com.saxonica.xslt3.instruct

Class IterateInstr

java.lang.Object

net.sf.saxon.expr.Expression

net.sf.saxon.expr.instruct.Instruction

com.saxonica.xslt3.instruct.IterateInstr

All Implemented Interfaces:

SourceLocator, ContextSwitchingExpression, TailCallReturner, IdentityComparable, InstructionInfo

public final class IterateInstr
extends Instruction
implements ContextSwitchingExpression

An IterateInstr is the compiled form of a saxon:iterate instruction

Field Summary

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

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

Constructor Summary

Constructors

Constructor and Description
IterateInstr(Expression select, LocalParamBlock initiallyExp, Expression action, Expression onCompletion) Create an xsl:iterate instruction

Method Summary

Methods

Modifier and Type	Method and Description
PathMap.PathMapNodeSet	addToPathMap(PathMap pathMap, PathMap.PathMapNodeSet pathMapNodeSet) Add a representation of this expression to a PathMap.
int	allocateParameterSlots(int nextFree) Ensure that slots are allocated to parameters and with-param instructions.
void	checkPermittedContents(SchemaType parentType, StaticContext env, boolean whole) Check that any elements and attributes constructed or returned by this expression are acceptable in the content model of a given complex type.
int	computeDependencies() Compute the dependencies of an expression, as the union of the dependencies of its subexpressions.
Expression	copy() Copy an expression.
boolean	createsNewNodes() Determine whether this instruction creates new nodes.
void	explain(ExpressionPresenter out) Diagnostic print of expression structure.
Expression	getActionExpression() Get the action expression (the content of the xsl:iterate)
ExpressionCompiler	getExpressionCompiler() Return the compiler of the IterateInstr expression
int	getImplementationMethod() An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process().
Expression	getInitialExpression() Get the initial expression, if any.
int	getInstructionNameCode() Get the namecode of the instruction for use in diagnostics
ItemType	getItemType() Determine the data type of the items returned by this expression
Expression	getOnCompletionExpression() Get the on-completion expression, if any
Expression	getSelectExpression() Get the select expression (the select attribute of the xsl:iterate)
IterateAdjunct	getStreamingAdjunct() Get a class that supports streamed evaluation of this expression
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.
TailCall	processLeavingTail(XPathContext context) ProcessLeavingTail: called to do the real work of this instruction.
protected void	promoteInst(PromotionOffer offer) Handle promotion offers, that is, non-local tree rewrites.
boolean	replaceOperand(Expression original, Expression replacement) Replace one subexpression by a replacement subexpression
Expression	typeCheck(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo) Type-check the expression

Methods inherited from class net.sf.saxon.expr.instruct.Instruction

assembleParams, assembleTunnelParams, computeCardinality, computeSpecialProperties, dynamicError, evaluateAsString, evaluateItem, getConstructType, getExpressionName, getInstructionName, getIteratorFromProcessMethod, getSourceLocator, isXSLT, iterate, process, promote, toStreamingPattern

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

adoptChildExpression, checkForUpdatingSubexpressions, clearStreamabilityData, computeStaticProperties, doPromotion, dynamicError, effectiveBooleanValue, evaluatePendingUpdates, explain, getCardinality, getColumnNumber, getConfiguration, getContainer, getDependencies, getEvaluationMethod, getHostLanguage, getIntegerBounds, getIntrinsicDependencies, getLineNumber, getLocationId, getObjectName, getPosture, getProperties, getProperty, getPublicId, getSlotsUsed, getSpecialProperties, getStreamability, getSweep, getSystemId, hasVariableBinding, identityHashCode, implementsStaticTypeCheck, isIdentical, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, iterateEvents, makeStreamingAdjunct, markTailFunctionCalls, operandList, resetLocalStaticProperties, setContainer, setEvaluationMethod, setFiltered, setFlattened, setLocationId, setPostureAndSweep, simplify, staticTypeCheck, suppressValidation, toPattern, toShortString, toString, typeError, unordered

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface javax.xml.transform.SourceLocator

getColumnNumber, getLineNumber, getPublicId, getSystemId

Constructor Detail

IterateInstr

public IterateInstr(Expression select,
            LocalParamBlock initiallyExp,
            Expression action,
            Expression onCompletion)

Create an xsl:iterate instruction

Parameters:

select - the select expression

initiallyExp - the initialization of the xsl:param elements

action - the body of the xsl:iterate loop

onCompletion - the expression to be evaluated before final completion, may be null

Method Detail

getInstructionNameCode

public int getInstructionNameCode()

Get the namecode of the instruction for use in diagnostics

Overrides:

getInstructionNameCode in class Instruction

Returns:

a code identifying the instruction: typically but not always the fingerprint of a name in the XSLT namespace

getSelectExpression

public Expression getSelectExpression()

Get the select expression (the select attribute of the xsl:iterate)

Specified by:

getSelectExpression in interface ContextSwitchingExpression

Returns:

the select expression

getInitialExpression

public Expression getInitialExpression()

Get the initial expression, if any. This comprises the instructions for initializing the parameters with their default values on first entry

Returns:

the expression from the xsl:on-completion child

getActionExpression

public Expression getActionExpression()

Get the action expression (the content of the xsl:iterate)

Specified by:

getActionExpression in interface ContextSwitchingExpression

Returns:

the body of the xsl:iterate loop

getOnCompletionExpression

public Expression getOnCompletionExpression()

Get the on-completion expression, if any

Returns:

the expression from the xsl:on-completion child

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)

allocateParameterSlots

public int allocateParameterSlots(int nextFree)

Ensure that slots are allocated to parameters and with-param instructions. This is normally done during compilation, but not in the case of an xsl:iterate instruction constructed dynamically to support xsl:copy/@on-empty

Parameters:

nextFree - the next slot available to be allocated, before allocating slots to this expression

Returns:

the next slot available to be allocated, after allocating slots to this expression

getItemType

public final ItemType getItemType()

Determine the data type of the items returned by this expression

Overrides:

getItemType in class Instruction

Returns:

the data type

createsNewNodes

public final boolean createsNewNodes()

Determine whether this instruction creates new nodes. This implementation returns true if the "action" creates new nodes. (Nodes created by the condition can't contribute to the result).

Overrides:

createsNewNodes in class Instruction

Returns:

true if the instruction creates new nodes (or if it can't be proved that it doesn't)

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.

computeDependencies

public int computeDependencies()

Compute the dependencies of an expression, as the union of the dependencies of its subexpressions. (This is overridden for path expressions and filter expressions, where the dependencies of a subexpression are not all propogated). This method should be called only once, to compute the dependencies; after that, getDependencies should be used.

Overrides:

computeDependencies in class Expression

Returns:

the depencies, as a bit-mask

promoteInst

protected void promoteInst(PromotionOffer offer)
                    throws XPathException

Handle promotion offers, that is, non-local tree rewrites.

Overrides:

promoteInst in class Instruction

Parameters:

offer - The type of rewrite being offered

Throws:

XPathException

getStreamingAdjunct

public IterateAdjunct getStreamingAdjunct()

Get a class that supports streamed evaluation of this expression

Overrides:

getStreamingAdjunct in class Expression

Returns:

the relevant StreamingAdjunct, or null if none is available

operands

public Iterable<Operand> operands()

Get the immediate sub-expressions of this expression, with information about the relationship of each expression to its parent expression. Default implementation returns a zero-length array, appropriate for an expression that has no sub-expressions.

Overrides:

operands in class Expression

Returns:

an iterator containing the sub-expressions of this expression

replaceOperand

public boolean replaceOperand(Expression original,
                     Expression replacement)

Replace one subexpression by a replacement subexpression

Overrides:

replaceOperand in class Expression

Parameters:

original - the original subexpression

replacement - the replacement subexpression

Returns:

true if the original subexpression is found

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 both iterate() and process() methods natively.

Overrides:

getImplementationMethod in class Instruction

Returns:

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

checkPermittedContents

public void checkPermittedContents(SchemaType parentType,
                          StaticContext env,
                          boolean whole)
                            throws XPathException

Check that any elements and attributes constructed or returned by this expression are acceptable in the content model of a given complex type. It's always OK to say yes, since the check will be repeated at run-time. The process of checking element and attribute constructors against the content model of a complex type also registers the type of content expected of those constructors, so the static validation can continue recursively.

Overrides:

checkPermittedContents in class Expression

Parameters:

parentType - the "given complex type": the method is checking that the nodes returned by this expression are acceptable members of the content model of this type

env - the static context

whole - if true, we want to check that the value of this expression satisfies the content model as a whole; if false we want to check that the value of the expression is acceptable as one part of the content

Throws:

XPathException - if the value delivered by this expression cannot be part of the content model of the given type

copy

public Expression copy()

Copy an expression. This makes a deep copy.

Specified by:

copy in class Expression

Returns:

the copy of the original expression

processLeavingTail

public TailCall processLeavingTail(XPathContext context)
                            throws XPathException

Description copied from class: Instruction

ProcessLeavingTail: called to do the real work of this instruction. This method must be implemented in each subclass. The results of the instruction are written to the current Receiver, which can be obtained via the Controller.

Specified by:

processLeavingTail in interface TailCallReturner

Specified by:

processLeavingTail in class Instruction

Parameters:

context - The dynamic context of the transformation, giving access to the current node, the current variables, etc.

Returns:

null if the instruction has completed execution; or a TailCall indicating a function call or template call that is delegated to the caller, to be made after the stack has been unwound so as to save stack space.

Throws:

XPathException - if a dynamic error occurs during the evaluation of the instruction

getExpressionCompiler

public ExpressionCompiler getExpressionCompiler()

Return the compiler of the IterateInstr expression

Overrides:

getExpressionCompiler in class Expression

Returns:

the relevant ExpressionCompiler

explain

public void explain(ExpressionPresenter out)

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

Specified by:

explain in class Expression

Parameters:

out - the expression presenter used to display the structure