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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) 2000, 2014 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
 *     James Blackburn (Broadcom Corp.) - ongoing development
 *******************************************************************************/
package org.eclipse.core.internal.localstore;

import java.io.*;
import java.nio.file.Files;
import java.nio.file.StandardCopyOption;

/**
 * This class should be used when there's a file already in the
 * destination and we don't want to lose its contents if a
 * failure writing this stream happens.
 * Basically, the new contents are written to a temporary location.
 * If everything goes OK, it is moved to the right place.
 */
public class SafeFileOutputStream extends OutputStream {
	protected File temp;
	protected File target;
	protected OutputStream output;
	protected boolean failed;
	protected static final String EXTENSION = ".bak"; //$NON-NLS-1$

	/**
	 * Creates an output stream on a file at the given location
	 * @param file The file to be written to
	 */
	public SafeFileOutputStream(File file) throws IOException {
		this(file.getAbsolutePath(), null);
	}

	/**
	 * Creates an output stream on a file at the given location
	 * @param targetPath The file to be written to
	 * @param tempPath The temporary location to use, or null to
	 * use the same location as the target path but with a different extension.
	 */
	public SafeFileOutputStream(String targetPath, String tempPath) throws IOException {
		failed = false;
		target = new File(targetPath);
		createTempFile(tempPath);
		if (!target.exists()) {
			if (!temp.exists()) {
				output = new BufferedOutputStream(new FileOutputStream(target));
				return;
			}
			// If we do not have a file at target location, but we do have at temp location,
			// it probably means something wrong happened the last time we tried to write it.
			// So, try to recover the backup file. And, if successful, write the new one.
			Files.copy(temp.toPath(), target.toPath());
		}
		output = new BufferedOutputStream(new FileOutputStream(temp));
	}

	@Override
	public void close() throws IOException {
		try {
			output.close();
		} catch (IOException e) {
			failed = true;
			throw e; // rethrow
		}
		if (failed)
			temp.delete();
		else
			commit();
	}

	protected void commit() throws IOException {
		if (!temp.exists())
			return;
		Files.copy(temp.toPath(), target.toPath(), StandardCopyOption.REPLACE_EXISTING);
		temp.delete();
	}

	protected void createTempFile(String tempPath) {
		if (tempPath == null)
			tempPath = target.getAbsolutePath() + EXTENSION;
		temp = new File(tempPath);
	}

	@Override
	public void flush() throws IOException {
		try {
			output.flush();
		} catch (IOException e) {
			failed = true;
			throw e; // rethrow
		}
	}

	public String getTempFilePath() {
		return temp.getAbsolutePath();
	}

	@Override
	public void write(int b) throws IOException {
		try {
			output.write(b);
		} catch (IOException e) {
			failed = true;
			throw e; // rethrow
		}
	}
}