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/****************************************************************************
**
** Copyright (C) 2013 Digia Plc and/or its subsidiary(-ies).
** Contact: http://www.qt-project.org/legal
**
** This file is part of the QtQml module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and Digia. For licensing terms and
** conditions see http://qt.digia.com/licensing. For further information
** use the contact form at http://qt.digia.com/contact-us.
**
** 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, Digia gives you certain additional
** rights. These rights are described in the Digia 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.
**
**
** $QT_END_LICENSE$
**
****************************************************************************/
#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
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