EmptyTreeIterator.java

/*
 * Copyright (C) 2008-2009, Google Inc.
 * Copyright (C) 2007, Robin Rosenberg <robin.rosenberg@dewire.com>
 * Copyright (C) 2008, 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.treewalk;

import java.io.IOException;

import org.eclipse.jgit.errors.CorruptObjectException;
import org.eclipse.jgit.errors.IncorrectObjectTypeException;
import org.eclipse.jgit.lib.ObjectId;
import org.eclipse.jgit.lib.ObjectReader;

/**
 * Iterator over an empty tree (a directory with no files).
 */
public class EmptyTreeIterator extends AbstractTreeIterator {
    /**
     * Create a new iterator with no parent.
     */
    public EmptyTreeIterator() {
        // Create a root empty tree.
    }

    EmptyTreeIterator(AbstractTreeIterator p) {
        super(p);
        pathLen = pathOffset;
    }

    /**
     * Create an iterator for a subtree of an existing iterator.
     * <p>
     * The caller is responsible for setting up the path of the child iterator.
     *
     * @param p
     *            parent tree iterator.
     * @param childPath
     *            path array to be used by the child iterator. This path must
     *            contain the path from the top of the walk to the first child
     *            and must end with a '/'.
     * @param childPathOffset
     *            position within <code>childPath</code> where the child can
     *            insert its data. The value at
     *            <code>childPath[childPathOffset-1]</code> must be '/'.
     */
    public EmptyTreeIterator(final AbstractTreeIterator p,
            final byte[] childPath, final int childPathOffset) {
        super(p, childPath, childPathOffset);
        pathLen = childPathOffset - 1;
    }

    /** {@inheritDoc} */
    @Override
    public AbstractTreeIterator createSubtreeIterator(ObjectReader reader)
            throws IncorrectObjectTypeException, IOException {
        return new EmptyTreeIterator(this);
    }

    /** {@inheritDoc} */
    @Override
    public boolean hasId() {
        return false;
    }

    /** {@inheritDoc} */
    @Override
    public ObjectId getEntryObjectId() {
        return ObjectId.zeroId();
    }

    /** {@inheritDoc} */
    @Override
    public byte[] idBuffer() {
        return zeroid;
    }

    /** {@inheritDoc} */
    @Override
    public int idOffset() {
        return 0;
    }

    /** {@inheritDoc} */
    @Override
    public void reset() {
        // Do nothing.
    }

    /** {@inheritDoc} */
    @Override
    public boolean first() {
        return true;
    }

    /** {@inheritDoc} */
    @Override
    public boolean eof() {
        return true;
    }

    /** {@inheritDoc} */
    @Override
    public void next(int delta) throws CorruptObjectException {
        // Do nothing.
    }

    /** {@inheritDoc} */
    @Override
    public void back(int delta) throws CorruptObjectException {
        // Do nothing.
    }

    /** {@inheritDoc} */
    @Override
    public void stopWalk() {
        if (parent != null)
            parent.stopWalk();
    }

    /** {@inheritDoc} */
    @Override
    protected boolean needsStopWalk() {
        return parent != null && parent.needsStopWalk();
    }
}