org.apache.xml.dtm.ref.DTMAxisIteratorBase Maven / Gradle / Ivy
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* 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: DTMAxisIteratorBase.java 468653 2006-10-28 07:07:05Z minchau $
*/
package org.apache.xml.dtm.ref;
import org.apache.xml.dtm.DTMAxisIterator;
/**
* This class serves as a default base for implementations of mutable
* DTMAxisIterators.
*/
public abstract class DTMAxisIteratorBase implements DTMAxisIterator
{
/** The position of the last node within the iteration, as defined by XPath.
* Note that this is _not_ the node's handle within the DTM. Also, don't
* confuse it with the current (most recently returned) position.
*/
protected int _last = -1;
/** The position of the current node within the iteration, as defined by XPath.
* Note that this is _not_ the node's handle within the DTM!
*/
protected int _position = 0;
/** The position of the marked node within the iteration;
* a saved itaration state that we may want to come back to.
* Note that only one mark is maintained; there is no stack.
*/
protected int _markedNode;
/** The handle to the start, or root, of the iteration.
* Set this to END to construct an empty iterator.
*/
protected int _startNode = DTMAxisIterator.END;
/** True if the start node should be considered part of the iteration.
* False will cause it to be skipped.
*/
protected boolean _includeSelf = false;
/** True if this iteration can be restarted. False otherwise (eg, if
* we are iterating over a stream that can not be re-scanned, or if
* the iterator was produced by cloning another iterator.)
*/
protected boolean _isRestartable = true;
/**
* Get start to END should 'close' the iterator,
* i.e. subsequent call to next() should return END.
*
* @return The root node of the iteration.
*/
public int getStartNode()
{
return _startNode;
}
/**
* @return A DTMAxisIterator which has been reset to the start node,
* which may or may not be the same as this iterator.
* */
public DTMAxisIterator reset()
{
final boolean temp = _isRestartable;
_isRestartable = true;
setStartNode(_startNode);
_isRestartable = temp;
return this;
}
/**
* Set the flag to include the start node in the iteration.
*
*
* @return This default method returns just returns this DTMAxisIterator,
* after setting the flag.
* (Returning "this" permits C++-style chaining of
* method calls into a single expression.)
*/
public DTMAxisIterator includeSelf()
{
_includeSelf = true;
return this;
}
/** Returns the position of the last node within the iteration, as
* defined by XPath. In a forward iterator, I believe this equals the number of nodes which this
* iterator will yield. In a reverse iterator, I believe it should return
* 1 (since the "last" is the first produced.)
*
* This may be an expensive operation when called the first time, since
* it may have to iterate through a large part of the document to produce
* its answer.
*
* @return The number of nodes in this iterator (forward) or 1 (reverse).
*/
public int getLast()
{
if (_last == -1) // Not previously established
{
// Note that we're doing both setMark() -- which saves _currentChild
// -- and explicitly saving our position counter (number of nodes
// yielded so far).
//
// %REVIEW% Should position also be saved by setMark()?
// (It wasn't in the XSLTC version, but I don't understand why not.)
final int temp = _position; // Save state
setMark();
reset(); // Count the nodes found by this iterator
do
{
_last++;
}
while (next() != END);
gotoMark(); // Restore saved state
_position = temp;
}
return _last;
}
/**
* @return The position of the current node within the set, as defined by
* XPath. Note that this is one-based, not zero-based.
*/
public int getPosition()
{
return _position == 0 ? 1 : _position;
}
/**
* @return true if this iterator has a reversed axis, else false
*/
public boolean isReverse()
{
return false;
}
/**
* Returns a deep copy of this iterator. Cloned iterators may not be
* restartable. The iterator being cloned may or may not become
* non-restartable as a side effect of this operation.
*
* @return a deep copy of this iterator.
*/
public DTMAxisIterator cloneIterator()
{
try
{
final DTMAxisIteratorBase clone = (DTMAxisIteratorBase) super.clone();
clone._isRestartable = false;
// return clone.reset();
return clone;
}
catch (CloneNotSupportedException e)
{
throw new org.apache.xml.utils.WrappedRuntimeException(e);
}
}
/**
* Do any final cleanup that is required before returning the node that was
* passed in, and then return it. The intended use is
*
* return returnNode(node);
*
* %REVIEW% If we're calling it purely for side effects, should we really
* be bothering with a return value? Something like
*
* accept(node); return node;
*
* would probably optimize just about as well and avoid questions
* about whether what's returned could ever be different from what's
* passed in.
*
* @param node Node handle which iteration is about to yield.
*
* @return The node handle passed in. */
protected final int returnNode(final int node)
{
_position++;
return node;
}
/**
* Reset the position to zero. NOTE that this does not change the iteration
* state, only the position number associated with that state.
*
* %REVIEW% Document when this would be used?
*
* @return This instance.
*/
protected final DTMAxisIterator resetPosition()
{
_position = 0;
return this;
}
/**
* 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;
}
public void setRestartable(boolean isRestartable) {
_isRestartable = isRestartable;
}
/**
* Return the node at the given position.
*
* @param position The position
* @return The node at the given position.
*/
public int getNodeByPosition(int position)
{
if (position > 0) {
final int pos = isReverse() ? getLast() - position + 1
: position;
int node;
while ((node = next()) != DTMAxisIterator.END) {
if (pos == getPosition()) {
return node;
}
}
}
return END;
}
}