Class ForEachGroup

All Implemented Interfaces:
Serializable, SourceLocator, Container, ContextMappingFunction, Expression, TailCallReturner, InstructionInfoProvider

public class ForEachGroup extends Instruction implements ContextMappingFunction
Handler for xsl:for-each-group elements in stylesheet. This is a new instruction defined in XSLT 2.0
See Also:
  • Field Details

  • Constructor Details

  • Method Details

    • getInstructionNameCode

      public int getInstructionNameCode()
      Get the name of this instruction for diagnostic and tracing purposes
      Overrides:
      getInstructionNameCode in class Instruction
    • getActionExpression

      public Expression getActionExpression()
      Get the action expression (the content of the for-each)
    • simplify

      public Expression simplify(StaticContext env) throws XPathException
      Simplify an expression. This performs any static optimization (by rewriting the expression as a different expression).
      Specified by:
      simplify in interface Expression
      Specified by:
      simplify in class Instruction
      Parameters:
      env - the static context
      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 interface: 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.

      Specified by:
      typeCheck in interface Expression
      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:
      XPathException
    • optimize

      public Expression optimize(Optimizer opt, StaticContext env, ItemType contextItemType) throws XPathException
      Description copied from interface: Expression
      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.

      Specified by:
      optimize in interface Expression
      Parameters:
      opt - the optimizer in use. This provides access to supporting functions; it also allows different optimization strategies to be used in different circumstances.
      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 if appropriate to optimize execution
      Throws:
      XPathException
    • getItemType

      public ItemType getItemType(TypeHierarchy th)
      Get the item type of the items returned by evaluating this instruction
      Specified by:
      getItemType in interface Expression
      Overrides:
      getItemType in class Instruction
      Parameters:
      th -
      Returns:
      the static item type of the instruction
    • 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 ComputedExpression
      Returns:
      the depencies, as a bit-mask
    • createsNewNodes

      public final boolean createsNewNodes()
      Determine whether this instruction creates new nodes. This implementation returns true if the "action" creates new nodes. (Nodes created by the condition can't contribute to the result).
      Overrides:
      createsNewNodes in class Instruction
    • promoteInst

      protected void promoteInst(PromotionOffer offer) throws XPathException
      Handle promotion offers, that is, non-local tree rewrites.
      Overrides:
      promoteInst in class Instruction
      Parameters:
      offer - The type of rewrite being offered
      Throws:
      XPathException
    • iterateSubExpressions

      public Iterator iterateSubExpressions()
      Get all the XPath expressions associated with this instruction (in XSLT terms, the expression present on attributes of the instruction, as distinct from the child instructions in a sequence construction)
      Specified by:
      iterateSubExpressions in interface Expression
      Overrides:
      iterateSubExpressions in class ComputedExpression
      Returns:
      an iterator containing the sub-expressions of this expression
    • replaceSubExpression

      public boolean replaceSubExpression(Expression original, Expression replacement)
      Replace one subexpression by a replacement subexpression
      Specified by:
      replaceSubExpression in interface Container
      Overrides:
      replaceSubExpression in class ComputedExpression
      Parameters:
      original - the original subexpression
      replacement - the replacement subexpression
      Returns:
      true if the original subexpression is found
    • checkPermittedContents

      public void checkPermittedContents(SchemaType parentType, StaticContext env, boolean whole) throws XPathException
      Check that any elements and attributes constructed or returned by this expression are acceptable in the content model of a given complex type. It's always OK to say yes, since the check will be repeated at run-time. The process of checking element and attribute constructors against the content model of a complex type also registers the type of content expected of those constructors, so the static validation can continue recursively.
      Specified by:
      checkPermittedContents in interface Expression
      Overrides:
      checkPermittedContents in class ComputedExpression
      Parameters:
      parentType - The schema type
      env - the static context
      whole - true if this expression is expected to make the whole content of the type, false if it is expected to make up only a part
      Throws:
      XPathException - if the expression doesn't match the required content type
    • 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
    • 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 default implementation relies on the process() method: it "pushes" the results of the instruction to a sequence in memory, and then iterates over this in-memory sequence.

      In principle instructions should implement a pipelined iterate() method that avoids the overhead of intermediate storage.

      Specified by:
      iterate in interface Expression
      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
    • map

      public SequenceIterator map(XPathContext context) throws XPathException
      Map one item to a sequence.
      Specified by:
      map in interface ContextMappingFunction
      Parameters:
      context - The processing context. This is supplied only for mapping constructs that set the context node, position, and size. Otherwise it is null.
      Returns:
      either (a) a SequenceIterator over the sequence of items that the supplied input item maps to, or (b) an Item if it maps to a single item, or (c) null if it maps to an empty sequence.
      Throws:
      XPathException
    • display

      public void display(int level, PrintStream out, Configuration config)
      Diagnostic print of expression structure. The expression is written to the System.err output stream
      Specified by:
      display in interface Expression
      Parameters:
      level - indentation level for this expression
      out -
      config -