Implements XPath 2.0's instance of expression. More...

#include <qinstanceof_p.h>

Inheritance diagram for QPatternist::InstanceOf:

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

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

virtual bool	evaluateEBV (const DynamicContext::Ptr &) const

virtual SequenceType::List	expectedOperandTypes () const

	InstanceOf (const Expression::Ptr &operand, const SequenceType::Ptr &targetType)

virtual SequenceType::Ptr	staticType () const

SequenceType::Ptr	targetType () 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 Item::Iterator::Ptr	evaluateSequence (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

virtual Properties	properties () 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 ()

Properties
const SequenceType::Ptr	m_targetType

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::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

Implements XPath 2.0's instance of expression.

See also: XML Path Language (XPath) 2.0, 3.10.1 Instance Of

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

Definition at line 72 of file qinstanceof_p.h.

Constructors and Destructors

◆ InstanceOf()

InstanceOf::InstanceOf	(	const Expression::Ptr &	operand,
		const SequenceType::Ptr &	targetType
	)

Definition at line 53 of file qinstanceof.cpp.

                                                      : SingleContainer(operand)
                                                        , m_targetType(tType)
 {
     Q_ASSERT(m_targetType);
 }

Functions

◆ accept()

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

virtual

Implements QPatternist::Expression.

Definition at line 124 of file qinstanceof.cpp.

 {
     return visitor->visit(this);
 }

◆ compress()

Expression::Ptr InstanceOf::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 84 of file qinstanceof.cpp.

 {
     const Expression::Ptr me(SingleContainer::compress(context));
 
     if(me != this || m_operand->has(DisableTypingDeduction))
         return me;
 
     const SequenceType::Ptr opType(m_operand->staticType());
     const ItemType::Ptr targetType(m_targetType->itemType());
     const ItemType::Ptr operandType(opType->itemType());
 
     if(m_targetType->cardinality().isMatch(opType->cardinality()))
     {
         if(*operandType == *CommonSequenceTypes::Empty || targetType->xdtTypeMatches(operandType))
             return wrapLiteral(CommonValues::BooleanTrue, context, this);
         else if(!operandType->xdtTypeMatches(targetType))
             return wrapLiteral(CommonValues::BooleanFalse, context, this);
     }
     /* Optimization: rule out the case where instance of will always fail. */
 
     return me;
 }

◆ evaluateEBV()

bool InstanceOf::evaluateEBV ( const DynamicContext::Ptr & context ) const

virtual

Determines the Effective Boolean Value of the expression.

The Effective Boolean Value of a value is not necessarily the same as converting the value to a new value of type xs:boolean.

Note that this function cannot return the empty sequence, evaluateSingleton() must be overridden in order to be able to do that.

The default implementation results in a type error. Hence, this function must be overridden if such behavior is not of interest.

See also: XML Path Language (XPath) 2.0, 2.4.3 Effective Boolean Value

Reimplemented from QPatternist::Expression.

Definition at line 60 of file qinstanceof.cpp.

 {
     const Item::Iterator::Ptr it(m_operand->evaluateSequence(context));
     Item item(it->next());
     unsigned int count = 1;
 
     if(!item)
         return m_targetType->cardinality().allowsEmpty();
 
     do
     {
         if(!m_targetType->itemType()->itemMatches(item))
             return false;
 
         if(count == 2 && !m_targetType->cardinality().allowsMany())
             return false;
 
         item = it->next();
         ++count;
     } while(item);
 
     return true;
 }

◆ expectedOperandTypes()

SequenceType::List InstanceOf::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 117 of file qinstanceof.cpp.

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

◆ staticType()

SequenceType::Ptr InstanceOf::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 112 of file qinstanceof.cpp.

 {
     return CommonSequenceTypes::ExactlyOneBoolean;
 }

◆ targetType()

SequenceType::Ptr InstanceOf::targetType ( ) const

Returns: the SequenceType that this instance of Expression is testing its operand against.

Definition at line 107 of file qinstanceof.cpp.

Referenced by compress().

 {
     return m_targetType;
 }

Properties

◆ m_targetType

const SequenceType::Ptr QPatternist::InstanceOf::m_targetType

private

Definition at line 93 of file qinstanceof_p.h.

Referenced by compress(), evaluateEBV(), InstanceOf(), and targetType().

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

/src/xmlpatterns/expr/qinstanceof_p.h
/src/xmlpatterns/expr/qinstanceof.cpp

Public Functions

Properties

Additional Inherited Members

Detailed Description

Constructors and Destructors

◆ InstanceOf()

Functions

◆ accept()

◆ compress()

◆ evaluateEBV()

◆ expectedOperandTypes()

◆ staticType()

◆ targetType()

Properties

◆ m_targetType