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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, 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
 *******************************************************************************/
package org.eclipse.core.internal.filesystem;

import java.net.URI;
import java.util.HashMap;
import org.eclipse.core.filesystem.*;
import org.eclipse.core.filesystem.provider.FileSystem;
import org.eclipse.core.runtime.*;
import org.eclipse.osgi.util.NLS;

/**
 * The class manages internal implementation of methods on EFS.
 * This includes maintaining a list of file system extensions.
 */
public class InternalFileSystemCore implements IRegistryChangeListener {
	private static final InternalFileSystemCore INSTANCE = new InternalFileSystemCore();

	/**
	 * A map (String -> (IConfigurationElement or IFileSystem)) mapping URI
	 * scheme to the file system for that scheme.  If the corresponding file
	 * system has never been accessed, then the map contains the configuration
	 * element for the extension.  Once the file system has been created, the
	 * map contains the IFileSystem instance for that scheme.
	 */
	private HashMap fileSystems;

	/**
	 * Returns the singleton instance of this class.
	 * @return The singleton instance.
	 */
	public static InternalFileSystemCore getInstance() {
		return INSTANCE;
	}

	/**
	 * This class has a singleton instance.
	 */
	private InternalFileSystemCore() {
		super();
		RegistryFactory.getRegistry().addRegistryChangeListener(this);
	}

	/**
	 * Implements the method {@link EFS#getFileSystem(String)}
	 *
	 * @param scheme The URI scheme of the file system
	 * @return The file system
	 * @throws CoreException on filesystem related errors
	 */
	public IFileSystem getFileSystem(String scheme) throws CoreException {
		if (scheme == null)
			throw new NullPointerException();
		final HashMap registry = getFileSystemRegistry();
		Object result = registry.get(scheme);
		if (result == null)
			Policy.error(EFS.ERROR_INTERNAL, NLS.bind(Messages.noFileSystem, scheme));
		if (result instanceof IFileSystem)
			return (IFileSystem) result;
		try {
			IConfigurationElement element = (IConfigurationElement) result;
			FileSystem fs = (FileSystem) element.createExecutableExtension("run"); //$NON-NLS-1$
			fs.initialize(scheme);
			//store the file system instance so we don't have to keep recreating it
			registry.put(scheme, fs);
			return fs;
		} catch (CoreException e) {
			//remove this invalid file system from the registry
			registry.remove(scheme);
			throw e;
		}
	}

	/**
	 * Implements the method {@link EFS#getLocalFileSystem()}
	 *
	 * @return The local file system
	 */
	public IFileSystem getLocalFileSystem() {
		try {
			return getFileSystem(EFS.SCHEME_FILE);
		} catch (CoreException e) {
			//the local file system is always present
			throw new Error(e);
		}
	}

	/**
	 * Implements the method {@link EFS#getStore(URI)}
	 *
	 * @param uri The URI of the store to retrieve
	 * @return The file store corresponding to the given URI
	 * @throws CoreException on filesystem related errors or missing URI scheme
	 */
	public IFileStore getStore(URI uri) throws CoreException {
		final String scheme = uri.getScheme();
		if (scheme == null)
			Policy.error(EFS.ERROR_INTERNAL, Messages.noScheme + uri);
		return getFileSystem(scheme).getStore(uri);
	}

	/**
	 * Returns the fully initialized file system registry
	 * @return The file system registry
	 */
	private synchronized HashMap getFileSystemRegistry() {
		if (fileSystems == null) {
			fileSystems = new HashMap<>();
			IExtensionPoint point = RegistryFactory.getRegistry().getExtensionPoint(EFS.PI_FILE_SYSTEM, EFS.PT_FILE_SYSTEMS);
			IExtension[] extensions = point.getExtensions();
			for (IExtension extension : extensions) {
				IConfigurationElement[] elements = extension.getConfigurationElements();
				for (IConfigurationElement element : elements) {
					if ("filesystem".equals(element.getName())) { //$NON-NLS-1$
						String scheme = element.getAttribute("scheme"); //$NON-NLS-1$
						if (scheme != null) {
							fileSystems.put(scheme, element);
						}
					}
				}
			}
		}
		return fileSystems;
	}

	@Override
	public void registryChanged(IRegistryChangeEvent event) {
		IExtensionDelta[] changes = event.getExtensionDeltas(EFS.PI_FILE_SYSTEM, EFS.PT_FILE_SYSTEMS);
		if (changes.length == 0)
			return;
		synchronized (this) {
			//let the registry be rebuilt lazily
			fileSystems = null;
		}
	}

	/**
	 * Implements {@link EFS#getNullFileSystem()}.
	 * @return The null file system
	 */
	public IFileSystem getNullFileSystem() {
		try {
			return getFileSystem(EFS.SCHEME_NULL);
		} catch (CoreException e) {
			//the local file system is always present
			throw new Error(e);
		}
	}
}