/****************************************************************************

**

** All rights reserved.

** Contact: Nokia Corporation (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 Technology Preview License Agreement accompanying

** this package.

**

** 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.

**

** If you have questions regarding the use of this file, please contact

** Nokia at qt-info@nokia.com.

**

**

**

**

**

**

**

**

** $QT_END_LICENSE$

**

****************************************************************************/

/**

 * @file

 * @short This file is included by qevaluationcache_p.h.

 * If you need includes in this file, put them in qevaluationcache_p.h, outside of the namespace.

 */

template<bool IsForGlobal>

EvaluationCache<IsForGlobal>::EvaluationCache(const Expression::Ptr &op,

                                              const VariableDeclaration::Ptr &varDecl,

                                              const VariableSlotID aSlot) : SingleContainer(op)

                                                                          , m_declaration(varDecl)

                                                                          , m_varSlot(aSlot)

{

    Q_ASSERT(m_declaration);

    Q_ASSERT(m_varSlot > -1);

}

template<bool IsForGlobal>

DynamicContext::Ptr EvaluationCache<IsForGlobal>::topFocusContext(const DynamicContext::Ptr &context)

{

    DynamicContext::Ptr result(context);

    while(true)

    {

        DynamicContext::Ptr candidate(result->previousContext());

        /* We want the top focus, not GenericDynamicContext. */

        if(candidate && candidate->focusIterator())

            result = candidate;

        else

            return result;

    }

}

template<bool IsForGlobal>

Item EvaluationCache<IsForGlobal>::evaluateSingleton(const DynamicContext::Ptr &context) const

{

    ItemCacheCell &cell = IsForGlobal ? context->globalItemCacheCell(m_varSlot) : context->itemCacheCell(m_varSlot);

    if(cell.cacheState == ItemCacheCell::Full)

        return cell.cachedItem;

    else

    {

        Q_ASSERT(cell.cacheState == ItemCacheCell::Empty);

        cell.cachedItem = m_operand->evaluateSingleton(IsForGlobal ? topFocusContext(context) : context);

        cell.cacheState = ItemCacheCell::Full;

        return cell.cachedItem;

    }

}

#if defined(Q_OS_IRIX) && defined(Q_CC_MIPS)

/**

 * @short Compile workaround for MIPSPro on IRIX.

 *

 * This function is never called.

 *

 * It's mere presence means the MIPSPro compiler can accept some other code below.

 *

 * I recommend Buddism.

 */

static inline Item::Iterator::Ptr workaroundIrixMIPSPro(const ItemSequenceCacheCell &cell)

{

  return Item::Iterator::Ptr(new ListIterator<Item, Item::List>(cell.cachedItems));

}

#endif

template<bool IsForGlobal>

Item::Iterator::Ptr EvaluationCache<IsForGlobal>::evaluateSequence(const DynamicContext::Ptr &context) const

{

    ItemSequenceCacheCell::Vector &cells = IsForGlobal ? context->globalItemSequenceCacheCells(m_varSlot) : context->itemSequenceCacheCells(m_varSlot);

    ItemSequenceCacheCell &cell = cells[m_varSlot];

    if(cell.inUse)

    {

        context->error(QtXmlPatterns::tr("Circularity detected"),

                       ReportContext::XTDE0640, this);

    }

    switch(cell.cacheState)

    {

        case ItemSequenceCacheCell::Full:

        {

            /**

             * We don't use makeListIterator() here because the MIPSPro compiler can't handle it.

             */

            return Item::Iterator::Ptr(new ListIterator<Item, Item::List>(cell.cachedItems));

        }

        case ItemSequenceCacheCell::Empty:

        {

            cell.inUse = true;

            cell.sourceIterator = m_operand->evaluateSequence(IsForGlobal ? topFocusContext(context) : context);

            cell.cacheState = ItemSequenceCacheCell::PartiallyPopulated;

            /* Fallthrough. */

        }

        case ItemSequenceCacheCell::PartiallyPopulated:

        {

            cell.inUse = false;

            Q_ASSERT_X(cells.at(m_varSlot).sourceIterator, Q_FUNC_INFO,

                       "This trigger for a cache bug which hasn't yet been analyzed.");

            return Item::Iterator::Ptr(new CachingIterator(cells, m_varSlot, IsForGlobal ? topFocusContext(context) : context));

        }

        default:

        {

            Q_ASSERT_X(false, Q_FUNC_INFO, "This path is not supposed to be run.");

            return Item::Iterator::Ptr();

        }

    }

}

template<bool IsForGlobal>

Expression::Ptr EvaluationCache<IsForGlobal>::typeCheck(const StaticContext::Ptr &context,

                                                        const SequenceType::Ptr &reqType)

{

    /* It's important that we do the typeCheck() before checking for the use of local variables,

     * because ExpressionVariableReference can reference an expression that is a local variable,

     * so it must rewrite itself to it operand before, and it does that in EvaluationCache::typeCheck(). */

    const Expression::Ptr me(SingleContainer::typeCheck(context, reqType));

    OperandsIterator it(me, OperandsIterator::ExcludeParent);

    Expression::Ptr next(it.next());

    /* If our operand or any sub operand gets its value from a for-loop, we cannot

     * cache it since then our cache would be filled -- but not invalidated -- on the

     * first for-iteration. Consider this query:

     *

     * <tt>for $i in expr

     * let $v := $i/p

     * return ($v, $v)</tt>

     *

     * An evaluation cache is inserted for the two operands in the return clause. However,

     * $i changes for each iteration so the cache can only be active on a per-iteration basis,

     * it it's possible(which it isn't).

     *

     * This means that for some queries we don't cache what we really should, and hence evaluate

     * in a sub-optimal way, since this DependsOnLocalVariable don't communicate whether it references

     * a loop that affects us. The correct fix for this would be to let ForExpression reset the

     * relevant caches only, but we don't know which ones that are. */

    while(next)

    {

        if(next->has(DependsOnLocalVariable))

            return m_operand->typeCheck(context, reqType);

        next = it.next();

    }

    return me;

}

template<bool IsForGlobal>

Expression::Ptr EvaluationCache<IsForGlobal>::compress(const StaticContext::Ptr &context)

{

    const Expression::Ptr me(SingleContainer::compress(context));

    if(me != this)

        return me;

    if(m_operand->is(IDRangeVariableReference))

        return m_operand;

    if(m_declaration->usedByMany())

    {

        /* If it's only an atomic value an EvaluationCache is overkill. However,

         * it's still needed for functions like fn:current-time() that must adhere to

         * query stability. */

        const Properties props(m_operand->properties());

        if(props.testFlag(EvaluationCacheRedundant) ||

           ((props.testFlag(IsEvaluated)) &&

            !props.testFlag(DisableElimination) &&

            CommonSequenceTypes::ExactlyOneAtomicType->matches(m_operand->staticType())))

        {

            return m_operand;

        }

        else

            return me;

    }

    else

    {

        /* If we're only used once, there's no need for an EvaluationCache. */

        return m_operand;

    }

}

template<bool IsForGlobal>

SequenceType::Ptr EvaluationCache<IsForGlobal>::staticType() const

{

    return m_operand->staticType();

}

template<bool IsForGlobal>

SequenceType::List EvaluationCache<IsForGlobal>::expectedOperandTypes() const

{

    /* Remember that EvaluationCache::typeCheck() will be called from multiple locations,

     * which potentially have different type requirements. For instance, one wants a node,

     * and another requires atomization and casting.

     *

     * Returning ZeroOrMoreItems is safe here because staticType() returns the operand's type

     * and therefore the convertors like Atomizer will be parents to us, and hence only affect

     * the relevant path.

     *

     * ZeroOrMoreItems also make sense logically since we're actually only used where the

     * variable references reference us. */

    SequenceType::List result;

    result.append(CommonSequenceTypes::ZeroOrMoreItems);

    return result;

}

template<bool IsForGlobal>

Expression::Properties EvaluationCache<IsForGlobal>::properties() const

{

    /* We cannot return the operand's properties unconditionally, because some

     * doesn't hold for this Expression.

     *

     * However, some of the properties must propagate through, which are the ones being OR'd here.

     */

    return m_operand->properties() & (DisableElimination | IsEvaluated | DisableTypingDeduction);

}

template<bool IsForGlobal>

ExpressionVisitorResult::Ptr

EvaluationCache<IsForGlobal>::accept(const ExpressionVisitor::Ptr &visitor) const

{

    return visitor->visit(this);

}

template<bool IsForGlobal>

const SourceLocationReflection *EvaluationCache<IsForGlobal>::actualReflection() const

{

    return m_operand->actualReflection();

}