1 /*
2 * Copyright (C) 2009, Google Inc.
3 * Copyright (C) 2008, Shawn O. Pearce <spearce@spearce.org>
4 * and other copyright owners as documented in the project's IP log.
5 *
6 * This program and the accompanying materials are made available
7 * under the terms of the Eclipse Distribution License v1.0 which
8 * accompanies this distribution, is reproduced below, and is
9 * available at http://www.eclipse.org/org/documents/edl-v10.php
10 *
11 * All rights reserved.
12 *
13 * Redistribution and use in source and binary forms, with or
14 * without modification, are permitted provided that the following
15 * conditions are met:
16 *
17 * - Redistributions of source code must retain the above copyright
18 * notice, this list of conditions and the following disclaimer.
19 *
20 * - Redistributions in binary form must reproduce the above
21 * copyright notice, this list of conditions and the following
22 * disclaimer in the documentation and/or other materials provided
23 * with the distribution.
24 *
25 * - Neither the name of the Eclipse Foundation, Inc. nor the
26 * names of its contributors may be used to endorse or promote
27 * products derived from this software without specific prior
28 * written permission.
29 *
30 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
31 * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
32 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
33 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
34 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
35 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
36 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
37 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
38 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
39 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
40 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
41 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
42 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
43 */
44
45 package org.eclipse.jgit.revwalk;
46
47 import java.io.IOException;
48
49 import org.eclipse.jgit.errors.IncorrectObjectTypeException;
50 import org.eclipse.jgit.errors.MissingObjectException;
51
52 /**
53 * Delays commits to be at least {@link PendingGenerator#OVER_SCAN} late.
54 * <p>
55 * This helps to "fix up" weird corner cases resulting from clock skew, by
56 * slowing down what we produce to the caller we get a better chance to ensure
57 * PendingGenerator reached back far enough in the graph to correctly mark
58 * commits {@link RevWalk#UNINTERESTING} if necessary.
59 * <p>
60 * This generator should appear before {@link FixUninterestingGenerator} if the
61 * lower level {@link #pending} isn't already fully buffered.
62 */
63 final class DelayRevQueue extends Generator {
64 private static final int OVER_SCAN = PendingGenerator.OVER_SCAN;
65
66 private final Generator pending;
67
68 private final FIFORevQueue delay;
69
70 private int size;
71
72 DelayRevQueue(Generator g) {
73 pending = g;
74 delay = new FIFORevQueue();
75 }
76
77 @Override
78 int outputType() {
79 return pending.outputType();
80 }
81
82 @Override
83 RevCommit next() throws MissingObjectException,
84 IncorrectObjectTypeException, IOException {
85 while (size < OVER_SCAN) {
86 final RevCommit c = pending.next();
87 if (c == null)
88 break;
89 delay.add(c);
90 size++;
91 }
92
93 final RevCommit c = delay.next();
94 if (c == null)
95 return null;
96 size--;
97 return c;
98 }
99 }