com.saxonica.ee.stream

Class StreamInstr

java.lang.Object

net.sf.saxon.expr.Expression

net.sf.saxon.expr.instruct.Instruction

net.sf.saxon.expr.instruct.SourceDocument

com.saxonica.ee.stream.StreamInstr

All Implemented Interfaces:

PushToPull.Pusher, ExportAgent, TailCallReturner, Locatable, IdentityComparable

public class StreamInstr
extends SourceDocument
implements PushToPull.Pusher

Implementation of the xsl:source-document (streamable="yes") instruction

Field Summary

Fields inherited from class net.sf.saxon.expr.instruct.SourceDocument

accumulators, bodyOp, hrefOp, parseOptions

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
StreamInstr(Expression hrefExp, Expression body, ParseOptions options)

Method Summary

Modifier and Type	Method and Description
Expression	checkStreamability(java.util.List<java.lang.String> reasons, int streamability, boolean strict)
int	computeDependencies() Compute the dependencies of an expression, as the union of the dependencies of its subexpressions.
int	computeSpecialProperties() Get the static properties of this expression (other than its type).
Expression	copy(RebindingMap rebindings) Copy an expression.
Inversion	getAction()
java.lang.String	getExportTag()
SequenceIterator<?>	iterate(XPathContext context) Return an Iterator to iterate over the values of a sequence.
boolean	mayCreateNewNodes() Determine whether this instruction creates new nodes.
Expression	optimize(ExpressionVisitor visitor, ContextItemStaticInfo contextItemType) Perform optimisation of an expression and its subexpressions.
void	prepareForStreaming()
Expression	prepareForStreaming(PackageData pack)
void	push(XPathContext context) Evaluate the instruction in push mode

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

allowExtractingCommonSubexpressions, export, getBody, getExpressionName, getHref, operands, processLeavingTail, setBody, setHref, setUsedAccumulators, typeCheck

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

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

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

addToPathMap, adoptChildExpression, checkedOperands, checkForUpdatingSubexpressions, checkPermittedContents, 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, hasCompatibleStaticContext, hashCode, hasSpecialProperty, hasVariableBinding, identityHashCode, implementsStaticTypeCheck, isCallOn, isEqual, isIdentical, isLiftable, isMultiThreaded, isStaticPropertiesKnown, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, markTailFunctionCalls, operandList, operandSparseList, optimizeChildren, 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

StreamInstr

public StreamInstr(Expression hrefExp,
                   Expression body,
                   ParseOptions options)

Method Detail

optimize

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

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 SourceDocument

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)

prepareForStreaming

public Expression prepareForStreaming(PackageData pack)
                               throws XPathException

Throws:

XPathException

prepareForStreaming

public void prepareForStreaming()
                         throws XPathException

Overrides:

prepareForStreaming in class Expression

Throws:

XPathException

checkStreamability

public Expression checkStreamability(java.util.List<java.lang.String> reasons,
                                     int streamability,
                                     boolean strict)
                              throws XPathException

Throws:

XPathException

mayCreateNewNodes

public boolean mayCreateNewNodes()

Determine whether this instruction creates new nodes. This implementation returns a default value of false

Overrides:

mayCreateNewNodes in class SourceDocument

Returns:

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

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 SourceDocument

Returns:

the depencies, as a bit-mask

computeSpecialProperties

public int computeSpecialProperties()

Get the static properties of this expression (other than its type). The result is bit-signficant. These properties are used for optimizations. In general, if property bit is set, it is true, but if it is unset, the value is unknown.

Overrides:

computeSpecialProperties in class SourceDocument

Returns:

a set of flags indicating static properties of this expression

getAction

public Inversion getAction()

copy

public Expression copy(RebindingMap rebindings)

Copy an expression. This makes a deep copy.

Overrides:

copy in class SourceDocument

Parameters:

rebindings - variables that need to be re-bound

Returns:

the copy of the original expression

push

public void push(XPathContext context)
          throws XPathException

Evaluate the instruction in push mode

Specified by:

push in interface PushToPull.Pusher

Overrides:

push in class SourceDocument

Parameters:

context - the evaluation context

Throws:

XPathException - in the event of a failure

QuitParsingException - if there was an early exit, that is, if the instruction was evaluated without reading the input to completion

iterate

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

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 implementation uses two threads: the instruction is evaluated in push mode in a child thread (using the process() method), putting its results on a queue, from which this method reads them.

Overrides:

iterate in class Instruction

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

getExportTag

public java.lang.String getExportTag()

Overrides:

getExportTag in class SourceDocument