Class DocumentInstr

All Implemented Interfaces:
Serializable, SourceLocator, LocationProvider, SaxonLocator, DivisibleInstruction, TailCallReturner, ValidatingInstruction, InstructionInfo, Locator

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:
  • Constructor Details

    • 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 Details

    • 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 ParentNodeConstructor
      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, int validation, SchemaType type) 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(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 - if a dynamic error occurs during the evaluation of the instruction
    • processLeft

      public void processLeft(Stack<XPathContext> contextStack, Stack<Object> state) throws XPathException
      In streaming mode, process the first half of the instruction (to start a new document or element)
      Parameters:
      contextStack - the dynamic evaluation context
      state - a stack on which the instruction can save state information for use during the corresponding
      Throws:
      XPathException - if a dynamic error occurs
    • processRight

      public void processRight(Stack<XPathContext> contextStack, Stack<Object> state) throws XPathException
      In streaming mode, proecss the right half of the instruction (to end a new document or element)
      Parameters:
      contextStack - the dynamic evaluation context
      state - a stack on which the instruction can save state information for use during the corresponding
      Throws:
      XPathException - if a dynamic error occurs
    • evaluateItem

      public Item 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