diff options
| -rw-r--r-- | doc/src/groups.qdoc | 111 | ||||
| -rw-r--r-- | doc/src/implicit-sharing.qdoc | 144 | ||||
| -rw-r--r-- | src/3rdparty/webkit/WebKit/qt/Api/qwebhistory.cpp | 15 | ||||
| -rw-r--r-- | src/corelib/tools/qshareddata.cpp | 2 |
4 files changed, 156 insertions, 116 deletions
diff --git a/doc/src/groups.qdoc b/doc/src/groups.qdoc index 731ac58..f7296a3 100644 --- a/doc/src/groups.qdoc +++ b/doc/src/groups.qdoc @@ -202,20 +202,6 @@ */ /*! - \group explicitly-shared - \ingroup groups - - \title Explicitly Shared Classes - \brief Classes that use explicit sharing to manage internal data. - - \keyword explicit sharing - \keyword explicitly shared - - Unlike many of Qt's data types, which use \l{implicit sharing}, these - classes use explicit sharing to manage internal data. -*/ - -/*! \group geomanagement \title Layout Classes \ingroup groups @@ -377,103 +363,6 @@ */ /*! - \group shared - \title Implicitly Shared Classes - \ingroup architecture - \ingroup groups - - \brief Classes that use reference counting for fast copying. - - \keyword implicit data sharing - \keyword implicit sharing - \keyword implicitly shared - \keyword reference counting - \keyword shared implicitly - \keyword shared classes - - Many C++ classes in Qt use implicit data sharing to maximize - resource usage and minimize copying. Implicitly shared classes are - both safe and efficient when passed as arguments, because only a - pointer to the data is passed around, and the data is copied only - if and when a function writes to it, i.e., \e {copy-on-write}. - - \tableofcontents - - \section1 Overview - - A shared class consists of a pointer to a shared data block that - contains a reference count and the data. - - When a shared object is created, it sets the reference count to 1. The - reference count is incremented whenever a new object references the - shared data, and decremented when the object dereferences the shared - data. The shared data is deleted when the reference count becomes - zero. - - \keyword deep copy - \keyword shallow copy - - When dealing with shared objects, there are two ways of copying an - object. We usually speak about \e deep and \e shallow copies. A deep - copy implies duplicating an object. A shallow copy is a reference - copy, i.e. just a pointer to a shared data block. Making a deep copy - can be expensive in terms of memory and CPU. Making a shallow copy is - very fast, because it only involves setting a pointer and incrementing - the reference count. - - Object assignment (with operator=()) for implicitly shared objects is - implemented using shallow copies. - - The benefit of sharing is that a program does not need to duplicate - data unnecessarily, which results in lower memory use and less copying - of data. Objects can easily be assigned, sent as function arguments, - and returned from functions. - - Implicit sharing takes place behind the scenes; the programmer - does not need to worry about it. Even in multithreaded - applications, implicit sharing takes place, as explained in - \l{Threads and Implicit Sharing}. - - \section1 Implicit Sharing in Detail - - Implicit sharing automatically detaches the object from a shared - block if the object is about to change and the reference count is - greater than one. (This is often called \e {copy-on-write} or - \e {value semantics}.) - - An implicitly shared class has total control of its internal data. In - any member functions that modify its data, it automatically detaches - before modifying the data. - - The QPen class, which uses implicit sharing, detaches from the shared - data in all member functions that change the internal data. - - Code fragment: - \snippet doc/src/snippets/code/doc_src_groups.qdoc 0 - - \section1 List of Classes - - The classes listed below automatically detach from common data if - an object is about to be changed. The programmer will not even - notice that the objects are shared. Thus you should treat - separate instances of them as separate objects. They will always - behave as separate objects but with the added benefit of sharing - data whenever possible. For this reason, you can pass instances - of these classes as arguments to functions by value without - concern for the copying overhead. - - Example: - \snippet doc/src/snippets/code/doc_src_groups.qdoc 1 - - In this example, \c p1 and \c p2 share data until QPainter::begin() - is called for \c p2, because painting a pixmap will modify it. - - \warning Do not copy an implicitly shared container (QMap, - QVector, etc.) while you are iterating over it using an non-const - \l{STL-style iterator}. -*/ - -/*! \group ssl \title Secure Sockets Layer (SSL) Classes \ingroup groups diff --git a/doc/src/implicit-sharing.qdoc b/doc/src/implicit-sharing.qdoc new file mode 100644 index 0000000..85630dc --- /dev/null +++ b/doc/src/implicit-sharing.qdoc @@ -0,0 +1,144 @@ +/**************************************************************************** +** +** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies). +** Contact: Nokia Corporation (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 http://www.qtsoftware.com/contact. +** $QT_END_LICENSE$ +** +****************************************************************************/ + +/* TODO: Move some of the documentation from QSharedDataPointer into this + document. */ + +/*! + \group shared + \title Implicitly Shared Classes + \ingroup architecture + \ingroup groups + + \brief Classes that use reference counting for fast copying. + + \keyword implicit data sharing + \keyword implicit sharing + \keyword implicitly shared + \keyword reference counting + \keyword shared implicitly + \keyword shared classes + + Many C++ classes in Qt use implicit data sharing to maximize + resource usage and minimize copying. Implicitly shared classes are + both safe and efficient when passed as arguments, because only a + pointer to the data is passed around, and the data is copied only + if and when a function writes to it, i.e., \e {copy-on-write}. + + \tableofcontents + + \section1 Overview + + A shared class consists of a pointer to a shared data block that + contains a reference count and the data. + + When a shared object is created, it sets the reference count to 1. The + reference count is incremented whenever a new object references the + shared data, and decremented when the object dereferences the shared + data. The shared data is deleted when the reference count becomes + zero. + + \keyword deep copy + \keyword shallow copy + + When dealing with shared objects, there are two ways of copying an + object. We usually speak about \e deep and \e shallow copies. A deep + copy implies duplicating an object. A shallow copy is a reference + copy, i.e. just a pointer to a shared data block. Making a deep copy + can be expensive in terms of memory and CPU. Making a shallow copy is + very fast, because it only involves setting a pointer and incrementing + the reference count. + + Object assignment (with operator=()) for implicitly shared objects is + implemented using shallow copies. + + The benefit of sharing is that a program does not need to duplicate + data unnecessarily, which results in lower memory use and less copying + of data. Objects can easily be assigned, sent as function arguments, + and returned from functions. + + Implicit sharing takes place behind the scenes; the programmer + does not need to worry about it. Even in multithreaded + applications, implicit sharing takes place, as explained in + \l{Threads and Implicit Sharing}. + + When implementing your own implicitly shared classes, use the + QSharedData and QSharedDataPointer classes. + + \section1 Implicit Sharing in Detail + + Implicit sharing automatically detaches the object from a shared + block if the object is about to change and the reference count is + greater than one. (This is often called \e {copy-on-write} or + \e {value semantics}.) + + An implicitly shared class has total control of its internal data. In + any member functions that modify its data, it automatically detaches + before modifying the data. + + The QPen class, which uses implicit sharing, detaches from the shared + data in all member functions that change the internal data. + + Code fragment: + \snippet doc/src/snippets/code/doc_src_groups.qdoc 0 + + + \section1 List of Classes + + The classes listed below automatically detach from common data if + an object is about to be changed. The programmer will not even + notice that the objects are shared. Thus you should treat + separate instances of them as separate objects. They will always + behave as separate objects but with the added benefit of sharing + data whenever possible. For this reason, you can pass instances + of these classes as arguments to functions by value without + concern for the copying overhead. + + Example: + \snippet doc/src/snippets/code/doc_src_groups.qdoc 1 + + In this example, \c p1 and \c p2 share data until QPainter::begin() + is called for \c p2, because painting a pixmap will modify it. + + \warning Do not copy an implicitly shared container (QMap, + QVector, etc.) while you are iterating over it using an non-const + \l{STL-style iterator}. +*/ diff --git a/src/3rdparty/webkit/WebKit/qt/Api/qwebhistory.cpp b/src/3rdparty/webkit/WebKit/qt/Api/qwebhistory.cpp index e5eb308..1c1c72a 100644 --- a/src/3rdparty/webkit/WebKit/qt/Api/qwebhistory.cpp +++ b/src/3rdparty/webkit/WebKit/qt/Api/qwebhistory.cpp @@ -32,7 +32,6 @@ /*! \class QWebHistoryItem - \ingroup explicitly-shared \since 4.4 \brief The QWebHistoryItem class represents one item in the history of a QWebPage @@ -52,13 +51,17 @@ \row \o userData() \o The user specific data that was stored with the history item. \endtable - \note QWebHistoryItem objects are value based and \l{explicitly shared}. + \note QWebHistoryItem objects are value based, but \e{explicitly shared}. Changing + a QWebHistoryItem instance by calling setUserData() will change all copies of that + instance. \sa QWebHistory, QWebPage::history(), QWebHistoryInterface */ /*! - Constructs a history item from \a other. + Constructs a history item from \a other. The new item and \a other + will share their data, and modifying either this item or \a other will + modify both instances. */ QWebHistoryItem::QWebHistoryItem(const QWebHistoryItem &other) : d(other.d) @@ -66,7 +69,9 @@ QWebHistoryItem::QWebHistoryItem(const QWebHistoryItem &other) } /*! - Assigns the \a other history item to this. + Assigns the \a other history item to this. This item and \a other + will share their data, and modifying either this item or \a other will + modify both instances. */ QWebHistoryItem &QWebHistoryItem::operator=(const QWebHistoryItem &other) { @@ -163,6 +168,8 @@ QVariant QWebHistoryItem::userData() const \since 4.5 Stores user specific data \a userData with the history item. + + \note All copies of this item will be modified. \sa userData() */ diff --git a/src/corelib/tools/qshareddata.cpp b/src/corelib/tools/qshareddata.cpp index 3cd37a7..6cd220c 100644 --- a/src/corelib/tools/qshareddata.cpp +++ b/src/corelib/tools/qshareddata.cpp @@ -51,7 +51,7 @@ QT_BEGIN_NAMESPACE QSharedData is designed to be used with QSharedDataPointer or QExplicitlySharedDataPointer to implement custom \l{implicitly - shared} or \l {explicitly shared} classes. QSharedData provides + shared} or explicitly shared classes. QSharedData provides \l{thread-safe} reference counting. See QSharedDataPointer and QExplicitlySharedDataPointer for details. |