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Diffstat (limited to 'src/qml/qml/ftw/qhashfield_p.h')
-rw-r--r-- | src/qml/qml/ftw/qhashfield_p.h | 120 |
1 files changed, 120 insertions, 0 deletions
diff --git a/src/qml/qml/ftw/qhashfield_p.h b/src/qml/qml/ftw/qhashfield_p.h new file mode 100644 index 0000000000..46df9a176c --- /dev/null +++ b/src/qml/qml/ftw/qhashfield_p.h @@ -0,0 +1,120 @@ +/**************************************************************************** +** +** Copyright (C) 2012 Nokia Corporation and/or its subsidiary(-ies). +** Contact: http://www.qt-project.org/ +** +** This file is part of the QtQml module of the Qt Toolkit. +** +** $QT_BEGIN_LICENSE:LGPL$ +** GNU Lesser General Public License Usage +** 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. +** +** 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. +** +** Other Usage +** Alternatively, this file may be used in accordance with the terms and +** conditions contained in a signed written agreement between you and Nokia. +** +** +** +** +** +** +** $QT_END_LICENSE$ +** +****************************************************************************/ + +#ifndef QHASHFIELD_P_H +#define QHASHFIELD_P_H + +// +// W A R N I N G +// ------------- +// +// This file is not part of the Qt API. It exists purely as an +// implementation detail. This header file may change from version to +// version without notice, or even be removed. +// +// We mean it. +// + + +#include <QtCore/qglobal.h> + +QT_BEGIN_NAMESPACE + +// QHashField can be used for doing coarse grained set testing, in +// cases where you do not expect the set to contain the item. For +// example where you would write: +// QSet<QString> strings; +// for (int ii = 0; ii < mystrings.count(); ++ii) { +// if (strings.contains(mystrings.at(ii))) +// qFatal("Duplication!"); +// strings.insert(mystrings); +// } +// You may write: +// QHashField strings; +// for (int ii = 0; ii < mystrings.count(); ++ii) { +// if (strings.testAndSet(qHash(mystrings.at(ii)))) { +// // The string *might* be duplicated +// for (int jj = 0; jj < ii; ++jj) { +// if (mystrings.at(ii) == mystrings.at(jj)) +// qFatal("Duplication!"); +// } +// } +// } +// For small lists of things, where the hash is cheap to calculate +// and you don't expect duplication this will be much faster. +class QHashField { +public: + inline QHashField(); + + inline void clear(); + + inline bool test(quint32 hash); + inline bool testAndSet(quint32 hash); +private: + quint32 m_field; +}; + +QHashField::QHashField() +: m_field(0) +{ +} + +void QHashField::clear() +{ + m_field = 0; +} + +bool QHashField::test(quint32 hash) +{ + return m_field & (1 << (hash % 31)); +} + +bool QHashField::testAndSet(quint32 hash) +{ + quint32 mask = 1 << (hash % 31); + bool rv = m_field & mask; + m_field |= mask; + return rv; +} + +QT_END_NAMESPACE + +#endif // QHASHFIELD_P_H |