Long live Qt!

1 files changed, 89 insertions, 0 deletions

diff --git a/doc/src/atomic-operations.qdoc b/doc/src/atomic-operations.qdoc
new file mode 100644
index 0000000..5c0973b
--- /dev/null
+++ b/doc/src/atomic-operations.qdoc
@@ -0,0 +1,89 @@
+/****************************************************************************
+**
+** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
+** Contact: Qt Software Information (qt-info@nokia.com)
+**
+** This file is part of the documentation of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** No Commercial Usage
+** This file contains pre-release code and may not be distributed.
+** You may use this file in accordance with the terms and conditions
+** contained in the either Technology Preview License Agreement or the
+** Beta Release License Agreement.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 2.1 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU Lesser General Public License version 2.1 requirements
+** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** In addition, as a special exception, Nokia gives you certain
+** additional rights. These rights are described in the Nokia Qt LGPL
+** Exception version 1.0, included in the file LGPL_EXCEPTION.txt in this
+** package.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3.0 as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL included in the
+** packaging of this file.  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.
+**
+** If you are unsure which license is appropriate for your use, please
+** contact the sales department at qt-sales@nokia.com.
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+/*!
+    \page atomic-operations.html
+    \title Implementing Atomic Operations
+    \ingroup architecture
+    \ingroup qt-embedded-linux
+    \brief A guide to implementing atomic operations on new architectures.
+
+    Qt uses an optimization called \l {Implicitly Shared
+    Classes}{implicit sharing} for many of its value classes.
+
+    Starting with Qt 4, all of Qt's implicitly shared classes can
+    safely be copied across threads like any other value classes,
+    i.e., they are fully \l {Thread Support in Qt#Reentrancy and
+    Thread-Safety}{reentrant}. This is accomplished by implementing
+    reference counting operations using atomic hardware instructions
+    on all the different platforms supported by Qt.
+
+    To support a new architecture, it is important to ensure that
+    these platform-specific atomic operations are implemented in a
+    corresponding header file (\c qatomic_ARCH.h), and that this file
+    is located in Qt's \c src/corelib/arch directory. For example, the
+    Intel 80386 implementation is located in \c
+    src/corelib/arch/qatomic_i386.h.
+
+    Currently, Qt provides two classes providing several atomic
+    operations, QAtomicInt and QAtomicPointer. These classes inherit
+    from QBasicAtomicInt and QBasicAtomicPointer, respectively.
+
+    When porting Qt to a new architecture, the QBasicAtomicInt and
+    QBasicAtomicPointer classes must be implemented, \e not QAtomicInt
+    and QAtomicPointer. The former classes do not have constructors,
+    which makes them POD (plain-old-data). Both classes only have a
+    single member variable called \c _q_value, which stores the
+    value. This is the value that all of the atomic operations read
+    and modify.
+
+    All of the member functions mentioned in the QAtomicInt and
+    QAtomicPointer API documentation must be implemented. Note that
+    these the implementations of the atomic operations in these
+    classes must be atomic with respect to both interrupts and
+    multiple processors.
+
+    \warning The QBasicAtomicInt and QBasicAtomicPointer classes
+    mentioned in this document are used internally by Qt and are not
+    part of the public API. They may change in future versions of
+    Qt. The purpose of this document is to aid people interested in
+    porting Qt to a new architecture.
+*/