bundles/org.eclipse.equinox.preferences/src/org/eclipse/core/internal/preferences/EclipsePreferences.java

/*******************************************************************************
 * Copyright (c) 2004, 2012 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
 *     Julian Chen - fix for bug #92572, jclRM
 *******************************************************************************/
package org.eclipse.core.internal.preferences;

import java.io.*;
import java.util.*;
import org.eclipse.core.internal.runtime.RuntimeLog;
import org.eclipse.core.runtime.*;
import org.eclipse.core.runtime.preferences.*;
import org.eclipse.osgi.util.NLS;
import org.osgi.service.prefs.BackingStoreException;
import org.osgi.service.prefs.Preferences;

/**
 * Represents a node in the Eclipse preference node hierarchy. This class
 * is used as a default implementation/super class for those nodes which
 * belong to scopes which are contributed by the Platform.
 * 
 * Implementation notes:
 * 
 *  - For thread safety, we always synchronize on the node object when writing
 * the children or properties fields.  Must ensure we don't synchronize when calling
 * client code such as listeners.
 * 
 * @since 3.0
 */
public class EclipsePreferences implements IEclipsePreferences, IScope {

	public static final String DEFAULT_PREFERENCES_DIRNAME = ".settings"; //$NON-NLS-1$
	public static final String PREFS_FILE_EXTENSION = "prefs"; //$NON-NLS-1$
	protected static final IEclipsePreferences[] EMPTY_NODE_ARRAY = new IEclipsePreferences[0];
	protected static final String[] EMPTY_STRING_ARRAY = new String[0];
	private static final String FALSE = "false"; //$NON-NLS-1$
	private static final String TRUE = "true"; //$NON-NLS-1$
	protected static final String VERSION_KEY = "eclipse.preferences.version"; //$NON-NLS-1$
	protected static final String VERSION_VALUE = "1"; //$NON-NLS-1$
	protected static final String PATH_SEPARATOR = String.valueOf(IPath.SEPARATOR);
	protected static final String DOUBLE_SLASH = "//"; //$NON-NLS-1$
	protected static final String EMPTY_STRING = ""; //$NON-NLS-1$

	private String cachedPath;
	protected Map children;
	protected boolean dirty = false;
	protected boolean loading = false;
	protected final String name;
	// the parent of an EclipsePreference node is always an EclipsePreference node. (or null)
	protected final EclipsePreferences parent;
	protected ImmutableMap properties = ImmutableMap.EMPTY;
	protected boolean removed = false;
	private ListenerList nodeChangeListeners;
	private ListenerList preferenceChangeListeners;

	public static boolean DEBUG_PREFERENCE_GENERAL = false;
	public static boolean DEBUG_PREFERENCE_SET = false;
	public static boolean DEBUG_PREFERENCE_GET = false;

	protected final static String debugPluginName = "org.eclipse.equinox.preferences"; //$NON-NLS-1$

	static {
		DEBUG_PREFERENCE_GENERAL = PreferencesOSGiUtils.getDefault().getBooleanDebugOption(debugPluginName + "/general", false); //$NON-NLS-1$
		DEBUG_PREFERENCE_SET = PreferencesOSGiUtils.getDefault().getBooleanDebugOption(debugPluginName + "/set", false); //$NON-NLS-1$
		DEBUG_PREFERENCE_GET = PreferencesOSGiUtils.getDefault().getBooleanDebugOption(debugPluginName + "/get", false); //$NON-NLS-1$
	}

	protected class SortedProperties extends Properties {

		private static final long serialVersionUID = 1L;

		public SortedProperties() {
			super();
		}

		/* (non-Javadoc)
		 * @see java.util.Hashtable#keys()
		 */
		public synchronized Enumeration keys() {
			TreeSet set = new TreeSet();
			for (Enumeration e = super.keys(); e.hasMoreElements();)
				set.add(e.nextElement());
			return Collections.enumeration(set);
		}

		/* (non-Javadoc)
		 * @see java.util.Hashtable#entrySet()
		 */
		public Set entrySet() {
			TreeSet set = new TreeSet(new Comparator() {
				public int compare(Object e1, Object e2) {
					String s1 = (String) ((Map.Entry) e1).getKey();
					String s2 = (String) ((Map.Entry) e2).getKey();
					return s1.compareTo(s2);
				}
			});
			for (Iterator i = super.entrySet().iterator(); i.hasNext();)
				set.add(i.next());
			return set;
		}
	}

	public EclipsePreferences() {
		this(null, null);
	}

	protected EclipsePreferences(EclipsePreferences parent, String name) {
		super();
		this.parent = parent;
		this.name = name;
		this.cachedPath = null; // make sure the cached path is cleared after setting the parent
	}

	/*
	 * @see org.osgi.service.prefs.Preferences#absolutePath()
	 */
	public String absolutePath() {
		if (cachedPath == null) {
			if (parent == null)
				cachedPath = PATH_SEPARATOR;
			else {
				String parentPath = parent.absolutePath();
				// if the parent is the root then we don't have to add a separator
				// between the parent path and our path
				if (parentPath.length() == 1)
					cachedPath = parentPath + name();
				else
					cachedPath = parentPath + PATH_SEPARATOR + name();
			}
		}
		return cachedPath;
	}

	public void accept(IPreferenceNodeVisitor visitor) throws BackingStoreException {
		if (!visitor.visit(this))
			return;
		IEclipsePreferences[] toVisit = getChildren(true);
		for (int i = 0; i < toVisit.length; i++)
			toVisit[i].accept(visitor);
	}

	protected synchronized IEclipsePreferences addChild(String childName, IEclipsePreferences child) {
		//Thread safety: synchronize method to protect modification of children field
		if (children == null)
			children = Collections.synchronizedMap(new HashMap());
		children.put(childName, child == null ? (Object) childName : child);
		return child;
	}

	/*
	 * @see org.eclipse.core.runtime.IEclipsePreferences#addNodeChangeListener(org.eclipse.core.runtime.IEclipsePreferences.INodeChangeListener)
	 */
	public void addNodeChangeListener(INodeChangeListener listener) {
		checkRemoved();
		if (nodeChangeListeners == null)
			nodeChangeListeners = new ListenerList();
		nodeChangeListeners.add(listener);
		if (DEBUG_PREFERENCE_GENERAL)
			PrefsMessages.message("Added preference node change listener: " + listener + " to: " + absolutePath()); //$NON-NLS-1$ //$NON-NLS-2$
	}

	/*
	 * @see org.eclipse.core.runtime.IEclipsePreferences#addPreferenceChangeListener(org.eclipse.core.runtime.IEclipsePreferences.IPreferenceChangeListener)
	 */
	public void addPreferenceChangeListener(IPreferenceChangeListener listener) {
		checkRemoved();
		if (preferenceChangeListeners == null)
			preferenceChangeListeners = new ListenerList();
		preferenceChangeListeners.add(listener);
		if (DEBUG_PREFERENCE_GENERAL)
			PrefsMessages.message("Added preference property change listener: " + listener + " to: " + absolutePath()); //$NON-NLS-1$ //$NON-NLS-2$
	}

	private IEclipsePreferences calculateRoot() {
		IEclipsePreferences result = this;
		while (result.parent() != null)
			result = (IEclipsePreferences) result.parent();
		return result;
	}

	/*
	 * Convenience method for throwing an exception when methods
	 * are called on a removed node.
	 */
	protected void checkRemoved() {
		if (removed)
			throw new IllegalStateException(NLS.bind(PrefsMessages.preferences_removedNode, name));
	}

	/*
	 * @see org.osgi.service.prefs.Preferences#childrenNames()
	 */
	public String[] childrenNames() {
		// illegal state if this node has been removed
		checkRemoved();
		return internalChildNames();
	}

	protected String[] internalChildNames() {
		Map temp = children;
		if (temp == null || temp.size() == 0)
			return EMPTY_STRING_ARRAY;
		return (String[]) temp.keySet().toArray(EMPTY_STRING_ARRAY);
	}

	/*
	 * @see org.osgi.service.prefs.Preferences#clear()
	 */
	public void clear() {
		// illegal state if this node has been removed
		checkRemoved();
		// call each one separately (instead of Properties.clear) so
		// clients get change notification
		String[] keys = properties.keys();
		for (int i = 0; i < keys.length; i++)
			remove(keys[i]);
		makeDirty();
	}

	protected String[] computeChildren(IPath root) {
		if (root == null)
			return EMPTY_STRING_ARRAY;
		IPath dir = root.append(DEFAULT_PREFERENCES_DIRNAME);
		final ArrayList result = new ArrayList();
		final String extension = '.' + PREFS_FILE_EXTENSION;
		File file = dir.toFile();
		File[] totalFiles = file.listFiles();
		if (totalFiles != null) {
			for (int i = 0; i < totalFiles.length; i++) {
				if (totalFiles[i].isFile()) {
					String filename = totalFiles[i].getName();
					if (filename.endsWith(extension)) {
						String shortName = filename.substring(0, filename.length() - extension.length());
						result.add(shortName);
					}
				}
			}
		}
		return (String[]) result.toArray(EMPTY_STRING_ARRAY);
	}

	protected IPath computeLocation(IPath root, String qualifier) {
		return root == null ? null : root.append(DEFAULT_PREFERENCES_DIRNAME).append(qualifier).addFileExtension(PREFS_FILE_EXTENSION);
	}

	/*
	 * Version 1 (current version)
	 * path/key=value
	 */
	protected static void convertFromProperties(EclipsePreferences node, Properties table, boolean notify) {
		String version = table.getProperty(VERSION_KEY);
		if (version == null || !VERSION_VALUE.equals(version)) {
			// ignore for now
		}
		table.remove(VERSION_KEY);
		for (Iterator i = table.keySet().iterator(); i.hasNext();) {
			String fullKey = (String) i.next();
			String value = table.getProperty(fullKey);
			if (value != null) {
				String[] splitPath = decodePath(fullKey);
				String path = splitPath[0];
				path = makeRelative(path);
				String key = splitPath[1];
				if (DEBUG_PREFERENCE_SET)
					PrefsMessages.message("Setting preference: " + path + '/' + key + '=' + value); //$NON-NLS-1$
				//use internal methods to avoid notifying listeners
				EclipsePreferences childNode = (EclipsePreferences) node.internalNode(path, false, null);
				String oldValue = childNode.internalPut(key, value);
				// notify listeners if applicable
				if (notify && !value.equals(oldValue))
					childNode.firePreferenceEvent(key, oldValue, value);
			}
		}
		PreferencesService.getDefault().shareStrings();
	}

	/*
	 * Helper method to persist a Properties object to the filesystem. We use this
	 * helper so we can remove the date/timestamp that Properties#store always 
	 * puts in the file.
	 */
	protected static void write(Properties properties, IPath location) throws BackingStoreException {
		// create the parent dirs if they don't exist
		File parentFile = location.toFile().getParentFile();
		if (parentFile == null)
			return;
		parentFile.mkdirs();

		OutputStream output = null;
		try {
			output = new BufferedOutputStream(new FileOutputStream(new File(location.toOSString())));
			output.write(removeTimestampFromTable(properties).getBytes("UTF-8")); //$NON-NLS-1$
			output.flush();
		} catch (IOException e) {
			String message = NLS.bind(PrefsMessages.preferences_saveException, location);
			log(new Status(IStatus.ERROR, PrefsMessages.OWNER_NAME, IStatus.ERROR, message, e));
			throw new BackingStoreException(message);
		} finally {
			if (output != null)
				try {
					output.close();
				} catch (IOException e) {
					// ignore
				}
		}
	}

	protected static String removeTimestampFromTable(Properties properties) throws IOException {
		// store the properties in a string and then skip the first line (date/timestamp)
		ByteArrayOutputStream output = new ByteArrayOutputStream();
		try {
			properties.store(output, null);
		} finally {
			output.close();
		}
		String string = output.toString("UTF-8"); //$NON-NLS-1$
		String separator = System.getProperty("line.separator"); //$NON-NLS-1$
		return string.substring(string.indexOf(separator) + separator.length());
	}

	/* 
	 * Helper method to convert this node to a Properties file suitable
	 * for persistence.
	 */
	protected Properties convertToProperties(Properties result, String prefix) throws BackingStoreException {
		// add the key/value pairs from this node
		boolean addSeparator = prefix.length() != 0;
		//thread safety: copy reference in case of concurrent change
		ImmutableMap temp = properties;
		String[] keys = temp.keys();
		for (int i = 0, imax = keys.length; i < imax; i++) {
			String value = temp.get(keys[i]);
			if (value != null)
				result.put(encodePath(prefix, keys[i]), value);
		}
		// recursively add the child information
		IEclipsePreferences[] childNodes = getChildren(true);
		for (int i = 0; i < childNodes.length; i++) {
			EclipsePreferences child = (EclipsePreferences) childNodes[i];
			String fullPath = addSeparator ? prefix + PATH_SEPARATOR + child.name() : child.name();
			child.convertToProperties(result, fullPath);
		}
		PreferencesService.getDefault().shareStrings();
		return result;
	}

	/*
	 * @see org.eclipse.core.runtime.preferences.IScope#create(org.eclipse.core.runtime.preferences.IEclipsePreferences)
	 */
	public IEclipsePreferences create(IEclipsePreferences nodeParent, String nodeName) {
		return create((EclipsePreferences) nodeParent, nodeName, null);
	}

	protected boolean isLoading() {
		return loading;
	}

	protected void setLoading(boolean isLoading) {
		loading = isLoading;
	}

	public IEclipsePreferences create(EclipsePreferences nodeParent, String nodeName, Object context) {
		EclipsePreferences result = internalCreate(nodeParent, nodeName, context);
		nodeParent.addChild(nodeName, result);
		IEclipsePreferences loadLevel = result.getLoadLevel();

		// if this node or a parent node is not the load level then return
		if (loadLevel == null)
			return result;

		// if the result node is not a load level, then a child must be
		if (result != loadLevel)
			return result;

		// the result node is a load level
		if (isAlreadyLoaded(result) || result.isLoading())
			return result;
		try {
			result.setLoading(true);
			result.loadLegacy();
			result.load();
			result.loaded();
			result.flush();
		} catch (BackingStoreException e) {
			IPath location = result.getLocation();
			String message = NLS.bind(PrefsMessages.preferences_loadException, location == null ? EMPTY_STRING : location.toString());
			IStatus status = new Status(IStatus.ERROR, PrefsMessages.OWNER_NAME, IStatus.ERROR, message, e);
			RuntimeLog.log(status);
		} finally {
			result.setLoading(false);
		}
		return result;
	}

	/*
	 * @see org.osgi.service.prefs.Preferences#flush()
	 */
	synchronized public void flush() throws BackingStoreException {
		internalFlush();
	}

	/*
	 * Do the real flushing in a non-synchronized internal method so sub-classes 
	 * (mainly ProjectPreferences and ProfilePreferences) don't cause deadlocks.
	 */
	protected void internalFlush() throws BackingStoreException {
		// illegal state if this node has been removed
		checkRemoved();

		IEclipsePreferences loadLevel = getLoadLevel();

		// if this node or a parent is not the load level, then flush the children
		if (loadLevel == null) {
			String[] childrenNames = childrenNames();
			for (int i = 0; i < childrenNames.length; i++)
				node(childrenNames[i]).flush();
			return;
		}

		// a parent is the load level for this node
		if (this != loadLevel) {
			loadLevel.flush();
			return;
		}

		// this node is a load level
		// any work to do?
		if (!dirty)
			return;
		//remove dirty bit before saving, to ensure that concurrent 
		//changes during save mark the store as dirty
		dirty = false;
		try {
			save();
		} catch (BackingStoreException e) {
			//mark it dirty again because the save failed
			dirty = true;
			throw e;
		}
	}

	/*
	 * @see org.osgi.service.prefs.Preferences#get(java.lang.String, java.lang.String)
	 */
	public String get(String key, String defaultValue) {
		String value = internalGet(key);
		return value == null ? defaultValue : value;
	}

	/*
	 * @see org.osgi.service.prefs.Preferences#getBoolean(java.lang.String, boolean)
	 */
	public boolean getBoolean(String key, boolean defaultValue) {
		String value = internalGet(key);
		return value == null ? defaultValue : TRUE.equalsIgnoreCase(value);
	}

	/*
	 * @see org.osgi.service.prefs.Preferences#getByteArray(java.lang.String, byte[])
	 */
	public byte[] getByteArray(String key, byte[] defaultValue) {
		String value = internalGet(key);
		return value == null ? defaultValue : Base64.decode(value.getBytes());
	}

	/*
	 * Return a boolean value indicating whether or not a child with the given
	 * name is known to this node.
	 */
	protected synchronized boolean childExists(String childName) {
		if (children == null)
			return false;
		return children.get(childName) != null;
	}

	/**
	 * Thread safe way to obtain a child for a given key. Returns the child
	 * that matches the given key, or null if there is no matching child.
	 */
	protected IEclipsePreferences getChild(String key, Object context, boolean create) {
		synchronized (this) {
			if (children == null)
				return null;
			Object value = children.get(key);
			if (value == null)
				return null;
			if (value instanceof IEclipsePreferences)
				return (IEclipsePreferences) value;
			// if we aren't supposed to create this node, then 
			// just return null
			if (!create)
				return null;
		}
		return addChild(key, create(this, key, context));
	}

	/**
	 * Thread safe way to obtain all children of this node. Never returns null.
	 */
	protected IEclipsePreferences[] getChildren(boolean create) {
		ArrayList result = new ArrayList();
		String[] names = internalChildNames();
		for (int i = 0; i < names.length; i++) {
			IEclipsePreferences child = getChild(names[i], null, create);
			if (child != null)
				result.add(child);
		}
		return (IEclipsePreferences[]) result.toArray(EMPTY_NODE_ARRAY);
	}

	/*
	 * @see org.osgi.service.prefs.Preferences#getDouble(java.lang.String, double)
	 */
	public double getDouble(String key, double defaultValue) {
		String value = internalGet(key);
		double result = defaultValue;
		if (value != null)
			try {
				result = Double.parseDouble(value);
			} catch (NumberFormatException e) {
				// use default
			}
		return result;
	}

	/*
	 * @see org.osgi.service.prefs.Preferences#getFloat(java.lang.String, float)
	 */
	public float getFloat(String key, float defaultValue) {
		String value = internalGet(key);
		float result = defaultValue;
		if (value != null)
			try {
				result = Float.parseFloat(value);
			} catch (NumberFormatException e) {
				// use default
			}
		return result;
	}

	/*
	 * @see org.osgi.service.prefs.Preferences#getInt(java.lang.String, int)
	 */
	public int getInt(String key, int defaultValue) {
		String value = internalGet(key);
		int result = defaultValue;
		if (value != null)
			try {
				result = Integer.parseInt(value);
			} catch (NumberFormatException e) {
				// use default
			}
		return result;
	}

	protected IEclipsePreferences getLoadLevel() {
		return null;
	}

	/*
	 * Subclasses to over-ride
	 */
	protected IPath getLocation() {
		return null;
	}

	/*
	 * @see org.osgi.service.prefs.Preferences#getLong(java.lang.String, long)
	 */
	public long getLong(String key, long defaultValue) {
		String value = internalGet(key);
		long result = defaultValue;
		if (value != null)
			try {
				result = Long.parseLong(value);
			} catch (NumberFormatException e) {
				// use default
			}
		return result;
	}

	protected EclipsePreferences internalCreate(EclipsePreferences nodeParent, String nodeName, Object context) {
		return new EclipsePreferences(nodeParent, nodeName);
	}

	/**
	 * Returns the existing value at the given key, or null if
	 * no such value exists.
	 */
	protected String internalGet(String key) {
		// throw NPE if key is null
		if (key == null)
			throw new NullPointerException();
		// illegal state if this node has been removed
		checkRemoved();
		String result = properties.get(key);
		if (DEBUG_PREFERENCE_GET)
			PrefsMessages.message("Getting preference value: " + absolutePath() + '/' + key + "->" + result); //$NON-NLS-1$ //$NON-NLS-2$
		return result;
	}

	/**
	 * Implements the node(String) method, and optionally notifies listeners.
	 */
	protected IEclipsePreferences internalNode(String path, boolean notify, Object context) {

		// illegal state if this node has been removed
		checkRemoved();

		// short circuit this node
		if (path.length() == 0)
			return this;

		// if we have an absolute path use the root relative to 
		// this node instead of the global root
		// in case we have a different hierarchy. (e.g. export)
		if (path.charAt(0) == IPath.SEPARATOR)
			return (IEclipsePreferences) calculateRoot().node(path.substring(1));

		int index = path.indexOf(IPath.SEPARATOR);
		String key = index == -1 ? path : path.substring(0, index);
		boolean added = false;
		IEclipsePreferences child = getChild(key, context, true);
		if (child == null) {
			child = create(this, key, context);
			added = true;
		}
		// notify listeners if a child was added
		if (added && notify)
			fireNodeEvent(new NodeChangeEvent(this, child), true);
		return (IEclipsePreferences) child.node(index == -1 ? EMPTY_STRING : path.substring(index + 1));
	}

	/**
	 * Stores the given (key,value) pair, performing lazy initialization of the
	 * properties field if necessary. Returns the old value for the given key,
	 * or null if no value existed.
	 */
	protected String internalPut(String key, String newValue) {
		// illegal state if this node has been removed
		checkRemoved();
		String oldValue = properties.get(key);
		if (oldValue != null && oldValue.equals(newValue))
			return oldValue;
		if (DEBUG_PREFERENCE_SET)
			PrefsMessages.message("Setting preference: " + absolutePath() + '/' + key + '=' + newValue); //$NON-NLS-1$
		properties = properties.put(key, newValue);
		return oldValue;
	}

	/*
	 * Subclasses to over-ride.
	 */
	protected boolean isAlreadyLoaded(IEclipsePreferences node) {
		return true;
	}

	/*
	 * @see org.osgi.service.prefs.Preferences#keys()
	 */
	public String[] keys() {
		// illegal state if this node has been removed
		checkRemoved();
		return properties.keys();
	}

	/**
	 * Loads the preference node. This method returns silently if the node does not exist
	 * in the backing store (for example non-existent project).
	 * 
	 * @throws BackingStoreException if the node exists in the backing store but it
	 * could not be loaded
	 */
	protected void load() throws BackingStoreException {
		load(getLocation());
	}

	protected static Properties loadProperties(IPath location) throws BackingStoreException {
		if (DEBUG_PREFERENCE_GENERAL)
			PrefsMessages.message("Loading preferences from file: " + location); //$NON-NLS-1$
		InputStream input = null;
		Properties result = new Properties();
		try {
			input = new BufferedInputStream(new FileInputStream(location.toFile()));
			result.load(input);
		} catch (FileNotFoundException e) {
			// file doesn't exist but that's ok.
			if (DEBUG_PREFERENCE_GENERAL)
				PrefsMessages.message("Preference file does not exist: " + location); //$NON-NLS-1$
			return result;
		} catch (IOException e) {
			String message = NLS.bind(PrefsMessages.preferences_loadException, location);
			log(new Status(IStatus.INFO, PrefsMessages.OWNER_NAME, IStatus.INFO, message, e));
			throw new BackingStoreException(message);
		} finally {
			if (input != null)
				try {
					input.close();
				} catch (IOException e) {
					// ignore
				}
		}
		return result;
	}

	protected void load(IPath location) throws BackingStoreException {
		if (location == null) {
			if (DEBUG_PREFERENCE_GENERAL)
				PrefsMessages.message("Unable to determine location of preference file for node: " + absolutePath()); //$NON-NLS-1$
			return;
		}
		Properties fromDisk = loadProperties(location);
		convertFromProperties(this, fromDisk, false);
	}

	protected void loaded() {
		// do nothing
	}

	protected void loadLegacy() {
		// sub-classes to over-ride if necessary
	}

	public static void log(IStatus status) {
		RuntimeLog.log(status);
	}

	protected void makeDirty() {
		EclipsePreferences node = this;
		while (node != null && !node.removed) {
			node.dirty = true;
			node = (EclipsePreferences) node.parent();
		}
	}

	public boolean isDirty() {
		return dirty;
	}

	/*
	 * @see org.osgi.service.prefs.Preferences#name()
	 */
	public String name() {
		return name;
	}

	/*
	 * @see org.osgi.service.prefs.Preferences#node(java.lang.String)
	 */
	public Preferences node(String pathName) {
		return internalNode(pathName, true, null);
	}

	protected void fireNodeEvent(final NodeChangeEvent event, final boolean added) {
		if (nodeChangeListeners == null)
			return;
		Object[] listeners = nodeChangeListeners.getListeners();
		for (int i = 0; i < listeners.length; i++) {
			final INodeChangeListener listener = (INodeChangeListener) listeners[i];
			ISafeRunnable job = new ISafeRunnable() {
				public void handleException(Throwable exception) {
					// already logged in Platform#run()
				}

				public void run() throws Exception {
					if (added)
						listener.added(event);
					else
						listener.removed(event);
				}
			};
			SafeRunner.run(job);
		}
	}

	/*
	 * @see org.osgi.service.prefs.Preferences#nodeExists(java.lang.String)
	 */
	public boolean nodeExists(String path) throws BackingStoreException {
		// short circuit for checking this node
		if (path.length() == 0)
			return !removed;

		// illegal state if this node has been removed.
		// do this AFTER checking for the empty string.
		checkRemoved();

		// use the root relative to this node instead of the global root
		// in case we have a different hierarchy. (e.g. export)
		if (path.charAt(0) == IPath.SEPARATOR)
			return calculateRoot().nodeExists(path.substring(1));

		int index = path.indexOf(IPath.SEPARATOR);
		boolean noSlash = index == -1;

		// if we are looking for a simple child then just look in the table and return
		if (noSlash)
			return childExists(path);

		// otherwise load the parent of the child and then recursively ask
		String childName = path.substring(0, index);
		if (!childExists(childName))
			return false;
		IEclipsePreferences child = getChild(childName, null, true);
		if (child == null)
			return false;
		return child.nodeExists(path.substring(index + 1));
	}

	/*
	 * @see org.osgi.service.prefs.Preferences#parent()
	 */
	public Preferences parent() {
		// illegal state if this node has been removed
		checkRemoved();
		return parent;
	}

	/*
	 * Convenience method for notifying preference change listeners.
	 */
	protected void firePreferenceEvent(String key, Object oldValue, Object newValue) {
		if (preferenceChangeListeners == null)
			return;
		Object[] listeners = preferenceChangeListeners.getListeners();
		final PreferenceChangeEvent event = new PreferenceChangeEvent(this, key, oldValue, newValue);
		for (int i = 0; i < listeners.length; i++) {
			final IPreferenceChangeListener listener = (IPreferenceChangeListener) listeners[i];
			ISafeRunnable job = new ISafeRunnable() {
				public void handleException(Throwable exception) {
					// already logged in Platform#run()
				}

				public void run() throws Exception {
					listener.preferenceChange(event);
				}
			};
			SafeRunner.run(job);
		}
	}

	/*
	 * @see org.osgi.service.prefs.Preferences#put(java.lang.String, java.lang.String)
	 */
	public void put(String key, String newValue) {
		if (key == null || newValue == null)
			throw new NullPointerException();
		String oldValue = internalPut(key, newValue);
		if (!newValue.equals(oldValue)) {
			makeDirty();
			firePreferenceEvent(key, oldValue, newValue);
		}
	}

	/*
	 * @see org.osgi.service.prefs.Preferences#putBoolean(java.lang.String, boolean)
	 */
	public void putBoolean(String key, boolean value) {
		if (key == null)
			throw new NullPointerException();
		String newValue = value ? TRUE : FALSE;
		String oldValue = internalPut(key, newValue);
		if (!newValue.equals(oldValue)) {
			makeDirty();
			firePreferenceEvent(key, oldValue, newValue);
		}
	}

	/*
	 * @see org.osgi.service.prefs.Preferences#putByteArray(java.lang.String, byte[])
	 */
	public void putByteArray(String key, byte[] value) {
		if (key == null || value == null)
			throw new NullPointerException();
		String newValue = new String(Base64.encode(value));
		String oldValue = internalPut(key, newValue);
		if (!newValue.equals(oldValue)) {
			makeDirty();
			firePreferenceEvent(key, oldValue, newValue);
		}
	}

	/*
	 * @see org.osgi.service.prefs.Preferences#putDouble(java.lang.String, double)
	 */
	public void putDouble(String key, double value) {
		if (key == null)
			throw new NullPointerException();
		String newValue = Double.toString(value);
		String oldValue = internalPut(key, newValue);
		if (!newValue.equals(oldValue)) {
			makeDirty();
			firePreferenceEvent(key, oldValue, newValue);
		}
	}

	/*
	 * @see org.osgi.service.prefs.Preferences#putFloat(java.lang.String, float)
	 */
	public void putFloat(String key, float value) {
		if (key == null)
			throw new NullPointerException();
		String newValue = Float.toString(value);
		String oldValue = internalPut(key, newValue);
		if (!newValue.equals(oldValue)) {
			makeDirty();
			firePreferenceEvent(key, oldValue, newValue);
		}
	}

	/*
	 * @see org.osgi.service.prefs.Preferences#putInt(java.lang.String, int)
	 */
	public void putInt(String key, int value) {
		if (key == null)
			throw new NullPointerException();
		String newValue = Integer.toString(value);
		String oldValue = internalPut(key, newValue);
		if (!newValue.equals(oldValue)) {
			makeDirty();
			firePreferenceEvent(key, oldValue, newValue);
		}
	}

	/*
	 * @see org.osgi.service.prefs.Preferences#putLong(java.lang.String, long)
	 */
	public void putLong(String key, long value) {
		if (key == null)
			throw new NullPointerException();
		String newValue = Long.toString(value);
		String oldValue = internalPut(key, newValue);
		if (!newValue.equals(oldValue)) {
			makeDirty();
			firePreferenceEvent(key, oldValue, newValue);
		}
	}

	/*
	 * @see org.osgi.service.prefs.Preferences#remove(java.lang.String)
	 */
	public void remove(String key) {
		// illegal state if this node has been removed
		checkRemoved();
		String oldValue = properties.get(key);
		if (oldValue == null)
			return;
		properties = properties.removeKey(key);
		makeDirty();
		firePreferenceEvent(key, oldValue, null);
	}

	/*
	 * @see org.osgi.service.prefs.Preferences#removeNode()
	 */
	public void removeNode() throws BackingStoreException {
		// illegal state if this node has been removed
		checkRemoved();
		// clear all the property values. do it "the long way" so 
		// everyone gets notification
		String[] keys = keys();
		for (int i = 0; i < keys.length; i++)
			remove(keys[i]);
		// don't remove the global root or the scope root from the 
		// parent but remove all its children
		if (parent != null && !(parent instanceof RootPreferences)) {
			// remove the node from the parent's collection and notify listeners
			removed = true;
			parent.removeNode(this);
		}
		IEclipsePreferences[] childNodes = getChildren(false);
		for (int i = 0; i < childNodes.length; i++)
			try {
				childNodes[i].removeNode();
			} catch (IllegalStateException e) {
				// ignore since we only get this exception if we have already
				// been removed. no work to do.
			}
	}

	/*
	 * Remove the child from the collection and notify the listeners if something
	 * was actually removed.
	 */
	protected void removeNode(IEclipsePreferences child) {
		boolean wasRemoved = false;
		synchronized (this) {
			if (children != null) {
				wasRemoved = children.remove(child.name()) != null;
				if (wasRemoved)
					makeDirty();
				if (children.isEmpty())
					children = null;
			}
		}
		if (wasRemoved)
			fireNodeEvent(new NodeChangeEvent(this, child), false);
	}

	/*
	 * Remove non-initialized node from the collection.
	 */
	protected void removeNode(String key) {
		synchronized (this) {
			if (children != null) {
				boolean wasRemoved = children.remove(key) != null;
				if (wasRemoved)
					makeDirty();
				if (children.isEmpty())
					children = null;
			}
		}
	}

	/*
	 * @see org.eclipse.core.runtime.IEclipsePreferences#removeNodeChangeListener(org.eclipse.core.runtime.IEclipsePreferences.removeNodeChangeListener)
	 */
	public void removeNodeChangeListener(INodeChangeListener listener) {
		checkRemoved();
		if (nodeChangeListeners == null)
			return;
		nodeChangeListeners.remove(listener);
		if (nodeChangeListeners.size() == 0)
			nodeChangeListeners = null;
		if (DEBUG_PREFERENCE_GENERAL)
			PrefsMessages.message("Removed preference node change listener: " + listener + " from: " + absolutePath()); //$NON-NLS-1$ //$NON-NLS-2$
	}

	/*
	 * @see org.eclipse.core.runtime.IEclipsePreferences#removePreferenceChangeListener(org.eclipse.core.runtime.IEclipsePreferences.IPreferenceChangeListener)
	 */
	public void removePreferenceChangeListener(IPreferenceChangeListener listener) {
		checkRemoved();
		if (preferenceChangeListeners == null)
			return;
		preferenceChangeListeners.remove(listener);
		if (preferenceChangeListeners.size() == 0)
			preferenceChangeListeners = null;
		if (DEBUG_PREFERENCE_GENERAL)
			PrefsMessages.message("Removed preference property change listener: " + listener + " from: " + absolutePath()); //$NON-NLS-1$ //$NON-NLS-2$
	}

	/**
	 * Saves the preference node. This method returns silently if the node does not exist
	 * in the backing store (for example non-existent project)
	 * 
	 * @throws BackingStoreException if the node exists in the backing store but it
	 * could not be saved
	 */
	protected void save() throws BackingStoreException {
		save(getLocation());
	}

	protected void save(IPath location) throws BackingStoreException {
		if (location == null) {
			if (DEBUG_PREFERENCE_GENERAL)
				PrefsMessages.message("Unable to determine location of preference file for node: " + absolutePath()); //$NON-NLS-1$
			return;
		}
		if (DEBUG_PREFERENCE_GENERAL)
			PrefsMessages.message("Saving preferences to file: " + location); //$NON-NLS-1$
		Properties table = convertToProperties(new SortedProperties(), EMPTY_STRING);
		if (table.isEmpty()) {
			// nothing to save. delete existing file if one exists.
			if (location.toFile().exists() && !location.toFile().delete()) {
				String message = NLS.bind(PrefsMessages.preferences_failedDelete, location);
				log(new Status(IStatus.WARNING, PrefsMessages.OWNER_NAME, IStatus.WARNING, message, null));
			}
			return;
		}
		table.put(VERSION_KEY, VERSION_VALUE);
		write(table, location);
	}

	/**
	 * Traverses the preference hierarchy rooted at this node, and adds
	 * all preference key and value strings to the provided pool.  If an added
	 * string was already in the pool, all references will be replaced with the
	 * canonical copy of the string.
	 * 
	 * @param pool The pool to share strings in
	 */
	public void shareStrings(StringPool pool) {
		properties.shareStrings(pool);
		IEclipsePreferences[] myChildren = getChildren(false);
		for (int i = 0; i < myChildren.length; i++)
			if (myChildren[i] instanceof EclipsePreferences)
				((EclipsePreferences) myChildren[i]).shareStrings(pool);
	}

	/*
	 * Encode the given path and key combo to a form which is suitable for
	 * persisting or using when searching. If the key contains a slash character
	 * then we must use a double-slash to indicate the end of the 
	 * path/the beginning of the key.
	 */
	public static String encodePath(String path, String key) {
		String result;
		int pathLength = path == null ? 0 : path.length();
		if (key.indexOf(IPath.SEPARATOR) == -1) {
			if (pathLength == 0)
				result = key;
			else
				result = path + IPath.SEPARATOR + key;
		} else {
			if (pathLength == 0)
				result = DOUBLE_SLASH + key;
			else
				result = path + DOUBLE_SLASH + key;
		}
		return result;
	}

	/*
	 * Return the segment from the given path or null.
	 * "segment" parameter is 0-based.
	 */
	public static String getSegment(String path, int segment) {
		int start = path.indexOf(IPath.SEPARATOR) == 0 ? 1 : 0;
		int end = path.indexOf(IPath.SEPARATOR, start);
		if (end == path.length() - 1)
			end = -1;
		for (int i = 0; i < segment; i++) {
			if (end == -1)
				return null;
			start = end + 1;
			end = path.indexOf(IPath.SEPARATOR, start);
		}
		if (end == -1)
			end = path.length();
		return path.substring(start, end);
	}

	public static int getSegmentCount(String path) {
		StringTokenizer tokenizer = new StringTokenizer(path, String.valueOf(IPath.SEPARATOR));
		return tokenizer.countTokens();
	}

	/*
	 * Return a relative path
	 */
	public static String makeRelative(String path) {
		String result = path;
		if (path == null)
			return EMPTY_STRING;
		if (path.length() > 0 && path.charAt(0) == IPath.SEPARATOR)
			result = path.length() == 0 ? EMPTY_STRING : path.substring(1);
		return result;
	}

	/*
	 * Return a 2 element String array.
	 * 	element 0 - the path
	 * 	element 1 - the key
	 * The path may be null.
	 * The key is never null.
	 */
	public static String[] decodePath(String fullPath) {
		String key = null;
		String path = null;

		// check to see if we have an indicator which tells us where the path ends
		int index = fullPath.indexOf(DOUBLE_SLASH);
		if (index == -1) {
			// we don't have a double-slash telling us where the path ends 
			// so the path is up to the last slash character
			int lastIndex = fullPath.lastIndexOf(IPath.SEPARATOR);
			if (lastIndex == -1) {
				key = fullPath;
			} else {
				path = fullPath.substring(0, lastIndex);
				key = fullPath.substring(lastIndex + 1);
			}
		} else {
			// the child path is up to the double-slash and the key
			// is the string after it
			path = fullPath.substring(0, index);
			key = fullPath.substring(index + 2);
		}

		// adjust if we have an absolute path
		if (path != null)
			if (path.length() == 0)
				path = null;
			else if (path.charAt(0) == IPath.SEPARATOR)
				path = path.substring(1);

		return new String[] {path, key};
	}

	/*
	 * @see org.osgi.service.prefs.Preferences#sync()
	 */

	public void sync() throws BackingStoreException {
		// illegal state if this node has been removed
		checkRemoved();
		IEclipsePreferences node = getLoadLevel();
		if (node == null) {
			if (DEBUG_PREFERENCE_GENERAL)
				PrefsMessages.message("Preference node is not a load root: " + absolutePath()); //$NON-NLS-1$
			return;
		}
		if (node instanceof EclipsePreferences) {
			((EclipsePreferences) node).load();
			node.flush();
		}
	}

	public String toDeepDebugString() {
		final StringBuffer buffer = new StringBuffer();
		IPreferenceNodeVisitor visitor = new IPreferenceNodeVisitor() {
			public boolean visit(IEclipsePreferences node) throws BackingStoreException {
				buffer.append(node);
				buffer.append('\n');
				String[] keys = node.keys();
				for (int i = 0; i < keys.length; i++) {
					buffer.append(node.absolutePath());
					buffer.append(PATH_SEPARATOR);
					buffer.append(keys[i]);
					buffer.append('=');
					buffer.append(node.get(keys[i], "*default*")); //$NON-NLS-1$
					buffer.append('\n');
				}
				return true;
			}
		};
		try {
			accept(visitor);
		} catch (BackingStoreException e) {
			System.out.println("Exception while calling #toDeepDebugString()"); //$NON-NLS-1$
			e.printStackTrace();
		}
		return buffer.toString();
	}

	public String toString() {
		return absolutePath();
	}
}