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AspectJ tools most notably contains the AspectJ compiler (AJC). AJC applies aspects to Java classes during compilation, fully replacing Javac for plain Java classes and also compiling native AspectJ or annotation-based @AspectJ syntax. Furthermore, AJC can weave aspects into existing class files in a post-compile binary weaving step. This library is a superset of AspectJ weaver and hence also of AspectJ runtime.
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/*******************************************************************************
 * Copyright (c) 2005 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.content;

import java.io.*;
import java.lang.ref.SoftReference;
import org.eclipse.core.runtime.CoreException;
import org.eclipse.core.runtime.QualifiedName;
import org.eclipse.core.runtime.content.*;
import org.eclipse.core.runtime.preferences.IScopeContext;

/**
 * The only content types exposed to clients. Allows the content type registry to change
 * underneath preserving handlers kept by clients.
 */
public class ContentTypeHandler implements IContentType {

	/**
	 * A dummy description object to be returned by getDescription when this
	 * handler's target cannot be determined.
	 */
	private class DummyContentDescription implements IContentDescription {
		@Override
		public String getCharset() {
			return null;
		}

		@Override
		public IContentType getContentType() {
			return ContentTypeHandler.this;
		}

		@Override
		public Object getProperty(QualifiedName key) {
			return null;
		}

		@Override
		public boolean isRequested(QualifiedName key) {
			return false;
		}

		@Override
		public void setProperty(QualifiedName key, Object value) {
			// don't do anything
		}
	}

	private int generation;
	String id;
	private SoftReference targetRef;

	ContentTypeHandler(ContentType target, int generation) {
		this.id = target.getId();
		this.targetRef = new SoftReference<>(target);
		this.generation = generation;
	}

	@Override
	public void addFileSpec(String fileSpec, int type) throws CoreException {
		final IContentType target = getTarget();
		if (target != null)
			target.addFileSpec(fileSpec, type);
	}

	@Override
	public boolean equals(Object another) {
		if (another instanceof ContentType)
			return id.equals(((ContentType) another).id);
		if (another instanceof ContentTypeHandler)
			return id.equals(((ContentTypeHandler) another).id);
		return false;
	}

	@Override
	public IContentType getBaseType() {
		final ContentType target = getTarget();
		if (target == null)
			return null;
		final ContentType baseType = (ContentType) target.getBaseType();
		return (baseType != null) ? new ContentTypeHandler(baseType, baseType.getCatalog().getGeneration()) : null;
	}

	@Override
	public String getDefaultCharset() {
		final IContentType target = getTarget();
		return (target != null) ? target.getDefaultCharset() : null;
	}

	@Override
	public IContentDescription getDefaultDescription() {
		final IContentType target = getTarget();
		return (target != null) ? target.getDefaultDescription() : new DummyContentDescription();
	}

	@Override
	public IContentDescription getDescriptionFor(InputStream contents, QualifiedName[] options) throws IOException {
		final IContentType target = getTarget();
		return (target != null) ? target.getDescriptionFor(contents, options) : null;
	}

	@Override
	public IContentDescription getDescriptionFor(Reader contents, QualifiedName[] options) throws IOException {
		final IContentType target = getTarget();
		return (target != null) ? target.getDescriptionFor(contents, options) : null;
	}

	@Override
	public String[] getFileSpecs(int type) {
		final IContentType target = getTarget();
		return (target != null) ? target.getFileSpecs(type) : new String[0];
	}

	@Override
	public String getId() {
		return id;
	}

	@Override
	public String getName() {
		final IContentType target = getTarget();
		return (target != null) ? target.getName() : id;
	}

	@Override
	public IContentTypeSettings getSettings(IScopeContext context) throws CoreException {
		final ContentType target = getTarget();
		if (target == null)
			return null;
		// the content type may returned itself as the settings object (instance scope context)
		final IContentTypeSettings settings = target.getSettings(context);
		// in that case, return this same handler; otherwise, just return the settings
		return settings == target ? this : settings;
	}

	/**
	 * Returns the content type this handler represents.
	 * Note that this handles the case of aliasing.
	 *
	 * Public for testing purposes only.
	 */
	public ContentType getTarget() {
		ContentType target = targetRef.get();
		ContentTypeCatalog catalog = ContentTypeManager.getInstance().getCatalog();
		if (target == null || catalog.getGeneration() != generation) {
			target = catalog.getContentType(id);
			targetRef = new SoftReference<>(target);
			generation = catalog.getGeneration();
		}
		return target == null ? null : target.getAliasTarget(true);
	}

	@Override
	public int hashCode() {
		return id.hashCode();
	}

	@Override
	public boolean isAssociatedWith(String fileName) {
		final IContentType target = getTarget();
		return (target != null) ? target.isAssociatedWith(fileName) : false;
	}

	@Override
	public boolean isAssociatedWith(String fileName, IScopeContext context) {
		final IContentType target = getTarget();
		return (target != null) ? target.isAssociatedWith(fileName, context) : false;
	}

	@Override
	public boolean isKindOf(IContentType another) {
		if (another instanceof ContentTypeHandler)
			another = ((ContentTypeHandler) another).getTarget();
		final IContentType target = getTarget();
		return (target != null) ? target.isKindOf(another) : false;
	}

	@Override
	public void removeFileSpec(String fileSpec, int type) throws CoreException {
		final IContentType target = getTarget();
		if (target != null)
			target.removeFileSpec(fileSpec, type);
	}

	@Override
	public void setDefaultCharset(String userCharset) throws CoreException {
		final IContentType target = getTarget();
		if (target != null)
			target.setDefaultCharset(userCharset);
	}

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

	@Override
	public boolean isUserDefined() {
		ContentType target = getTarget();
		if (target != null) {
			return target.isUserDefined();
		}
		return false;
	}

}