QPatternist::ElementConstructor Class Reference

Constructs an element node. This covers both computed and directly constructed element nodes. More...

#include <qelementconstructor_p.h>

Inheritance diagram for QPatternist::ElementConstructor:

Public Functions
virtual ExpressionVisitorResult::Ptr	accept (const ExpressionVisitor::Ptr &visitor) const
	ElementConstructor (const Expression::Ptr &operand1, const Expression::Ptr &operand2, const bool isXSLT)
virtual Item	evaluateSingleton (const DynamicContext::Ptr &context) const
virtual void	evaluateToSequenceReceiver (const DynamicContext::Ptr &context) const
virtual SequenceType::List	expectedOperandTypes () const
virtual Properties	properties () const
virtual SequenceType::Ptr	staticType () const
virtual Expression::Ptr	typeCheck (const StaticContext::Ptr &context, const SequenceType::Ptr &reqType)
Public Functions inherited from QPatternist::PairContainer
virtual bool	compressOperands (const StaticContext::Ptr &)
virtual Expression::List	operands () const
virtual void	setOperands (const Expression::List &operands)
Public Functions inherited from QPatternist::Expression
virtual const SourceLocationReflection *	actualReflection () const
	Returns this. More...
virtual void	announceFocusType (const ItemType::Ptr &itemType)
virtual Expression::Ptr	compress (const StaticContext::Ptr &context)
Properties	deepProperties () const
	Computes the union of properties for this Expression and all its descending children. More...
virtual Properties	dependencies () const
virtual QString	description () const
virtual bool	evaluateEBV (const DynamicContext::Ptr &context) const
virtual Item::Iterator::Ptr	evaluateSequence (const DynamicContext::Ptr &context) const
virtual ItemType::Ptr	expectedContextItemType () const
	Expression ()
bool	has (const Property prop) const
bool	hasDependency (const Property prop) const
virtual ID	id () const
bool	is (const ID id) const
bool	isEvaluated () const
virtual ItemType::Ptr	newFocusType () const
virtual QList< QExplicitlySharedDataPointer< OptimizationPass > >	optimizationPasses () const
virtual PatternPriority	patternPriority () const
const Expression::Ptr &	rewrite (const Expression::Ptr &to, const StaticContext::Ptr &context) const
	Rewrites this Expression to to, and return to. More...
virtual	~Expression ()
Public Functions inherited from QSharedData
	QSharedData ()
	Constructs a QSharedData object with a reference count of 0. More...
	QSharedData (const QSharedData &)
	Constructs a QSharedData object with reference count 0. More...
Public Functions inherited from QPatternist::CppCastingHelper< Expression >
const TCastTarget *	as () const
TCastTarget *	as ()
Public Functions inherited from QPatternist::SourceLocationReflection
virtual QSourceLocation	sourceLocation () const
	SourceLocationReflection ()
virtual	~SourceLocationReflection ()

Properties
const bool	m_isXSLT
QUrl	m_staticBaseURI

Additional Inherited Members
Public Types inherited from QPatternist::Expression
typedef QExplicitlySharedDataPointer< const Expression >	ConstPtr
	A smart pointer wrapping const Expression instances. More...
enum	ID {   IDBooleanValue = 1, IDCountFN, IDEmptyFN, IDExistsFN,   IDExpressionSequence, IDGeneralComparison, IDIfThenClause, IDIgnorableExpression,   IDIntegerValue, IDPositionFN, IDStringValue, IDValueComparison,   IDRangeVariableReference, IDContextItem, IDUserFunctionCallsite, IDExpressionVariableReference,   IDAttributeConstructor, IDUpperCaseFN, IDLowerCaseFN, IDFirstItemPredicate,   IDEmptySequence, IDReturnOrderBy, IDLetClause, IDForClause,   IDPath, IDNamespaceConstructor, IDArgumentReference, IDGenericPredicate,   IDAxisStep, IDFloat, IDCombineNodes, IDUnresolvedVariableReference,   IDCardinalityVerifier }
typedef QList< Expression::Ptr >	List
typedef QFlags< Property >	Properties
enum	Property {   UseContextItem = 1, DisableElimination = 1 << 1, IsEvaluated = 1 << 2, DisableTypingDeduction = 1 << 3,   EmptynessFollowsChild = 1 << 4, RewriteToEmptyOnEmpty = 1 << 5, RequiresFocus = 1 << 6, AffectsOrderOnly = 1 << 7,   RequiresContextItem = (1 << 8) | RequiresFocus, CreatesFocusForLast = 1 << 9, LastOperandIsCollation = 1 << 10, DependsOnLocalVariable = (1 << 11) | DisableElimination,   EvaluationCacheRedundant = (1 << 12), IsNodeConstructor = 1 << 13, RequiresCurrentItem = 1 << 14 }
typedef QExplicitlySharedDataPointer< Expression >	Ptr
	A smart pointer wrapping mutable Expression instances. More...
typedef ::QAbstractXmlForwardIterator< Expression::Ptr >	QAbstractXmlForwardIterator
typedef QVector< Expression::Ptr >	Vector
Static Public Functions inherited from QPatternist::Expression
static void	rewrite (Expression::Ptr &old, const Expression::Ptr &New, const StaticContext::Ptr &context)
Public Variables inherited from QSharedData
QAtomicInt	ref
Protected Functions inherited from QPatternist::PairContainer
	PairContainer (const Expression::Ptr &operand1, const Expression::Ptr &operand2)
Protected Functions inherited from QPatternist::Expression
void	typeCheckOperands (const StaticContext::Ptr &context)
Protected Functions inherited from QPatternist::CppCastingHelper< Expression >
	CppCastingHelper ()
Protected Variables inherited from QPatternist::PairContainer
Expression::Ptr	m_operand1
Expression::Ptr	m_operand2

Detailed Description

Constructs an element node. This covers both computed and directly constructed element nodes.

See also

XQuery 1.0: An XML Query Language, 3.7 Constructors

Author

Frans Englich frans.nosp@m..eng.nosp@m.lich@.nosp@m.noki.nosp@m.a.com

Definition at line 74 of file qelementconstructor_p.h.

Constructors and Destructors

ElementConstructor()

ElementConstructor::ElementConstructor	(	const Expression::Ptr &	operand1,
		const Expression::Ptr &	operand2,
		const bool	isXSLT
	)

Definition at line 56 of file qelementconstructor.cpp.

                                                          : PairContainer(op1, op2)
                                                          , m_isXSLT(isXSLT)
{
}

Functions

accept()

ExpressionVisitorResult::Ptr ElementConstructor::accept ( const ExpressionVisitor::Ptr &  visitor ) const

virtual

Implements QPatternist::Expression.

Definition at line 155 of file qelementconstructor.cpp.

{
    return visitor->visit(this);
}

evaluateSingleton()

Item ElementConstructor::evaluateSingleton ( const DynamicContext::Ptr &  context ) const

virtual

Reimplemented from QPatternist::Expression.

Definition at line 63 of file qelementconstructor.cpp.

{
    const Item name(m_operand1->evaluateSingleton(context));

    const NodeBuilder::Ptr nodeBuilder(context->nodeBuilder(m_staticBaseURI));
    OutputValidator validator(nodeBuilder.data(), context, this, m_isXSLT);

    const DynamicContext::Ptr receiverContext(context->createReceiverContext(&validator));

    nodeBuilder->startElement(name.as<QNameValue>()->qName());
    m_operand2->evaluateToSequenceReceiver(receiverContext);
    nodeBuilder->endElement();

    const QAbstractXmlNodeModel::Ptr nm(nodeBuilder->builtDocument());
    context->addNodeModel(nm);

    return nm->root(QXmlNodeModelIndex());
}

evaluateToSequenceReceiver()

void ElementConstructor::evaluateToSequenceReceiver ( const DynamicContext::Ptr &  context ) const

virtual

Evaluates this Expression by sending its output to DynamicContext::outputReceiver().

Reimplemented from QPatternist::Expression.

Definition at line 82 of file qelementconstructor.cpp.

{
    /* We create an OutputValidator here too. If we're serializing(a common
     * case, unfortunately) the receiver is already validating in order to
     * catch cases where a computed attribute constructor is followed by an
     * element constructor, but in the cases where we're not serializing it's
     * necessary that we validate in this step. */
    const Item name(m_operand1->evaluateSingleton(context));
    QAbstractXmlReceiver *const receiver = context->outputReceiver();

    OutputValidator validator(receiver, context, this, m_isXSLT);
    const DynamicContext::Ptr receiverContext(context->createReceiverContext(&validator));

    receiver->startElement(name.as<QNameValue>()->qName());
    m_operand2->evaluateToSequenceReceiver(receiverContext);
    receiver->endElement();
}

expectedOperandTypes()

SequenceType::List ElementConstructor::expectedOperandTypes ( ) const

virtual

The first operand must be exactly one xs:QName, and the second argument can be zero or more items.

Implements QPatternist::Expression.

Definition at line 141 of file qelementconstructor.cpp.

{
    SequenceType::List result;
    result.append(CommonSequenceTypes::ExactlyOneQName);
    result.append(CommonSequenceTypes::ZeroOrMoreItems);
    return result;
}

properties()

Expression::Properties ElementConstructor::properties ( ) const

virtual

Returns

a bitwise OR'd value of properties, describing the characteristics of the expression. These properties affects how this Expression is treated in for example type checking stages.

The default implementation returns 0. Override and let the function return a different value, if that's of interest.

An important decision when re-implementing properties() is whether to OR in the properties() of ones operands. For instance, if an operand has RequiresFocus set, that flag nost likely applies to the apparent as well, since it depends on its operand.

See also

deepProperties()

Returns

Expression::None, meaning no special properties

Reimplemented from QPatternist::Expression.

Definition at line 149 of file qelementconstructor.cpp.

{
    return DisableElimination | IsNodeConstructor;
}

staticType()

SequenceType::Ptr ElementConstructor::staticType ( ) const

virtual

Returns

the static type of this Expression. For example, an 'and' expression have as static type xs:boolean

Implements QPatternist::Expression.

Definition at line 136 of file qelementconstructor.cpp.

{
    return CommonSequenceTypes::ExactlyOneElement;
}

typeCheck()

Expression::Ptr ElementConstructor::typeCheck ( const StaticContext::Ptr &  context, const SequenceType::Ptr &  reqType  )

virtual

This implementation guarantees to never rewrite away this Expression, but at most rewrite it as a child of another expression(that presumably have a type checking role). It is therefore always safe to override this function and call this implementation and not worry about that this Expression becomes deleted.

Many Expressions override typeCheck() and performs optimizations, as opposed to doing it in the compress() stage. This is due to that the design of those Expressions often are tied to that certain simplifications are done at the typeCheck() stage of the compilation process or that it in some other way is related to what the typeCheck() do. Also, the earlier the AST can be simplified, the better the chances are for subsequent optimizations.

It is important that the super class's typeCheck() is called before doing any custom type checking, since the call can change the children(notably, the childrens' static types). For example, if the Expression, MyExpression in the example, does not match the required type, typeCheck returns the Expression wrapped in for example ItemVerifier, CardinalityVerifier, or both.

typeCheck() may be called many times. typeCheck() must either raise an error if this Expression is an invalid expression. Thus, it is guaranteed that an Expression is valid after typeCheck() is called.

Parameters

context	supplies information, such as namespace bindings and available function signatures, that can be needed at compilation time. context is guaranteed by the caller to never null.
reqType	the static type that this Expression must match when evaluated. reqType is guaranteed by the caller to never null.

Returns

an Expression that can be this Expression, or another expression, which somehow is necessary for making this Expression conforming to reqType

Reimplemented from QPatternist::Expression.

Definition at line 100 of file qelementconstructor.cpp.

{
    /* What does this code do? When type checking our children, our namespace
     * bindings, which are also children of the form of NamespaceConstructor
     * instances, must be statically in-scope for them, so find them and
     * shuffle their bindings into the StaticContext. */

    m_staticBaseURI = context->baseURI();

    /* Namespace declarations changes the in-scope bindings, so let's
     * first lookup our child NamespaceConstructors. */
    const ID operandID = m_operand2->id();

    NamespaceResolver::Bindings overrides;
    if(operandID == IDExpressionSequence)
    {
        const Expression::List operands(m_operand2->operands());
        const int len = operands.count();

        for(int i = 0; i < len; ++i)
        {
            if(operands.at(i)->is(IDNamespaceConstructor))
            {
                const QXmlName &nb = operands.at(i)->as<NamespaceConstructor>()->namespaceBinding();
                overrides.insert(nb.prefix(), nb.namespaceURI());
            }
        }
    }

    const NamespaceResolver::Ptr newResolver(new DelegatingNamespaceResolver(context->namespaceBindings(), overrides));
    const StaticContext::Ptr augmented(new StaticNamespaceContext(newResolver, context));

    return PairContainer::typeCheck(augmented, reqType);
}

Properties

m_isXSLT

const bool QPatternist::ElementConstructor::m_isXSLT

private

Definition at line 99 of file qelementconstructor_p.h.

Referenced by evaluateSingleton(), and evaluateToSequenceReceiver().

m_staticBaseURI

QUrl QPatternist::ElementConstructor::m_staticBaseURI

private

Definition at line 98 of file qelementconstructor_p.h.

Referenced by evaluateSingleton(), and typeCheck().

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The documentation for this class was generated from the following files:

• /src/xmlpatterns/expr/qelementconstructor_p.h
• /src/xmlpatterns/expr/qelementconstructor.cpp