De-duplicates and sorts in document order the content that its operand returns. More...

#include <qnodesort_p.h>

Inheritance diagram for QPatternist::NodeSortExpression:

Public Functions
virtual ExpressionVisitorResult::Ptr	accept (const ExpressionVisitor::Ptr &visitor) const

virtual Expression::Ptr	compress (const StaticContext::Ptr &context)

virtual Item::Iterator::Ptr	evaluateSequence (const DynamicContext::Ptr &context) const

virtual SequenceType::List	expectedOperandTypes () const

	NodeSortExpression (const Expression::Ptr &operand)

virtual Properties	properties () const

virtual SequenceType::Ptr	staticType () const

Public Functions inherited from QPatternist::SingleContainer
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)

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	evaluateSingleton (const DynamicContext::Ptr &context) const

virtual void	evaluateToSequenceReceiver (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::Ptr	typeCheck (const StaticContext::Ptr &context, const SequenceType::Ptr &reqType)

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 ()

Static Public Functions
static Expression::Ptr	wrapAround (const Expression::Ptr &operand, const StaticContext::Ptr &context)

Static Public Functions inherited from QPatternist::Expression
static void	rewrite (Expression::Ptr &old, const Expression::Ptr &New, const StaticContext::Ptr &context)

Static Private Functions
static bool	lessThanUsingNodeModel (const Item &n1, const Item &n2)

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

Public Variables inherited from QSharedData
QAtomicInt	ref

Protected Functions inherited from QPatternist::SingleContainer
	SingleContainer (const Expression::Ptr &operand)

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::SingleContainer
Expression::Ptr	m_operand

Detailed Description

De-duplicates and sorts in document order the content that its operand returns.

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

Definition at line 70 of file qnodesort_p.h.

Constructors and Destructors

◆ NodeSortExpression()

NodeSortExpression::NodeSortExpression ( const Expression::Ptr & operand )

Definition at line 50 of file qnodesort.cpp.

Referenced by wrapAround().

                                                               : SingleContainer(op)
 {
 }

Functions

◆ accept()

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

virtual

Implements QPatternist::Expression.

Definition at line 127 of file qnodesort.cpp.

 {
     return visitor->visit(this);
 }

◆ compress()

Expression::Ptr NodeSortExpression::compress ( const StaticContext::Ptr & context )

virtual

compress() is the last stage performs in compiling an expression, done after the initial AST build and calling typeCheck(). compress() performs crucial simplifications, either by having drastic performance implications or that some expressions depend on it for proper behavior.

The default implementation performs a sparse conditional constant propagation. In short, a recursive process is performed in the AST which examines if the Expression's operands are constant values, and if so, performs a const fold(AST rewrite) into the result of evaluating the expression in question. This default behavior can be disabled by letting properties() return DisableElimination.

This compress() stage can be relative effective due to the design of XPath, in part because intrinsic functions are heavily used. Many Expressions override compress() and do optimizations specific to what they do. Also, many Expressions performs optimizations in their typeCheck().

Parameters

context the static context. Supplies compile time information, and is the channel for communicating error messages.

See also: Wikipedia, the free encyclopedia, Sparse conditional constant propagation; Wikipedia, the free encyclopedia, Intrinsic function; Wikipedia, the free encyclopedia, Compiler optimization

Reimplemented from QPatternist::Expression.

Definition at line 103 of file qnodesort.cpp.

 {
     const Expression::Ptr me(SingleContainer::compress(context));
 
     /* It make no sense to sort & deduplicate a single node. */
     if(m_operand->staticType()->cardinality().allowsMany())
         return me;
     else
         return m_operand;
 }

◆ evaluateSequence()

Item::Iterator::Ptr NodeSortExpression::evaluateSequence ( const DynamicContext::Ptr & context ) const

virtual

Evaluate this Expression by iterating over it. This is a central function for evaluating expressions.

Expressions must always always return a valid QAbstractXmlForwardIterator and may never return 0. If an empty result is of interest to be returned, the EmptyIterator should be returned.

The default implementation returns a SingletonIterator over the item returned from evaluateSingleton().

Note: This function may raise an exception when calling, not only when QAbstractXmlForwardIterator::next() is called on the return value. This is because in some cases evaluateSingleton() is called directly.

Reimplemented from QPatternist::Expression.

Definition at line 73 of file qnodesort.cpp.

 {
     Q_ASSERT_X(m_operand->staticType()->cardinality().allowsMany(), Q_FUNC_INFO,
                "It makes no sense to sort a single node.");
 
     Item::List nodes(m_operand->evaluateSequence(context)->toList());
 
     if(nodes.isEmpty())
         return CommonValues::emptyIterator;
     else if(nodes.first().isAtomicValue())
         return makeListIterator(nodes);
     else
     {
         qSort(nodes.begin(), nodes.end(), lessThanUsingNodeModel);
 
         return Item::Iterator::Ptr(new DeduplicateIterator(nodes));
     }
 }

◆ expectedOperandTypes()

SequenceType::List NodeSortExpression::expectedOperandTypes ( ) const

virtual

Returns a list of Sequence Types, describing the type of each of the expression's operands. Hence, this function has a relationship to the operands() function:

- The lengths of the lists returned by expectedOperandTypes()
and operands() should always be equal in length, since one
cannot describe the type of a non-existent operand(and all
operands must have type information).
- A significant difference between the two functions is that while
the type of objects in the list returned by operands() may vary
between compilations/static context, simply because the particular
Expression is part of different XPath expressions, the
types in the list returned by expectedOperandTypes is always the same
since the function/operator signature never changes.

This function should not be confused with staticType(), which returns the static type of the expression itself, not its operands. The function call is an expression where this is clear: the type of the return value is not the same as the arguments' types. The static type of the operands supplied to the expression can be determined via the staticType() function of the instances returned by operands().

If the expression has no operands, an empty list should be returned.

Implements QPatternist::Expression.

Definition at line 119 of file qnodesort.cpp.

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

◆ lessThanUsingNodeModel()

bool NodeSortExpression::lessThanUsingNodeModel	(	const Item &	n1,
		const Item &	n2
	)

inlinestaticprivate

Definition at line 54 of file qnodesort.cpp.

Referenced by evaluateSequence().

 {
     Q_ASSERT(n1.isNode());
     Q_ASSERT(n2.isNode());
 
     if(n1.asNode().model() == n2.asNode().model())
         return n1.asNode().compareOrder(n2.asNode()) == QXmlNodeModelIndex::Precedes;
     else
     {
         /* The two nodes are from different trees. The sort order is implementation
          * defined, but it must be stable.
          *
          * We do this by looking at the pointer difference. The value means nothing,
          * but it is stable, and that's what we're looking for. */
         return n1.asNode().model() - n2.asNode().model() < 0;
     }
 }

◆ properties()

Expression::Properties NodeSortExpression::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 132 of file qnodesort.cpp.

 {
     /* The reason we disable elimination is that the assert for sorting a
      * single node in evaluateSequence() triggers unless our compress() routine
      * has been run. Anyhow, it's not that we would manage to write away anyway,
      * since the node source in most(all?) cases prevents it.
      */
     return AffectsOrderOnly | DisableElimination;
 }

◆ staticType()

SequenceType::Ptr NodeSortExpression::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 114 of file qnodesort.cpp.

 {
     return m_operand->staticType();
 }

◆ wrapAround()

Expression::Ptr NodeSortExpression::wrapAround	(	const Expression::Ptr &	operand,
		const StaticContext::Ptr &	context
	)

static

Ensures that result delivered from operand, is in document order.

Definition at line 92 of file qnodesort.cpp.

Referenced by QPatternist::CombineNodes::typeCheck(), QPatternist::Path::typeCheck(), and QPatternist::yyparse().

 {
     Q_ASSERT(operand);
     Q_ASSERT(context);
 
     const Expression::Ptr sort(new NodeSortExpression(operand));
     context->wrapExpressionWith(operand.data(), sort);
     return sort;
 }

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

/src/xmlpatterns/expr/qnodesort_p.h
/src/xmlpatterns/expr/qnodesort.cpp

Public Functions

Static Public Functions

Static Private Functions

Additional Inherited Members

Detailed Description

Constructors and Destructors

◆ NodeSortExpression()

Functions

◆ accept()

◆ compress()

◆ evaluateSequence()

◆ expectedOperandTypes()

◆ lessThanUsingNodeModel()

◆ properties()

◆ staticType()

◆ wrapAround()