diff options
Diffstat (limited to 'src/qml/qml/ftw/qprimefornumbits_p.h')
-rw-r--r-- | src/qml/qml/ftw/qprimefornumbits_p.h | 80 |
1 files changed, 80 insertions, 0 deletions
diff --git a/src/qml/qml/ftw/qprimefornumbits_p.h b/src/qml/qml/ftw/qprimefornumbits_p.h new file mode 100644 index 0000000000..6e9acbf7fd --- /dev/null +++ b/src/qml/qml/ftw/qprimefornumbits_p.h @@ -0,0 +1,80 @@ +/**************************************************************************** +** +** Copyright (C) 2019 The Qt Company Ltd. +** Contact: https://www.qt.io/licensing/ +** +** 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 The Qt Company. For licensing terms +** and conditions see https://www.qt.io/terms-conditions. For further +** information use the contact form at https://www.qt.io/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 3 as published by the Free Software +** Foundation and appearing in the file LICENSE.LGPL3 included in the +** packaging of this file. Please review the following information to +** ensure the GNU Lesser General Public License version 3 requirements +** will be met: https://www.gnu.org/licenses/lgpl-3.0.html. +** +** GNU General Public License Usage +** Alternatively, this file may be used under the terms of the GNU +** General Public License version 2.0 or (at your option) the GNU General +** Public license version 3 or any later version approved by the KDE Free +** Qt Foundation. The licenses are as published by the Free Software +** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3 +** included in the packaging of this file. Please review the following +** information to ensure the GNU General Public License requirements will +** be met: https://www.gnu.org/licenses/gpl-2.0.html and +** https://www.gnu.org/licenses/gpl-3.0.html. +** +** $QT_END_LICENSE$ +** +****************************************************************************/ + +#ifndef QPRIMEFORNUMBITS_P_H +#define QPRIMEFORNUMBITS_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 <private/qtqmlglobal_p.h> + +QT_BEGIN_NAMESPACE + +/* + The prime_deltas array is a table of selected prime values, even + though it doesn't look like one. The primes we are using are 1, + 2, 5, 11, 17, 37, 67, 131, 257, ..., i.e. primes in the immediate + surrounding of a power of two. + + The qPrimeForNumBits() function returns the prime associated to a + power of two. For example, qPrimeForNumBits(8) returns 257. +*/ + +inline int qPrimeForNumBits(int numBits) +{ + static constexpr const uchar prime_deltas[] = { + 0, 0, 1, 3, 1, 5, 3, 3, 1, 9, 7, 5, 3, 9, 25, 3, + 1, 21, 3, 21, 7, 15, 9, 5, 3, 29, 15, 0, 0, 0, 0, 0 + }; + + return (1 << numBits) + prime_deltas[numBits]; +} + +QT_END_NAMESPACE + +#endif // QPRIMEFORNUMBITS_P_H |