1 /*
2 * Copyright (C) 2009, Google Inc.
3 * Copyright (C) 2009, Jonas Fonseca <fonseca@diku.dk>
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.revwalk;
47
48 import java.text.MessageFormat;
49 import java.util.AbstractList;
50
51 import org.eclipse.jgit.internal.JGitText;
52
53 /**
54 * An ordered list of {@link org.eclipse.jgit.revwalk.RevObject} subclasses.
55 *
56 * @param <E>
57 * type of subclass of RevObject the list is storing.
58 */
59 public class RevObjectList<E extends RevObject> extends AbstractList<E> {
60 static final int BLOCK_SHIFT = 8;
61
62 static final int BLOCK_SIZE = 1 << BLOCK_SHIFT;
63
64 /**
65 * Items stored in this list.
66 * <p>
67 * If {@link Block#shift} = 0 this block holds the list elements; otherwise
68 * it holds pointers to other {@link Block} instances which use a shift that
69 * is {@link #BLOCK_SHIFT} smaller.
70 */
71 protected Block contents = new Block(0);
72
73 /** Current number of elements in the list. */
74 protected int size = 0;
75
76 /**
77 * Create an empty object list.
78 */
79 public RevObjectList() {
80 // Initialized above.
81 }
82
83 /** {@inheritDoc} */
84 @Override
85 public void add(int index, E element) {
86 if (index != size)
87 throw new UnsupportedOperationException(MessageFormat.format(
88 JGitText.get().unsupportedOperationNotAddAtEnd,
89 Integer.valueOf(index)));
90 set(index, element);
91 size++;
92 }
93
94 /** {@inheritDoc} */
95 @Override
96 @SuppressWarnings("unchecked")
97 public E set(int index, E element) {
98 Block s = contents;
99 while (index >> s.shift >= BLOCK_SIZE) {
100 s = new Block(s.shift + BLOCK_SHIFT);
101 s.contents[0] = contents;
102 contents = s;
103 }
104 while (s.shift > 0) {
105 final int i = index >> s.shift;
106 index -= i << s.shift;
107 if (s.contents[i] == null)
108 s.contents[i] = new Block(s.shift - BLOCK_SHIFT);
109 s = (Block) s.contents[i];
110 }
111 final Object old = s.contents[index];
112 s.contents[index] = element;
113 return (E) old;
114 }
115
116 /** {@inheritDoc} */
117 @Override
118 @SuppressWarnings("unchecked")
119 public E get(int index) {
120 Block s = contents;
121 if (index >> s.shift >= 1024)
122 return null;
123 while (s != null && s.shift > 0) {
124 final int i = index >> s.shift;
125 index -= i << s.shift;
126 s = (Block) s.contents[i];
127 }
128 return s != null ? (E) s.contents[index] : null;
129 }
130
131 /** {@inheritDoc} */
132 @Override
133 public int size() {
134 return size;
135 }
136
137 /** {@inheritDoc} */
138 @Override
139 public void clear() {
140 contents = new Block(0);
141 size = 0;
142 }
143
144 /** One level of contents, either an intermediate level or a leaf level. */
145 protected static class Block {
146 final Object[] contents = new Object[BLOCK_SIZE];
147
148 final int shift;
149
150 Block(int s) {
151 shift = s;
152 }
153 }
154 }