/****************************************************************************+
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**+
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** Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies).+
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** All rights reserved.+
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** Contact: Nokia Corporation (qt-info@nokia.com)+
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**+
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** This file is part of the QtXmlPatterns module of the Qt Toolkit.+
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**+
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** $QT_BEGIN_LICENSE:LGPL$+
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** No Commercial Usage+
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** This file contains pre-release code and may not be distributed.+
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** You may use this file in accordance with the terms and conditions+
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** contained in the Technology Preview License Agreement accompanying+
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** this package.+
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**+
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** GNU Lesser General Public License Usage+
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** Alternatively, this file may be used under the terms of the GNU Lesser+
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** General Public License version 2.1 as published by the Free Software+
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** Foundation and appearing in the file LICENSE.LGPL included in the+
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** packaging of this file.  Please review the following information to+
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** ensure the GNU Lesser General Public License version 2.1 requirements+
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** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.+
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**+
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** In addition, as a special exception, Nokia gives you certain additional+
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** rights.  These rights are described in the Nokia Qt LGPL Exception+
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** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.+
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**+
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** If you have questions regarding the use of this file, please contact+
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** Nokia at qt-info@nokia.com.+
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**+
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**+
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**+
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**+
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**+
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**+
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**+
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** $QT_END_LICENSE$+
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**+
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****************************************************************************/+
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+
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//+
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//  W A R N I N G+
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//  -------------+
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//+
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// This file is not part of the Qt API.  It exists purely as an+
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// implementation detail.  This header file may change from version to+
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// version without notice, or even be removed.+
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//+
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// We mean it.+
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+
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#ifndef Patternist_CompressedWhitespace_H+
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#define Patternist_CompressedWhitespace_H+
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+
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#include <QtGlobal>+
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+
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QT_BEGIN_HEADER+
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+
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QT_BEGIN_NAMESPACE+
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+
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class QChar;+
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class QString;+
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class QStringRef;+
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+
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namespace QPatternist+
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{+
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    /**+
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     * @short A compression facility for whitespace nodes.+
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     *+
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     * CompressedWhitespace compresses and decompresses strings that consists of+
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     * whitespace only, and do so with a scheme that is designed to do this+
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     * specialized task in an efficient way. The approach is simple: each+
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     * sequence of equal whitespace in the input gets coded into one byte,+
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     * where the first two bits signals the type, CharIdentifier, and the+
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     * remininding six bits is the count.+
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     *+
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     * For instance, this scheme manages to compress a sequence of spaces+
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     * followed by a new line into 16 bits(one QChar), and QString stores+
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     * strings of one QChar quite efficiently, by avoiding a heap allocation.+
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     *+
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     * There is no way to tell whether a QString is compressed or not.+
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     *+
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     * The compression scheme originates from Saxon, by Michael Kay.+
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     *+
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     * @author Frans Englich <frans.englich@nokia.com>+
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     */+
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    class Q_AUTOTEST_EXPORT CompressedWhitespace+
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    {+
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        public:+
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            /**+
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             * @short Compresses @p input into a compressed format, returned+
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             * as a QString.+
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             *+
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             * The caller guarantees that input is not empty+
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             * and consists only of whitespace.+
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             *+
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             * The returned format is opaque. There is no way to find out+
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             * whether a QString contains compressed data or not.+
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             *+
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             * @see decompress()+
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             */+
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            static QString compress(const QStringRef &input);+
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+
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            /**+
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             * @short Decompresses @p input into a usual QString.+
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             *+
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             * @p input must be a QString as per returned from compress().+
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             *+
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             * @see compress()+
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             */+
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            static QString decompress(const QString &input);+
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+
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        private:+
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            /**+
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             * We use the two upper bits for communicating what space it is.+
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             */+
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            enum CharIdentifier+
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            {+
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                Space   = 0x0,+
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+
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                /**+
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                 * 0xA, \\r+
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                 *+
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                 * Binary: 10000000+
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                 */+
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                CR      = 0x80,+
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+
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                /**+
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                 * 0xD, \\n+
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                 *+
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                 * Binary: 01000000+
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                 */+
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                LF      = 0x40,+
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+
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                /**+
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                 * Binary: 11000000+
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                 */+
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                Tab     = 0xC0+
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            };+
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+
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            enum Constants+
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            {+
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                /* We can at maximum store this many consecutive characters+
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                 * of one type. We use 6 bits for the count. */+
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                MaxCharCount = (1 << 6) - 1,+
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+
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                /**+
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                 * Binary: 11111111+
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                 */+
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                Lower8Bits = (1 << 8) - 1,+
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+
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                /**+
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                 * Binary: 111111+
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                 */+
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                Lower6Bits = (1 << 6) - 1,+
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+
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                /*+
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                 * Binary: 11000000+
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                 */+
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                UpperTwoBits = 3 << 6+
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            };+
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+
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            static inline CharIdentifier toIdentifier(const QChar ch);+
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+
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            static inline quint8 toCompressedChar(const QChar ch, const int len);+
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            static inline QChar toChar(const CharIdentifier id);+
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+
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            /**+
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             * @short Returns @c true if @p number is an even number, otherwise+
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             * @c false.+
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             */+
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            static inline bool isEven(const int number);+
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+
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            /**+
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             * @short This class can only be used via its static members.+
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             */+
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            inline CompressedWhitespace();+
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            Q_DISABLE_COPY(CompressedWhitespace)+
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    };+
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}+
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+
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QT_END_NAMESPACE+
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+
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QT_END_HEADER+
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+
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#endif+
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