not possible to install two socket notifiers of the same type (\l Read, \l Write, \l Exception) on the same socket. The setEnabled() function allows you to disable as well as enable the socket notifier. It is generally advisable to explicitly enable or disable the socket notifier, especially for write notifiers. A disabled notifier ignores socket events (the same effect as not creating the socket notifier). Use the isEnabled() function to determine the notifier's current status. Finally, you can use the socket() function to retrieve the socket identifier. Although the class is called QSocketNotifier, it is normally used for other types of devices than sockets. QTcpSocket and QUdpSocket provide notification through signals, so there is normally no need to use a QSocketNotifier on them. \section1 Notes for Windows Users The socket passed to QSocketNotifier will become non-blocking, even if it was created as a blocking socket. The activated() signal is sometimes triggered by high general activity on the host, even if there is nothing to read. A subsequent read from the socket can then fail, the error indicating that there is no data available (e.g., \c{WSAEWOULDBLOCK}). This is an operating system limitation, and not a bug in QSocketNotifier. To ensure that the socket notifier handles read notifications correctly, follow these steps when you receive a notification: \list 1 \o Disable the notifier. \o Read data from the socket. \o Re-enable the notifier if you are interested in more data (such as after having written a new command to a remote server). \endlist To ensure that the socket notifier handles write notifications correctly, follow these steps when you receive a notification: \list 1 \o Disable the notifier. \o Write as much data as you can (before \c EWOULDBLOCK is returned). \o Re-enable notifier if you have more data to write. \endlist \bold{Further information:} On Windows, Qt always disables the notifier after getting a notification, and only re-enables it if more data is expected. For example, if data is read from the socket and it can be used to read more, or if reading or writing is not possible because the socket would block, in which case it is necessary to wait before attempting to read or write again. \sa QFile, QProcess, QTcpSocket, QUdpSocket */ /*! \enum QSocketNotifier::Type This enum describes the various types of events that a socket notifier can recognize. The type must be specified when constructing the socket notifier. Note that if you need to monitor both reads and writes for the same file descriptor, you must create two socket notifiers. Note also that it is not possible to install two socket notifiers of the same type (Read, Write, Exception) on the same socket. \value Read There is data to be read. \value Write Data can be written. \value Exception An exception has occurred. We recommend against using this. \sa QSocketNotifier(), type() */ /*! Constructs a socket notifier with the given \a parent. It enables the \a socket, and watches for events of the given \a type. It is generally advisable to explicitly enable or disable the socket notifier, especially for write notifiers. \bold{Note for Windows users:} The socket passed to QSocketNotifier will become non-blocking, even if it was created as a blocking socket. \sa setEnabled(), isEnabled() */ QSocketNotifier::QSocketNotifier(int socket, Type type, QObject *parent) : QObject(parent) { sockfd = socket; sntype = type; snenabled = true; Q_D(QObject); if (socket < 0) qWarning("QSocketNotifier: Invalid socket specified"); else if (!d->threadData->eventDispatcher) qWarning("QSocketNotifier: Can only be used with threads started with QThread"); else d->threadData->eventDispatcher->registerSocketNotifier(this); } #ifdef QT3_SUPPORT /*! \obsolete Use the QSocketNotifier() constructor combined with the QObject::setObjectName() function instead. \oldcode QSocketNotifier *notifier = new QSocketNotifier(socket, type, parent, name); \newcode QSocketNotifier *notifier = new QSocketNotifier(socket, type, parent); notifier->setObjectName(name); \endcode */ QSocketNotifier::QSocketNotifier(int socket, Type type, QObject *parent, const char *name) : QObject(parent) { setObjectName(QString::fromAscii(name)); if (socket < 0) qWarning("QSocketNotifier: Invalid socket specified"); sockfd = socket; sntype = type; snenabled = true; Q_D(QObject); if (!d->threadData->eventDispatcher) { qWarning("QSocketNotifier: Can only be used with threads started with QThread"); } else { d->threadData->eventDispatcher->registerSocketNotifier(this); } } #endif /*! Destroys this socket notifier. */ QSocketNotifier::~QSocketNotifier() { setEnabled(false); } /*! \fn void QSocketNotifier::activated(int socket) This signal is emitted whenever the socket notifier is enabled and a socket event corresponding to its \l {Type}{type} occurs. The socket identifier is passed in the \a socket parameter. \sa type(), socket() */ /*! \fn int QSocketNotifier::socket() const Returns the socket identifier specified to the constructor. \sa type() */ /*! \fn Type QSocketNotifier::type() const Returns the socket event type specified to the constructor. \sa socket() */ /*! \fn bool QSocketNotifier::isEnabled() const Returns true if the notifier is enabled; otherwise returns false. \sa setEnabled() */ /*! If \a enable is true, the notifier is enabled; otherwise the notifier is disabled. The notifier is enabled by default, i.e. it emits the activated() signal whenever a socket event corresponding to its \l{type()}{type} occurs. If it is disabled, it ignores socket events (the same effect as not creating the socket notifier). Write notifiers should normally be disabled immediately after the activated() signal has been emitted \sa isEnabled(), activated() */ void QSocketNotifier::setEnabled(bool enable) { if (sockfd < 0) return; if (snenabled == enable) // no change return; snenabled = enable; Q_D(QObject); if (!d->threadData->eventDispatcher) // perhaps application/thread is shutting down return; if (snenabled) d->threadData->eventDispatcher->registerSocketNotifier(this); else d->threadData->eventDispatcher->unregisterSocketNotifier(this); } /*!\reimp */ bool QSocketNotifier::event(QEvent *e) { // Emits the activated() signal when a QEvent::SockAct is // received. if (e->type() == QEvent::ThreadChange) { if (snenabled) { QMetaObject::invokeMethod(this, "setEnabled", Qt::QueuedConnection, Q_ARG(bool, snenabled)); setEnabled(false); } } QObject::event(e); // will activate filters if (e->type() == QEvent::SockAct) { emit activated(sockfd); return true; } return false; } QT_END_NAMESPACE