Package org.loboevolution.apache.xpath.axes

Class LocPathIterator

java.lang.Object
org.loboevolution.apache.xpath.Expression
org.loboevolution.apache.xpath.patterns.NodeTest
org.loboevolution.apache.xpath.axes.PredicatedNodeTest
org.loboevolution.apache.xpath.axes.LocPathIterator
All Implemented Interfaces:
Cloneable, SourceLocator, DTMIterator, PathComponent, SubContextList, ExpressionNode, XPathVisitable
Direct Known Subclasses:
BasicTestIterator, ChildIterator, DescendantIterator, SelfIteratorNoPredicate, UnionPathIterator, WalkingIterator
public abstract class LocPathIterator extends PredicatedNodeTest implements Cloneable, DTMIterator, PathComponent
This class extends NodeSetDTM, which implements NodeIterator, and fetches nodes one at a time in document order based on a XPath LocationPath.

If setShouldCacheNodes(true) is called, as each node is iterated via nextNode(), the node is also stored in the NodeVector, so that previousNode() can easily be done, except in the case where the LocPathIterator is "owned" by a UnionPathIterator, in which case the UnionPathIterator will cache the nodes.

  • Field Details

    • m_allowDetach

      protected boolean m_allowDetach
      Control over whether it is OK for detach to reset the iterator.

    • m_clones

      protected final transient IteratorPool m_clones
      The pool for cloned iterators. Iterators need to be cloned because the hold running state, and thus the original iterator expression from the stylesheet pool can not be used.

    • m_cdtm

      protected transient DTM m_cdtm
      The dtm of the context node. Careful about using this... it may not be the dtm of the current node.

    • m_lastFetched

      public transient int m_lastFetched
      The last node that was fetched, usually by nextNode.

    • m_context

      protected transient int m_context
      The context node for this iterator, which doesn't change through the course of the iteration.

    • m_currentContextNode

      protected transient int m_currentContextNode
      The node context from where the expression is being executed from (i.e. for current() support). Different from m_context in that this is the context for the entire expression, rather than the context for the subexpression.

    • m_pos

      protected transient int m_pos
      The current position of the context node.

    • m_length

      protected transient int m_length

    • m_execContext

      protected transient XPathContext m_execContext
      The XPathContext reference, needed for execution of many operations.

  • Constructor Details

    • LocPathIterator

      protected LocPathIterator()
      Create a LocPathIterator object.

    • LocPathIterator

      protected LocPathIterator(PrefixResolver nscontext)
      Create a LocPathIterator object.
      Parameters:
      nscontext - The namespace context for this iterator, should be OK if null.

    • LocPathIterator

      protected LocPathIterator(int analysis) throws TransformerException
      Create a LocPathIterator object, including creation of step walkers from the opcode list, and call back into the Compiler to create predicate expressions.
      Throws:
      TransformerException - if any

    • LocPathIterator

      protected LocPathIterator(int analysis, boolean shouldLoadWalkers) throws TransformerException
      Create a LocPathIterator object, including creation of step walkers from the opcode list, and call back into the Compiler to create predicate expressions.
      Parameters:
      shouldLoadWalkers - True if walkers should be loaded, or false if this is a derived iterator and it doesn't wish to load child walkers.
      Throws:
      TransformerException - if any

  • Method Details

    • getAnalysisBits

      public int getAnalysisBits()
      Get the analysis bits for this path component, as defined in the WalkerFactory.
      Specified by:
      getAnalysisBits in interface PathComponent
      Returns:
      One of WalkerFactory#BIT_DESCENDANT, etc.

    • getDTM

      public DTM getDTM(int nodeHandle)
      Get an instance of a DTM that "owns" a node handle. Since a node iterator may be passed without a DTMManager, this allows the caller to easily get the DTM using just the iterator.
      Specified by:
      getDTM in interface DTMIterator
      Parameters:
      nodeHandle - the nodeHandle.
      Returns:
      a non-null DTM reference.

    • getDTMManager

      public DTMManager getDTMManager()
      Get an instance of the DTMManager. Since a node iterator may be passed without a DTMManager, this allows the caller to easily get the DTMManager using just the iterator.
      Specified by:
      getDTMManager in interface DTMIterator
      Returns:
      a non-null DTMManager reference.

    • execute

      public XObject execute(XPathContext xctxt) throws TransformerException
      Execute an expression in the XPath runtime context, and return the result of the expression.
      Overrides:
      execute in class NodeTest
      Parameters:
      xctxt - The XPath runtime context.
      Returns:
      The result of the expression in the form of a XObject.
      Throws:
      TransformerException - if a runtime exception occurs.

    • asIterator

      public DTMIterator asIterator(XPathContext xctxt, int contextNode)
      Given an select expression and a context, evaluate the XPath and return the resulting iterator.
      Overrides:
      asIterator in class Expression
      Parameters:
      xctxt - The execution context.
      contextNode - The node that "." expresses.
      Returns:
      A valid DTMIterator.

    • asNode

      public int asNode(XPathContext xctxt) throws TransformerException
      Return the first node out of the nodeset, if this expression is a nodeset expression.
      Overrides:
      asNode in class Expression
      Parameters:
      xctxt - The XPath runtime context.
      Returns:
      the first node out of the nodeset, or DTM.NULL.
      Throws:
      TransformerException - if any

    • bool

      public boolean bool(XPathContext xctxt) throws TransformerException
      Evaluate expression to a boolean.
      Overrides:
      bool in class Expression
      Parameters:
      xctxt - The XPath runtime context.
      Returns:
      false
      Throws:
      TransformerException - if any

    • setIsTopLevel

      public void setIsTopLevel(boolean b)
      Set if this is an iterator at the upper level of the XPath.
      Parameters:
      b - true if this location path is at the top level of the expression.

    • getIsTopLevel

      public boolean getIsTopLevel()
      Get if this is an iterator at the upper level of the XPath.
      Returns:
      true if this location path is at the top level of the expression.

    • setRoot

      public void setRoot(int context, Object environment)
      Reset the root node of the DTMIterator, overriding the value specified when it was created. Note the root node is not the root node of the document tree, but the context node from where the iteration begins.
      Specified by:
      setRoot in interface DTMIterator
      Parameters:
      context - int Handle of the context node.
      environment - The environment object. The environment in which this iterator operates, which should provide:

      a node (the context node... same value as "root" defined below)

      a pair of non-zero positive integers (the context position and the context size)

      a set of variable bindings

      a function library

      the set of namespace declarations in scope for the expression.

      At this time the exact implementation of this environment is application dependent. Probably a proper interface will be created fairly soon.

    • getCurrentPos

      public final int getCurrentPos()
      Get the current position within the cached list, which is one less than the next nextNode() call will retrieve. i.e. if you call getCurrentPos() and the return is 0, the next fetch will take place at index 1.
      Specified by:
      getCurrentPos in interface DTMIterator
      Returns:
      The position of the iteration.

    • setShouldCacheNodes

      public void setShouldCacheNodes(boolean b)
      If setShouldCacheNodes(true) is called, then nodes will be cached, enabling random access, and giving the ability to do sorts and the like. They are not cached by default.

      %REVIEW% Shouldn't the other random-access methods throw an exception if they're called on a DTMIterator with this flag set false?

      Specified by:
      setShouldCacheNodes in interface DTMIterator
      Parameters:
      b - true if the nodes should be cached.

    • setCurrentPos

      public void setCurrentPos(int i)
      Set the current position in the node set.
      Specified by:
      setCurrentPos in interface DTMIterator
      Parameters:
      i - Must be a valid index.

    • incrementCurrentPos

      public void incrementCurrentPos()
      Increment the current position in the node set.

    • item

      public int item(int index)
      Returns the node handle of an item in the collection. If index is greater than or equal to the number of nodes in the list, this returns null.
      Specified by:
      item in interface DTMIterator
      Parameters:
      index - of the item.
      Returns:
      The node handle at the indexth position in the DTMIterator, or -1 if that is not a valid index.

    • getLength

      public int getLength()
      The number of nodes in the list. The range of valid child node indices is 0 to length-1 inclusive. Note that this requires running the iterator to completion, and presumably filling the cache.
      Specified by:
      getLength in interface DTMIterator
      Returns:
      The number of nodes in the list.

    • isFresh

      public boolean isFresh()
      Tells if this NodeSetDTM is "fresh", in other words, if the first nextNode() that is called will return the first node in the set.
      Specified by:
      isFresh in interface DTMIterator
      Returns:
      true if the iteration of this list has not yet begun.

    • previousNode

      public int previousNode()
      Returns the previous node in the set and moves the position of the DTMIterator backwards in the set.
      Specified by:
      previousNode in interface DTMIterator
      Returns:
      The previous node handle in the set being iterated over, or DTM.NULL if there are no more members in that set.

    • getWhatToShow

      public int getWhatToShow()
      This attribute determines which node types are accepted. These constants are defined in the NodeFilter interface.
      Specified by:
      getWhatToShow in interface DTMIterator
      Overrides:
      getWhatToShow in class NodeTest
      Returns:
      bitset mainly defined in NodeFilter.

    • getRoot

      public int getRoot()
      The root node of the DTMIterator, as specified when it was created. Note the root node is not the root node of the document tree, but the context node from where the iteration begins and ends.
      Specified by:
      getRoot in interface DTMIterator
      Returns:
      nodeHandle int Handle of the context node.

    • getExpandEntityReferences

      public boolean getExpandEntityReferences()
      The value of this flag determines whether the children of entity reference nodes are visible to the iterator. If false, they and their descendants will be rejected. Note that this rejection takes precedence over whatToShow and the filter.

      To produce a view of the document that has entity references expanded and does not expose the entity reference node itself, use the whatToShow flags to hide the entity reference node and set expandEntityReferences to true when creating the iterator. To produce a view of the document that has entity reference nodes but no entity expansion, use the whatToShow flags to show the entity reference node and set expandEntityReferences to false.

      NOTE: In Xalan's use of DTM we will generally have fully expanded entity references when the document tree was built, and thus this flag will have no effect.

      Specified by:
      getExpandEntityReferences in interface DTMIterator
      Returns:
      true if entity references will be expanded.

    • allowDetachToRelease

      public void allowDetachToRelease(boolean allowRelease)
      Specify if it's OK for detach to release the iterator for reuse.
      Specified by:
      allowDetachToRelease in interface DTMIterator
      Parameters:
      allowRelease - true if it is OK for detach to release this iterator for pooling.

    • detach

      public void detach()
      Detaches the DTMIterator from the set which it iterated over, releasing any computational resources and placing the iterator in the INVALID state. After detach has been invoked, calls to nextNode or previousNode will raise a runtime exception.
      Specified by:
      detach in interface DTMIterator

    • reset

      public void reset()
      Reset the iterator to the start. After resetting, the next node returned will be the root node -- or, if that's filtered out, the first node within the root's subtree which is _not_ skipped by the filters.
      Specified by:
      reset in interface DTMIterator

    • cloneWithReset

      public DTMIterator cloneWithReset() throws CloneNotSupportedException
      Get a cloned Iterator that is reset to the start of the iteration.
      Specified by:
      cloneWithReset in interface DTMIterator
      Returns:
      A clone of this iteration that has been reset.
      Throws:
      CloneNotSupportedException - if any

    • nextNode

      public abstract int nextNode()
      Returns the next node in the set and advances the position of the iterator in the set. After a DTMIterator has setRoot called, the first call to nextNode() returns that root or (if it is rejected by the filters) the first node within its subtree which is not filtered out.
      Specified by:
      nextNode in interface DTMIterator
      Returns:
      The next node handle in the set being iterated over, or DTM.NULL if there are no more members in that set.

    • returnNextNode

      protected int returnNextNode(int nextNode)
      Bottleneck the return of a next node, to make returns easier from nextNode().
      Parameters:
      nextNode - The next node found, may be null.
      Returns:
      The same node that was passed as an argument.

    • getCurrentNode

      public int getCurrentNode()
      Get the current node in the iterator. Note that this differs from the DOM's NodeIterator, where the current position lies between two nodes (as part of the maintain-relative-position semantic).
      Specified by:
      getCurrentNode in interface DTMIterator
      Returns:
      The current node handle, or -1.

    • runTo

      public void runTo(int index)
      If an index is requested, NodeSetDTM will call this method to run the iterator to the index. By default this sets m_next to the index. If the index argument is -1, this signals that the iterator should be run to the end and completely fill the cache.
      Specified by:
      runTo in interface DTMIterator
      Parameters:
      index - The index to run to, or -1 if the iterator should be run to the end.

    • getXPathContext

      public final XPathContext getXPathContext()
      The XPath execution context we are operating on.
      Returns:
      XPath execution context this iterator is operating on, or null if setRoot has not been called.

    • getPrefixResolver

      public final PrefixResolver getPrefixResolver()
      Return the saved reference to the prefix resolver that was in effect when this iterator was created.
      Returns:
      The prefix resolver or this iterator, which may be null.

    • callVisitors

      public void callVisitors(XPathVisitor visitor)
      This will traverse the hierarchy, calling the visitor for each member. If the called visitor method returns false, the subtree should not be called.
      Specified by:
      callVisitors in interface XPathVisitable
      Overrides:
      callVisitors in class NodeTest
      Parameters:
      visitor - The visitor whose appropriate method will be called.

    • isDocOrdered

      public boolean isDocOrdered()
      Returns true if all the nodes in the iteration well be returned in document order.
      Specified by:
      isDocOrdered in interface DTMIterator
      Returns:
      true if all the nodes in the iteration well be returned in document order.

    • getAxis

      public int getAxis()
      Returns the axis being iterated, if it is known.
      Specified by:
      getAxis in interface DTMIterator
      Returns:
      Axis.CHILD, etc., or -1 if the axis is not known or is of multiple types.

    • getLastPos

      public int getLastPos(XPathContext xctxt)
      Get the number of nodes in the node list, which, in the XSLT 1 based counting system, is the last index position.
      Specified by:
      getLastPos in interface SubContextList
      Specified by:
      getLastPos in class PredicatedNodeTest
      Parameters:
      xctxt - The XPath runtime context.
      Returns:
      the number of nodes in the node list.