Copyright (c) 2000, 2009 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
/*******************************************************************************
 * Copyright (c) 2000, 2009 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
 *******************************************************************************/
package org.eclipse.core.internal.registry;

import java.io.File;
import java.lang.ref.SoftReference;
import org.eclipse.core.runtime.IContributor;

An object which represents the user-defined extension point in a
plug-in manifest.
/**
 * An object which represents the user-defined extension point in a
 * plug-in manifest.
 */
public class ExtensionPoint extends RegistryObject {
	public static final ExtensionPoint[] EMPTY_ARRAY = new ExtensionPoint[0];

	//Place holder for the label and the schema. It contains either a String[] or a SoftReference to a String[].
	//The array layout is [label, schemaReference, fullyQualifiedName, namespace, contributorId]
	private Object extraInformation;
	//Indexes of the various fields
	private static final byte LABEL = 0; //The human readable name for the extension point
	private static final byte SCHEMA = 1; //The schema of the extension point
	private static final byte QUALIFIED_NAME = 2; //The fully qualified name of the extension point
	private static final byte NAMESPACE = 3; //The name of the namespace of the extension point
	private static final byte CONTRIBUTOR_ID = 4; //The ID of the actual contributor of the extension point
	private static final int EXTRA_SIZE = 5;

	protected ExtensionPoint(ExtensionRegistry registry, boolean persist) {
		super(registry, persist);
	}

	protected ExtensionPoint(int self, int[] children, int dataOffset, ExtensionRegistry registry, boolean persist) {
		super(registry, persist);

		setObjectId(self);
		setRawChildren(children);
		setExtraDataOffset(dataOffset);
	}

	protected String getSimpleIdentifier() {
		return getUniqueIdentifier().substring(getUniqueIdentifier().lastIndexOf('.') + 1);
	}

	private String[] getExtraData() {
		//The extension point has been created by parsing, or does not have any extra data
		if (noExtraData()) { //When this is true, the extraInformation is always a String[]. This happens when the object is created by the parser.
			if (extraInformation != null)
				return (String[]) extraInformation;
			return new String[EXTRA_SIZE];
		}

		//The extension point has been loaded from the cache.
		String[] result = null;
		if (extraInformation == null || (result = ((extraInformation instanceof SoftReference) ? (String[]) ((SoftReference<?>) extraInformation).get() : (String[]) extraInformation)) == null) {
			result = registry.getTableReader().loadExtensionPointExtraData(getExtraDataOffset());
			extraInformation = new SoftReference<>(result);
		}
		return result;
	}

	
At the end of this method, extra information will be a string[]
/**
	 * At the end of this method, extra information will be a string[]
	 */
	private void ensureExtraInformationType() {
		if (extraInformation instanceof SoftReference) {
			extraInformation = ((SoftReference<?>) extraInformation).get();
		}
		if (extraInformation == null) {
			extraInformation = new String[EXTRA_SIZE];
		}
	}

	protected String getSchemaReference() {
		String[] result = getExtraData();
		return result[1] == null ? "" : result[SCHEMA].replace(File.separatorChar, '/'); //$NON-NLS-1$
	}

	protected String getLabel() {
		String[] result = getExtraData();
		return result[0] == null ? "" : result[LABEL]; //$NON-NLS-1$
	}

	protected String getUniqueIdentifier() {
		return getExtraData()[QUALIFIED_NAME];
	}

	public String getNamespace() {
		return getExtraData()[NAMESPACE];
	}

	protected String getContributorId() {
		return getExtraData()[CONTRIBUTOR_ID];
	}

	public IContributor getContributor() {
		return registry.getObjectManager().getContributor(getContributorId());
	}

	void setSchema(String value) {
		ensureExtraInformationType();
		((String[]) extraInformation)[SCHEMA] = value;
	}

	void setLabel(String value) {
		ensureExtraInformationType();
		((String[]) extraInformation)[LABEL] = value;
	}

	void setUniqueIdentifier(String value) {
		ensureExtraInformationType();
		((String[]) extraInformation)[QUALIFIED_NAME] = value;
	}

	void setNamespace(String value) {
		ensureExtraInformationType();
		((String[]) extraInformation)[NAMESPACE] = value;
	}

	void setContributorId(String id) {
		ensureExtraInformationType();
		((String[]) extraInformation)[CONTRIBUTOR_ID] = id;
	}

	@Override
	public String toString() {
		return getUniqueIdentifier();
	}

	protected String getLabelAsIs() {
		String[] result = getExtraData();
		return result[0] == null ? "" : result[LABEL]; //$NON-NLS-1$
	}

	protected String getLabel(String locale) {
		registry.logMultiLangError();
		return getLabel();
	}

}