BundleWriter.java

/*
 * Copyright (C) 2008-2010, Google Inc. 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.transport;

import static java.nio.charset.StandardCharsets.UTF_8;

import java.io.IOException;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.Writer;
import java.text.MessageFormat;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.TreeMap;

import org.eclipse.jgit.internal.JGitText;
import org.eclipse.jgit.internal.storage.pack.CachedPack;
import org.eclipse.jgit.internal.storage.pack.PackWriter;
import org.eclipse.jgit.lib.AnyObjectId;
import org.eclipse.jgit.lib.Constants;
import org.eclipse.jgit.lib.ObjectId;
import org.eclipse.jgit.lib.ObjectReader;
import org.eclipse.jgit.lib.ProgressMonitor;
import org.eclipse.jgit.lib.Ref;
import org.eclipse.jgit.lib.Repository;
import org.eclipse.jgit.revwalk.RevCommit;
import org.eclipse.jgit.storage.pack.PackConfig;

/**
 * Creates a Git bundle file, for sneaker-net transport to another system.
 * <p>
 * Bundles generated by this class can be later read in from a file URI using
 * the bundle transport, or from an application controlled buffer by the more
 * generic {@link org.eclipse.jgit.transport.TransportBundleStream}.
 * <p>
 * Applications creating bundles need to call one or more <code>include</code>
 * calls to reflect which objects should be available as refs in the bundle for
 * the other side to fetch. At least one include is required to create a valid
 * bundle file, and duplicate names are not permitted.
 * <p>
 * Optional <code>assume</code> calls can be made to declare commits which the
 * recipient must have in order to fetch from the bundle file. Objects reachable
 * from these assumed commits can be used as delta bases in order to reduce the
 * overall bundle size.
 */
public class BundleWriter {
    private final Repository db;

    private final ObjectReader reader;

    private final Map<String, ObjectId> include;

    private final Set<RevCommit> assume;

    private final Set<ObjectId> tagTargets;

    private final List<CachedPack> cachedPacks = new ArrayList<>();

    private PackConfig packConfig;

    private ObjectCountCallback callback;

    /**
     * Create a writer for a bundle.
     *
     * @param repo
     *            repository where objects are stored.
     */
    public BundleWriter(Repository repo) {
        db = repo;
        reader = null;
        include = new TreeMap<>();
        assume = new HashSet<>();
        tagTargets = new HashSet<>();
    }

    /**
     * Create a writer for a bundle.
     *
     * @param or
     *            reader for reading objects. Will be closed at the end of {@link
     *            #writeBundle(ProgressMonitor, OutputStream)}, but readers may be
     *            reused after closing.
     * @since 4.8
     */
    public BundleWriter(ObjectReader or) {
        db = null;
        reader = or;
        include = new TreeMap<>();
        assume = new HashSet<>();
        tagTargets = new HashSet<>();
    }

    /**
     * Set the configuration used by the pack generator.
     *
     * @param pc
     *            configuration controlling packing parameters. If null the
     *            source repository's settings will be used, or the default
     *            settings if constructed without a repo.
     */
    public void setPackConfig(PackConfig pc) {
        this.packConfig = pc;
    }

    /**
     * Include an object (and everything reachable from it) in the bundle.
     *
     * @param name
     *            name the recipient can discover this object as from the
     *            bundle's list of advertised refs . The name must be a valid
     *            ref format and must not have already been included in this
     *            bundle writer.
     * @param id
     *            object to pack. Multiple refs may point to the same object.
     */
    public void include(String name, AnyObjectId id) {
        boolean validRefName = Repository.isValidRefName(name) || Constants.HEAD.equals(name);
        if (!validRefName)
            throw new IllegalArgumentException(MessageFormat.format(JGitText.get().invalidRefName, name));
        if (include.containsKey(name))
            throw new IllegalStateException(JGitText.get().duplicateRef + name);
        include.put(name, id.toObjectId());
    }

    /**
     * Include a single ref (a name/object pair) in the bundle.
     * <p>
     * This is a utility function for:
     * <code>include(r.getName(), r.getObjectId())</code>.
     *
     * @param r
     *            the ref to include.
     */
    public void include(Ref r) {
        include(r.getName(), r.getObjectId());

        if (r.getPeeledObjectId() != null)
            tagTargets.add(r.getPeeledObjectId());

        else if (r.getObjectId() != null
                && r.getName().startsWith(Constants.R_HEADS))
            tagTargets.add(r.getObjectId());
    }

    /**
     * Add objects to the bundle file.
     *
     * <p>
     * When this method is used, object traversal is disabled and specified pack
     * files are directly saved to the Git bundle file.
     *
     * <p>
     * Unlike {@link #include}, this doesn't affect the refs. Even if the
     * objects are not reachable from any ref, they will be included in the
     * bundle file.
     *
     * @param c
     *            pack to include
     * @since 5.9
     */
    public void addObjectsAsIs(Collection<? extends CachedPack> c) {
        cachedPacks.addAll(c);
    }

    /**
     * Assume a commit is available on the recipient's side.
     * <p>
     * In order to fetch from a bundle the recipient must have any assumed
     * commit. Each assumed commit is explicitly recorded in the bundle header
     * to permit the recipient to validate it has these objects.
     *
     * @param c
     *            the commit to assume being available. This commit should be
     *            parsed and not disposed in order to maximize the amount of
     *            debugging information available in the bundle stream.
     */
    public void assume(RevCommit c) {
        if (c != null)
            assume.add(c);
    }

    /**
     * Generate and write the bundle to the output stream.
     * <p>
     * This method can only be called once per BundleWriter instance.
     *
     * @param monitor
     *            progress monitor to report bundle writing status to.
     * @param os
     *            the stream the bundle is written to. The stream should be
     *            buffered by the caller. The caller is responsible for closing
     *            the stream.
     * @throws java.io.IOException
     *             an error occurred reading a local object's data to include in
     *             the bundle, or writing compressed object data to the output
     *             stream.
     */
    public void writeBundle(ProgressMonitor monitor, OutputStream os)
            throws IOException {
        try (PackWriter packWriter = newPackWriter()) {
            packWriter.setObjectCountCallback(callback);

            packWriter.setIndexDisabled(true);
            packWriter.setDeltaBaseAsOffset(true);
            packWriter.setReuseValidatingObjects(false);
            if (cachedPacks.isEmpty()) {
                HashSet<ObjectId> inc = new HashSet<>();
                HashSet<ObjectId> exc = new HashSet<>();
                inc.addAll(include.values());
                for (RevCommit r : assume) {
                    exc.add(r.getId());
                }
                if (exc.isEmpty()) {
                    packWriter.setTagTargets(tagTargets);
                }
                packWriter.setThin(!exc.isEmpty());
                packWriter.preparePack(monitor, inc, exc);
            } else {
                packWriter.preparePack(cachedPacks);
            }

            final Writer w = new OutputStreamWriter(os, UTF_8);
            w.write(TransportBundle.V2_BUNDLE_SIGNATURE);
            w.write('\n');

            final char[] tmp = new char[Constants.OBJECT_ID_STRING_LENGTH];
            for (RevCommit a : assume) {
                w.write('-');
                a.copyTo(tmp, w);
                if (a.getRawBuffer() != null) {
                    w.write(' ');
                    w.write(a.getShortMessage());
                }
                w.write('\n');
            }
            for (Map.Entry<String, ObjectId> e : include.entrySet()) {
                e.getValue().copyTo(tmp, w);
                w.write(' ');
                w.write(e.getKey());
                w.write('\n');
            }

            w.write('\n');
            w.flush();
            packWriter.writePack(monitor, monitor, os);
        }
    }

    private PackWriter newPackWriter() {
        PackConfig pc = packConfig;
        if (pc == null) {
            pc = db != null ? new PackConfig(db) : new PackConfig();
        }
        return new PackWriter(pc, reader != null ? reader : db.newObjectReader());
    }

    /**
     * Set the {@link org.eclipse.jgit.transport.ObjectCountCallback}.
     * <p>
     * It should be set before calling
     * {@link #writeBundle(ProgressMonitor, OutputStream)}.
     * <p>
     * This callback will be passed on to
     * {@link org.eclipse.jgit.internal.storage.pack.PackWriter#setObjectCountCallback}.
     *
     * @param callback
     *            the callback to set
     * @return this object for chaining.
     * @since 4.1
     */
    public BundleWriter setObjectCountCallback(ObjectCountCallback callback) {
        this.callback = callback;
        return this;
    }
}