org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/internal/AtomicObjectOutputStream.java

/*
 * Copyright (C) 2015, Matthias Sohn <matthias.sohn@sap.com> and others
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Distribution License v. 1.0 which is available at
 * https://www.eclipse.org/org/documents/edl-v10.php.
 *
 * SPDX-License-Identifier: BSD-3-Clause
 */
package org.eclipse.jgit.lfs.internal;

import java.io.IOException;
import java.io.OutputStream;
import java.nio.file.Path;
import java.security.DigestOutputStream;
import java.text.MessageFormat;

import org.eclipse.jgit.annotations.Nullable;
import org.eclipse.jgit.internal.storage.file.LockFile;
import org.eclipse.jgit.lfs.errors.CorruptLongObjectException;
import org.eclipse.jgit.lfs.lib.AnyLongObjectId;
import org.eclipse.jgit.lfs.lib.Constants;
import org.eclipse.jgit.lfs.lib.LongObjectId;

/**
 * Output stream writing content to a
 * {@link org.eclipse.jgit.internal.storage.file.LockFile} which is committed on
 * close(). The stream checks if the hash of the stream content matches the id.
 */
public class AtomicObjectOutputStream extends OutputStream {

	private LockFile locked;

	private DigestOutputStream out;

	private boolean aborted;

	private AnyLongObjectId id;

	/**
	 * Constructor for AtomicObjectOutputStream.
	 *
	 * @param path
	 *            a {@link java.nio.file.Path} object.
	 * @param id
	 *            a {@link org.eclipse.jgit.lfs.lib.AnyLongObjectId} object.
	 * @throws java.io.IOException
	 */
	public AtomicObjectOutputStream(Path path, AnyLongObjectId id)
			throws IOException {
		locked = new LockFile(path.toFile());
		locked.lock();
		this.id = id;
		out = new DigestOutputStream(locked.getOutputStream(),
				Constants.newMessageDigest());
	}

	/**
	 * Constructor for AtomicObjectOutputStream.
	 *
	 * @param path
	 *            a {@link java.nio.file.Path} object.
	 * @throws java.io.IOException
	 */
	public AtomicObjectOutputStream(Path path) throws IOException {
		this(path, null);
	}

	/**
	 * Get the <code>id</code>.
	 *
	 * @return content hash of the object which was streamed through this
	 *         stream. May return {@code null} if called before closing this
	 *         stream.
	 */
	@Nullable
	public AnyLongObjectId getId() {
		return id;
	}

	/** {@inheritDoc} */
	@Override
	public void write(int b) throws IOException {
		out.write(b);
	}

	/** {@inheritDoc} */
	@Override
	public void write(byte[] b) throws IOException {
		out.write(b);
	}

	/** {@inheritDoc} */
	@Override
	public void write(byte[] b, int off, int len) throws IOException {
		out.write(b, off, len);
	}

	/** {@inheritDoc} */
	@Override
	public void close() throws IOException {
		out.close();
		if (!aborted) {
			if (id != null) {
				verifyHash();
			} else {
				id = LongObjectId.fromRaw(out.getMessageDigest().digest());
			}
			locked.commit();
		}
	}

	private void verifyHash() {
		AnyLongObjectId contentHash = LongObjectId
				.fromRaw(out.getMessageDigest().digest());
		if (!contentHash.equals(id)) {
			abort();
			throw new CorruptLongObjectException(id, contentHash,
					MessageFormat.format(LfsText.get().corruptLongObject,
							contentHash, id));
		}
	}

	/**
	 * Aborts the stream. Temporary file will be deleted
	 */
	public void abort() {
		locked.unlock();
		aborted = true;
	}
}