1 /****************************************************************************
3 ** Copyright (C) 2012 Nokia Corporation and/or its subsidiary(-ies).
4 ** All rights reserved.
5 ** Contact: http://www.qt-project.org/
7 ** This file is part of the QtDeclarative module of the Qt Toolkit.
9 ** $QT_BEGIN_LICENSE:LGPL$
10 ** GNU Lesser General Public License Usage
11 ** This file may be used under the terms of the GNU Lesser General Public
12 ** License version 2.1 as published by the Free Software Foundation and
13 ** appearing in the file LICENSE.LGPL included in the packaging of this
14 ** file. Please review the following information to ensure the GNU Lesser
15 ** General Public License version 2.1 requirements will be met:
16 ** http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
18 ** In addition, as a special exception, Nokia gives you certain additional
19 ** rights. These rights are described in the Nokia Qt LGPL Exception
20 ** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
22 ** GNU General Public License Usage
23 ** Alternatively, this file may be used under the terms of the GNU General
24 ** Public License version 3.0 as published by the Free Software Foundation
25 ** and appearing in the file LICENSE.GPL included in the packaging of this
26 ** file. Please review the following information to ensure the GNU General
27 ** Public License version 3.0 requirements will be met:
28 ** http://www.gnu.org/copyleft/gpl.html.
31 ** Alternatively, this file may be used in accordance with the terms and
32 ** conditions contained in a signed written agreement between you and Nokia.
40 ****************************************************************************/
42 #ifndef QHASHFIELD_P_H
43 #define QHASHFIELD_P_H
49 // This file is not part of the Qt API. It exists purely as an
50 // implementation detail. This header file may change from version to
51 // version without notice, or even be removed.
57 #include <QtCore/qglobal.h>
61 // QHashField can be used for doing coarse grained set testing, in
62 // cases where you do not expect the set to contain the item. For
63 // example where you would write:
64 // QSet<QString> strings;
65 // for (int ii = 0; ii < mystrings.count(); ++ii) {
66 // if (strings.contains(mystrings.at(ii)))
67 // qFatal("Duplication!");
68 // strings.insert(mystrings);
71 // QHashField strings;
72 // for (int ii = 0; ii < mystrings.count(); ++ii) {
73 // if (strings.testAndSet(qHash(mystrings.at(ii)))) {
74 // // The string *might* be duplicated
75 // for (int jj = 0; jj < ii; ++jj) {
76 // if (mystrings.at(ii) == mystrings.at(jj))
77 // qFatal("Duplication!");
81 // For small lists of things, where the hash is cheap to calculate
82 // and you don't expect duplication this will be much faster.
89 inline bool test(quint32 hash);
90 inline bool testAndSet(quint32 hash);
95 QHashField::QHashField()
100 void QHashField::clear()
105 bool QHashField::test(quint32 hash)
107 return m_field & (1 << (hash % 31));
110 bool QHashField::testAndSet(quint32 hash)
112 quint32 mask = 1 << (hash % 31);
113 bool rv = m_field & mask;
120 #endif // QHASHFIELD_P_H