org.eclipse.platform/org.eclipse.core.resources/3.13.600 : org/eclipse/core/internal/resources/AliasManager.java

AliasManager
http://www.eclipse.org/platform: Core Resource Management (Eclipse Foundation)
Eclipse Public License - v 2.0
Copyright (c) 2000, 2015 IBM Corporation and others.
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:
    IBM Corporation - initial API and implementation
    manklu@web.de - fix for bug 156082
    Bert Vingerhoets - fix for bug 169975
    Serge Beauchamp (Freescale Semiconductor) - [229633] Fix Concurency Exception
    Sergey Prigogin (Google) - [338010] Resource.createLink() does not preserve symbolic links
    Lars Vogel  - Bug 473427
/*******************************************************************************
 * Copyright (c) 2000, 2015 IBM Corporation and others.
 *
 * 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:
 *     IBM Corporation - initial API and implementation
 *     manklu@web.de - fix for bug 156082
 *     Bert Vingerhoets - fix for bug 169975
 *     Serge Beauchamp (Freescale Semiconductor) - [229633] Fix Concurency Exception
 *     Sergey Prigogin (Google) - [338010] Resource.createLink() does not preserve symbolic links
 *     Lars Vogel <Lars.Vogel@vogella.com> - Bug 473427
 *******************************************************************************/
package org.eclipse.core.internal.resources;

import java.net.URI;
import java.util.*;
import org.eclipse.core.filesystem.EFS;
import org.eclipse.core.filesystem.IFileStore;
import org.eclipse.core.internal.events.ILifecycleListener;
import org.eclipse.core.internal.events.LifecycleEvent;
import org.eclipse.core.internal.localstore.FileSystemResourceManager;
import org.eclipse.core.internal.utils.*;
import org.eclipse.core.resources.*;
import org.eclipse.core.runtime.*;
import org.eclipse.osgi.util.NLS;

An alias is a resource that occupies the same file system location as another
resource in the workspace.  When a resource is modified in a way that affects
the file on disk, all aliases need to be updated.  This class is used to
maintain data structures for quickly computing the set of aliases for a given
resource, and for efficiently updating all aliases when a resource changes on
disk.
The approach for computing aliases is optimized for alias-free workspaces and
alias-free projects.  That is, if the workspace contains no aliases, then
updating should be very quick.  If a resource is changed in a project that
contains no aliases, it should also be very fast.
The data structures maintained by the alias manager can be seen as a cache,
that is, they store no information that cannot be recomputed from other
available information.  On shutdown, the alias manager discards all state; on
startup, the alias manager eagerly rebuilds its state.  The reasoning is
that it's better to incur this cost on startup than on the first attempt to
modify a resource.  After startup, the state is updated incrementally on the
following occasions:
 -  when projects are deleted, opened, closed, or moved
 - when linked resources are created, deleted, or moved.
/**
 * An alias is a resource that occupies the same file system location as another
 * resource in the workspace.  When a resource is modified in a way that affects
 * the file on disk, all aliases need to be updated.  This class is used to
 * maintain data structures for quickly computing the set of aliases for a given
 * resource, and for efficiently updating all aliases when a resource changes on
 * disk.
 *
 * The approach for computing aliases is optimized for alias-free workspaces and
 * alias-free projects.  That is, if the workspace contains no aliases, then
 * updating should be very quick.  If a resource is changed in a project that
 * contains no aliases, it should also be very fast.
 *
 * The data structures maintained by the alias manager can be seen as a cache,
 * that is, they store no information that cannot be recomputed from other
 * available information.  On shutdown, the alias manager discards all state; on
 * startup, the alias manager eagerly rebuilds its state.  The reasoning is
 * that it's better to incur this cost on startup than on the first attempt to
 * modify a resource.  After startup, the state is updated incrementally on the
 * following occasions:
 *  -  when projects are deleted, opened, closed, or moved
 *  - when linked resources are created, deleted, or moved.
 */
public class AliasManager implements IManager, ILifecycleListener, IResourceChangeListener {
	public class AddToCollectionDoit implements Doit {
		Collection<IResource> collection;

		@Override
		public void doit(IResource resource) {
			collection.add(resource);
		}

		public void setCollection(Collection<IResource> collection) {
			this.collection = collection;
		}
	}

	interface Doit {
		void doit(IResource resource);
	}

	class FindAliasesDoit implements Doit {
		private int aliasType;
		private IPath searchPath;

		@Override
		public void doit(IResource match) {
			//don't record the resource we're computing aliases against as a match
			if (match.getFullPath().isPrefixOf(searchPath))
				return;
			IPath aliasPath = null;
			switch (match.getType()) {
				case IResource.PROJECT :
					//first check if there is a linked resource that blocks the project location
					if (suffix.segmentCount() > 0) {
						IResource testResource = ((IProject) match).findMember(suffix.segment(0));
						if (testResource != null && testResource.isLinked())
							return;
					}
					//there is an alias under this project
					aliasPath = match.getFullPath().append(suffix);
					break;
				case IResource.FOLDER :
					aliasPath = match.getFullPath().append(suffix);
					break;
				case IResource.FILE :
					if (suffix.segmentCount() == 0)
						aliasPath = match.getFullPath();
					break;
			}
			if (aliasPath != null)
				if (aliasType == IResource.FILE) {
					aliases.add(workspace.getRoot().getFile(aliasPath));
				} else {
					if (aliasPath.segmentCount() == 1)
						aliases.add(workspace.getRoot().getProject(aliasPath.lastSegment()));
					else
						aliases.add(workspace.getRoot().getFolder(aliasPath));
				}
		}

		Sets the resource that we are searching for aliases for.
/**
		 * Sets the resource that we are searching for aliases for.
		 */
		public void setSearchAlias(IResource aliasResource) {
			this.aliasType = aliasResource.getType();
			this.searchPath = aliasResource.getFullPath();
		}
	}

	Maintains a mapping of FileStore->IResource, such that multiple resources
mapped from the same location are tolerated.
/**
	 * Maintains a mapping of FileStore-&gt;IResource, such that multiple resources
	 * mapped from the same location are tolerated.
	 */
	class LocationMap {
		Map of FileStore->IResource OR FileStore->ArrayList of (IResource)
/**
		 * Map of FileStore-&gt;IResource OR FileStore-&gt;ArrayList of (IResource)
		 */
		private final SortedMap<IFileStore, Object> map = new TreeMap<>(getComparator());

		Adds the given resource to the map, keyed by the given location.
Returns true if a new entry was added, and false otherwise.
/**
		 * Adds the given resource to the map, keyed by the given location.
		 * Returns true if a new entry was added, and false otherwise.
		 */
		public boolean add(IFileStore location, IResource resource) {
			Object oldValue = map.get(location);
			if (oldValue == null) {
				map.put(location, resource);
				return true;
			}
			if (oldValue instanceof IResource) {
				if (resource.equals(oldValue))
					return false;//duplicate
				ArrayList<Object> newValue = new ArrayList<>(2);
				newValue.add(oldValue);
				newValue.add(resource);
				map.put(location, newValue);
				return true;
			}
			@SuppressWarnings("unchecked")
			ArrayList<IResource> list = (ArrayList<IResource>) oldValue;
			if (list.contains(resource))
				return false;//duplicate
			list.add(resource);
			return true;
		}

		Method clear.
/**
		 * Method clear.
		 */
		public void clear() {
			map.clear();
		}

		Invoke the given doit for every resource whose location has the
given location as a prefix.
/**
		 * Invoke the given doit for every resource whose location has the
		 * given location as a prefix.
		 */
		public void matchingPrefixDo(IFileStore prefix, Doit doit) {
			SortedMap<IFileStore, Object> matching;
			IFileStore prefixParent = prefix.getParent();
			if (prefixParent != null) {
				//endPoint is the smallest possible path greater than the prefix that doesn't
				//match the prefix
				IFileStore endPoint = prefixParent.getChild(prefix.getName() + "\0"); //$NON-NLS-1$
				matching = map.subMap(prefix, endPoint);
			} else {
				matching = map;
			}
			for (Object value : matching.values()) {
				if (value == null)
					return;
				if (value instanceof List) {
					@SuppressWarnings("unchecked")
					Iterator<IResource> duplicates = ((List<IResource>) value).iterator();
					while (duplicates.hasNext())
						doit.doit(duplicates.next());
				} else {
					doit.doit((IResource) value);
				}
			}
		}

		Invoke the given doit for every resource that matches the given
location.
/**
		 * Invoke the given doit for every resource that matches the given
		 * location.
		 */
		public void matchingResourcesDo(IFileStore location, Doit doit) {
			Object value = map.get(location);
			if (value == null)
				return;
			if (value instanceof List) {
				@SuppressWarnings("unchecked")
				Iterator<IResource> duplicates = ((List<IResource>) value).iterator();
				while (duplicates.hasNext())
					doit.doit(duplicates.next());
			} else {
				doit.doit((IResource) value);
			}
		}

		Calls the given doit with the project of every resource in the map
whose location overlaps another resource in the map.
/**
		 * Calls the given doit with the project of every resource in the map
		 * whose location overlaps another resource in the map.
		 */
		public void overLappingResourcesDo(Doit doit) {
			Iterator<Map.Entry<IFileStore, Object>> entries = map.entrySet().iterator();
			IFileStore previousStore = null;
			IResource previousResource = null;
			while (entries.hasNext()) {
				Map.Entry<IFileStore, Object> current = entries.next();
				//value is either single resource or List of resources
				IFileStore currentStore = current.getKey();
				IResource currentResource = null;
				Object value = current.getValue();
				if (value instanceof List) {
					//if there are several then they're all overlapping
					@SuppressWarnings("unchecked")
					Iterator<IResource> duplicates = ((List<IResource>) value).iterator();
					while (duplicates.hasNext())
						doit.doit(duplicates.next().getProject());
				} else {
					//value is a single resource
					currentResource = (IResource) value;
				}
				if (previousStore != null) {
					//check for overlap with previous
					//Note: previous is always shorter due to map sorting rules
					if (previousStore.isParentOf(currentStore)) {
						//resources will be null if they were in a list, in which case
						//they've already been passed to the doit
						if (previousResource != null) {
							doit.doit(previousResource.getProject());
							//null out previous resource so we don't call doit twice with same resource
							previousResource = null;
						}
						if (currentResource != null)
							doit.doit(currentResource.getProject());
						//keep iterating with the same previous store because there may be more overlaps
						continue;
					}
				}
				previousStore = currentStore;
				previousResource = currentResource;
			}
		}

		Removes the given location from the map.  Returns true if anything
was actually removed, and false otherwise.
/**
		 * Removes the given location from the map.  Returns true if anything
		 * was actually removed, and false otherwise.
		 */
		public boolean remove(IFileStore location, IResource resource) {
			Object oldValue = map.get(location);
			if (oldValue == null)
				return false;
			if (oldValue instanceof IResource) {
				if (resource.equals(oldValue)) {
					map.remove(location);
					return true;
				}
				return false;
			}
			@SuppressWarnings("unchecked")
			ArrayList<IResource> list = (ArrayList<IResource>) oldValue;
			boolean wasRemoved = list.remove(resource);
			if (list.isEmpty())
				map.remove(location);
			return wasRemoved;
		}
	}

	Doit convenience class for adding items to a list
/**
	 * Doit convenience class for adding items to a list
	 */
	private final AddToCollectionDoit addToCollection = new AddToCollectionDoit();

	The set of IProjects that have aliases.
/**
	 * The set of IProjects that have aliases.
	 */
	protected final Set<IResource> aliasedProjects = new HashSet<>();

	A temporary set of aliases.  Used during computeAliases, but maintained
as a field as an optimization to prevent recreating the set.
/**
	 * A temporary set of aliases.  Used during computeAliases, but maintained
	 * as a field as an optimization to prevent recreating the set.
	 */
	protected final HashSet<IResource> aliases = new HashSet<>();

	The set of resources that have had structure changes that might
invalidate the locations map or aliased projects set.  These will be
updated incrementally on the next alias request.
/**
	 * The set of resources that have had structure changes that might
	 * invalidate the locations map or aliased projects set.  These will be
	 * updated incrementally on the next alias request.
	 */
	private final Set<IResource> changedLinks = new HashSet<>();

	This flag is true when projects have been created or deleted and the
location map has not been updated accordingly.
/**
	 * This flag is true when projects have been created or deleted and the
	 * location map has not been updated accordingly.
	 */
	private boolean changedProjects = false;

	The Doit class used for finding aliases.
/**
	 * The Doit class used for finding aliases.
	 */
	private final FindAliasesDoit findAliases = new FindAliasesDoit();

	This maps IFileStore -> IResource, associating a file system location
with the projects and/or linked resources that are rooted at that location.
/**
	 * This maps IFileStore -&gt; IResource, associating a file system location
	 * with the projects and/or linked resources that are rooted at that location.
	 */
	protected final LocationMap locationsMap = new LocationMap();
	The total number of resources in the workspace that are not in the default
location. This includes all linked resources, including linked resources
that don't currently have valid locations due to an undefined path variable.
This also includes projects that are not in their default location.
This value is used as a quick optimization, because a workspace with
all resources in their default locations cannot have any aliases.
/**
	 * The total number of resources in the workspace that are not in the default
	 * location. This includes all linked resources, including linked resources
	 * that don't currently have valid locations due to an undefined path variable.
	 * This also includes projects that are not in their default location.
	 * This value is used as a quick optimization, because a workspace with
	 * all resources in their default locations cannot have any aliases.
	 */
	private int nonDefaultResourceCount = 0;

	The suffix object is also used only during the computeAliases method.
In this case it is a field because it is referenced from an inner class
and we want to avoid creating a pointer array.  It is public to eliminate
the need for synthetic accessor methods.
/**
	 * The suffix object is also used only during the computeAliases method.
	 * In this case it is a field because it is referenced from an inner class
	 * and we want to avoid creating a pointer array.  It is public to eliminate
	 * the need for synthetic accessor methods.
	 */
	public IPath suffix;

	the workspace /** the workspace */
	protected final Workspace workspace;

	public AliasManager(Workspace workspace) {
		this.workspace = workspace;
	}

	private void addToLocationsMap(IProject project) {
		IFileStore location = ((Resource) project).getStore();
		if (location != null)
			locationsMap.add(location, project);
		ProjectDescription description = ((Project) project).internalGetDescription();
		if (description == null)
			return;
		if (description.getLocationURI() != null)
			nonDefaultResourceCount++;
		HashMap<IPath, LinkDescription> links = description.getLinks();
		if (links == null)
			return;
		for (LinkDescription linkDesc : links.values()) {
			IResource link = project.findMember(linkDesc.getProjectRelativePath());
			if (link != null) {
				try {
					URI locationURI = linkDesc.getLocationURI();
					locationURI = FileUtil.canonicalURI(locationURI);
					locationURI = link.getPathVariableManager().resolveURI(locationURI);
					addToLocationsMap(link, EFS.getStore(locationURI));
				} catch (CoreException e) {
					//ignore links with invalid locations
				}
			}
		}
	}

	private void addToLocationsMap(IResource link, IFileStore location) {
		if (location != null && !link.isVirtual())
			if (locationsMap.add(location, link))
				nonDefaultResourceCount++;
	}

	Builds the table of aliased projects from scratch.
/**
	 * Builds the table of aliased projects from scratch.
	 */
	private void buildAliasedProjectsSet() {
		aliasedProjects.clear();
		//if there are no resources in non-default locations then there can't be any aliased projects
		if (nonDefaultResourceCount <= 0)
			return;
		//for every resource that overlaps another, marked its project as aliased
		addToCollection.setCollection(aliasedProjects);
		locationsMap.overLappingResourcesDo(addToCollection);
	}

	Builds the table of resource locations from scratch.  Also computes an
initial value for the linked resource counter.
/**
	 * Builds the table of resource locations from scratch.  Also computes an
	 * initial value for the linked resource counter.
	 */
	private void buildLocationsMap() {
		locationsMap.clear();
		nonDefaultResourceCount = 0;
		//build table of IPath (file system location) -> IResource (project or linked resource)
		IProject[] projects = workspace.getRoot().getProjects(IContainer.INCLUDE_HIDDEN);
		for (IProject project : projects)
			if (project.isAccessible())
				addToLocationsMap(project);
	}

	A project alias needs updating.  If the project location has been deleted,
then the project should be deleted from the workspace.  This differs
from the refresh local strategy, but operations performed from within
the workspace must never leave a resource out of sync.
Params: project – The project to check for deletion
location – The project location
Throws: CoreException – 
Returns: true if the project has been deleted, and false otherwise/**
	 * A project alias needs updating.  If the project location has been deleted,
	 * then the project should be deleted from the workspace.  This differs
	 * from the refresh local strategy, but operations performed from within
	 * the workspace must never leave a resource out of sync.
	 * @param project The project to check for deletion
	 * @param location The project location
	 * @return <code>true</code> if the project has been deleted, and <code>false</code> otherwise
	 * @exception CoreException
	 */
	private boolean checkDeletion(Project project, IFileStore location) throws CoreException {
		if (project.exists() && !location.fetchInfo().exists()) {
			//perform internal deletion of project from workspace tree because
			// it is already deleted from disk and we can't acquire a different
			//scheduling rule in this context (none is needed because we are
			//within scope of the workspace lock)
			Assert.isTrue(workspace.getWorkManager().getLock().getDepth() > 0);
			project.deleteResource(false, null);
			return true;
		}
		return false;
	}

	Returns all aliases of the given resource, or null if there are none.
/**
	 * Returns all aliases of the given resource, or null if there are none.
	 */
	public IResource[] computeAliases(final IResource resource, IFileStore location) {
		//nothing to do if we are or were in an alias-free workspace or project
		if (hasNoAliases(resource))
			return null;

		aliases.clear();
		internalComputeAliases(resource, location);
		int size = aliases.size();
		if (size == 0)
			return null;
		return aliases.toArray(new IResource[size]);
	}

	Returns all resources pointing to the given location, or an empty array if there are none.
/**
	 * Returns all resources pointing to the given location, or an empty array if there are none.
	 */
	public IResource[] findResources(IFileStore location) {
		final ArrayList<IResource> resources = new ArrayList<>();
		locationsMap.matchingResourcesDo(location, resource -> resources.add(resource));
		return resources.toArray(new IResource[0]);
	}

	Returns all aliases of this resource, and any aliases of subtrees of this
resource.  Returns null if no aliases are found.
/**
	 * Returns all aliases of this resource, and any aliases of subtrees of this
	 * resource.  Returns null if no aliases are found.
	 */
	private void computeDeepAliases(IResource resource, IFileStore location) {
		//if the location is invalid then there won't be any aliases to update
		if (location == null)
			return;
		//get the normal aliases (resources rooted in parent locations)
		internalComputeAliases(resource, location);
		//get all resources rooted below this resource's location
		addToCollection.setCollection(aliases);
		locationsMap.matchingPrefixDo(location, addToCollection);
		//if this is a project, get all resources rooted below links in this project
		if (resource.getType() == IResource.PROJECT) {
			try {
				IResource[] members = ((IProject) resource).members();
				final FileSystemResourceManager localManager = workspace.getFileSystemManager();
				for (IResource member : members) {
					if (member.isLinked()) {
						IFileStore linkLocation = localManager.getStore(member);
						if (linkLocation != null)
							locationsMap.matchingPrefixDo(linkLocation, addToCollection);
					}
				}
			} catch (CoreException e) {
				//skip inaccessible projects
			}
		}
	}

	Returns the comparator to use when sorting the locations map.  Comparison
is based on segments, so that paths with the most segments in common will
always be adjacent.  This is equivalent to the natural order on the path
strings, with the extra condition that the path separator is ordered
before all other characters. (Ex: "/foo" < "/foo/zzz" < "/fooaaa").
/**
	 * Returns the comparator to use when sorting the locations map.  Comparison
	 * is based on segments, so that paths with the most segments in common will
	 * always be adjacent.  This is equivalent to the natural order on the path
	 * strings, with the extra condition that the path separator is ordered
	 * before all other characters. (Ex: "/foo" &lt; "/foo/zzz" &lt; "/fooaaa").
	 */
	Comparator<IFileStore> getComparator() {
		return new Comparator<IFileStore>() {
			@Override
			public int compare(IFileStore store1, IFileStore store2) {
				//scheme takes precedence over all else
				int compare = compareStringOrNull(store1.getFileSystem().getScheme(), store2.getFileSystem().getScheme());
				if (compare != 0)
					return compare;
				// compare based on URI path segment values
				final URI uri1;
				final URI uri2;
				try {
					uri1 = store1.toURI();
					uri2 = store2.toURI();
				} catch (Exception e) {
					//protect against misbehaving 3rd party code in file system implementations
					Policy.log(e);
					return 1;
				}

				// compare hosts
				compare = compareStringOrNull(uri1.getHost(), uri2.getHost());
				if (compare != 0)
					return compare;
				// compare user infos
				compare = compareStringOrNull(uri1.getUserInfo(), uri2.getUserInfo());
				if (compare != 0)
					return compare;
				// compare ports
				int port1 = uri1.getPort();
				int port2 = uri2.getPort();
				if (port1 != port2)
					return port1 - port2;

				IPath path1 = new Path(uri1.getPath());
				IPath path2 = new Path(uri2.getPath());
				// compare devices
				compare = compareStringOrNull(path1.getDevice(), path2.getDevice());
				if (compare != 0)
					return compare;
				// compare segments
				int segmentCount1 = path1.segmentCount();
				int segmentCount2 = path2.segmentCount();
				for (int i = 0; (i < segmentCount1) && (i < segmentCount2); i++) {
					compare = path1.segment(i).compareTo(path2.segment(i));
					if (compare != 0)
						return compare;
				}
				//all segments are equal, so compare based on number of segments
				compare = segmentCount1 - segmentCount2;
				if (compare != 0)
					return compare;
				//same number of segments, so compare query
				return compareStringOrNull(uri1.getQuery(), uri2.getQuery());
			}

			Compares two strings that are possibly null.
/**
			 * Compares two strings that are possibly null.
			 */
			private int compareStringOrNull(String string1, String string2) {
				if (string1 == null) {
					if (string2 == null)
						return 0;
					return 1;
				}
				if (string2 == null)
					return -1;
				return string1.compareTo(string2);

			}
		};
	}

	@Override
	public void handleEvent(LifecycleEvent event) {
		/*
		 * We can't determine the end state for most operations because they may
		 * fail after we receive pre-notification.  In these cases, we remember
		 * the invalidated resources and recompute their state lazily on the
		 * next alias request.
		 */
		switch (event.kind) {
			case LifecycleEvent.PRE_LINK_CHANGE :
			case LifecycleEvent.PRE_LINK_DELETE :
				Resource link = (Resource) event.resource;
				if (link.isLinked())
					removeFromLocationsMap(link, link.getStore());
				//fall through
			case LifecycleEvent.PRE_FILTER_ADD :
				changedLinks.add(event.resource);
				break;
			case LifecycleEvent.PRE_FILTER_REMOVE :
				changedLinks.add(event.resource);
				break;
			case LifecycleEvent.PRE_LINK_CREATE :
				changedLinks.add(event.resource);
				break;
			case LifecycleEvent.PRE_LINK_COPY :
				changedLinks.add(event.newResource);
				break;
			case LifecycleEvent.PRE_LINK_MOVE :
				link = (Resource) event.resource;
				if (link.isLinked())
					removeFromLocationsMap(link, link.getStore());
				changedLinks.add(event.newResource);
				break;
		}
	}

	Returns true if this resource is guaranteed to have no aliases, and false
otherwise.
/**
	 * Returns true if this resource is guaranteed to have no aliases, and false
	 * otherwise.
	 */
	private boolean hasNoAliases(final IResource resource) {
		//check if we're in an aliased project or workspace before updating structure changes.  In the
		//deletion case, we need to know if the resource was in an aliased project *before* deletion.
		IProject project = resource.getProject();
		boolean noAliases = !aliasedProjects.contains(project);

		//now update any structure changes and check again if an update is needed
		if (hasStructureChanges()) {
			updateStructureChanges();
			noAliases &= nonDefaultResourceCount <= 0 || !aliasedProjects.contains(project);
		}
		return noAliases;
	}

	Returns whether there are any structure changes that we have not yet processed.
/**
	 * Returns whether there are any structure changes that we have not yet processed.
	 */
	private boolean hasStructureChanges() {
		return changedProjects || !changedLinks.isEmpty();
	}

	Computes the aliases of the given resource at the given location, and
adds them to the "aliases" collection.
/**
	 * Computes the aliases of the given resource at the given location, and
	 * adds them to the "aliases" collection.
	 */
	private void internalComputeAliases(IResource resource, IFileStore location) {
		IFileStore searchLocation = location;
		if (searchLocation == null)
			searchLocation = ((Resource) resource).getStore();
		//if the location is invalid then there won't be any aliases to update
		if (searchLocation == null)
			return;

		suffix = Path.EMPTY;
		findAliases.setSearchAlias(resource);
		/*
		 * Walk up the location segments for this resource, looking for a
		 * resource with a matching location.  All matches are then added to the
		 * "aliases" set.
		 */
		do {
			locationsMap.matchingResourcesDo(searchLocation, findAliases);
			suffix = new Path(searchLocation.getName()).append(suffix);
			searchLocation = searchLocation.getParent();
		} while (searchLocation != null);
	}

	private void removeFromLocationsMap(IResource link, IFileStore location) {
		if (location != null)
			if (locationsMap.remove(location, link))
				nonDefaultResourceCount--;
	}

	@Override
	public void resourceChanged(IResourceChangeEvent event) {
		final IResourceDelta delta = event.getDelta();
		if (delta == null)
			return;
		//invalidate location map if there are added or removed projects.
		if (delta.getAffectedChildren(IResourceDelta.ADDED | IResourceDelta.REMOVED, IContainer.INCLUDE_HIDDEN).length > 0)
			changedProjects = true;

		// invalidate location map if any project has the description changed
		// or was closed/opened
		IResourceDelta[] changed = delta.getAffectedChildren(IResourceDelta.CHANGED, IContainer.INCLUDE_HIDDEN);
		for (IResourceDelta element : changed) {
			if ((element.getFlags() & IResourceDelta.DESCRIPTION) == IResourceDelta.DESCRIPTION || (element.getFlags() & IResourceDelta.OPEN) == IResourceDelta.OPEN) {
				changedProjects = true;
				break;
			}
		}
	}

	@Override
	public void shutdown(IProgressMonitor monitor) {
		workspace.removeResourceChangeListener(this);
		locationsMap.clear();
	}

	@Override
	public void startup(IProgressMonitor monitor) {
		workspace.addLifecycleListener(this);
		workspace.addResourceChangeListener(this, IResourceChangeEvent.POST_CHANGE);
		buildLocationsMap();
		buildAliasedProjectsSet();
	}

	The file underlying the given resource has changed on disk.  Compute all
aliases for this resource and update them.  This method will not attempt
to incur any units of work on the given progress monitor, but it may
update the subtask to reflect what aliases are being updated.
Params: resource – the resource to compute aliases for
location – the file system location of the resource (passed as a
parameter because in the project deletion case the resource is no longer
accessible at time of update).
depth – whether to search for aliases on all children of the given
resource.  Only depth ZERO and INFINITE are used./**
	 * The file underlying the given resource has changed on disk.  Compute all
	 * aliases for this resource and update them.  This method will not attempt
	 * to incur any units of work on the given progress monitor, but it may
	 * update the subtask to reflect what aliases are being updated.
	 * @param resource the resource to compute aliases for
	 * @param location the file system location of the resource (passed as a
	 * parameter because in the project deletion case the resource is no longer
	 * accessible at time of update).
	 * @param depth whether to search for aliases on all children of the given
	 * resource.  Only depth ZERO and INFINITE are used.
	 */
	@SuppressWarnings({"unchecked"})
	public void updateAliases(IResource resource, IFileStore location, int depth, IProgressMonitor monitor) throws CoreException {
		if (hasNoAliases(resource))
			return;
		aliases.clear();
		if (depth == IResource.DEPTH_ZERO)
			internalComputeAliases(resource, location);
		else
			computeDeepAliases(resource, location);
		if (aliases.isEmpty())
			return;
		FileSystemResourceManager localManager = workspace.getFileSystemManager();
		HashSet<IResource> aliasesCopy = (HashSet<IResource>) aliases.clone();
		for (IResource alias : aliasesCopy) {
			monitor.subTask(NLS.bind(Messages.links_updatingDuplicate, alias.getFullPath()));
			if (alias.getType() == IResource.PROJECT) {
				if (checkDeletion((Project) alias, location))
					continue;
				//project did not require deletion, so fall through below and refresh it
			}
			if (!((Resource) alias).isFiltered())
				localManager.refresh(alias, IResource.DEPTH_INFINITE, false, null);
		}
	}

	Process any structural changes that have occurred since the last alias
request.
/**
	 * Process any structural changes that have occurred since the last alias
	 * request.
	 */
	private void updateStructureChanges() {
		boolean hadChanges = false;
		if (changedProjects) {
			//if a project is added or removed, just recompute the whole world
			changedProjects = false;
			hadChanges = true;
			buildLocationsMap();
		} else {
			//incrementally update location map for changed links
			for (IResource resource : changedLinks) {
				hadChanges = true;
				if (!resource.isAccessible())
					continue;
				if (resource.isLinked())
					addToLocationsMap(resource, ((Resource) resource).getStore());
			}
		}
		changedLinks.clear();
		if (hadChanges)
			buildAliasedProjectsSet();
		changedProjects = false;
	}
}
Params:	project – The project to check for deletion location – The project location
Throws:	CoreException –
Returns:	`true` if the project has been deleted, and `false` otherwise
/

org.eclipse.platform/ org.eclipse.core.resources/ 3.13.600/ org/eclipse/core/internal/resources/AliasManager.java
