Reduce multi-level buffered streams in transport code

[jgit/MarioXXX.git] / org.eclipse.jgit / src / org / eclipse / jgit / transport / BundleWriter.java

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package org.eclipse.jgit.transport;

import java.io.IOException;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.Writer;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
import java.util.TreeMap;

import org.eclipse.jgit.lib.AnyObjectId;
import org.eclipse.jgit.lib.Constants;
import org.eclipse.jgit.lib.ObjectId;
import org.eclipse.jgit.lib.PackWriter;
import org.eclipse.jgit.lib.ProgressMonitor;
import org.eclipse.jgit.lib.Ref;
import org.eclipse.jgit.lib.Repository;
import org.eclipse.jgit.revwalk.RevCommit;

/**
 * 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 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 PackWriter packWriter;

        private final Map<String, ObjectId> include;

        private final Set<RevCommit> assume;

        /**
         * Create a writer for a bundle.
         *
         * @param repo
         *            repository where objects are stored.
         * @param monitor
         *            operations progress monitor.
         */
        public BundleWriter(final Repository repo, final ProgressMonitor monitor) {
                packWriter = new PackWriter(repo, monitor);
                include = new TreeMap<String, ObjectId>();
                assume = new HashSet<RevCommit>();
        }

        /**
         * 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(final String name, final AnyObjectId id) {
                if (!Repository.isValidRefName(name))
                        throw new IllegalArgumentException("Invalid ref name: " + name);
                if (include.containsKey(name))
                        throw new IllegalStateException("Duplicate ref: " + 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(final Ref r) {
                include(r.getName(), r.getObjectId());
        }

        /**
         * 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(final 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 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 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(OutputStream os) throws IOException {
                final HashSet<ObjectId> inc = new HashSet<ObjectId>();
                final HashSet<ObjectId> exc = new HashSet<ObjectId>();
                inc.addAll(include.values());
                for (final RevCommit r : assume)
                        exc.add(r.getId());
                packWriter.setThin(exc.size() > 0);
                packWriter.preparePack(inc, exc);

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

                final char[] tmp = new char[Constants.OBJECT_ID_STRING_LENGTH];
                for (final RevCommit a : assume) {
                        w.write('-');
                        a.copyTo(tmp, w);
                        if (a.getRawBuffer() != null) {
                                w.write(' ');
                                w.write(a.getShortMessage());
                        }
                        w.write('\n');
                }
                for (final 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(os);
        }
}