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 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 /** Create an empty object list. */
77 public RevObjectList() {
78 // Initialized above.
79 }
80
81 @Override
82 public void add(final int index, final E element) {
83 if (index != size)
84 throw new UnsupportedOperationException(MessageFormat.format(
85 JGitText.get().unsupportedOperationNotAddAtEnd,
86 Integer.valueOf(index)));
87 set(index, element);
88 size++;
89 }
90
91 @Override
92 @SuppressWarnings("unchecked")
93 public E set(int index, E element) {
94 Block s = contents;
95 while (index >> s.shift >= BLOCK_SIZE) {
96 s = new Block(s.shift + BLOCK_SHIFT);
97 s.contents[0] = contents;
98 contents = s;
99 }
100 while (s.shift > 0) {
101 final int i = index >> s.shift;
102 index -= i << s.shift;
103 if (s.contents[i] == null)
104 s.contents[i] = new Block(s.shift - BLOCK_SHIFT);
105 s = (Block) s.contents[i];
106 }
107 final Object old = s.contents[index];
108 s.contents[index] = element;
109 return (E) old;
110 }
111
112 @Override
113 @SuppressWarnings("unchecked")
114 public E get(int index) {
115 Block s = contents;
116 if (index >> s.shift >= 1024)
117 return null;
118 while (s != null && s.shift > 0) {
119 final int i = index >> s.shift;
120 index -= i << s.shift;
121 s = (Block) s.contents[i];
122 }
123 return s != null ? (E) s.contents[index] : null;
124 }
125
126 @Override
127 public int size() {
128 return size;
129 }
130
131 @Override
132 public void clear() {
133 contents = new Block(0);
134 size = 0;
135 }
136
137 /** One level of contents, either an intermediate level or a leaf level. */
138 protected static class Block {
139 final Object[] contents = new Object[BLOCK_SIZE];
140
141 final int shift;
142
143 Block(final int s) {
144 shift = s;
145 }
146 }
147 }