net.sf.saxon.expr.instruct

Class DocumentInstr

java.lang.Object

net.sf.saxon.expr.Expression

net.sf.saxon.expr.instruct.Instruction

net.sf.saxon.expr.instruct.ParentNodeConstructor

net.sf.saxon.expr.instruct.DocumentInstr

All Implemented Interfaces:

SourceLocator, TailCallReturner, ValidatingInstruction, IdentityComparable, InstructionInfo

public class DocumentInstr
extends ParentNodeConstructor

An instruction to create a document node. This corresponds to the xsl:document-node instruction in XSLT. It is also used to support the document node constructor expression in XQuery, and is generated implicitly within an xsl:variable that constructs a temporary tree.

Conceptually it represents an XSLT instruction xsl:document-node, with no attributes, whose content is a complex content constructor for the children of the document node.

Field Summary

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

content, preservingTypes

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
DocumentInstr(boolean textOnly, String constantText, String baseURI) Create a document constructor instruction

Method Summary

Methods

Modifier and Type	Method and Description
protected void	checkContentSequence(StaticContext env) Check statically that the sequence of child instructions doesn't violate any obvious constraints on the content of the node
protected static void	checkContentSequence(StaticContext env, Expression content, ParseOptions validationOptions)
int	computeSpecialProperties() Get the static properties of this expression (other than its type).
Expression	copy() Copy an expression.
DocumentInfo	evaluateItem(XPathContext context) Evaluate as an item.
void	explain(ExpressionPresenter out) Diagnostic print of expression structure.
CharSequence	getConstantText() For a text-only instruction, determine if the text value is fixed and if so return it; otherwise return null
ExpressionCompiler	getExpressionCompiler() Return the compiler of the DocumentInstr expression
int	getImplementationMethod() An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process().
int	getInstructionNameCode() Get the name of this instruction for diagnostic and tracing purposes (the string "document-constructor")
ItemType	getItemType() Get the item type
DocumentInstrAdjunct	getStreamingAdjunct() Get a class that supports streamed evaluation of this expression
Expression	getStringValueExpression() In the case of a text-only instruction (xsl:variable containing a text node or one or more xsl:value-of instructions), return an expression that evaluates to the textual content as an instance of xs:untypedAtomic
boolean	isTextOnly() Determine whether this is a "text only" document: essentially, an XSLT xsl:variable that contains a single text node or xsl:value-of instruction.
EventIterator	iterateEvents(XPathContext context) Deliver the result of the expression as a sequence of events.
TailCall	processLeavingTail(XPathContext context) ProcessLeavingTail: called to do the real work of this instruction.
Expression	simplify(ExpressionVisitor visitor) Simplify an expression.

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

addToPathMap, computeCardinality, createsNewNodes, getBaseURI, getCardinality, getContentExpression, getSchemaType, getValidationAction, getValidationOptions, isLazyConstruction, isPreservingTypes, operands, optimize, promoteInst, replaceOperand, setBaseURI, setContentExpression, setLazyConstruction, setNoNeedToStrip, setValidationAction, typeCheck

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

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

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

adoptChildExpression, checkForUpdatingSubexpressions, checkPermittedContents, clearStreamabilityData, computeDependencies, computeStaticProperties, doPromotion, dynamicError, effectiveBooleanValue, evaluatePendingUpdates, explain, 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, makeStreamingAdjunct, markTailFunctionCalls, operandList, resetLocalStaticProperties, setContainer, setEvaluationMethod, setFiltered, setFlattened, setLocationId, setPostureAndSweep, 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

DocumentInstr

public DocumentInstr(boolean textOnly,
             String constantText,
             String baseURI)

Create a document constructor instruction

Parameters:

textOnly - true if the content contains text nodes only

constantText - if the content contains text nodes only and the text is known at compile time, supplies the textual content

baseURI - the base URI of the instruction

Method Detail

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 prefered. For instructions this is the process() method.

Overrides:

getImplementationMethod in class Instruction

Returns:

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

isTextOnly

public boolean isTextOnly()

Determine whether this is a "text only" document: essentially, an XSLT xsl:variable that contains a single text node or xsl:value-of instruction.

Returns:

true if this is a text-only document

getConstantText

public CharSequence getConstantText()

For a text-only instruction, determine if the text value is fixed and if so return it; otherwise return null

Returns:

the fixed text value if appropriate; otherwise null

simplify

public Expression simplify(ExpressionVisitor visitor)
                    throws XPathException

Simplify an expression. This performs any static optimization (by rewriting the expression as a different expression). The default implementation does nothing.

Overrides:

simplify in class Expression

Parameters:

visitor - an expression visitor

Returns:

the simplified expression

Throws:

XPathException - if an error is discovered during expression rewriting

checkContentSequence

protected void checkContentSequence(StaticContext env)
                             throws XPathException

Check statically that the sequence of child instructions doesn't violate any obvious constraints on the content of the node

Specified by:

checkContentSequence in class ParentNodeConstructor

Parameters:

env - the static context

Throws:

XPathException

checkContentSequence

protected static void checkContentSequence(StaticContext env,
                        Expression content,
                        ParseOptions validationOptions)
                                    throws XPathException

Throws:

XPathException

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

getStringValueExpression

public Expression getStringValueExpression()

In the case of a text-only instruction (xsl:variable containing a text node or one or more xsl:value-of instructions), return an expression that evaluates to the textual content as an instance of xs:untypedAtomic

Returns:

an expression that evaluates to the textual content

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

getItemType

public ItemType getItemType()

Get the item type

Overrides:

getItemType in class Instruction

Returns:

the in

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

evaluateItem

public DocumentInfo evaluateItem(XPathContext context)
                          throws XPathException

Evaluate as an item.

Overrides:

evaluateItem in class Instruction

Parameters:

context - The context in which the expression is to be evaluated

Returns:

the node or atomic value that results from evaluating the expression; or null to indicate that the result is an empty sequence

Throws:

XPathException - if any dynamic error occurs evaluating the expression

iterateEvents

public EventIterator iterateEvents(XPathContext context)
                            throws XPathException

Description copied from class: Expression

Deliver the result of the expression as a sequence of events.

The events (of class PullEvent) are either complete items, or one of startElement, endElement, startDocument, or endDocument, known as semi-nodes. The stream of events may also include a nested EventIterator. If a start-end pair exists in the sequence, then the events between this pair represent the content of the document or element. The content sequence will have been processed to the extent that any attribute and namespace nodes in the content sequence will have been merged into the startElement event. Namespace fixup will have been performed: that is, unique prefixes will have been allocated to element and attribute nodes, and all namespaces will be declared by means of a namespace node in the startElement event or in an outer startElement forming part of the sequence. However, duplicate namespaces may appear in the sequence.

The content of an element or document may include adjacent or zero-length text nodes, atomic values, and nodes represented as nodes rather than broken down into events.

Overrides:

iterateEvents in class Expression

Parameters:

context - The dynamic evaluation context

Returns:

the result of the expression as an iterator over a sequence of PullEvent objects

Throws:

XPathException - if a dynamic error occurs during expression evaluation

getInstructionNameCode

public int getInstructionNameCode()

Get the name of this instruction for diagnostic and tracing purposes (the string "document-constructor")

Overrides:

getInstructionNameCode in class Instruction

Returns:

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

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

getExpressionCompiler

public ExpressionCompiler getExpressionCompiler()

Return the compiler of the DocumentInstr expression

Overrides:

getExpressionCompiler in class Expression

Returns:

the relevant ExpressionCompiler

getStreamingAdjunct

public DocumentInstrAdjunct 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