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290 lines
9.9 KiB
C++
290 lines
9.9 KiB
C++
/****************************************************************************
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**
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** Copyright (C) 2015 The Qt Company Ltd.
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** Contact: http://www.qt.io/licensing/
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**
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** This file is part of the QtCore module of the Qt Toolkit.
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**
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** $QT_BEGIN_LICENSE:LGPL$
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** Commercial License Usage
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** Licensees holding valid commercial Qt licenses may use this file in
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** accordance with the commercial license agreement provided with the
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** Software or, alternatively, in accordance with the terms contained in
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** a written agreement between you and The Qt Company. For licensing terms
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** and conditions see http://www.qt.io/terms-conditions. For further
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** information use the contact form at http://www.qt.io/contact-us.
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**
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** GNU Lesser General Public License Usage
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** Alternatively, this file may be used under the terms of the GNU Lesser
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** General Public License version 2.1 or version 3 as published by the Free
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** Software Foundation and appearing in the file LICENSE.LGPLv21 and
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** LICENSE.LGPLv3 included in the packaging of this file. Please review the
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** following information to ensure the GNU Lesser General Public License
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** requirements will be met: https://www.gnu.org/licenses/lgpl.html and
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** http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
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**
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** As a special exception, The Qt Company gives you certain additional
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** rights. These rights are described in The Qt Company LGPL Exception
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** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
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**
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** GNU General Public License Usage
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** Alternatively, this file may be used under the terms of the GNU
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** General Public License version 3.0 as published by the Free Software
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** Foundation and appearing in the file LICENSE.GPL included in the
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** packaging of this file. Please review the following information to
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** ensure the GNU General Public License version 3.0 requirements will be
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** met: http://www.gnu.org/copyleft/gpl.html.
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**
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** $QT_END_LICENSE$
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**
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****************************************************************************/
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#include "qsocketnotifier.h"
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#include "qplatformdefs.h"
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#include "qabstracteventdispatcher.h"
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#include "qcoreapplication.h"
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#include "qobject_p.h"
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#include <qthread_p.h>
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QT_BEGIN_NAMESPACE
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/*!
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\class QSocketNotifier
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\brief The QSocketNotifier class provides support for monitoring
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activity on a file descriptor.
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\ingroup network
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\ingroup io
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The QSocketNotifier makes it possible to integrate Qt's event
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loop with other event loops based on file descriptors. For
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example, the \l{CORBA Framework} uses it to process CORBA
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events. File descriptor action is detected in Qt's main event
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loop (QCoreApplication::exec()).
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\target write notifiers
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Once you have opened a device using a low-level (usually
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platform-specific) API, you can create a socket notifier to
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monitor the file descriptor. The socket notifier is enabled by
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default, i.e. it emits the activated() signal whenever a socket
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event corresponding to its type occurs. Connect the activated()
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signal to the slot you want to be called when an event
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corresponding to your socket notifier's type occurs.
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There are three types of socket notifiers: read, write, and
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exception. The type is described by the \l Type enum, and must be
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specified when constructing the socket notifier. After
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construction it can be determined using the type() function. Note
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that if you need to monitor both reads and writes for the same
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file descriptor, you must create two socket notifiers. Note also
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that it is not possible to install two socket notifiers of the
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same type (\l Read, \l Write, \l Exception) on the same socket.
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The setEnabled() function allows you to disable as well as enable
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the socket notifier. It is generally advisable to explicitly
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enable or disable the socket notifier, especially for write
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notifiers. A disabled notifier ignores socket events (the same
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effect as not creating the socket notifier). Use the isEnabled()
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function to determine the notifier's current status.
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Finally, you can use the socket() function to retrieve the
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socket identifier. Although the class is called QSocketNotifier,
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it is normally used for other types of devices than sockets.
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QTcpSocket and QUdpSocket provide notification through signals, so
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there is normally no need to use a QSocketNotifier on them.
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\section1 Notes for Windows Users
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The socket passed to QSocketNotifier will become non-blocking, even if
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it was created as a blocking socket.
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The activated() signal is sometimes triggered by high general activity
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on the host, even if there is nothing to read. A subsequent read from
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the socket can then fail, the error indicating that there is no data
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available (e.g., \c{WSAEWOULDBLOCK}). This is an operating system
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limitation, and not a bug in QSocketNotifier.
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To ensure that the socket notifier handles read notifications correctly,
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follow these steps when you receive a notification:
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\list 1
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\o Disable the notifier.
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\o Read data from the socket.
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\o Re-enable the notifier if you are interested in more data (such as after
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having written a new command to a remote server).
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\endlist
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To ensure that the socket notifier handles write notifications correctly,
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follow these steps when you receive a notification:
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\list 1
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\o Disable the notifier.
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\o Write as much data as you can (before \c EWOULDBLOCK is returned).
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\o Re-enable notifier if you have more data to write.
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\endlist
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\bold{Further information:}
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On Windows, Qt always disables the notifier after getting a notification,
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and only re-enables it if more data is expected. For example, if data is
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read from the socket and it can be used to read more, or if reading or
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writing is not possible because the socket would block, in which case
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it is necessary to wait before attempting to read or write again.
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\sa QFile, QProcess, QTcpSocket, QUdpSocket
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*/
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/*!
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\enum QSocketNotifier::Type
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This enum describes the various types of events that a socket
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notifier can recognize. The type must be specified when
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constructing the socket notifier.
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Note that if you need to monitor both reads and writes for the
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same file descriptor, you must create two socket notifiers. Note
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also that it is not possible to install two socket notifiers of
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the same type (Read, Write, Exception) on the same socket.
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\value Read There is data to be read.
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\value Write Data can be written.
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\value Exception An exception has occurred. We recommend against using this.
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\sa QSocketNotifier(), type()
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*/
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/*!
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Constructs a socket notifier with the given \a parent. It enables
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the \a socket, and watches for events of the given \a type.
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It is generally advisable to explicitly enable or disable the
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socket notifier, especially for write notifiers.
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\bold{Note for Windows users:} The socket passed to QSocketNotifier
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will become non-blocking, even if it was created as a blocking socket.
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\sa setEnabled(), isEnabled()
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*/
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QSocketNotifier::QSocketNotifier(int socket, Type type, QObject *parent)
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: QObject(parent)
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{
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sockfd = socket;
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sntype = type;
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snenabled = true;
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Q_D(QObject);
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if (socket < 0)
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qWarning("QSocketNotifier: Invalid socket specified");
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else if (!d->threadData->eventDispatcher)
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qWarning("QSocketNotifier: Can only be used with threads started with QThread");
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else
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d->threadData->eventDispatcher->registerSocketNotifier(this);
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}
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/*!
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Destroys this socket notifier.
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*/
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QSocketNotifier::~QSocketNotifier()
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{
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setEnabled(false);
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}
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/*!
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\fn void QSocketNotifier::activated(int socket)
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This signal is emitted whenever the socket notifier is enabled and
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a socket event corresponding to its \l {Type}{type} occurs.
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The socket identifier is passed in the \a socket parameter.
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\sa type(), socket()
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*/
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/*!
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\fn int QSocketNotifier::socket() const
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Returns the socket identifier specified to the constructor.
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\sa type()
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*/
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/*!
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\fn Type QSocketNotifier::type() const
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Returns the socket event type specified to the constructor.
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\sa socket()
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*/
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/*!
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\fn bool QSocketNotifier::isEnabled() const
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Returns true if the notifier is enabled; otherwise returns false.
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\sa setEnabled()
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*/
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/*!
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If \a enable is true, the notifier is enabled; otherwise the notifier
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is disabled.
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The notifier is enabled by default, i.e. it emits the activated()
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signal whenever a socket event corresponding to its
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\l{type()}{type} occurs. If it is disabled, it ignores socket
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events (the same effect as not creating the socket notifier).
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Write notifiers should normally be disabled immediately after the
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activated() signal has been emitted
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\sa isEnabled(), activated()
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*/
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void QSocketNotifier::setEnabled(bool enable)
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{
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if (sockfd < 0)
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return;
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if (snenabled == enable) // no change
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return;
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snenabled = enable;
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Q_D(QObject);
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if (!d->threadData->eventDispatcher) // perhaps application/thread is shutting down
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return;
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if (snenabled)
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d->threadData->eventDispatcher->registerSocketNotifier(this);
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else
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d->threadData->eventDispatcher->unregisterSocketNotifier(this);
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}
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/*!\reimp
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*/
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bool QSocketNotifier::event(QEvent *e)
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{
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// Emits the activated() signal when a QEvent::SockAct is
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// received.
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if (e->type() == QEvent::ThreadChange) {
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if (snenabled) {
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QMetaObject::invokeMethod(this, "setEnabled", Qt::QueuedConnection,
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Q_ARG(bool, snenabled));
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setEnabled(false);
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}
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}
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QObject::event(e); // will activate filters
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if (e->type() == QEvent::SockAct) {
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emit activated(sockfd);
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return true;
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}
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return false;
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}
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#include "moc_qsocketnotifier.h"
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QT_END_NAMESPACE
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