org.eclipse.jgit/src/org/eclipse/jgit/treewalk/EmptyTreeIterator.java

   1 /*
   2  * Copyright (C) 2008-2009, Google Inc.
   3  * Copyright (C) 2007, Robin Rosenberg <robin.rosenberg@dewire.com>
   4  * Copyright (C) 2008, Shawn O. Pearce <spearce@spearce.org>
   5  * and other copyright owners as documented in the project's IP log.
   6  *
   7  * This program and the accompanying materials are made available
   8  * under the terms of the Eclipse Distribution License v1.0 which
   9  * accompanies this distribution, is reproduced below, and is
  10  * available at http://www.eclipse.org/org/documents/edl-v10.php
  11  *
  12  * All rights reserved.
  13  *
  14  * Redistribution and use in source and binary forms, with or
  15  * without modification, are permitted provided that the following
  16  * conditions are met:
  17  *
  18  * - Redistributions of source code must retain the above copyright
  19  *   notice, this list of conditions and the following disclaimer.
  20  *
  21  * - Redistributions in binary form must reproduce the above
  22  *   copyright notice, this list of conditions and the following
  23  *   disclaimer in the documentation and/or other materials provided
  24  *   with the distribution.
  25  *
  26  * - Neither the name of the Eclipse Foundation, Inc. nor the
  27  *   names of its contributors may be used to endorse or promote
  28  *   products derived from this software without specific prior
  29  *   written permission.
  30  *
  31  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
  32  * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
  33  * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  34  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  35  * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
  36  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  37  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  38  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  39  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  40  * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  41  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  42  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
  43  * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  44  */
  45
  46 package org.eclipse.jgit.treewalk;
  47
  48 import java.io.IOException;
  49
  50 import org.eclipse.jgit.errors.CorruptObjectException;
  51 import org.eclipse.jgit.errors.IncorrectObjectTypeException;
  52 import org.eclipse.jgit.lib.ObjectId;
  53 import org.eclipse.jgit.lib.ObjectReader;
  54
  55 /** Iterator over an empty tree (a directory with no files). */
  56 public class EmptyTreeIterator extends AbstractTreeIterator {
  57         /** Create a new iterator with no parent. */
  58         public EmptyTreeIterator() {
  59                 // Create a root empty tree.
  60         }
  61
  62         EmptyTreeIterator(final AbstractTreeIterator p) {
  63                 super(p);
  64                 pathLen = pathOffset;
  65         }
  66
  67         /**
  68          * Create an iterator for a subtree of an existing iterator.
  69          * <p>
  70          * The caller is responsible for setting up the path of the child iterator.
  71          *
  72          * @param p
  73          *            parent tree iterator.
  74          * @param childPath
  75          *            path array to be used by the child iterator. This path must
  76          *            contain the path from the top of the walk to the first child
  77          *            and must end with a '/'.
  78          * @param childPathOffset
  79          *            position within <code>childPath</code> where the child can
  80          *            insert its data. The value at
  81          *            <code>childPath[childPathOffset-1]</code> must be '/'.
  82          */
  83         public EmptyTreeIterator(final AbstractTreeIterator p,
  84                         final byte[] childPath, final int childPathOffset) {
  85                 super(p, childPath, childPathOffset);
  86                 pathLen = childPathOffset - 1;
  87         }
  88
  89         @Override
  90         public AbstractTreeIterator createSubtreeIterator(final ObjectReader reader)
  91                         throws IncorrectObjectTypeException, IOException {
  92                 return new EmptyTreeIterator(this);
  93         }
  94
  95         @Override
  96         public ObjectId getEntryObjectId() {
  97                 return ObjectId.zeroId();
  98         }
  99
 100         @Override
 101         public byte[] idBuffer() {
 102                 return zeroid;
 103         }
 104
 105         @Override
 106         public int idOffset() {
 107                 return 0;
 108         }
 109
 110         @Override
 111         public boolean first() {
 112                 return true;
 113         }
 114
 115         @Override
 116         public boolean eof() {
 117                 return true;
 118         }
 119
 120         @Override
 121         public void next(final int delta) throws CorruptObjectException {
 122                 // Do nothing.
 123         }
 124
 125         @Override
 126         public void back(final int delta) throws CorruptObjectException {
 127                 // Do nothing.
 128         }
 129
 130         @Override
 131         public void stopWalk() {
 132                 if (parent != null)
 133                         parent.stopWalk();
 134         }
 135 }