In implementing the form submit feature for HTML I (first) made use of
the ElementIterator class. There have been a couple of problems. Most
importantly, the iteration seemed to go beyong the root element upwards
in the element tree.
I found the implementation a little hard to grok and then a little
fragile. I have changed it a little to keep the state together with the
elements on a Stack and fixed my problems while doing so.
2006-11-30 Roman Kennke <[EMAIL PROTECTED]>
* javax/swing/text/ElementIterator.java
(ElementRef): New inner class.
(currentDepth): Removed.
(currentElement): Removed.
(previousItem): Removed.
(stack): New field. Holds the iteration stack.
(state): Removed.
(ElementIterator(Document)): Removed init of removed fields.
(ElementIterator(Element)): Removed init of removed fields.
(current): Changed to stack based algorithm.
(deepestLeaf): New helper method.
(depth): Changed to stack based algorithm.
(first): Changed to stack based algorithm.
(next): Changed to stack based algorithm.
(previous): Changed to stack based algorithm.
/Roman
Index: javax/swing/text/ElementIterator.java
===================================================================
RCS file: /cvsroot/classpath/classpath/javax/swing/text/ElementIterator.java,v
retrieving revision 1.2
diff -u -1 -5 -r1.2 ElementIterator.java
--- javax/swing/text/ElementIterator.java 22 Aug 2005 11:35:23 -0000 1.2
+++ javax/swing/text/ElementIterator.java 30 Nov 2006 19:00:17 -0000
@@ -25,157 +25,248 @@
As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
modules, and to copy and distribute the resulting executable under
terms of your choice, provided that you also meet, for each linked
independent module, the terms and conditions of the license of that
module. An independent module is a module which is not derived from
or based on this library. If you modify this library, you may extend
this exception to your version of the library, but you are not
obligated to do so. If you do not wish to do so, delete this
exception statement from your version. */
package javax.swing.text;
+import java.util.Stack;
+
/**
* This class can be used to iterate over the [EMAIL PROTECTED] Element} tree of
* a [EMAIL PROTECTED] Document} or an [EMAIL PROTECTED] Element}. This iterator performs
* an "in-order" traversal -- first it visits a node, then each of the
* node's children in order. No locking is performed during the
* iteration; that is up to the caller.
*/
public class ElementIterator implements Cloneable
{
+ /**
+ * Uses to track the iteration on the stack.
+ */
+ private class ElementRef
+ {
+ /**
+ * The element.
+ */
+ Element element;
+
+ /**
+ * The child index. -1 means the element itself. >= 0 values mean the
+ * n-th child of the element.
+ */
+ int index;
+
+ /**
+ * Creates a new ElementRef.
+ *
+ * @param el the element
+ */
+ ElementRef(Element el)
+ {
+ element = el;
+ index = -1;
+ }
+ }
+
// The root element.
private Element root;
- // The current element.
- private Element currentElement;
- // The depth to which we have descended in the tree.
- private int currentDepth;
-
- // This is at least as big as the current depth, and at index N
- // contains the index of the child element we're currently
- // examining.
- private int[] state;
- // The previous item.
- private Element previousItem;
+ /**
+ * Holds ElementRefs.
+ */
+ private Stack stack;
/**
* Create a new ElementIterator to iterate over the given document.
* @param document the Document over which we iterate
*/
public ElementIterator(Document document)
{
- this.root = document.getDefaultRootElement();
- this.currentElement = root;
- this.state = new int[5];
+ root = document.getDefaultRootElement();
}
/**
* Create a new ElementIterator to iterate over the given document.
* @param root the Document over which we iterate
*/
public ElementIterator(Element root)
{
this.root = root;
- this.currentElement = root;
- this.state = new int[5];
}
/**
* Returns a new ElementIterator which is a clone of this
* ElementIterator.
*/
public Object clone()
{
try
{
return super.clone();
}
catch (CloneNotSupportedException _)
{
// Can't happen.
return null;
}
}
/**
* Returns the current element.
*/
public Element current()
{
- return currentElement;
+ Element current;
+ if (stack == null)
+ current = first();
+ else
+ {
+ current = null;
+ if (! stack.isEmpty())
+ {
+ ElementRef ref = (ElementRef) stack.peek();
+ Element el = ref.element;
+ int index = ref.index;
+ if (index == -1)
+ current = el;
+ else
+ current = el.getElement(index);
+ }
+ }
+ return current;
}
/**
* Returns the depth to which we have descended in the tree.
*/
public int depth()
{
- return currentDepth;
+ int depth = 0;
+ if (stack != null)
+ depth = stack.size();
+ return depth;
}
/**
* Returns the first element in the tree.
*/
public Element first()
{
- // Reset the iterator.
- currentElement = root;
- currentDepth = 0;
- previousItem = null;
- return root;
+ Element first = null;
+ if (root != null)
+ {
+ stack = new Stack();
+ if (root.getElementCount() > 0)
+ stack.push(new ElementRef(root));
+ first = root;
+ }
+ return first;
}
/**
* Advance the iterator and return the next element of the tree,
* performing an "in-order" traversal.
*/
public Element next()
{
- previousItem = currentElement;
- if (currentElement == null)
- return null;
- if (! currentElement.isLeaf())
- {
- ++currentDepth;
- if (currentDepth > state.length)
- {
- int[] newState = new int[state.length * 2];
- System.arraycopy(state, 0, newState, 0, state.length);
- state = newState;
- }
- state[currentDepth] = 0;
- currentElement = currentElement.getElement(0);
- return currentElement;
- }
-
- while (currentDepth > 0)
- {
- // At a leaf, or done with a non-leaf's children, so go up a
- // level.
- --currentDepth;
- currentElement = currentElement.getParentElement();
- ++state[currentDepth];
- if (state[currentDepth] < currentElement.getElementCount())
- {
- currentElement = currentElement.getElement(state[currentDepth]);
- return currentElement;
- }
+ Element next;
+ if (stack == null)
+ next = first();
+ else
+ {
+ next = null;
+ if (! stack.isEmpty())
+ {
+ ElementRef ref = (ElementRef) stack.peek();
+ Element el = ref.element;
+ int index = ref.index;
+ if (el.getElementCount() > index + 1)
+ {
+ Element child = el.getElement(index + 1);
+ if (child.isLeaf())
+ ref.index++;
+ else
+ stack.push(new ElementRef(child));
+ next = child;
+ next = child;
+ }
+ else
+ {
+ stack.pop();
+ if (! stack.isEmpty())
+ {
+ ElementRef top = (ElementRef) stack.peek();
+ top.index++;
+ next = next();
+ }
+ }
+ }
+ // else return null.
}
-
- currentElement = null;
- return currentElement;
+ return next;
}
/**
* Returns the previous item. Does not modify the iterator state.
*/
public Element previous()
{
- if (currentElement == null || currentElement == root)
- return null;
- return previousItem;
+ Element previous = null;
+ int stackSize;
+ if (stack != null && (stackSize = stack.size()) > 0)
+ {
+ ElementRef ref = (ElementRef) stack.peek();
+ Element el = ref.element;
+ int index = ref.index;
+ if (index > 0)
+ {
+ previous = deepestLeaf(el.getElement(--index));
+ }
+ else if (index == 0)
+ {
+ previous = el;
+ }
+ else if (index == -1)
+ {
+ ElementRef top = (ElementRef) stack.pop();
+ ElementRef item = (ElementRef) stack.peek();
+ stack.push(top);
+ index = item.index;
+ el = item.element;
+ previous = index == -1 ? el : deepestLeaf(el.getElement(index));
+ }
+ }
+ return previous;
+ }
+
+ /**
+ * Determines and returns the deepest leaf of the element <code>el</code>.
+ *
+ * @param el the base element
+ *
+ * @returnthe deepest leaf of the element <code>el</code>
+ */
+ private Element deepestLeaf(Element el)
+ {
+ Element leaf;
+ if (el.isLeaf())
+ leaf = el;
+ else
+ {
+ int count = el.getElementCount();
+ if (count == 0)
+ leaf = el;
+ else
+ leaf = deepestLeaf(el.getElement(count - 1));
+ }
+ return leaf;
}
}
