org.apache.xpath.axes.LocPathIterator Maven / Gradle / Ivy
/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/*
* $Id: LocPathIterator.java 468655 2006-10-28 07:12:06Z minchau $
*/
package org.apache.xpath.axes;
import org.apache.xalan.res.XSLMessages;
import org.apache.xml.dtm.DTM;
import org.apache.xml.dtm.DTMFilter;
import org.apache.xml.dtm.DTMIterator;
import org.apache.xml.dtm.DTMManager;
import org.apache.xml.utils.PrefixResolver;
import org.apache.xpath.ExpressionOwner;
import org.apache.xpath.XPathContext;
import org.apache.xpath.XPathVisitor;
import org.apache.xpath.compiler.Compiler;
import org.apache.xpath.objects.XNodeSet;
import org.apache.xpath.objects.XObject;
import org.apache.xpath.res.XPATHErrorResources;
/**
* This class extends NodeSetDTM, which implements NodeIterator,
* and fetches nodes one at a time in document order based on a XPath
*
* @xsl.usage advanced
*/
public abstract class LocPathIterator extends PredicatedNodeTest
implements Cloneable, DTMIterator, java.io.Serializable, PathComponent
{
static final long serialVersionUID = -4602476357268405754L;
/**
* Create a LocPathIterator object.
*
*/
protected LocPathIterator()
{
}
/**
* Create a LocPathIterator object.
*
* @param nscontext The namespace context for this iterator,
* should be OK if null.
*/
protected LocPathIterator(PrefixResolver nscontext)
{
setLocPathIterator(this);
m_prefixResolver = nscontext;
}
/**
* Create a LocPathIterator object, including creation
* of step walkers from the opcode list, and call back
* into the Compiler to create predicate expressions.
*
* @param compiler The Compiler which is creating
* this expression.
* @param opPos The position of this iterator in the
* opcode list from the compiler.
*
* @throws javax.xml.transform.TransformerException
*/
protected LocPathIterator(Compiler compiler, int opPos, int analysis)
throws javax.xml.transform.TransformerException
{
this(compiler, opPos, analysis, true);
}
/**
* Create a LocPathIterator object, including creation
* of step walkers from the opcode list, and call back
* into the Compiler to create predicate expressions.
*
* @param compiler The Compiler which is creating
* this expression.
* @param opPos The position of this iterator in the
* opcode list from the compiler.
* @param 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 javax.xml.transform.TransformerException
*/
protected LocPathIterator(
Compiler compiler, int opPos, int analysis, boolean shouldLoadWalkers)
throws javax.xml.transform.TransformerException
{
setLocPathIterator(this);
}
/**
* Get the analysis bits for this walker, as defined in the WalkerFactory.
* @return One of WalkerFactory#BIT_DESCENDANT, etc.
*/
public int getAnalysisBits()
{
int axis = getAxis();
int bit = WalkerFactory.getAnalysisBitFromAxes(axis);
return bit;
}
/**
* Read the object from a serialization stream.
*
* @param stream Input stream to read from
*
* @throws java.io.IOException
* @throws javax.xml.transform.TransformerException
*/
private void readObject(java.io.ObjectInputStream stream)
throws java.io.IOException, javax.xml.transform.TransformerException
{
try
{
stream.defaultReadObject();
m_clones = new IteratorPool(this);
}
catch (ClassNotFoundException cnfe)
{
throw new javax.xml.transform.TransformerException(cnfe);
}
}
/**
* Set 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.
*
* @param environment The environment object.
*/
public void setEnvironment(Object environment)
{
// no-op for now.
}
/**
* 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.
*
* @param nodeHandle the nodeHandle.
*
* @return a non-null DTM reference.
*/
public DTM getDTM(int nodeHandle)
{
// %OPT%
return m_execContext.getDTM(nodeHandle);
}
/**
* 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.
*
* @return a non-null DTMManager reference.
*/
public DTMManager getDTMManager()
{
return m_execContext.getDTMManager();
}
/**
* Execute this iterator, meaning create a clone that can
* store state, and initialize it for fast execution from
* the current runtime state. When this is called, no actual
* query from the current context node is performed.
*
* @param xctxt The XPath execution context.
*
* @return An XNodeSet reference that holds this iterator.
*
* @throws javax.xml.transform.TransformerException
*/
public XObject execute(XPathContext xctxt)
throws javax.xml.transform.TransformerException
{
XNodeSet iter = new XNodeSet((LocPathIterator)m_clones.getInstance());
iter.setRoot(xctxt.getCurrentNode(), xctxt);
return iter;
}
/**
* Execute an expression in the XPath runtime context, and return the
* result of the expression.
*
*
* @param xctxt The XPath runtime context.
* @param handler The target content handler.
*
* @return The result of the expression in the form of a XObject.
*
* @throws javax.xml.transform.TransformerException if a runtime exception
* occurs.
* @throws org.xml.sax.SAXException
*/
public void executeCharsToContentHandler(
XPathContext xctxt, org.xml.sax.ContentHandler handler)
throws javax.xml.transform.TransformerException,
org.xml.sax.SAXException
{
LocPathIterator clone = (LocPathIterator)m_clones.getInstance();
int current = xctxt.getCurrentNode();
clone.setRoot(current, xctxt);
int node = clone.nextNode();
DTM dtm = clone.getDTM(node);
clone.detach();
if(node != DTM.NULL)
{
dtm.dispatchCharactersEvents(node, handler, false);
}
}
/**
* Given an select expression and a context, evaluate the XPath
* and return the resulting iterator.
*
* @param xctxt The execution context.
* @param contextNode The node that "." expresses.
* @throws TransformerException thrown if the active ProblemListener decides
* the error condition is severe enough to halt processing.
*
* @throws javax.xml.transform.TransformerException
* @xsl.usage experimental
*/
public DTMIterator asIterator(
XPathContext xctxt, int contextNode)
throws javax.xml.transform.TransformerException
{
XNodeSet iter = new XNodeSet((LocPathIterator)m_clones.getInstance());
iter.setRoot(contextNode, xctxt);
return iter;
}
/**
* Tell if the expression is a nodeset expression.
*
* @return true if the expression can be represented as a nodeset.
*/
public boolean isNodesetExpr()
{
return true;
}
/**
* Return the first node out of the nodeset, if this expression is
* a nodeset expression. This is the default implementation for
* nodesets. Derived classes should try and override this and return a
* value without having to do a clone operation.
* @param xctxt The XPath runtime context.
* @return the first node out of the nodeset, or DTM.NULL.
*/
public int asNode(XPathContext xctxt)
throws javax.xml.transform.TransformerException
{
DTMIterator iter = (DTMIterator)m_clones.getInstance();
int current = xctxt.getCurrentNode();
iter.setRoot(current, xctxt);
int next = iter.nextNode();
// m_clones.freeInstance(iter);
iter.detach();
return next;
}
/**
* Evaluate this operation directly to a boolean.
*
* @param xctxt The runtime execution context.
*
* @return The result of the operation as a boolean.
*
* @throws javax.xml.transform.TransformerException
*/
public boolean bool(XPathContext xctxt)
throws javax.xml.transform.TransformerException
{
return (asNode(xctxt) != DTM.NULL);
}
/**
* Set if this is an iterator at the upper level of
* the XPath.
*
* @param b true if this location path is at the top level of the
* expression.
* @xsl.usage advanced
*/
public void setIsTopLevel(boolean b)
{
m_isTopLevel = b;
}
/**
* Get if this is an iterator at the upper level of
* the XPath.
*
* @return true if this location path is at the top level of the
* expression.
* @xsl.usage advanced
*/
public boolean getIsTopLevel()
{
return m_isTopLevel;
}
/**
* Initialize the context values for this expression
* after it is cloned.
*
* @param context The XPath runtime context for this
* transformation.
*/
public void setRoot(int context, Object environment)
{
m_context = context;
XPathContext xctxt = (XPathContext)environment;
m_execContext = xctxt;
m_cdtm = xctxt.getDTM(context);
m_currentContextNode = context; // only if top level?
// Yech, shouldn't have to do this. -sb
if(null == m_prefixResolver)
m_prefixResolver = xctxt.getNamespaceContext();
m_lastFetched = DTM.NULL;
m_foundLast = false;
m_pos = 0;
m_length = -1;
if (m_isTopLevel)
this.m_stackFrame = xctxt.getVarStack().getStackFrame();
// reset();
}
/**
* Set the next position index of this iterator.
*
* @param next A value greater than or equal to zero that indicates the next
* node position to fetch.
*/
protected void setNextPosition(int next)
{
assertion(false, "setNextPosition not supported in this iterator!");
}
/**
* Get the current position, 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.
*
* @return A value greater than or equal to zero that indicates the next
* node position to fetch.
*/
public final int getCurrentPos()
{
return m_pos;
}
/**
* If setShouldCacheNodes(true) is called, then nodes will
* be cached. They are not cached by default.
*
* @param b True if this iterator should cache nodes.
*/
public void setShouldCacheNodes(boolean b)
{
assertion(false, "setShouldCacheNodes not supported by this iterater!");
}
/**
* Tells if this iterator can have nodes added to it or set via
* the setItem(int node, int index) method.
*
* @return True if the nodelist can be mutated.
*/
public boolean isMutable()
{
return false;
}
/**
* Set the current position in the node set.
*
* @param i Must be a valid index greater
* than or equal to zero and less than m_cachedNodes.size().
*/
public void setCurrentPos(int i)
{
assertion(false, "setCurrentPos not supported by this iterator!");
}
/**
* Increment the current position in the node set.
*/
public void incrementCurrentPos()
{
m_pos++;
}
/**
* Get the length of the cached nodes.
*
* Note: for the moment at least, this only returns
* the size of the nodes that have been fetched to date,
* it doesn't attempt to run to the end to make sure we
* have found everything. This should be reviewed.
*
* @return The size of the current cache list.
*/
public int size()
{
assertion(false, "size() not supported by this iterator!");
return 0;
}
/**
* Returns the index th item in the collection. If
* index is greater than or equal to the number of nodes in
* the list, this returns null .
* @param index Index into the collection.
* @return The node at the index th position in the
* NodeList , or null if that is not a valid
* index.
*/
public int item(int index)
{
assertion(false, "item(int index) not supported by this iterator!");
return 0;
}
/**
* Sets the node at the specified index of this vector to be the
* specified node. The previous component at that position is discarded.
*
* The index must be a value greater than or equal to 0 and less
* than the current size of the vector.
* The iterator must be in cached mode.
*
* Meant to be used for sorted iterators.
*
* @param node Node to set
* @param index Index of where to set the node
*/
public void setItem(int node, int index)
{
assertion(false, "setItem not supported by this iterator!");
}
/**
* The number of nodes in the list. The range of valid child node indices
* is 0 to length-1 inclusive.
*
* @return The number of nodes in the list, always greater or equal to zero.
*/
public int getLength()
{
// Tell if this is being called from within a predicate.
boolean isPredicateTest = (this == m_execContext.getSubContextList());
// And get how many total predicates are part of this step.
int predCount = getPredicateCount();
// If we have already calculated the length, and the current predicate
// is the first predicate, then return the length. We don't cache
// the anything but the length of the list to the first predicate.
if (-1 != m_length && isPredicateTest && m_predicateIndex < 1)
return m_length;
// I'm a bit worried about this one, since it doesn't have the
// checks found above. I suspect it's fine. -sb
if (m_foundLast)
return m_pos;
// Create a clone, and count from the current position to the end
// of the list, not taking into account the current predicate and
// predicates after the current one.
int pos = (m_predicateIndex >= 0) ? getProximityPosition() : m_pos;
LocPathIterator clone;
try
{
clone = (LocPathIterator) clone();
}
catch (CloneNotSupportedException cnse)
{
return -1;
}
// We want to clip off the last predicate, but only if we are a sub
// context node list, NOT if we are a context list. See pos68 test,
// also test against bug4638.
if (predCount > 0 && isPredicateTest)
{
// Don't call setPredicateCount, because it clones and is slower.
clone.m_predCount = m_predicateIndex;
// The line above used to be:
// clone.m_predCount = predCount - 1;
// ...which looks like a dumb bug to me. -sb
}
int next;
while (DTM.NULL != (next = clone.nextNode()))
{
pos++;
}
if (isPredicateTest && m_predicateIndex < 1)
m_length = pos;
return pos;
}
/**
* Tells if this NodeSetDTM is "fresh", in other words, if
* the first nextNode() that is called will return the
* first node in the set.
*
* @return true of nextNode has not been called.
*/
public boolean isFresh()
{
return (m_pos == 0);
}
/**
* Returns the previous node in the set and moves the position of the
* iterator backwards in the set.
* @return The previous Node in the set being iterated over,
* ornull if there are no more members in that set.
*/
public int previousNode()
{
throw new RuntimeException(
XSLMessages.createXPATHMessage(XPATHErrorResources.ER_NODESETDTM_CANNOT_ITERATE, null)); //"This NodeSetDTM can not iterate to a previous node!");
}
/**
* This attribute determines which node types are presented via the
* iterator. The available set of constants is defined in the
* NodeFilter interface.
*
* This is somewhat useless at this time, since it doesn't
* really return information that tells what this iterator will
* show. It is here only to fullfill the DOM NodeIterator
* interface.
*
* @return For now, always NodeFilter.SHOW_ALL & ~NodeFilter.SHOW_ENTITY_REFERENCE.
* @see org.w3c.dom.traversal.NodeIterator
*/
public int getWhatToShow()
{
// TODO: ??
return DTMFilter.SHOW_ALL & ~DTMFilter.SHOW_ENTITY_REFERENCE;
}
/**
* The filter used to screen nodes. Not used at this time,
* this is here only to fullfill the DOM NodeIterator
* interface.
*
* @return Always null.
* @see org.w3c.dom.traversal.NodeIterator
*/
public DTMFilter getFilter()
{
return null;
}
/**
* The root node of the Iterator, as specified when it was created.
*
* @return The "root" of this iterator, which, in XPath terms,
* is the node context for this iterator.
*/
public int getRoot()
{
return m_context;
}
/**
* The value of this flag determines whether the children of entity
* reference nodes are visible to the iterator. If false, they will be
* skipped over.
*
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.
*
* @return Always true, since entity reference nodes are not
* visible in the XPath model.
*/
public boolean getExpandEntityReferences()
{
return true;
}
/** Control over whether it is OK for detach to reset the iterator. */
protected boolean m_allowDetach = true;
/**
* Specify if it's OK for detach to release the iterator for reuse.
*
* @param allowRelease true if it is OK for detach to release this iterator
* for pooling.
*/
public void allowDetachToRelease(boolean allowRelease)
{
m_allowDetach = allowRelease;
}
/**
* Detaches the iterator from the set which it iterated over, releasing
* any computational resources and placing the iterator in the INVALID
* state. Afterdetach has been invoked, calls to
* nextNode orpreviousNode will raise the
* exception INVALID_STATE_ERR.
*/
public void detach()
{
if(m_allowDetach)
{
// sb: allow reusing of cached nodes when possible?
// m_cachedNodes = null;
m_execContext = null;
// m_prefixResolver = null; sb: Why would this ever want to be null?
m_cdtm = null;
m_length = -1;
m_pos = 0;
m_lastFetched = DTM.NULL;
m_context = DTM.NULL;
m_currentContextNode = DTM.NULL;
m_clones.freeInstance(this);
}
}
/**
* Reset the iterator.
*/
public void reset()
{
assertion(false, "This iterator can not reset!");
}
/**
* Get a cloned Iterator that is reset to the beginning
* of the query.
*
* @return A cloned NodeIterator set of the start of the query.
*
* @throws CloneNotSupportedException
*/
public DTMIterator cloneWithReset() throws CloneNotSupportedException
{
LocPathIterator clone;
// clone = (LocPathIterator) clone();
clone = (LocPathIterator)m_clones.getInstanceOrThrow();
clone.m_execContext = m_execContext;
clone.m_cdtm = m_cdtm;
clone.m_context = m_context;
clone.m_currentContextNode = m_currentContextNode;
clone.m_stackFrame = m_stackFrame;
// clone.reset();
return clone;
}
// /**
// * Get a cloned LocPathIterator that holds the same
// * position as this iterator.
// *
// * @return A clone of this iterator that holds the same node position.
// *
// * @throws CloneNotSupportedException
// */
// public Object clone() throws CloneNotSupportedException
// {
//
// LocPathIterator clone = (LocPathIterator) super.clone();
//
// return clone;
// }
/**
* Returns the next node in the set and advances the position of the
* iterator in the set. After a NodeIterator is created, the first call
* to nextNode() returns the first node in the set.
* @return The next Node in the set being iterated over, or
* null if there are no more members in that set.
*/
public abstract int nextNode();
/**
* Bottleneck the return of a next node, to make returns
* easier from nextNode().
*
* @param nextNode The next node found, may be null.
*
* @return The same node that was passed as an argument.
*/
protected int returnNextNode(int nextNode)
{
if (DTM.NULL != nextNode)
{
m_pos++;
}
m_lastFetched = nextNode;
if (DTM.NULL == nextNode)
m_foundLast = true;
return nextNode;
}
/**
* Return the last fetched node. Needed to support the UnionPathIterator.
*
* @return The last fetched node, or null if the last fetch was null.
*/
public int getCurrentNode()
{
return m_lastFetched;
}
/**
* 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.
*
* @param index The index to run to, or -1 if the iterator
* should run to the end.
*/
public void runTo(int index)
{
if (m_foundLast || ((index >= 0) && (index <= getCurrentPos())))
return;
int n;
if (-1 == index)
{
while (DTM.NULL != (n = nextNode()));
}
else
{
while (DTM.NULL != (n = nextNode()))
{
if (getCurrentPos() >= index)
break;
}
}
}
/**
* Tells if we've found the last node yet.
*
* @return true if the last nextNode returned null.
*/
public final boolean getFoundLast()
{
return m_foundLast;
}
/**
* The XPath execution context we are operating on.
*
* @return XPath execution context this iterator is operating on,
* or null if setRoot has not been called.
*/
public final XPathContext getXPathContext()
{
return m_execContext;
}
/**
* The node context for the iterator.
*
* @return The node context, same as getRoot().
*/
public final int getContext()
{
return m_context;
}
/**
* The node context from where the expression is being
* executed from (i.e. for current() support).
*
* @return The top-level node context of the entire expression.
*/
public final int getCurrentContextNode()
{
return m_currentContextNode;
}
/**
* Set the current context node for this iterator.
*
* @param n Must be a non-null reference to the node context.
*/
public final void setCurrentContextNode(int n)
{
m_currentContextNode = n;
}
// /**
// * Set the current context node for this iterator.
// *
// * @param n Must be a non-null reference to the node context.
// */
// public void setRoot(int n)
// {
// m_context = n;
// m_cdtm = m_execContext.getDTM(n);
// }
/**
* Return the saved reference to the prefix resolver that
* was in effect when this iterator was created.
*
* @return The prefix resolver or this iterator, which may be null.
*/
public final PrefixResolver getPrefixResolver()
{
if(null == m_prefixResolver)
{
m_prefixResolver = (PrefixResolver)getExpressionOwner();
}
return m_prefixResolver;
}
// /**
// * Get the analysis pattern built by the WalkerFactory.
// *
// * @return The analysis pattern built by the WalkerFactory.
// */
// int getAnalysis()
// {
// return m_analysis;
// }
// /**
// * Set the analysis pattern built by the WalkerFactory.
// *
// * @param a The analysis pattern built by the WalkerFactory.
// */
// void setAnalysis(int a)
// {
// m_analysis = a;
// }
/**
* @see org.apache.xpath.XPathVisitable#callVisitors(ExpressionOwner, XPathVisitor)
*/
public void callVisitors(ExpressionOwner owner, XPathVisitor visitor)
{
if(visitor.visitLocationPath(owner, this))
{
visitor.visitStep(owner, this);
callPredicateVisitors(visitor);
}
}
//============= State Data =============
/**
* 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.
*/
transient protected IteratorPool m_clones = new IteratorPool(this);
/**
* The dtm of the context node. Careful about using this... it may not
* be the dtm of the current node.
*/
transient protected DTM m_cdtm;
/**
* The stack frame index for this iterator.
*/
transient int m_stackFrame = -1;
/**
* Value determined at compile time, indicates that this is an
* iterator at the top level of the expression, rather than inside
* a predicate.
* @serial
*/
private boolean m_isTopLevel = false;
/** The last node that was fetched, usually by nextNode. */
transient public int m_lastFetched = DTM.NULL;
/**
* The context node for this iterator, which doesn't change through
* the course of the iteration.
*/
transient protected int m_context = DTM.NULL;
/**
* 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.
*/
transient protected int m_currentContextNode = DTM.NULL;
/**
* The current position of the context node.
*/
transient protected int m_pos = 0;
transient protected int m_length = -1;
/**
* Fast access to the current prefix resolver. It isn't really
* clear that this is needed.
* @serial
*/
private PrefixResolver m_prefixResolver;
/**
* The XPathContext reference, needed for execution of many
* operations.
*/
transient protected XPathContext m_execContext;
/**
* Returns true if all the nodes in the iteration well be returned in document
* order.
*
* @return true as a default.
*/
public boolean isDocOrdered()
{
return true;
}
/**
* Returns the axis being iterated, if it is known.
*
* @return Axis.CHILD, etc., or -1 if the axis is not known or is of multiple
* types.
*/
public int getAxis()
{
return -1;
}
// /**
// * The analysis pattern built by the WalkerFactory.
// * TODO: Move to LocPathIterator.
// * @see org.apache.xpath.axes.WalkerFactory
// * @serial
// */
// protected int m_analysis = 0x00000000;
/**
* @see PredicatedNodeTest#getLastPos(XPathContext)
*/
public int getLastPos(XPathContext xctxt)
{
return getLength();
}
}