DepthGenerator.java

/*
 * Copyright (C) 2010, Garmin International
 * Copyright (C) 2010, Matt Fischer <matt.fischer@garmin.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.revwalk;

import java.io.IOException;

import org.eclipse.jgit.errors.IncorrectObjectTypeException;
import org.eclipse.jgit.errors.MissingObjectException;
import org.eclipse.jgit.lib.ObjectId;

/**
 * Only produce commits which are below a specified depth.
 *
 * @see DepthWalk
 */
class DepthGenerator extends Generator {
    private final FIFORevQueue pending;

    private final int depth;

    private final int deepenSince;

    private final RevWalk walk;

    /**
     * Commits which used to be shallow in the client, but which are
     * being extended as part of this fetch.  These commits should be
     * returned to the caller as UNINTERESTING so that their blobs/trees
     * can be marked appropriately in the pack writer.
     */
    private final RevFlag UNSHALLOW;

    /**
     * Commits which the normal framework has marked as UNINTERESTING,
     * but which we now care about again.  This happens if a client is
     * extending a shallow checkout to become deeper--the new commits at
     * the bottom of the graph need to be sent, even though they are
     * below other commits which the client already has.
     */
    private final RevFlag REINTERESTING;

    /**
     * Commits reachable from commits that the client specified using --shallow-exclude.
     */
    private final RevFlag DEEPEN_NOT;

    /**
     * @param w
     * @param s Parent generator
     * @throws MissingObjectException
     * @throws IncorrectObjectTypeException
     * @throws IOException
     */
    DepthGenerator(DepthWalk w, Generator s) throws MissingObjectException,
            IncorrectObjectTypeException, IOException {
        super(s.firstParent);
        pending = new FIFORevQueue(firstParent);
        walk = (RevWalk)w;

        this.depth = w.getDepth();
        this.deepenSince = w.getDeepenSince();
        this.UNSHALLOW = w.getUnshallowFlag();
        this.REINTERESTING = w.getReinterestingFlag();
        this.DEEPEN_NOT = w.getDeepenNotFlag();

        s.shareFreeList(pending);

        // Begin by sucking out all of the source's commits, and
        // adding them to the pending queue
        FIFORevQueue unshallowCommits = new FIFORevQueue();
        for (;;) {
            RevCommit c = s.next();
            if (c == null)
                break;
            if (c.has(UNSHALLOW)) {
                unshallowCommits.add(c);
            } else if (((DepthWalk.Commit) c).getDepth() == 0) {
                pending.add(c);
            }
        }
        // Move unshallow commits to the front so that the REINTERESTING flag
        // carry over code is executed first.
        for (;;) {
            RevCommit c = unshallowCommits.next();
            if (c == null) {
                break;
            }
            pending.unpop(c);
        }

        // Mark DEEPEN_NOT on all deepen-not commits and their ancestors.
        // TODO(jonathantanmy): This implementation is somewhat
        // inefficient in that any "deepen-not <ref>" in the request
        // results in all commits reachable from that ref being parsed
        // and marked, even if the commit topology is such that it is
        // not necessary.
        for (ObjectId oid : w.getDeepenNots()) {
            RevCommit c;
            try {
                c = walk.parseCommit(oid);
            } catch (IncorrectObjectTypeException notCommit) {
                // The C Git implementation silently tolerates
                // non-commits, so do the same here.
                continue;
            }

            FIFORevQueue queue = new FIFORevQueue();
            queue.add(c);
            while ((c = queue.next()) != null) {
                if (c.has(DEEPEN_NOT)) {
                    continue;
                }

                walk.parseHeaders(c);
                c.add(DEEPEN_NOT);
                for (RevCommit p : c.getParents()) {
                    queue.add(p);
                }
            }
        }
    }

    @Override
    int outputType() {
        return pending.outputType() | HAS_UNINTERESTING;
    }

    @Override
    void shareFreeList(BlockRevQueue q) {
        pending.shareFreeList(q);
    }

    @Override
    RevCommit next() throws MissingObjectException,
            IncorrectObjectTypeException, IOException {
        // Perform a breadth-first descent into the commit graph,
        // marking depths as we go.  This means that if a commit is
        // reachable by more than one route, we are guaranteed to
        // arrive by the shortest route first.
        for (;;) {
            final DepthWalk.Commit c = (DepthWalk.Commit) pending.next();
            if (c == null)
                return null;

            if ((c.flags & RevWalk.PARSED) == 0)
                c.parseHeaders(walk);

            if (c.getCommitTime() < deepenSince) {
                continue;
            }

            if (c.has(DEEPEN_NOT)) {
                continue;
            }

            int newDepth = c.depth + 1;

            int n = c.getParentCount();
            for (int i = 0; i < n; i++) {
                if (firstParent && i > 0) {
                    break;
                }
                RevCommit p = c.getParent(i);
                DepthWalk.Commit dp = (DepthWalk.Commit) p;

                // If no depth has been assigned to this commit, assign
                // it now.  Since we arrive by the shortest route first,
                // this depth is guaranteed to be the smallest value that
                // any path could produce.
                if (dp.depth == -1) {
                    boolean failsDeepenSince = false;
                    if (deepenSince != 0) {
                        if ((p.flags & RevWalk.PARSED) == 0) {
                            p.parseHeaders(walk);
                        }
                        failsDeepenSince =
                            p.getCommitTime() < deepenSince;
                    }

                    dp.depth = newDepth;

                    // If the parent is not too deep and was not excluded, add
                    // it to the queue so that we can produce it later
                    if (newDepth <= depth && !failsDeepenSince &&
                            !p.has(DEEPEN_NOT)) {
                        pending.add(p);
                    } else {
                        dp.makesChildBoundary = true;
                    }
                }

                if (dp.makesChildBoundary) {
                    c.isBoundary = true;
                }

                // If the current commit has become unshallowed, everything
                // below us is new to the client.  Mark its parent as
                // re-interesting, and carry that flag downward to all
                // of its ancestors.
                if(c.has(UNSHALLOW) || c.has(REINTERESTING)) {
                    p.add(REINTERESTING);
                    p.flags &= ~RevWalk.UNINTERESTING;
                }
            }

            boolean produce = true;

            // Unshallow commits are uninteresting, but still need to be sent
            // up to the PackWriter so that it will exclude objects correctly.
            // All other uninteresting commits should be omitted.
            if ((c.flags & RevWalk.UNINTERESTING) != 0 && !c.has(UNSHALLOW))
                produce = false;

            if (c.getCommitTime() < deepenSince) {
                produce = false;
            }

            if (produce)
                return c;
        }
    }
}