net.sf.saxon.instruct
Class DocumentInstr

java.lang.Object
  net.sf.saxon.expr.Expression
      net.sf.saxon.instruct.Instruction
          net.sf.saxon.instruct.ParentNodeConstructor
              net.sf.saxon.instruct.DocumentInstr

All Implemented Interfaces:

Serializable, SourceLocator, Container, EvaluableItem, SequenceIterable, TailCallReturner, InstructionInfoProvider

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.

See Also:

Serialized Form

Field Summary

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

EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD

Constructor Summary

DocumentInstr(boolean textOnly, String constantText, String baseURI)

Method Summary

void	display(int level, PrintStream out, Configuration config) Display this instruction as an expression, for diagnostics
Item	evaluateItem(XPathContext context) Evaluate as an 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(TypeHierarchy th) Get the item type
Expression	getStringValueExpression(StaticContext env) 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.
TailCall	processLeavingTail(XPathContext context) ProcessLeavingTail: called to do the real work of this instruction.
void	setValidationAction(int action) Set the validation action
Expression	simplify(StaticContext env) Simplify an expression.
Expression	typeCheck(StaticContext env, ItemType contextItemType) Perform type checking of an expression and its subexpressions.

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

computeCardinality, createsNewNodes, getBaseURI, getCardinality, getContentExpression, getSchemaType, getValidationMode, isLazyConstruction, isNamespaceSensitive, iterateSubExpressions, optimize, replaceSubExpression, setBaseURI, setContentExpression, setLazyConstruction, setSchemaType, setValidationMode

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

appendItem, computeSpecialProperties, evaluateAsString, getInstructionInfo, getSourceLocator, isXSLT, iterate, process, promote

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

adoptChildExpression, checkPermittedContents, computeDependencies, computeStaticProperties, doPromotion, effectiveBooleanValue, getColumnNumber, getContainingProcedure, getDependencies, getExecutable, getHostLanguage, getIntrinsicDependencies, getLineNumber, getLocationId, getLocationProvider, getParentExpression, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, hasBadParentPointer, markTailFunctionCalls, resetStaticProperties, setLocationId, setParentExpression, setParentExpression, suppressValidation

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, 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)

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

setValidationAction

public void setValidationAction(int action)

Set the validation action

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.

simplify

public Expression simplify(StaticContext env)
                    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 ParentNodeConstructor

Returns:

the simplified expression

Throws:

XPathException - if an error is discovered during expression rewriting

typeCheck

public Expression typeCheck(StaticContext env,
                            ItemType contextItemType)
                     throws XPathException

Description copied from class: Expression

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

This checks statically that the operands of the expression have the correct type; if necessary it generates code to do run-time type checking or type conversion. A static type error is reported only if execution cannot possibly succeed, that is, if a run-time type error is inevitable. The call may return a modified form of the expression.

This method is called after all references to functions and variables have been resolved to the declaration of the function or variable. However, the types of such functions and variables may not be accurately known if they have not been explicitly declared.

If the implementation returns a value other than "this", then it is required to ensure that the parent pointer and location information in the returned expression have been set up correctly. It should not rely on the caller to do this, although for historical reasons many callers do so.

Overrides:

typeCheck in class ParentNodeConstructor

Parameters:

env - the static context of the expression

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 to perform necessary run-time type checks, and to perform other type-related optimizations

Throws:

StaticError - if an error is discovered during this phase (typically a type error)

XPathException

getStringValueExpression

public Expression getStringValueExpression(StaticContext env)

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

getItemType

public ItemType getItemType(TypeHierarchy th)

Get the item type

Overrides:

getItemType in class Instruction

Parameters:

th - The TypeHierarchy

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

evaluateItem

public Item evaluateItem(XPathContext context)
                  throws XPathException

Evaluate as an expression.

Specified by:

evaluateItem in interface EvaluableItem

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

display

public void display(int level,
                    PrintStream out,
                    Configuration config)

Display this instruction as an expression, for diagnostics

Specified by:

display in class Expression

Parameters:

level - indentation level for this expression

out - Output destination