| /******************************************************************************* |
| * Copyright (c) 2011 VMware Inc. |
| * |
| * This program and the accompanying materials |
| * are made available under the terms of the Eclipse Public License 2.0 |
| * which accompanies this distribution, and is available at |
| * https://www.eclipse.org/legal/epl-2.0/ |
| * |
| * SPDX-License-Identifier: EPL-2.0 |
| * |
| * Contributors: |
| * SpringSource, a division of VMware - initial API and implementation and/or initial documentation |
| *******************************************************************************/ |
| |
| package org.eclipse.equinox.internal.region.hook; |
| |
| import java.util.*; |
| import org.eclipse.equinox.region.*; |
| |
| /** |
| * {@link RegionDigraphVisitorBase} is an abstract base class for {@link RegionDigraphVisitor} implementations in the |
| * framework hooks. |
| * <p /> |
| * |
| * <strong>Concurrent Semantics</strong><br /> |
| * This class is thread safe. |
| */ |
| abstract class RegionDigraphVisitorBase<C> implements RegionDigraphVisitor { |
| |
| private final Collection<C> allCandidates; |
| |
| private final Stack<Set<C>> allowedStack = new Stack<Set<C>>(); |
| private final Stack<Collection<C>> filteredStack = new Stack<Collection<C>>(); |
| |
| private Object monitor = new Object(); |
| |
| private Set<C> allowed; |
| |
| protected RegionDigraphVisitorBase(Collection<C> candidates) { |
| this.allCandidates = candidates; |
| synchronized (this.monitor) { |
| this.allowed = new HashSet<C>(); |
| } |
| } |
| |
| Collection<C> getAllowed() { |
| synchronized (this.monitor) { |
| return this.allowed; |
| } |
| } |
| |
| private void allow(C candidate) { |
| synchronized (this.monitor) { |
| this.allowed.add(candidate); |
| } |
| } |
| |
| private void allow(Collection<C> candidates) { |
| synchronized (this.monitor) { |
| this.allowed.addAll(candidates); |
| } |
| } |
| |
| private void pushAllowed() { |
| synchronized (this.monitor) { |
| this.allowedStack.push(this.allowed); |
| this.allowed = new HashSet<C>(); |
| } |
| } |
| |
| private Collection<C> popAllowed() { |
| synchronized (this.monitor) { |
| Collection<C> a = this.allowed; |
| this.allowed = this.allowedStack.pop(); |
| return a; |
| } |
| } |
| |
| private void pushFiltered(Collection<C> filtered) { |
| synchronized (this.monitor) { |
| this.filteredStack.push(filtered); |
| } |
| } |
| |
| private Collection<C> popFiltered() { |
| synchronized (this.monitor) { |
| return this.filteredStack.isEmpty() ? allCandidates : this.filteredStack.pop(); |
| } |
| } |
| |
| private Collection<C> peekFiltered() { |
| synchronized (this.monitor) { |
| return this.filteredStack.isEmpty() ? allCandidates : this.filteredStack.peek(); |
| } |
| } |
| |
| /** |
| * {@inheritDoc} |
| */ |
| @Override |
| public boolean visit(Region region) { |
| Collection<C> candidates = peekFiltered(); |
| for (C candidate : candidates) { |
| if (contains(region, candidate)) { |
| allow(candidate); |
| } |
| } |
| if (allowed.containsAll(candidates)) { |
| // there is no need to traverse edges of this region, |
| // it contains all the remaining filtered candidates |
| return false; |
| } |
| return true; |
| } |
| |
| /** |
| * Determines whether the given region contains the given candidate. |
| * |
| * @param region the {@link Region} |
| * @param candidate the candidate |
| * @return <code>true</code> if and only if the given region contains the given candidate |
| */ |
| protected abstract boolean contains(Region region, C candidate); |
| |
| /** |
| * {@inheritDoc} |
| */ |
| @Override |
| public boolean preEdgeTraverse(RegionFilter regionFilter) { |
| // Find the candidates filtered by the previous edge |
| Collection<C> candidates = new ArrayList<C>(peekFiltered()); |
| // remove any candidates contained in the current region |
| candidates.removeAll(allowed); |
| // apply the filter across remaining candidates |
| filter(candidates, regionFilter); |
| if (candidates.isEmpty()) |
| return false; // this filter does not apply; avoid traversing this edge |
| // push the filtered candidates for the next region |
| pushFiltered(candidates); |
| // push the allowed |
| pushAllowed(); |
| return true; |
| } |
| |
| /** |
| * {@inheritDoc} |
| */ |
| @Override |
| public void postEdgeTraverse(RegionFilter regionFilter) { |
| popFiltered(); |
| Collection<C> candidates = popAllowed(); |
| allow(candidates); |
| } |
| |
| private void filter(Collection<C> candidates, RegionFilter filter) { |
| Iterator<C> i = candidates.iterator(); |
| while (i.hasNext()) { |
| C candidate = i.next(); |
| if (!isAllowed(candidate, filter)) { |
| i.remove(); |
| } |
| } |
| } |
| |
| /** |
| * Determines whether the given candidate is allowed by the given {@link RegionFilter}. |
| * |
| * @param candidate the candidate |
| * @param filter the filter |
| * @return <code>true</code> if and only if the given candidate is allowed by the given filter |
| */ |
| protected abstract boolean isAllowed(C candidate, RegionFilter filter); |
| } |