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- /*
- * 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.
- */
-
- /* $Id$ */
-
- package org.apache.fop.layoutmgr;
-
- import java.util.Iterator;
- import java.util.NoSuchElementException;
-
- /**
- * An iterator over {@link Position} instances, that is wrapped around
- * another 'parent' {@link Iterator}. The parent can be either another
- * {@code PositionIterator}, or an iterator over {@link KnuthElement}s,
- * for example.<br>
- * The {@link #next()} method always returns a {@link Position}. The
- * {@link #getPos(Object)} method can be overridden in subclasses
- * to take care of obtaining the {@link LayoutManager} or {@link Position}
- * from the object returned by the parent iterator's {@code next()} method.
- */
- public class PositionIterator implements Iterator<Position> {
-
- private Iterator parentIter;
- private Object nextObj;
- private LayoutManager childLM;
- private boolean hasNext;
-
- /**
- * Construct position iterator.
- * @param parentIter an iterator to use as parent
- */
- public PositionIterator(Iterator parentIter) {
- this.parentIter = parentIter;
- lookAhead();
- //checkNext();
- }
-
- /** @return layout manager of next child layout manager or null */
- public LayoutManager getNextChildLM() {
- // Move to next "segment" of iterator, ie: new childLM
- if (childLM == null && nextObj != null) {
- childLM = getLM(nextObj);
- hasNext = true;
- }
- return childLM;
- }
-
- /**
- * @param nextObj next object from which to obtain position
- * @return layout manager
- */
- protected LayoutManager getLM(Object nextObj) {
- return getPos(nextObj).getLM();
- }
-
- /**
- * Default implementation assumes that the passed
- * {@code nextObj} is itself a {@link Position}, and just returns it.
- * Subclasses for which this is not the case, <em>must</em> provide a
- * suitable override this method.
- * @param nextObj next object from which to obtain position
- * @return position of next object.
- */
- protected Position getPos(Object nextObj) {
- if (nextObj instanceof Position) {
- return (Position)nextObj;
- }
- throw new IllegalArgumentException(
- "Cannot obtain Position from the given object.");
- }
-
- private void lookAhead() {
- if (parentIter.hasNext()) {
- hasNext = true;
- nextObj = parentIter.next();
- } else {
- endIter();
- }
- }
-
- /** @return true if not at end of sub-sequence with same child layout manager */
- protected boolean checkNext() {
- LayoutManager lm = getLM(nextObj);
- if (childLM == null) {
- childLM = lm;
- } else if (childLM != lm && lm != null) {
- // End of this sub-sequence with same child LM
- hasNext = false;
- childLM = null;
- return false;
- }
- return true;
- }
-
- /** end (reset) iterator */
- protected void endIter() {
- hasNext = false;
- nextObj = null;
- childLM = null;
- }
-
- /** {@inheritDoc} */
- public boolean hasNext() {
- return (hasNext && checkNext());
- }
-
-
- /** {@inheritDoc} */
- public Position next() throws NoSuchElementException {
- if (hasNext) {
- Position retPos = getPos(nextObj);
- lookAhead();
- return retPos;
- } else {
- throw new NoSuchElementException("PosIter");
- }
- }
-
- /** @return peek at next object */
- public Object peekNext() {
- return nextObj;
- }
-
- /** {@inheritDoc} */
- public void remove() throws UnsupportedOperationException {
- throw new UnsupportedOperationException("PositionIterator doesn't support remove");
- }
- }
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