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;
    }
}