| /******************************************************************************* |
| * Copyright (c) 2006, 2009 IBM Corporation and others. |
| * All rights reserved. This program and the accompanying materials |
| * are made available under the terms of the Eclipse Public License v1.0 |
| * which accompanies this distribution, and is available at |
| * http://www.eclipse.org/legal/epl-v10.html |
| * |
| * Contributors: |
| * IBM Corporation - initial API and implementation |
| * Matthew Hall - bugs 208858, 251884, 194734, 272651 |
| *******************************************************************************/ |
| |
| package org.eclipse.core.databinding.observable.list; |
| |
| import java.util.List; |
| |
| import org.eclipse.core.databinding.observable.IDiff; |
| import org.eclipse.core.internal.databinding.observable.Util; |
| |
| /** |
| * Object describing a diff between two lists. |
| * |
| * @since 1.0 |
| */ |
| public abstract class ListDiff implements IDiff { |
| |
| /** |
| * Returns a ListDiffEntry array representing the differences in the list, |
| * in the order they are to be processed. |
| * |
| * @return a ListDiffEntry array representing the differences in the list, |
| * in the order they are to be processed. |
| */ |
| public abstract ListDiffEntry[] getDifferences(); |
| |
| /** |
| * Traverses the {@link #getDifferences()} array, calling the appropriate |
| * method in <code>visitor</code> for each difference. |
| * <ol> |
| * <li>{@link ListDiffVisitor#handleReplace(int, Object, Object)} is called |
| * whenever an add entry is adjacent to a remove entry, and both entries |
| * operate on the same location in the list. |
| * <li>{@link ListDiffVisitor#handleMove(int, int, Object)} is called |
| * whenever an add entry is adjacent to a remove entry, and both entries |
| * have equivalent elements. |
| * <li>{@link ListDiffVisitor#handleRemove(int, Object)} is called whenever |
| * a remove entry does not match conditions 1 or 2. |
| * <li>{@link ListDiffVisitor#handleAdd(int, Object)} is called whenever an |
| * add entry does not match conditions in 1 or 2. |
| * </ol> |
| * |
| * @param visitor |
| * the visitor to receive callbacks. |
| * @see ListDiffVisitor |
| * @since 1.1 |
| */ |
| public void accept(ListDiffVisitor visitor) { |
| ListDiffEntry[] differences = getDifferences(); |
| for (int i = 0; i < differences.length; i++) { |
| ListDiffEntry entry = differences[i]; |
| Object elem = entry.getElement(); |
| int pos = entry.getPosition(); |
| boolean add = entry.isAddition(); |
| |
| if (i + 1 < differences.length) { |
| ListDiffEntry nextEntry = differences[i + 1]; |
| if (add != nextEntry.isAddition()) { |
| int addPos; |
| Object addElem; |
| |
| int removePos; |
| Object removeElem; |
| |
| if (add) { |
| addPos = pos; |
| addElem = elem; |
| |
| removePos = nextEntry.getPosition(); |
| removeElem = nextEntry.getElement(); |
| |
| if (addPos > removePos) { |
| // a b c d e f -- start |
| // a b c b d e f -- add b at 4 |
| // a c b d e f -- remove b at 2 |
| |
| // net effect is the same as: |
| // a b c d e f -- start |
| // a c d e f -- remove b at 2 |
| // a c b d e f -- add b at 3 |
| |
| addPos--; |
| } else if (removePos > addPos) { |
| // a b c d e f -- start |
| // a d b c d e f -- add d at 2 |
| // a d b c e f -- remove d at 5 |
| |
| // net effect is the same as |
| // a b c d e f -- start |
| // a b c e f -- remove d at 4 |
| // a d b c d e f -- add d at 2 |
| |
| // So we adjust the remove index to fit the indices |
| // of the remove-then-add scenario |
| removePos--; |
| } else { |
| // rare case: element is added and then immediately |
| // removed. Handle the add entry and then continue |
| // iterating starting at the remove entry |
| visitor.handleAdd(pos, elem); |
| continue; |
| } |
| } else { |
| removePos = pos; |
| removeElem = elem; |
| |
| addPos = nextEntry.getPosition(); |
| addElem = nextEntry.getElement(); |
| } |
| |
| if (removePos == addPos) { |
| visitor.handleReplace(pos, removeElem, addElem); |
| i++; |
| continue; |
| } |
| |
| if (Util.equals(removeElem, addElem)) { |
| visitor.handleMove(removePos, addPos, elem); |
| i++; |
| continue; |
| } |
| } |
| } |
| |
| if (add) |
| visitor.handleAdd(pos, elem); |
| else |
| visitor.handleRemove(pos, elem); |
| } |
| } |
| |
| /** |
| * Returns true if the diff contains no added, removed, moved or replaced |
| * elements. |
| * |
| * @return true if the diff contains no added, removed, moved or replaced |
| * elements. |
| * @since 1.2 |
| */ |
| public boolean isEmpty() { |
| return getDifferences().length == 0; |
| } |
| |
| /** |
| * Applies the changes in this diff to the given list |
| * |
| * @param list |
| * the list to which the diff will be applied |
| * @since 1.2 |
| */ |
| public void applyTo(final List list) { |
| accept(new ListDiffVisitor() { |
| public void handleAdd(int index, Object element) { |
| list.add(index, element); |
| } |
| |
| public void handleRemove(int index, Object element) { |
| list.remove(index); |
| } |
| |
| public void handleReplace(int index, Object oldElement, |
| Object newElement) { |
| list.set(index, newElement); |
| } |
| }); |
| } |
| |
| /** |
| * @see java.lang.Object#toString() |
| */ |
| public String toString() { |
| ListDiffEntry[] differences = getDifferences(); |
| StringBuffer buffer = new StringBuffer(); |
| buffer.append(getClass().getName()); |
| |
| if (differences == null || differences.length == 0) { |
| buffer.append("{}"); //$NON-NLS-1$ |
| } else { |
| buffer.append("{"); //$NON-NLS-1$ |
| |
| for (int i = 0; i < differences.length; i++) { |
| if (i > 0) |
| buffer.append(", "); //$NON-NLS-1$ |
| |
| buffer.append("difference[") //$NON-NLS-1$ |
| .append(i).append("] [") //$NON-NLS-1$ |
| .append( |
| differences[i] != null ? differences[i] |
| .toString() : "null") //$NON-NLS-1$ |
| .append("]"); //$NON-NLS-1$ |
| } |
| buffer.append("}"); //$NON-NLS-1$ |
| } |
| |
| return buffer.toString(); |
| } |
| } |