source: trunk/src/xmlpatterns/expr/qrangeexpression.cpp@ 729

/****************************************************************************
**
** Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies).
** All rights reserved.
** Contact: Nokia Corporation ([email protected])
**
** This file is part of the QtXmlPatterns 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 1.1, 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 have questions regarding the use of this file, please contact
** Nokia at [email protected].
** $QT_END_LICENSE$
**
****************************************************************************/

#include "qbuiltintypes_p.h"
#include "qcommonsequencetypes_p.h"
#include "qcommonvalues_p.h"
#include "qgenericsequencetype_p.h"
#include "qinteger_p.h"
#include "qliteral_p.h"
#include "qrangeiterator_p.h"

#include "qrangeexpression_p.h"

QT_BEGIN_NAMESPACE

using namespace QPatternist;

RangeExpression::RangeExpression(const Expression::Ptr &operand1,
                                 const Expression::Ptr &operand2) : PairContainer(operand1, operand2)
{
}

Item::Iterator::Ptr RangeExpression::evaluateSequence(const DynamicContext::Ptr &context) const
{
    const Item s(m_operand1->evaluateSingleton(context));

    if(!s)
        return CommonValues::emptyIterator;

    const Item e(m_operand2->evaluateSingleton(context));
    if(!e)
        return CommonValues::emptyIterator;

    const xsInteger start = s.as<Numeric>()->toInteger();
    const xsInteger end = e.as<Numeric>()->toInteger();

    if(start > end)
        return CommonValues::emptyIterator;
    else if(start == end)
        return makeSingletonIterator(s);
    else
        return Item::Iterator::Ptr(new RangeIterator(start, RangeIterator::Forward, end));
}

Item RangeExpression::evaluateSingleton(const DynamicContext::Ptr &context) const
{
    return m_operand1->evaluateSingleton(context);
}

SequenceType::List RangeExpression::expectedOperandTypes() const
{
    SequenceType::List result;
    result.append(CommonSequenceTypes::ZeroOrOneInteger);
    result.append(CommonSequenceTypes::ZeroOrOneInteger);
    return result;
}

SequenceType::Ptr RangeExpression::staticType() const
{
    /* This logic makes the Cardinality more specific. */
    Cardinality::Count from;
    bool hasFrom;

    if(m_operand1->is(IDIntegerValue))
    {
        from = m_operand1->as<Literal>()->item().as<Integer>()->toInteger();
        hasFrom = true;
    }
    else
    {
        hasFrom = false;
        from = 0;
    }

    /* We can't check whether to is -1 since maybe the user wrote -1. Hence
     * hasTo is required. */
    bool hasTo;
    Cardinality::Count to;

    if(m_operand2->is(IDIntegerValue))
    {
        const xsInteger asInt = m_operand2->as<Literal>()->item().as<Integer>()->toInteger();
        to = asInt;

        if(to == asInt)
            hasTo = true;
        else
        {
            /* Cardinality::Count is not the same as type xsInteger. We had overflow. */
            to = -1;
            hasTo = false;
        }
    }
    else
    {
        to = -1;
        hasTo = false;
    }

    if(hasTo && hasFrom)
    {
        if(from > to)
        {
            /* The query is incorrectly written, we'll evaluate to the empty sequence.
             * Just return what's correct. */
            return CommonSequenceTypes::ZeroOrMoreIntegers;
        }
        else
        {
            Cardinality::Count count = (to - from) + 1; /* + 1, since it's inclusive. */
            return makeGenericSequenceType(BuiltinTypes::xsInteger, Cardinality::fromExact(count));
        }
    }
    else
    {
        /* We can't do fromExact(from, -1) since the latter can evaluate to a value that actually is
         * lower than from, although that unfortunately is very unlikely. */
        return CommonSequenceTypes::ZeroOrMoreIntegers;
    }
}

Expression::Properties RangeExpression::properties() const
{
    return Expression::DisableElimination;
}

ExpressionVisitorResult::Ptr RangeExpression::accept(const ExpressionVisitor::Ptr &visitor) const
{
    return visitor->visit(this);
}

QT_END_NAMESPACE