Package net.sf.saxon.expr

Class AtomicSequenceConverter

java.lang.Object

net.sf.saxon.expr.Expression

net.sf.saxon.expr.UnaryExpression

net.sf.saxon.expr.AtomicSequenceConverter

All Implemented Interfaces:

ExportAgent, Locatable, IdentityComparable, Traceable

Direct Known Subclasses:

UntypedSequenceConverter

public class AtomicSequenceConverter
extends UnaryExpression

An AtomicSequenceConverter is an expression that performs a cast (or other supplied conversion) on each member of a supplied sequence

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	AtomicSequenceConverter.AtomicSequenceConverterElaborator	Elaborator for an AtomicSequenceConverter (including an UntypedAtomicConverter, which is the same except that it uses a different converter internally)
static class	AtomicSequenceConverter.AtomicSequenceMappingFunction	Mapping function wrapped around a converter
static class	AtomicSequenceConverter.ToStringMappingFunction	Mapping function that converts every item in a sequence to a string

Field Summary

Fields

Modifier and Type	Field	Description
protected Converter	converter
protected PlainType	requiredItemType
static AtomicSequenceConverter.ToStringMappingFunction	TO_STRING_MAPPER

Fields inherited from class net.sf.saxon.expr.Expression

EFFECTIVE_BOOLEAN_VALUE, EVALUATE_METHOD, ITEM_FEED_METHOD, ITERATE_METHOD, MAX_COST, MAX_SEQUENCE_LENGTH, MAX_STRING_LENGTH, PROCESS_METHOD, staticProperties, UNBOUNDED_LOWER, UNBOUNDED_UPPER, UPDATE_METHOD, WATCH_METHOD

Constructor Summary

Constructors

Constructor	Description
AtomicSequenceConverter(Expression sequence, PlainType requiredItemType)	Constructor

Method Summary

Modifier and Type	Method	Description
Converter	allocateConverter(Configuration config, boolean allowNull)
Converter	allocateConverter(Configuration config, boolean allowNull, ItemType sourceType)
void	allocateConverterStatically(Configuration config, boolean allowNull)
protected int	computeCardinality()	Determine the static cardinality of the expression
protected int	computeHashCode()	get HashCode for comparing two expressions.
protected int	computeSpecialProperties()	Determine the special properties of this expression
AtomicValue	convertItem(AtomicValue item, XPathContext context)
Expression	copy(RebindingMap rebindings)	Copy an expression.
protected String	displayOperator(Configuration config)	Give a string representation of the operator for use in diagnostics
boolean	equals(Object other)	Is this expression the same as another expression?
AtomicValue	evaluateItem(XPathContext context)	Evaluate as an Item.
void	export(ExpressionPresenter destination)	Diagnostic print of expression structure.
Converter	getConverter()	Get the converter used to convert the items in the sequence
protected Converter	getConverterDynamically(XPathContext context)
ItemMappingIterator	getConvertingIterator(XPathContext context, SequenceIterator base)
Elaborator	getElaborator()	Make an elaborator for this expression
String	getExpressionName()	Get a name identifying the kind of expression, in terms meaningful to a user.
int	getImplementationMethod()	An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process().
ItemType	getItemType()	Determine the data type of the items returned by the expression, if possible
protected OperandRole	getOperandRole()	Get the usage (in terms of streamability analysis) of the single operand
PlainType	getRequiredItemType()	Get the required item type (the target type of the conversion
Supplier<RoleDiagnostic>	getRoleSupplier()	Get the RoleDiagnostic, used to give more precise error information if the conversion fails
String	getStreamerName()	Get the (partial) name of a class that supports streaming of this kind of expression
SequenceIterator	iterate(XPathContext context)	Iterate over the sequence of values
static AtomicSequenceConverter	makeDownCaster(Expression sequence, AtomicType requiredItemType, Configuration config)
Expression	optimize(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo)	Perform optimisation of an expression and its subexpressions.
void	setConverter(Converter converter)
void	setRoleDiagnostic(Supplier<RoleDiagnostic> roleSupplier)	Set a RoleDiagnostic, used to give more precise error information if the conversion fails
Expression	simplify()	Simplify an expression
String	toString()	The toString() method for an expression attempts to give a representation of the expression in an XPath-like form, but there is no guarantee that the syntax will actually be true XPath.
Expression	typeCheck(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo)	Type-check the expression

Methods inherited from class net.sf.saxon.expr.UnaryExpression

emitExtraAttributes, getBaseExpression, getOperand, operands, setBaseExpression, toShortString

Methods inherited from class net.sf.saxon.expr.Expression

addToPathMap, adoptChildExpression, allowExtractingCommonSubexpressions, checkedOperands, checkForUpdatingSubexpressions, checkPermittedContents, computeDependencies, computeStaticProperties, dispatchTailCall, dynamicError, effectiveBooleanValue, evaluateAsString, explain, getCardinality, getConfiguration, getCost, getDependencies, getEvaluationMethod, getExtraProperty, getIntegerBounds, getIntrinsicDependencies, getLocalRetainedStaticContext, getLocation, getNetCost, getObjectName, getPackageData, getParentExpression, getProperties, getProperty, getRetainedStaticContext, getScopingExpression, getSlotsUsed, getSpecialProperties, getStaticBaseURI, getStaticBaseURIString, getStaticType, getStaticUType, getTracingTag, hasCompatibleStaticContext, hashCode, hasSpecialProperty, hasVariableBinding, identityHashCode, implementsStaticTypeCheck, isCallOn, isEqual, isIdentical, isInstruction, isLiftable, isMultiThreaded, isStaticPropertiesKnown, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, makeElaborator, markTailFunctionCalls, operandList, operandSparseList, optimizeChildren, prepareForStreaming, process, resetLocalStaticProperties, restoreParentPointers, setEvaluationMethod, setExtraProperty, setFiltered, setFlattened, setLocation, setParentExpression, setRetainedStaticContext, setRetainedStaticContextLocally, setRetainedStaticContextThoroughly, setStaticProperty, simplifyChildren, staticTypeCheck, supportsLazyEvaluation, suppressValidation, toPattern, typeCheckChildren, typeError, unordered, verifyParentPointers, withLocation

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface net.sf.saxon.trace.Traceable

gatherProperties

Field Details

TO_STRING_MAPPER

public static AtomicSequenceConverter.ToStringMappingFunction TO_STRING_MAPPER

requiredItemType

protected PlainType requiredItemType

converter

protected Converter converter

Constructor Details

AtomicSequenceConverter

public AtomicSequenceConverter(Expression sequence,
 PlainType requiredItemType)

Constructor

Parameters:

sequence - this must be a sequence of atomic values. This is not checked; a ClassCastException will occur if the precondition is not satisfied.

requiredItemType - the item type to which all items in the sequence should be converted,

Method Details

makeDownCaster

public static AtomicSequenceConverter makeDownCaster(Expression sequence,
 AtomicType requiredItemType,
 Configuration config)

allocateConverterStatically

public void allocateConverterStatically(Configuration config,
 boolean allowNull)

allocateConverter

public Converter allocateConverter(Configuration config,
 boolean allowNull)

getConverterDynamically

protected Converter getConverterDynamically(XPathContext context)

allocateConverter

public Converter allocateConverter(Configuration config,
 boolean allowNull,
 ItemType sourceType)

getOperandRole

protected OperandRole getOperandRole()

Description copied from class: UnaryExpression

Get the usage (in terms of streamability analysis) of the single operand

Specified by:

getOperandRole in class UnaryExpression

Returns:

the operand usage

getRequiredItemType

public PlainType getRequiredItemType()

Get the required item type (the target type of the conversion

Returns:

the required item type

getConverter

public Converter getConverter()

Get the converter used to convert the items in the sequence

Returns:

the converter. Note that a converter is always allocated during the typeCheck() phase, even if the source type is not known.

setConverter

public void setConverter(Converter converter)

setRoleDiagnostic

public void setRoleDiagnostic(Supplier<RoleDiagnostic> roleSupplier)

Set a RoleDiagnostic, used to give more precise error information if the conversion fails

Parameters:

roleSupplier - provides more precise error information, in particular the error code to be used.

getRoleSupplier

public Supplier<RoleDiagnostic> getRoleSupplier()

Get the RoleDiagnostic, used to give more precise error information if the conversion fails

Returns:

the RoleDiagnostic, or null if none has been set

simplify

public Expression simplify()
                    throws XPathException

Simplify an expression

Overrides:

simplify in class Expression

Returns:

the simplified expression (or the original if unchanged, or if modified in-situ)

Throws:

XPathException - if an error is discovered during expression rewriting

typeCheck

public Expression typeCheck(ExpressionVisitor visitor,
 ContextItemStaticInfo contextInfo)
                     throws XPathException

Type-check the expression

Overrides:

typeCheck in class UnaryExpression

Parameters:

visitor - an expression visitor

contextInfo - Information available statically about the context item: whether it is (possibly) absent; its static type; its streaming posture.

Returns:

the original expression, rewritten to perform necessary run-time type checks, and to perform other type-related optimizations

Throws:

XPathException - if an error is discovered during this phase (typically a type error)

optimize

public Expression optimize(ExpressionVisitor visitor,
 ContextItemStaticInfo contextInfo)
                    throws XPathException

Perform optimisation of an expression and its subexpressions.

Overrides:

optimize in class UnaryExpression

Parameters:

visitor - an expression visitor

contextInfo - the static type of "." at the point where this expression is invoked. The parameter is set to null if it is known statically that the context item will be undefined. If the type of the context item is not known statically, the argument is set to Type.ITEM_TYPE

Returns:

the original expression, rewritten if appropriate to optimize execution

Throws:

XPathException - if an error is discovered during this phase (typically a type error)

getImplementationMethod

public int getImplementationMethod()

An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process(). This method indicates which of these methods is provided directly. The other methods will always be available indirectly, using an implementation that relies on one of the other methods.

Specified by:

getImplementationMethod in class Expression

Returns:

the implementation method, for example Expression.ITERATE_METHOD or Expression.EVALUATE_METHOD or Expression.PROCESS_METHOD

computeSpecialProperties

protected int computeSpecialProperties()

Determine the special properties of this expression

Overrides:

computeSpecialProperties in class UnaryExpression

Returns:

StaticProperty.NO_NODES_NEWLY_CREATED.

getStreamerName

public String getStreamerName()

Description copied from class: Expression

Get the (partial) name of a class that supports streaming of this kind of expression

Overrides:

getStreamerName in class Expression

Returns:

the partial name of a class that can be instantiated to provide streaming support in Saxon-EE, or null if there is no such class

copy

public Expression copy(RebindingMap rebindings)

Copy an expression. This makes a deep copy.

Specified by:

copy in class Expression

Parameters:

rebindings - variables that need to be re-bound

Returns:

the copy of the original expression

iterate

public SequenceIterator iterate(XPathContext context)
                         throws XPathException

Iterate over the sequence of values

Overrides:

iterate in class Expression

Parameters:

context - supplies the context for evaluation

Returns:

a SequenceIterator that can be used to iterate over the result of the expression

Throws:

XPathException - if any dynamic error occurs evaluating the expression

getConvertingIterator

public ItemMappingIterator getConvertingIterator(XPathContext context,
 SequenceIterator base)

evaluateItem

public AtomicValue evaluateItem(XPathContext context)
                         throws XPathException

Evaluate as an Item. This should only be called if the AtomicSequenceConverter has cardinality zero-or-one

Overrides:

evaluateItem in class Expression

Parameters:

context - The context in which the expression is to be evaluated

Returns:

the node or atomic value that results from evaluating the expression; or null to indicate that the result is an empty sequence

Throws:

XPathException - if any dynamic error occurs evaluating the expression

convertItem

public AtomicValue convertItem(AtomicValue item,
 XPathContext context)
                        throws XPathException

Throws:

XPathException

getItemType

public ItemType getItemType()

Determine the data type of the items returned by the expression, if possible

Overrides:

getItemType in class UnaryExpression

Returns:

a value such as Type.STRING, Type.BOOLEAN, Type.NUMBER, Type.NODE, or Type.ITEM (meaning not known in advance)

computeCardinality

protected int computeCardinality()

Determine the static cardinality of the expression

Overrides:

computeCardinality in class UnaryExpression

Returns:

the computed cardinality, as one of the values StaticProperty.ALLOWS_ZERO_OR_ONE, StaticProperty.EXACTLY_ONE, StaticProperty.ALLOWS_ONE_OR_MORE, StaticProperty.ALLOWS_ZERO_OR_MORE. May also return StaticProperty.ALLOWS_ZERO if the result is known to be an empty sequence, or StaticProperty.ALLOWS_MANY if if is known to return a sequence of length two or more.

toString

public String toString()

The toString() method for an expression attempts to give a representation of the expression in an XPath-like form, but there is no guarantee that the syntax will actually be true XPath. In the case of XSLT instructions, the toString() method gives an abstracted view of the syntax

Overrides:

toString in class UnaryExpression

Returns:

a representation of the expression as a string

equals

public boolean equals(Object other)

Is this expression the same as another expression?

Overrides:

equals in class UnaryExpression

Parameters:

other - the other operand; the result is false if this is not an Expression

Returns:

true if the other operand is an expression and if it can be determined that the two expressions are equivalent, in the sense that they will always return the same result.

computeHashCode

protected int computeHashCode()

get HashCode for comparing two expressions. Note that this hashcode gives the same result for (A op B) and for (B op A), whether or not the operator is commutative.

Overrides:

computeHashCode in class UnaryExpression

Returns:

a computed hash code

getExpressionName

public String getExpressionName()

Get a name identifying the kind of expression, in terms meaningful to a user.

Overrides:

getExpressionName in class Expression

Returns:

a name identifying the kind of expression, in terms meaningful to a user. The name will always be in the form of a lexical XML QName, and should match the name used in explain() output displaying the expression.

displayOperator

protected String displayOperator(Configuration config)

Description copied from class: UnaryExpression

Give a string representation of the operator for use in diagnostics

Overrides:

displayOperator in class UnaryExpression

Parameters:

config - the Saxon configuration

Returns:

the operator, as a string

export

public void export(ExpressionPresenter destination)
            throws XPathException

Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.

Specified by:

export in interface ExportAgent

Overrides:

export in class UnaryExpression

Parameters:

destination - the expression presenter used to display the structure

Throws:

XPathException - if the export fails, for example if an expression is found that won't work in the target environment.

getElaborator

public Elaborator getElaborator()

Make an elaborator for this expression

Overrides:

getElaborator in class Expression

Returns:

a suitable elaborator