com.saxonica.trans

Class EvaluateInstr

java.lang.Object

net.sf.saxon.expr.Expression

com.saxonica.trans.EvaluateInstr

All Implemented Interfaces:

ExportAgent, Locatable, IdentityComparable

public final class EvaluateInstr
extends Expression

An EvaluateInstr is the compiled form of an xsl:evaluate instruction

The implementation maintains a cache of compiled expressions, provided that the namespace context is not constructed dynamically. The cache is an LRU cache with a fixed size of 100 entries. This is to avoid uncontrolled use of memory when the XPath expressions are completely dynamic and each one is unique.

Field Summary

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 and Description
EvaluateInstr(Expression xpath, SequenceType requiredType, Expression contextItemExpr, Expression baseUriExpr, Expression namespaceContextExpr, Expression schemaAwareExpr) Create an xsl:evaluate instruction

Method Summary

Modifier and Type	Method and Description
PathMap.PathMapNodeSet	addToPathMap(PathMap pathMap, PathMap.PathMapNodeSet pathMapNodeSet) Add a representation of this expression to a PathMap.
protected int	computeCardinality() Compute the static cardinality of this expression
Expression	copy(RebindingMap rebindings) Copy an expression.
void	export(ExpressionPresenter out) Diagnostic print of expression structure.
WithParam[]	getActualParams()
Expression	getBaseUriExpr()
Expression	getContextItemExpr()
Expression	getDynamicParams()
int	getImplementationMethod() An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process().
int	getIntrinsicDependencies() Determine the intrinsic dependencies of an expression, that is, those which are not derived from the dependencies of its subexpressions.
ItemType	getItemType() Determine the data type of the items returned by this expression
Expression	getNamespaceContextExpr()
Expression	getSchemaAwareExpr()
Expression	getXpath()
void	importSchemaNamespace(java.lang.String ns) Add an imported schema namespace
boolean	isActualParam(StructuredQName name)
boolean	isInstruction() Ask whether this expression is an instruction.
SequenceIterator<?>	iterate(XPathContext context) Return an Iterator to iterate over the values of a sequence.
java.lang.Iterable<Operand>	operands() Get the immediate sub-expressions of this expression, with information about the relationship of each expression to its parent expression.
Expression	optimize(ExpressionVisitor visitor, ContextItemStaticInfo contextItemType) Perform optimisation of an expression and its subexpressions.
void	setActualParameters(WithParam[] params)
void	setActualParams(WithParam[] actualParams)
void	setBaseUriExpr(Expression baseUriExpr)
void	setContextItemExpr(Expression contextItemExpr)
void	setDefaultXPathNamespace(java.lang.String defaultXPathNamespace)
void	setDynamicParams(Expression params)
void	setNamespaceContextExpr(Expression namespaceContextExpr)
void	setOptionsExpression(Expression options)
void	setSchemaAwareExpr(Expression schemaAwareExpr)
void	setXpath(Expression xpath)
Expression	typeCheck(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo) Type-check the expression

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

adoptChildExpression, allowExtractingCommonSubexpressions, checkedOperands, checkForUpdatingSubexpressions, checkPermittedContents, computeDependencies, computeHashCode, computeSpecialProperties, computeStaticProperties, dynamicError, effectiveBooleanValue, equals, evaluateAsString, evaluateItem, evaluatePendingUpdates, explain, getCardinality, getConfiguration, getConstructType, getCost, getDependencies, getEvaluationMethod, getExpressionName, getExtraProperty, getIntegerBounds, getInterpretedExpression, getLocalRetainedStaticContext, getLocation, getNetCost, getObjectName, getPackageData, getParentExpression, getProperties, getProperty, getRetainedStaticContext, getScopingExpression, getSlotsUsed, getSpecialProperties, getStaticBaseURI, getStaticBaseURIString, getStaticType, getStaticUType, getStreamerName, hasCompatibleStaticContext, hashCode, hasSpecialProperty, hasVariableBinding, identityHashCode, implementsStaticTypeCheck, isCallOn, isEqual, isIdentical, isLiftable, isMultiThreaded, isStaticPropertiesKnown, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, markTailFunctionCalls, operandList, operandSparseList, optimizeChildren, prepareForStreaming, process, resetLocalStaticProperties, restoreParentPointers, setEvaluationMethod, setExtraProperty, setFiltered, setFlattened, setLocation, setParentExpression, setRetainedStaticContext, setRetainedStaticContextLocally, setRetainedStaticContextThoroughly, setStaticProperty, simplify, simplifyChildren, staticTypeCheck, suppressValidation, toPattern, toShortString, toString, typeCheckChildren, typeError, unordered, verifyParentPointers

Methods inherited from class java.lang.Object

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

Constructor Detail

EvaluateInstr

public EvaluateInstr(Expression xpath,
                     SequenceType requiredType,
                     Expression contextItemExpr,
                     Expression baseUriExpr,
                     Expression namespaceContextExpr,
                     Expression schemaAwareExpr)

Create an xsl:evaluate instruction

Parameters:

xpath - The expression that returns the string that is to be parsed as an XPath expression

requiredType - the required type of the result of evaluating the XPath expression

contextItemExpr - The expression that delivers the context item

baseUriExpr - the expression whose value is used as the static base URI of the XPath expression

namespaceContextExpr - the expression that delivers a node whose namespace context provides the static namespace context for the XPath expression

schemaAwareExpr - an expression whose value is true if the XPath expression is to be treated as schema aware, or false otherwise

Method Detail

setOptionsExpression

public void setOptionsExpression(Expression options)

setActualParameters

public void setActualParameters(WithParam[] params)

setDefaultXPathNamespace

public void setDefaultXPathNamespace(java.lang.String defaultXPathNamespace)

isInstruction

public boolean isInstruction()

Ask whether this expression is an instruction. In XSLT streamability analysis this is used to distinguish constructs corresponding to XSLT instructions from other constructs, typically XPath expressions.

Overrides:

isInstruction in class Expression

Returns:

true (if this construct exists at all in an XSLT environment, then it represents an instruction)

importSchemaNamespace

public void importSchemaNamespace(java.lang.String ns)

Add an imported schema namespace

Parameters:

ns - the namespace to be imported ("" for the non-namespace)

typeCheck

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

Type-check the expression

Overrides:

typeCheck in class Expression

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 contextItemType)
                    throws XPathException

Description copied from class: Expression

Perform optimisation of an expression and its subexpressions. This is the third and final phase of static optimization.

This method is called after all references to functions and variables have been resolved to the declaration of the function or variable, and after all type checking has been done.

Overrides:

optimize in class Expression

Parameters:

visitor - an expression visitor

contextItemType - 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)

getItemType

public final ItemType getItemType()

Determine the data type of the items returned by this expression

Specified by:

getItemType in class Expression

Returns:

the data type

computeCardinality

protected int computeCardinality()

Description copied from class: Expression

Compute the static cardinality of this expression

Specified by:

computeCardinality in class Expression

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.

addToPathMap

public PathMap.PathMapNodeSet addToPathMap(PathMap pathMap,
                                           PathMap.PathMapNodeSet pathMapNodeSet)

Add a representation of this expression to a PathMap. The PathMap captures a map of the nodes visited by an expression in a source tree.

The default implementation of this method assumes that an expression does no navigation other than the navigation done by evaluating its subexpressions, and that the subexpressions are evaluated in the same context as the containing expression. The method must be overridden for any expression where these assumptions do not hold. For example, implementations exist for AxisExpression, ParentExpression, and RootExpression (because they perform navigation), and for the doc(), document(), and collection() functions because they create a new navigation root. Implementations also exist for PathExpression and FilterExpression because they have subexpressions that are evaluated in a different context from the calling expression.

Overrides:

addToPathMap in class Expression

Parameters:

pathMap - the PathMap to which the expression should be added

pathMapNodeSet - the set of nodes in the path map that are affected

Returns:

the pathMapNode representing the focus established by this expression, in the case where this expression is the first operand of a path expression or filter expression. For an expression that does navigation, it represents the end of the arc in the path map that describes the navigation route. For other expressions, it is the same as the input pathMapNode.

getIntrinsicDependencies

public int getIntrinsicDependencies()

Description copied from class: Expression

Determine the intrinsic dependencies of an expression, that is, those which are not derived from the dependencies of its subexpressions. For example, position() has an intrinsic dependency on the context position, while (position()+1) does not. The default implementation of the method returns 0, indicating "no dependencies".

Overrides:

getIntrinsicDependencies in class Expression

Returns:

a set of bit-significant flags identifying the "intrinsic" dependencies. The flags are documented in class net.sf.saxon.value.StaticProperty

operands

public java.lang.Iterable<Operand> operands()

Description copied from class: Expression

Get the immediate sub-expressions of this expression, with information about the relationship of each expression to its parent expression. Default implementation works off the results of iterateSubExpressions()

If the expression is a Callable, then it is required that the order of the operands returned by this function is the same as the order of arguments supplied to the corresponding call() method.

Overrides:

operands in class Expression

Returns:

an iterator containing the sub-expressions of this expression

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. This implementation provides the iterate() method natively.

Specified by:

getImplementationMethod in class Expression

Returns:

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

copy

public Expression copy(RebindingMap rebindings)

Copy an expression. This makes a deep copy.

Specified by:

copy in class Expression

Parameters:

rebindings - a mutable list of (old binding, new binding) pairs that is used to update the bindings held in any local variable references that are copied.

Returns:

the copy of the original expression

iterate

public SequenceIterator<?> iterate(XPathContext context)
                            throws XPathException

Description copied from class: Expression

Return an Iterator to iterate over the values of a sequence. The value of every expression can be regarded as a sequence, so this method is supported for all expressions. This default implementation handles iteration for expressions that return singleton values: for non-singleton expressions, the subclass must provide its own implementation.

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

export

public void export(ExpressionPresenter out)
            throws XPathException

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

Specified by:

export in interface ExportAgent

Specified by:

export in class Expression

Parameters:

out - 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.

getXpath

public Expression getXpath()

setXpath

public void setXpath(Expression xpath)

getContextItemExpr

public Expression getContextItemExpr()

setContextItemExpr

public void setContextItemExpr(Expression contextItemExpr)

getBaseUriExpr

public Expression getBaseUriExpr()

setBaseUriExpr

public void setBaseUriExpr(Expression baseUriExpr)

getNamespaceContextExpr

public Expression getNamespaceContextExpr()

setNamespaceContextExpr

public void setNamespaceContextExpr(Expression namespaceContextExpr)

getSchemaAwareExpr

public Expression getSchemaAwareExpr()

setSchemaAwareExpr

public void setSchemaAwareExpr(Expression schemaAwareExpr)

getActualParams

public WithParam[] getActualParams()

setActualParams

public void setActualParams(WithParam[] actualParams)

isActualParam

public boolean isActualParam(StructuredQName name)

setDynamicParams

public void setDynamicParams(Expression params)

getDynamicParams

public Expression getDynamicParams()