From f65b7aa11d18ab710bc2e6720d7a6dbc8f169c65 Mon Sep 17 00:00:00 2001 From: Shane Kearns Date: Mon, 17 Jan 2011 13:35:58 +0000 Subject: Add QScopedValueRollback tools class. This template allows a value to be automatically rolled back to a previous state when the class goes out of scope. This can be used to maintain a valid state when an exception is thrown. Reviewed-by: mread Reviewed-by: joao --- src/corelib/tools/qscopedvaluerollback.cpp | 84 ++++++++++++++++++++++++++++++ src/corelib/tools/qscopedvaluerollback.h | 81 ++++++++++++++++++++++++++++ src/corelib/tools/tools.pri | 7 +-- 3 files changed, 169 insertions(+), 3 deletions(-) create mode 100644 src/corelib/tools/qscopedvaluerollback.cpp create mode 100644 src/corelib/tools/qscopedvaluerollback.h diff --git a/src/corelib/tools/qscopedvaluerollback.cpp b/src/corelib/tools/qscopedvaluerollback.cpp new file mode 100644 index 0000000..8933efc --- /dev/null +++ b/src/corelib/tools/qscopedvaluerollback.cpp @@ -0,0 +1,84 @@ +/**************************************************************************** +** +** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies). +** All rights reserved. +** Contact: Nokia Corporation (qt-info@nokia.com) +** +** This file is part of the QtCore module 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 Technology Preview License Agreement accompanying +** this package. +** +** 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 1.1, included in the file LGPL_EXCEPTION.txt in this package. +** +** If you have questions regarding the use of this file, please contact +** Nokia at qt-info@nokia.com. +** +** +** +** +** +** +** +** +** $QT_END_LICENSE$ +** +****************************************************************************/ + +#include "qscopedvaluerollback.h" + +QT_BEGIN_NAMESPACE + +/*! + \class QScopedValueRollback + \brief The QScopedValueRollback resets a variable to its previous value on destruction + \since 4.8 + \ingroup misc + + The QScopedAssignment class can be used to revert state when an + exception is thrown without needing to write try-catch blocks. + + It can also be used to manage variables that are temporarily set, + such as reentrancy guards. By using this class, the variable will + be reset whether the function is exited normally, exited early by + a return statement, or exited by an exception. + + The template can only be instantiated with a type that supports assignment. + + \sa QScopedPointer +*/ + +/*! + \fn QScopedValueRollback::QScopedValueRollback(T &var) + + Stores the previous value of var internally, for revert on destruction. +*/ + +/*! + \fn QScopedValueRollback::~QScopedValueRollback() + + Assigns the previous value to the managed variable. + This is the value at construction time, or at the last call to commit() +*/ + +/*! + \fn void QScopedValueRollback::commit() + + Updates the previous value of the managed variable to its current value. +*/ + +QT_END_NAMESPACE diff --git a/src/corelib/tools/qscopedvaluerollback.h b/src/corelib/tools/qscopedvaluerollback.h new file mode 100644 index 0000000..d344ed8 --- /dev/null +++ b/src/corelib/tools/qscopedvaluerollback.h @@ -0,0 +1,81 @@ +/**************************************************************************** +** +** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies). +** All rights reserved. +** Contact: Nokia Corporation (qt-info@nokia.com) +** +** This file is part of the QtCore module 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 Technology Preview License Agreement accompanying +** this package. +** +** 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 1.1, included in the file LGPL_EXCEPTION.txt in this package. +** +** If you have questions regarding the use of this file, please contact +** Nokia at qt-info@nokia.com. +** +** +** +** +** +** +** +** +** $QT_END_LICENSE$ +** +****************************************************************************/ + +#ifndef QSCOPEDVALUEROLLBACK_H +#define QSCOPEDVALUEROLLBACK_H + +#include + +QT_BEGIN_HEADER +QT_BEGIN_NAMESPACE +QT_MODULE(Core) + +template +class QScopedValueRollback +{ +public: + QScopedValueRollback(T &var) : + varRef(var) + { + oldValue = varRef; + } + + ~QScopedValueRollback() + { + varRef = oldValue; + } + + void commit() + { + oldValue = varRef; + } + +private: + T& varRef; + T oldValue; + + Q_DISABLE_COPY(QScopedValueRollback); +}; + +QT_END_NAMESPACE +QT_END_HEADER + +#endif // QSCOPEDVALUEROLLBACK_H diff --git a/src/corelib/tools/tools.pri b/src/corelib/tools/tools.pri index 03bb32d..9d564a1 100644 --- a/src/corelib/tools/tools.pri +++ b/src/corelib/tools/tools.pri @@ -29,6 +29,9 @@ HEADERS += \ tools/qrect.h \ tools/qregexp.h \ tools/qringbuffer_p.h \ + tools/qscopedpointer.h \ + tools/qscopedpointer_p.h \ + tools/qscopedvaluerollback.h \ tools/qshareddata.h \ tools/qsharedpointer.h \ tools/qsharedpointer_impl.h \ @@ -45,9 +48,7 @@ HEADERS += \ tools/qelapsedtimer.h \ tools/qunicodetables_p.h \ tools/qvarlengtharray.h \ - tools/qvector.h \ - tools/qscopedpointer.h \ - tools/qscopedpointer_p.h + tools/qvector.h SOURCES += \ -- cgit v0.12