com.saxonica.ee.stream

Class StreamInstr

java.lang.Object

net.sf.saxon.expr.Expression

net.sf.saxon.expr.instruct.Instruction

com.saxonica.ee.stream.StreamInstr

All Implemented Interfaces:

PushToPull.Pusher, ExportAgent, TailCallReturner, IdentityComparable

public class StreamInstr
extends Instruction
implements PushToPull.Pusher

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

Field Summary

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

EFFECTIVE_BOOLEAN_VALUE, EVALUATE_METHOD, ITEM_FEED_METHOD, ITERATE_METHOD, 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
boolean	allowExtractingCommonSubexpressions() Ask whether common subexpressions found in the operands of this expression can be extracted and evaluated outside the expression itself.
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.
void	export(ExpressionPresenter out) Diagnostic print of expression structure.
Inversion	getAction()
Expression	getBody()
java.lang.String	getExpressionName() Get a name identifying the kind of expression, in terms meaningful to a user.
Expression	getHref()
SequenceIterator	iterate(XPathContext context) Return an Iterator to iterate over the values of a sequence.
boolean	mayCreateNewNodes() Determine whether this instruction creates 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.
Expression	optimize(ExpressionVisitor visitor, ContextItemStaticInfo contextItemType) Perform optimisation of an expression and its subexpressions.
Expression	prepareForStreaming(PackageData pack)
TailCall	processLeavingTail(XPathContext context) ProcessLeavingTail: called to do the real work of this instruction.
void	push(XPathContext context) Evaluate the instruction in push mode
void	setBody(Expression body)
void	setHref(Expression href)
void	setUsedAccumulators(java.util.Set<? extends Accumulator> used)
Expression	typeCheck(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo) Perform type checking of an expression and its subexpressions.

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

alwaysCreatesNewNodes, assembleParams, assembleTunnelParams, computeCardinality, dynamicError, evaluateAsString, evaluateItem, getConstructType, getImplementationMethod, getInstructionName, 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, 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, hasVariableBinding, identityHashCode, implementsStaticTypeCheck, isCallOn, isCallOnSystemFunction, isIdentical, isLiftable, isMultiThreaded, isSameExpression, 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, verifyParentPointers

Methods inherited from class java.lang.Object

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

Constructor Detail

StreamInstr

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

Method Detail

getExpressionName

public java.lang.String getExpressionName()

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.

getHref

public Expression getHref()

setHref

public void setHref(Expression href)

getBody

public Expression getBody()

setBody

public void setBody(Expression body)

setUsedAccumulators

public void setUsedAccumulators(java.util.Set<? extends Accumulator> used)

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

allowExtractingCommonSubexpressions

public boolean allowExtractingCommonSubexpressions()

Ask whether common subexpressions found in the operands of this expression can be extracted and evaluated outside the expression itself. The result is irrelevant in the case of operands evaluated with a different focus, which will never be extracted in this way, even if they have no focus dependency.

Overrides:

allowExtractingCommonSubexpressions in class Expression

Returns:

false for this kind of expression

typeCheck

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

Perform type checking of an expression and its subexpressions. This is the second phase of static optimization.

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

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)

prepareForStreaming

public Expression prepareForStreaming(PackageData pack)
                               throws XPathException

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 Instruction

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 Expression

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 Instruction

Returns:

a set of flags indicating static properties of this expression

getAction

public Inversion getAction()

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.

copy

public Expression copy(RebindingMap rebindings)

Copy an expression. This makes a deep copy.

Specified by:

copy in class Expression

Parameters:

rebindings -

Returns:

the copy of the original expression

processLeavingTail

public TailCall processLeavingTail(XPathContext context)
                            throws XPathException

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

push

public void push(XPathContext context)
          throws XPathException

Evaluate the instruction in push mode

Specified by:

push in interface PushToPull.Pusher

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