Package net.sf.saxon.expr.instruct

Class BreakInstr

java.lang.Object

net.sf.saxon.expr.Expression

net.sf.saxon.expr.instruct.Instruction

net.sf.saxon.expr.instruct.BreakInstr

All Implemented Interfaces:

ExportAgent, TailCallReturner, Locatable, TailCallLoop.TailCallInfo, IdentityComparable, Traceable

public class BreakInstr
extends Instruction
implements TailCallLoop.TailCallInfo

A compiled xsl:break instruction. The effect of executing this instruction is to register with the dynamic context that a tail call on a pseudo-function break() has been made; the enclosing xsl:iterate loop detects this tail call request and uses it as a signal to terminate execution of the loop.

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	Description
BreakInstr()	Create the instruction

Method Summary

Modifier and Type	Method	Description
Expression	copy(RebindingMap rebindings)	Copy an expression.
void	export(ExpressionPresenter out)	Diagnostic print of expression structure.
java.lang.String	getExpressionName()	Get a name identifying the kind of expression, in terms meaningful to a user.
int	getInstructionNameCode()	Get the namecode of the instruction for use in diagnostics
boolean	isLiftable(boolean forStreaming)	Ask whether the expression can be lifted out of a loop, assuming it has no dependencies on the controlling variable/focus of the loop
void	markContext(XPathContext context)
boolean	mayCreateNewNodes()	Ask whether this instruction potentially creates and returns new nodes.
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.
TailCall	processLeavingTail(Outputter output, XPathContext context)	ProcessLeavingTail: called to do the real work of this instruction.

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

alwaysCreatesNewNodes, assembleParams, assembleTunnelParams, computeCardinality, computeSpecialProperties, dynamicError, evaluateAsString, evaluateItem, getImplementationMethod, getItemType, getNetCost, getSourceLocator, isInstruction, isXSLT, iterate, process, someOperandCreatesNewNodes

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

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

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

Constructor Detail

BreakInstr

public BreakInstr()

Create the instruction

Method Detail

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.

Specified by:

operands in class Instruction

Returns:

an iterator containing the sub-expressions of this expression

copy

public Expression copy(RebindingMap rebindings)

Description copied from class: Expression

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

mayCreateNewNodes

public boolean mayCreateNewNodes()

Description copied from class: Instruction

Ask whether this instruction potentially creates and returns new nodes. Returns true if some branches or dynamic conditions result in new nodes being created. This implementation returns a default value of false

Overrides:

mayCreateNewNodes in class Instruction

Returns:

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

isLiftable

public boolean isLiftable(boolean forStreaming)

Ask whether the expression can be lifted out of a loop, assuming it has no dependencies on the controlling variable/focus of the loop

Overrides:

isLiftable in class Expression

Parameters:

forStreaming - true if we are optimizing for streamed evaluation

Returns:

for a BreakInstr, always false

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

processLeavingTail

public TailCall processLeavingTail(Outputter output,
                                   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:

output - the destination for the result

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

markContext

public void markContext(XPathContext context)

getExpressionName

public java.lang.String getExpressionName()

Description copied from class: Instruction

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

Overrides:

getExpressionName in class Instruction

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.

export

public void export(ExpressionPresenter out)
            throws XPathException

Description copied from class: Expression

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.