[jdom-interest] Bug in ListIterator.add() method
Rolf Lear
rlear at algorithmics.com
Fri Apr 22 10:58:43 PDT 2005
Since I dug up some of my JDOM stuff from years ago, here is my patch.
I have run this through the JDom test harness (JDom-test), and all tests
pass. (The harness did point out a couple of bugs .... which are now
corrected.)
Feel free to apply as you wish, I pass any ownership/copyright to Jason,
etc.
In essense, the patch completely re-writes the ListIterator in ContentList.
Rolf
Index: ContentList.java
===================================================================
RCS file: /home/cvspublic/jdom/src/java/org/jdom/ContentList.java,v
retrieving revision 1.39
diff -u -r1.39 ContentList.java
--- ContentList.java 28 Feb 2004 03:30:27 -0000 1.39
+++ ContentList.java 22 Apr 2005 17:56:44 -0000
@@ -84,19 +84,6 @@
private static final int INITIAL_ARRAY_SIZE = 5;
- /**
- * Used inner class FilterListIterator to help hasNext and
- * hasPrevious the next index of our cursor (must be here
- * for JDK1.1).
- */
- private static final int CREATE = 0;
- private static final int HASPREV = 1;
- private static final int HASNEXT = 2;
- private static final int PREV = 3;
- private static final int NEXT = 4;
- private static final int ADD = 5;
- private static final int REMOVE = 6;
-
/** Our backing list */
// protected ArrayList list;
private Content elementData[];
@@ -719,77 +706,91 @@
/** The Filter that applies */
Filter filter;
- /** The last operation performed */
- int lastOperation;
-
- /** Initial start index in backing list */
- int initialCursor;
-
+ /** Whether this iterator is in forward or reverse. */
+ private boolean forward = false;
+ /** Whether a call to remove() is valid */
+ private boolean canremove = false;
+ /** Whether a call to set() is valid */
+ private boolean canset = false;
+
/** Index in backing list of next object */
- int cursor;
-
- /** Index in backing list of last object returned */
- int last;
+ private int cursor = -1;
+ /** the backing index to use if we actually DO move */
+ private int tmpcursor = -1;
+ /** Index in ListIterator */
+ private int index = -1;
/** Expected modCount in our backing list */
- int expected;
+ private int expected = -1;
+
+ /** Number of elements matching the filter. */
+ private int fsize = 0;
/**
* Default constructor
*/
FilterListIterator(Filter filter, int start) {
this.filter = filter;
- initialCursor = initializeCursor(start);
- last = -1;
expected = ContentList.this.getModCount();
- lastOperation = CREATE;
+ // always start list iterators in backward mode ....
+ // it makes sense... really.
+ forward = false;
+
+ if (start < 0) {
+ throw new IndexOutOfBoundsException("Index: " + start);
+ }
+
+ // the number of matching elements....
+ fsize = 0;
+
+ // go through the list, count the matching elements...
+ for (int i = 0; i < ContentList.this.size(); i++) {
+ if (filter.matches(ContentList.this.get(i))) {
+ if (start == fsize) {
+ // set the back-end cursor to the matching
element....
+ cursor = i;
+ // set the front-end cursor too.
+ index = fsize;
+ }
+ fsize++;
+ }
+ }
+
+ if (start > fsize) {
+ throw new IndexOutOfBoundsException("Index: " + start +
+ " Size: " + fsize);
+ }
+
+ if (cursor == -1) {
+ // implies that start == fsize (i.e. after the last element
- valid for a ListIterator cursor.
+ // put the insertion point at the end of the Underlying
content list ....
+ // i.e. an add() at this point may potentially end up with
filtered content between previous() and next()
+ // the alternative is to put the cursor on the Content
after the last Content that the filter passed
+ // The implications are ambiguous.
+ cursor = ContentList.this.size();
+ index = fsize;
+ }
+
}
/**
* Returns <code>true</code> if this list iterator has a next
element.
*/
public boolean hasNext() {
- checkConcurrentModification();
-
- switch(lastOperation) {
- case CREATE: cursor = initialCursor;
- break;
- case PREV: cursor = last;
- break;
- case ADD:
- case NEXT: cursor = moveForward(last + 1);
- break;
- case REMOVE: cursor = moveForward(last);
- break;
- case HASPREV: cursor = moveForward(cursor + 1);
- break;
- case HASNEXT: break;
- default: throw new IllegalStateException("Unknown
operation");
- }
-
- if (lastOperation != CREATE) {
- lastOperation = HASNEXT;
- }
-
- return (cursor < ContentList.this.size()) ? true : false;
+ return nextIndex() < fsize;
}
/**
* Returns the next element in the list.
*/
public Object next() {
- checkConcurrentModification();
-
- if (hasNext()) {
- last = cursor;
- }
- else {
- last = ContentList.this.size();
- throw new NoSuchElementException();
- }
-
- lastOperation = NEXT;
- return ContentList.this.get(last);
+ if (! hasNext()) throw new NoSuchElementException("next() is
beyond the end of the Iterator.");
+ index = nextIndex();
+ cursor = tmpcursor;
+ forward = true;
+ canremove = true;
+ canset = true;
+ return ContentList.this.get(cursor);
}
/**
@@ -797,50 +798,20 @@
* elements when traversing the list in the reverse direction.
*/
public boolean hasPrevious() {
- checkConcurrentModification();
-
- switch(lastOperation) {
- case CREATE: cursor = initialCursor;
- int size = ContentList.this.size();
- if (cursor >= size) {
- cursor = moveBackward(size - 1);
- }
- break;
- case PREV:
- case REMOVE: cursor = moveBackward(last - 1);
- break;
- case HASNEXT: cursor = moveBackward(cursor - 1);
- break;
- case ADD:
- case NEXT: cursor = last;
- break;
- case HASPREV: break;
- default: throw new IllegalStateException("Unknown
operation");
- }
-
- if (lastOperation != CREATE) {
- lastOperation = HASPREV;
- }
-
- return (cursor < 0) ? false : true;
+ return previousIndex() >= 0;
}
/**
* Returns the previous element in the list.
*/
public Object previous() {
- checkConcurrentModification();
-
- if (hasPrevious()) {
- last = cursor;
- }
- else {
- last = -1;
- throw new NoSuchElementException();
- }
-
- lastOperation = PREV;
- return ContentList.this.get(last);
+ if (! hasPrevious()) throw new
NoSuchElementException("previous() is before the start of the Iterator.");
+ index = previousIndex();
+ cursor = tmpcursor;
+ forward = false;
+ canremove = true;
+ canset = true;
+ return ContentList.this.get(cursor);
}
/**
@@ -849,19 +820,23 @@
*/
public int nextIndex() {
checkConcurrentModification();
- hasNext();
-
- int count = 0;
- for (int i = 0; i < ContentList.this.size(); i++) {
- if (filter.matches(ContentList.this.get(i))) {
- if (i == cursor) {
- return count;
+
+ if (forward) {
+ // starting with next possibility ....
+ for (int i = cursor + 1; i < ContentList.this.size(); i++)
{
+ if (filter.matches(ContentList.this.get(i))) {
+ tmpcursor = i;
+ return index + 1;
}
- count++;
}
- }
- expected = ContentList.this.getModCount();
- return count;
+ // never found another match.... put the insertion point at
the end of the list....
+ tmpcursor = ContentList.this.size();
+ return index + 1;
+ }
+
+ // we've been going backwards ... so nextIndex() returns the
same element.
+ tmpcursor = cursor;
+ return index;
}
/**
@@ -871,37 +846,40 @@
*/
public int previousIndex() {
checkConcurrentModification();
-
- if (hasPrevious()) {
- int count = 0;
- for (int i = 0; i < ContentList.this.size(); i++) {
+ if (!forward) {
+ // starting with next possibility ....
+ for (int i = cursor - 1; i >= 0; i--) {
if (filter.matches(ContentList.this.get(i))) {
- if (i == cursor) {
- return count;
- }
- count++;
+ tmpcursor = i;
+ return index - 1;
}
}
- }
- return -1;
+ // never found another match.... put the insertion point at
the start of the list....
+ tmpcursor = -1;
+ return index -1;
+ }
+
+ // we've been going forwards ... so previousIndex() returns the
same element.
+ tmpcursor = cursor;
+ return index;
+
}
/**
* Inserts the specified element into the list.
*/
public void add(Object obj) {
- checkConcurrentModification();
-
- if (filter.matches(obj)) {
- last = cursor + 1;
- ContentList.this.add(last, obj);
- }
- else {
- throw new IllegalAddException("Filter won't allow add of "
+
- (obj.getClass()).getName());
- }
- expected = ContentList.this.getModCount();
- lastOperation = ADD;
+ // call to nextIndex() will check concurrent.
+ nextIndex();
+ // tmpcursor is the backing cursor of the next element
+ // remember that List.add(index,obj) is really an insert....
+ ContentList.this.add(tmpcursor, obj);
+ forward = true;
+ expected = getModCount();
+ canremove = canset = false;
+ index = nextIndex();
+ cursor = tmpcursor;
+ fsize++;
}
/**
@@ -910,28 +888,15 @@
* the last call to <code>next</code> or <code>previous</code>.
*/
public void remove() {
- checkConcurrentModification();
-
- if ((last < 0) || (lastOperation == REMOVE)) {
- throw new IllegalStateException("no preceeding call to " +
- "prev() or next()");
- }
-
- if (lastOperation == ADD) {
- throw new IllegalStateException("cannot call remove() " +
- "after add()");
- }
-
- Object old = ContentList.this.get(last);
- if (filter.matches(old)) {
- ContentList.this.remove(last);
- }
- else throw new IllegalAddException("Filter won't allow " +
- (old.getClass()).getName()
+
- " (index " + last +
- ") to be removed");
- expected = ContentList.this.getModCount();
- lastOperation = REMOVE;
+ if (!canremove) throw new IllegalStateException("Can not remove
an element unless either next() or previous() has been called since the last
remove()");
+ nextIndex(); // to get out cursor ...
+ ContentList.this.remove(cursor);
+ cursor = tmpcursor - 1;
+ expected = getModCount();
+ forward = false;
+ canremove = false;
+ canset = false;
+ fsize--;
}
/**
@@ -939,98 +904,17 @@
* <code>previous</code> with the specified element.
*/
public void set(Object obj) {
+ if (!canset) throw new IllegalStateException("Can not set an
element unless either next() or previous() has been called since the last
remove() or set()");
checkConcurrentModification();
-
- if ((lastOperation == ADD) || (lastOperation == REMOVE)) {
- throw new IllegalStateException("cannot call set() after "
+
- "add() or remove()");
- }
-
- if (last < 0) {
- throw new IllegalStateException("no preceeding call to " +
- "prev() or next()");
- }
-
- if (filter.matches(obj)) {
- Object old = ContentList.this.get(last);
- if (!filter.matches(old)) {
- throw new IllegalAddException("Filter won't allow " +
- (old.getClass()).getName() + " (index " +
- last + ") to be removed");
- }
- ContentList.this.set(last, obj);
- }
- else {
+
+ if (!filter.matches(obj)) {
throw new IllegalAddException("Filter won't allow index " +
- last + " to be set to " +
+ index + " to be set to " +
(obj.getClass()).getName());
}
+ ContentList.this.set(cursor, obj);
expected = ContentList.this.getModCount();
- // Don't set lastOperation
- }
-
- /**
- * Returns index in the backing list by moving forward start
- * objects that match our filter.
- */
- private int initializeCursor(int start) {
- if (start < 0) {
- throw new IndexOutOfBoundsException("Index: " + start);
- }
-
- int count = 0;
- for (int i = 0; i < ContentList.this.size(); i++) {
- Object obj = ContentList.this.get(i);
- if (filter.matches(obj)) {
- if (start == count) {
- return i;
- }
- count++;
- }
- }
-
- if (start > count) {
- throw new IndexOutOfBoundsException("Index: " + start +
- " Size: " + count);
- }
-
- return ContentList.this.size();
- }
-
- /**
- * Returns index in the backing list of the next object matching
- * our filter, starting at the given index and moving forwards.
- */
- private int moveForward(int start) {
- if (start < 0) {
- start = 0;
- }
- for (int i = start; i < ContentList.this.size(); i++) {
- Object obj = ContentList.this.get(i);
- if (filter.matches(obj)) {
- return i;
- }
- }
- return ContentList.this.size();
- }
-
- /**
- * Returns index in the backing list of the next object matching
- * our filter, starting at the given index and moving backwards.
- */
- private int moveBackward(int start) {
- if (start >= ContentList.this.size()) {
- start = ContentList.this.size() - 1;
- }
-
- for (int i = start; i >= 0; --i) {
- Object obj = ContentList.this.get(i);
- if (filter.matches(obj)) {
- return i;
- }
- }
- return -1;
}
/**
-----Original Message-----
From: jdom-interest-bounces at jdom.org
[mailto:jdom-interest-bounces at jdom.org]On Behalf Of Rolf Lear
Sent: Friday, April 22, 2005 11:34 AM
To: 'Bradley S. Huffman'; Christian Gruber
Cc: jdom-interest at jdom.org
Subject: RE: [jdom-interest] Bug in ListIterator.add() method
The complete iterator stuff in JDom is based on pre-collections stuff. There
is a lot of scope to re-hash the iterator problem.
I'll volunteer a patch in the next couple of days if people want to see the
iterator stuff re-written. When I was looking at the Parent/Child stuff a
year or so ago I odentified the iterator processes as being a weak point in
JDom in the sense that it was just plain complex. The wayu I though I would
re-do it implied Java1.2 logic IIRC.
Anyways, I'll use the weekend to produce a patch if people want.
Rolf
-----Original Message-----
From: jdom-interest-bounces at jdom.org
[mailto:jdom-interest-bounces at jdom.org]On Behalf Of Bradley S. Huffman
Sent: Friday, April 22, 2005 10:57 AM
To: Christian Gruber
Cc: jdom-interest at jdom.org
Subject: Re: [jdom-interest] Bug in ListIterator.add() method
Christian Gruber writes:
> As I suppose, Jdoms ListIterator.add() implementation has a problem
> when it is called more than once and when it is called at the end of
> the list.
Looking at the code it looks like the sequence
listIterator.add(new Element("a"));
listIterator.add(new Element("b"));
listIterator.add(new Element("c"));
will produce <c><b><a> instead of <a><b><c> and continue iterating on
element 2 (<b>) instead of after the last new element. That is a bug.
Brad
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proprietary to Algorithmics Incorporated and its affiliates
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and notify sender. Sender does not waive confidentiality or privilege.
Internet communications cannot be guaranteed to be timely, secure, error or
virus-free. Algorithmics does not accept liability for any errors or
omissions. Any commitment intended to bind Algorithmics must be reduced to
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