PedestrianReachabilityChecker.java

/*
 * Copyright (C) 2019, Google LLC. 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.internal.revwalk;

import java.io.IOException;
import java.util.Collection;
import java.util.Iterator;
import java.util.Optional;
import java.util.stream.Stream;

import org.eclipse.jgit.errors.IncorrectObjectTypeException;
import org.eclipse.jgit.errors.MissingObjectException;
import org.eclipse.jgit.revwalk.ReachabilityChecker;
import org.eclipse.jgit.revwalk.RevCommit;
import org.eclipse.jgit.revwalk.RevSort;
import org.eclipse.jgit.revwalk.RevWalk;

/**
 * Checks the reachability walking the graph from the starters towards the
 * target.
 */
public class PedestrianReachabilityChecker implements ReachabilityChecker {

    private final boolean topoSort;

    private final RevWalk walk;

    /**
     * New instance of the reachability checker using a existing walk.
     *
     * @param topoSort
     *            walk commits in topological order
     * @param walk
     *            RevWalk instance to reuse. Caller retains ownership.
     */
    public PedestrianReachabilityChecker(boolean topoSort,
            RevWalk walk) {
        this.topoSort = topoSort;
        this.walk = walk;
    }

    @Override
    public Optional<RevCommit> areAllReachable(Collection<RevCommit> targets,
            Stream<RevCommit> starters)
                    throws MissingObjectException, IncorrectObjectTypeException,
                    IOException {
        walk.reset();
        if (topoSort) {
            walk.sort(RevSort.TOPO);
        }

        for (RevCommit target: targets) {
            walk.markStart(target);
        }

        Iterator<RevCommit> iterator = starters.iterator();
        while (iterator.hasNext()) {
            walk.markUninteresting(iterator.next());
        }

        return Optional.ofNullable(walk.next());
    }
}