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:

ExportAgent, InstructionWithComplexContent, TailCallReturner, ValidatingInstruction, Locatable, IdentityComparable

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

contentOp, preservingTypes

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
DocumentInstr(boolean textOnly, java.lang.String constantText) Create a document constructor instruction

Method Summary

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, Operand content, ParseOptions validationOptions)
int	computeSpecialProperties() Get the static properties of this expression (other than its type).
Expression	copy(RebindingMap rebindings) Copy an expression.
NodeInfo	evaluateItem(XPathContext context) Evaluate as an item.
void	export(ExpressionPresenter out) Diagnostic print of expression structure.
java.lang.CharSequence	getConstantText() For a text-only instruction, determine if the text value is fixed and if so return it; otherwise return null
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
java.lang.String	getStreamerName() Get the (partial) name of a class that supports streaming of this kind of 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.
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(XPathContext context) ProcessLeavingTail: called to do the real work of this instruction.

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

addToPathMap, allowExtractingCommonSubexpressions, alwaysCreatesNewNodes, computeCardinality, getCardinality, getContentExpression, getContentOperand, getSchemaType, getValidationAction, getValidationOptions, isLazyConstruction, isLocal, isPreservingTypes, mayCreateNewNodes, optimize, setBaseURI, setContentExpression, setLazyConstruction, setNoNeedToStrip, setValidationAction, typeCheck

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

assembleParams, assembleTunnelParams, dynamicError, evaluateAsString, getConstructType, getExpressionName, getNetCost, getSourceLocator, isInstruction, isXSLT, iterate, process, someOperandCreatesNewNodes

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

adoptChildExpression, checkedOperands, checkForUpdatingSubexpressions, checkPermittedContents, computeDependencies, computeHashCode, computeStaticProperties, dynamicError, effectiveBooleanValue, equals, evaluatePendingUpdates, explain, getConfiguration, getCost, getDependencies, getEvaluationMethod, getExtraProperty, getIntegerBounds, getInterpretedExpression, getIntrinsicDependencies, getLocalRetainedStaticContext, getLocation, getObjectName, getPackageData, getParentExpression, getProperties, getProperty, getRetainedStaticContext, getScopingExpression, getSlotsUsed, getSpecialProperties, getStaticBaseURI, getStaticBaseURIString, getStaticType, getStaticUType, hasCompatibleStaticContext, hashCode, hasSpecialProperty, hasVariableBinding, identityHashCode, implementsStaticTypeCheck, isCallOn, isEqual, isIdentical, isLiftable, isMultiThreaded, isStaticPropertiesKnown, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, markTailFunctionCalls, operandList, operandSparseList, optimizeChildren, prepareForStreaming, 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

DocumentInstr

public DocumentInstr(boolean textOnly,
                     java.lang.String constantText)

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

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

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 java.lang.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

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,
                                           Operand 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(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

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 NodeInfo 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

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

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.

getStreamerName

public java.lang.String getStreamerName()

Get the (partial) name of a class that supports streaming of this kind of expression

Overrides:

getStreamerName in class Expression

Returns:

the partial name of a class that can be instantiated to provide streaming support in Saxon-EE, or null if there is no such class