PlotCommit.java

/*
 * Copyright (C) 2008, 2014 Shawn O. Pearce <spearce@spearce.org> 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.revplot;

import org.eclipse.jgit.lib.AnyObjectId;
import org.eclipse.jgit.lib.Ref;
import org.eclipse.jgit.revwalk.RevCommit;

/**
 * A commit reference to a commit in the DAG.
 *
 * @param <L>
 *            type of lane being used by the plotter.
 * @see PlotCommitList
 */
public class PlotCommit<L extends PlotLane> extends RevCommit {
    static final PlotCommit[] NO_CHILDREN = {};

    static final PlotLane[] NO_LANES = {};

    static final Ref[] NO_REFS = {};

    PlotLane[] forkingOffLanes;

    PlotLane[] passingLanes;

    PlotLane[] mergingLanes;

    PlotLane lane;

    PlotCommit[] children;

    Ref[] refs;

    /**
     * Create a new commit.
     *
     * @param id
     *            the identity of this commit.
     */
    protected PlotCommit(AnyObjectId id) {
        super(id);
        forkingOffLanes = NO_LANES;
        passingLanes = NO_LANES;
        mergingLanes = NO_LANES;
        children = NO_CHILDREN;
        refs = NO_REFS;
    }

    void addForkingOffLane(PlotLane f) {
        forkingOffLanes = addLane(f, forkingOffLanes);
    }

    void addPassingLane(PlotLane c) {
        passingLanes = addLane(c, passingLanes);
    }

    void addMergingLane(PlotLane m) {
        mergingLanes = addLane(m, mergingLanes);
    }

    private static PlotLane[] addLane(PlotLane l, PlotLane[] lanes) {
        final int cnt = lanes.length;
        switch (cnt) {
        case 0:
            lanes = new PlotLane[] { l };
            break;
        case 1:
            lanes = new PlotLane[] { lanes[0], l };
            break;
        default:
            final PlotLane[] n = new PlotLane[cnt + 1];
            System.arraycopy(lanes, 0, n, 0, cnt);
            n[cnt] = l;
            lanes = n;
            break;
        }
        return lanes;
    }

    void addChild(PlotCommit c) {
        final int cnt = children.length;
        switch (cnt) {
        case 0:
            children = new PlotCommit[] { c };
            break;
        case 1:
            if (!c.getId().equals(children[0].getId()))
                children = new PlotCommit[] { children[0], c };
            break;
        default:
            for (PlotCommit pc : children)
                if (c.getId().equals(pc.getId()))
                    return;
            final PlotCommit[] n = new PlotCommit[cnt + 1];
            System.arraycopy(children, 0, n, 0, cnt);
            n[cnt] = c;
            children = n;
            break;
        }
    }

    /**
     * Get the number of child commits listed in this commit.
     *
     * @return number of children; always a positive value but can be 0.
     */
    public final int getChildCount() {
        return children.length;
    }

    /**
     * Get the nth child from this commit's child list.
     *
     * @param nth
     *            child index to obtain. Must be in the range 0 through
     *            {@link #getChildCount()}-1.
     * @return the specified child.
     * @throws java.lang.ArrayIndexOutOfBoundsException
     *             an invalid child index was specified.
     */
    public final PlotCommit getChild(int nth) {
        return children[nth];
    }

    /**
     * Determine if the given commit is a child (descendant) of this commit.
     *
     * @param c
     *            the commit to test.
     * @return true if the given commit built on top of this commit.
     */
    @SuppressWarnings("ReferenceEquality")
    public final boolean isChild(PlotCommit c) {
        for (PlotCommit a : children)
            if (a == c)
                return true;
        return false;
    }

    /**
     * Get the number of refs for this commit.
     *
     * @return number of refs; always a positive value but can be 0.
     */
    public final int getRefCount() {
        return refs.length;
    }

    /**
     * Get the nth Ref from this commit's ref list.
     *
     * @param nth
     *            ref index to obtain. Must be in the range 0 through
     *            {@link #getRefCount()}-1.
     * @return the specified ref.
     * @throws java.lang.ArrayIndexOutOfBoundsException
     *             an invalid ref index was specified.
     */
    public final Ref getRef(int nth) {
        return refs[nth];
    }

    /**
     * Obtain the lane this commit has been plotted into.
     *
     * @return the assigned lane for this commit.
     */
    @SuppressWarnings("unchecked")
    public final L getLane() {
        return (L) lane;
    }

    /** {@inheritDoc} */
    @Override
    public void reset() {
        forkingOffLanes = NO_LANES;
        passingLanes = NO_LANES;
        mergingLanes = NO_LANES;
        children = NO_CHILDREN;
        lane = null;
        super.reset();
    }
}