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Diffstat (limited to 'src/xmlpatterns/acceltree/qcompressedwhitespace_p.h')
| -rw-r--r-- | src/xmlpatterns/acceltree/qcompressedwhitespace_p.h | 186 |
1 files changed, 186 insertions, 0 deletions
diff --git a/src/xmlpatterns/acceltree/qcompressedwhitespace_p.h b/src/xmlpatterns/acceltree/qcompressedwhitespace_p.h new file mode 100644 index 0000000..92bc0a5 --- /dev/null +++ b/src/xmlpatterns/acceltree/qcompressedwhitespace_p.h @@ -0,0 +1,186 @@ +/**************************************************************************** +** +** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies). +** Contact: Qt Software Information (qt-info@nokia.com) +** +** This file is part of the QtXmlPatterns module of the Qt Toolkit. +** +** $QT_BEGIN_LICENSE:LGPL$ +** No Commercial Usage +** This file contains pre-release code and may not be distributed. +** You may use this file in accordance with the terms and conditions +** contained in the either Technology Preview License Agreement or the +** Beta Release License Agreement. +** +** 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, Nokia gives you certain +** additional rights. These rights are described in the Nokia Qt LGPL +** Exception version 1.0, 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. +** +** If you are unsure which license is appropriate for your use, please +** contact the sales department at qt-sales@nokia.com. +** $QT_END_LICENSE$ +** +****************************************************************************/ + +// +// 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. + +#ifndef Patternist_CompressedWhitespace_H +#define Patternist_CompressedWhitespace_H + +#include <QtGlobal> + +QT_BEGIN_HEADER + +QT_BEGIN_NAMESPACE + +class QChar; +class QString; +class QStringRef; + +namespace QPatternist +{ + /** + * @short A compression facility for whitespace nodes. + * + * CompressedWhitespace compresses and decompresses strings that consists of + * whitespace only, and do so with a scheme that is designed to do this + * specialized task in an efficient way. The approach is simple: each + * sequence of equal whitespace in the input gets coded into one byte, + * where the first two bits signals the type, CharIdentifier, and the + * remininding six bits is the count. + * + * For instance, this scheme manages to compress a sequence of spaces + * followed by a new line into 16 bits(one QChar), and QString stores + * strings of one QChar quite efficiently, by avoiding a heap allocation. + * + * There is no way to tell whether a QString is compressed or not. + * + * The compression scheme originates from Saxon, by Michael Kay. + * + * @author Frans Englich <fenglich@trolltech.com> + */ + class CompressedWhitespace + { + public: + /** + * @short Compresses @p input into a compressed format, returned + * as a QString. + * + * The caller guarantees that input is not empty + * and consists only of whitespace. + * + * The returned format is opaque. There is no way to find out + * whether a QString contains compressed data or not. + * + * @see decompress() + */ + static QString compress(const QStringRef &input); + + /** + * @short Decompresses @p input into a usual QString. + * + * @p input must be a QString as per returned from compress(). + * + * @see compress() + */ + static QString decompress(const QString &input); + + private: + /** + * We use the two upper bits for communicating what space it is. + */ + enum CharIdentifier + { + Space = 0x0, + + /** + * 0xA, \\r + * + * Binary: 10000000 + */ + CR = 0x80, + + /** + * 0xD, \\n + * + * Binary: 01000000 + */ + LF = 0x40, + + /** + * Binary: 11000000 + */ + Tab = 0xC0 + }; + + enum Constants + { + /* We can at maximum store this many consecutive characters + * of one type. We use 6 bits for the count. */ + MaxCharCount = (1 << 6) - 1, + + /** + * Binary: 11111111 + */ + Lower8Bits = (1 << 8) - 1, + + /** + * Binary: 111111 + */ + Lower6Bits = (1 << 6) - 1, + + /* + * Binary: 11000000 + */ + UpperTwoBits = 3 << 6 + }; + + static inline CharIdentifier toIdentifier(const QChar ch); + + static inline quint8 toCompressedChar(const QChar ch, const int len); + static inline QChar toChar(const CharIdentifier id); + + /** + * @short Returns @c true if @p number is an even number, otherwise + * @c false. + */ + static inline bool isEven(const int number); + + /** + * @short This class can only be used via its static members. + */ + inline CompressedWhitespace(); + Q_DISABLE_COPY(CompressedWhitespace) + }; +} + +QT_END_NAMESPACE + +QT_END_HEADER + +#endif |