Commit feb34c0e authored by hjk's avatar hjk

Introduce a new QStringBuilder helper class to speed up building strings

from smaller chunks using expression templates.

Simple test and benchmark included, the class is not yet complete.
parent b72b4142
/****************************************************************************
**
** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
** Contact: Qt Software Information (qt-info@nokia.com)
**
** This file is part of the $MODULE$ of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** Commercial Usage
** Licensees holding valid Qt Commercial licenses may use this file in
** accordance with the Qt Commercial License Agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and Nokia.
**
** 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.
** $QT_END_LICENSE$
**
****************************************************************************/
#include "qstringbuilder.h"
/*!
\class QLatin1Literal
\reentrant
\brief The QLatin1Literal class provides a thin wrapper of string literal
used in source codes.
The main use of \c QLatin1Literal is in conjunction with \c QStringBuilder
to reduce the number of reallocations needed to build up a string from
smaller chunks.
Contrary to \c QLatin1String, a \c QLatin1Literal can retrieve its size
int \i{O(1)}.
\ingroup tools
\ingroup shared
\ingroup text
\mainclass
\sa QStringBuilder, QLatin1String, QString
*/
/*! \fn QLatin1Literal::QLatin1Literal(const char(&literal)[])
The only constructor of the class.
*/
/*! \fn int QLatin1Literal::size() const
Returns the number of characters in the literal \i{not} including
the trailing NUL char.
*/
/*! \fn char *QLatin1Literal::size() const
Returns a pointer to the first character of the string literal.
The string literal is terminated by a NUL character.
*/
/*! \fn QLatin1Literal::operator QString() const
Converts the \c QLatin1Literal into a \c QString object.
*/
/*!
\class QStringBuilderPair
\reentrant
\brief QStringBuilderPair is a helper class template for building
QStringBuilder objects wrapping two smaller QStringBuilder object.
*/
/*!
\class QStringBuilder
\reentrant
\brief QStringBuilder is a template class providing a facility to build
up QStrings from smaller chunks.
\ingroup tools
\ingroup shared
\ingroup text
\mainclass
When creating strings from smaller chunks, typically \c QString::operator+()
is used, resulting \i{n - 1} reallocations when operating on \i{n} chunks.
QStringBuilder uses expression
templates to collect the individual parts, compute the total size,
allocate memory for the resulting QString object, and copy the contents
of the chunks into the result.
Using \c QStringBuilder::operator%() yield generally better performance then
using \c QString::operator+() on the same chunks if there are three or
more of them, and equal performance otherwise.
\sa QLatin1Literal, QString
*/
/* !fn template <class A, class B> QStringBuilder< QStringBuilderPair<A, B> > operator%(const A &a, const B &b)
Creates a helper object containing both parameters.
This is the main function to build up
*/
/****************************************************************************
**
** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
** Contact: Qt Software Information (qt-info@nokia.com)
**
** This file is part of the $MODULE$ of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** Commercial Usage
** Licensees holding valid Qt Commercial licenses may use this file in
** accordance with the Qt Commercial License Agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and Nokia.
**
** 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.
** $QT_END_LICENSE$
**
****************************************************************************/
#ifndef QSTRINGBUILDER_H
#define QSTRINGBUILDER_H
#include <QtCore/qstring.h>
#include <string.h>
class QLatin1Literal
{
public:
template <int N>
QLatin1Literal(const char (&str)[N]) : m_size(N - 1), m_data(str) {}
int size() const { return m_size; }
const char *data() const { return m_data; }
void append(QChar *&out) const
{
const char *s = m_data;
for (int i = m_size; --i >= 0;)
*out++ = *s++;
}
operator QString() const
{
QString s;
s.resize(m_size);
QChar *d = s.data();
append(d);
return s;
}
private:
const int m_size;
const char *m_data;
};
template <class A>
class QStringBuilder : public A
{
public:
QStringBuilder(A a_) : A(a_) {}
operator QString() const
{
QString s;
s.resize(this->size());
QChar *d = s.data();
this->append(d);
return s;
}
};
template <>
class QStringBuilder<QString>
{
public:
QStringBuilder(const QString &a_) : a(&a_) {}
inline int size() const { return a->size(); }
inline void append(QChar *&out) const
{
const int n = a->size();
memcpy(out, (char*)a->constData(), sizeof(QChar) * n);
out += n;
}
inline operator QString() const { return *a; }
private:
const QString *a;
};
template <class A, class B>
class QStringBuilderPair
{
public:
QStringBuilderPair(A a_, B b_) : a(a_), b(b_) {}
inline int size() const { return a.size() + b.size(); }
inline void append(QChar *&out) const { a.append(out); b.append(out); }
private:
A a;
B b;
};
template <class A, class B>
QStringBuilder< QStringBuilderPair<A, B> >
operator%(const A &a, const B &b)
{
return QStringBuilderPair<A, B> (a, b);
}
template <class A>
inline QStringBuilder< QStringBuilderPair<A, QStringBuilder<QString> > >
operator%(const A &a, const QString &b)
{
return QStringBuilderPair<A, QStringBuilder<QString> > (a, b);
}
template <class B>
inline QStringBuilder< QStringBuilderPair<QStringBuilder<QString>, B> >
operator%(const QString &a, const B &b)
{
return QStringBuilderPair<QStringBuilder<QString>, B> (a, b);
}
inline QStringBuilder<
QStringBuilderPair<QStringBuilder<QString>,
QStringBuilder<QString> >
>
operator%(const QString &a, const QString &b)
{
return QStringBuilderPair< QStringBuilder<QString>,
QStringBuilder<QString> > (a, b);
}
#endif // QSTRINGBUILDER_H
load(qttest_p4)
SOURCES += tst_qstringbuilder.cpp
QT -= gui
QT = core
DEFINES += QT_NO_CAST_TO_ASCII
/****************************************************************************
**
** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
** Contact: Qt Software Information (qt-info@nokia.com)
**
****************************************************************************/
#include <QtTest/QtTest>
#include "../../../src/libs/utils/qstringbuilder.h"
//TESTED_CLASS=QStringBuilder
//TESTED_FILES=qstringbuilder.h
class tst_QStringBuilder : public QObject
{
Q_OBJECT
public:
tst_QStringBuilder();
~tst_QStringBuilder() {}
public slots:
void init() {}
void cleanup() {}
private slots:
void operator_percent();
};
tst_QStringBuilder::tst_QStringBuilder()
{
//QTextCodec::setCodecForLocale(QTextCodec::codecForName("ISO 8859-1"));
}
void tst_QStringBuilder::operator_percent()
{
QLatin1Literal l1literal("a literal");
QLatin1String l1string("a literal");
QLatin1Char l1char('c');
QChar qchar(l1char);
QCOMPARE(QString(l1literal % l1literal), QString(l1string + l1string));
}
QTEST_APPLESS_MAIN(tst_QStringBuilder)
#include "tst_qstringbuilder.moc"
#include <QDebug>
#include <QString>
#include "../../../src/libs/utils/qstringbuilder.h"
#include <qtest.h>
class tst_qstringbuilder : public QObject
{
Q_OBJECT
public:
tst_qstringbuilder();
private slots:
// QStringBuilder based
void builderbased_l1literal_l1literal();
void builderbased_l1literal_l1literal_l1literal();
void builderbased_l1literal_l1literal_l1literal_l1literal();
// QString based for comparison
void stringbased_l1string_l1string();
void stringbased_l1string_l1string_l1string();
void stringbased_l1string_l1string_l1string_l1string();
private:
const QLatin1Literal l1literal;
const QLatin1String l1string;
};
tst_qstringbuilder::tst_qstringbuilder()
: l1literal("some literal"), l1string("some literal")
{}
void tst_qstringbuilder::builderbased_l1literal_l1literal()
{
QString result;
QBENCHMARK { result = l1literal % l1literal; }
QCOMPARE(result, l1string + l1string);
}
void tst_qstringbuilder::builderbased_l1literal_l1literal_l1literal()
{
QString result;
QBENCHMARK { result = l1literal % l1literal % l1literal; }
QCOMPARE(result, l1string + l1string + l1string);
}
void tst_qstringbuilder::builderbased_l1literal_l1literal_l1literal_l1literal()
{
QString result;
QBENCHMARK { result = l1literal % l1literal % l1literal % l1literal; }
QCOMPARE(result, l1string + l1string + l1string + l1string);
}
void tst_qstringbuilder::stringbased_l1string_l1string()
{
QString result;
QBENCHMARK { result = l1string + l1string; }
QCOMPARE(result, QString(l1literal % l1literal));
}
void tst_qstringbuilder::stringbased_l1string_l1string_l1string()
{
QString result;
QBENCHMARK { result = l1string + l1string + l1string; }
QCOMPARE(result, QString(l1literal % l1literal % l1literal));
}
void tst_qstringbuilder::stringbased_l1string_l1string_l1string_l1string()
{
QString result;
QBENCHMARK { result = l1string + l1string + l1string + l1string; }
QCOMPARE(result, QString(l1literal % l1literal % l1literal % l1literal));
}
QTEST_MAIN(tst_qstringbuilder)
#include "main.moc"
load(qttest_p4)
TEMPLATE = app
TARGET = tst_qstringbuilder
DEPENDPATH += .
INCLUDEPATH += .
QT -= gui
CONFIG += release
# Input
SOURCES += main.cpp
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