1 /*
2 * Copyright (C) 2008, Shawn O. Pearce <spearce@spearce.org>
3 * and other copyright owners as documented in the project's IP log.
4 *
5 * This program and the accompanying materials are made available
6 * under the terms of the Eclipse Distribution License v1.0 which
7 * accompanies this distribution, is reproduced below, and is
8 * available at http://www.eclipse.org/org/documents/edl-v10.php
9 *
10 * All rights reserved.
11 *
12 * Redistribution and use in source and binary forms, with or
13 * without modification, are permitted provided that the following
14 * conditions are met:
15 *
16 * - Redistributions of source code must retain the above copyright
17 * notice, this list of conditions and the following disclaimer.
18 *
19 * - Redistributions in binary form must reproduce the above
20 * copyright notice, this list of conditions and the following
21 * disclaimer in the documentation and/or other materials provided
22 * with the distribution.
23 *
24 * - Neither the name of the Eclipse Foundation, Inc. nor the
25 * names of its contributors may be used to endorse or promote
26 * products derived from this software without specific prior
27 * written permission.
28 *
29 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
30 * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
31 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
32 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
33 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
34 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
35 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
36 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
37 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
38 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
39 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
40 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
41 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
42 */
43
44 package org.eclipse.jgit.revwalk;
45
46 import java.io.IOException;
47
48 import org.eclipse.jgit.errors.IncorrectObjectTypeException;
49 import org.eclipse.jgit.errors.MissingObjectException;
50
51 /** Sorts commits in topological order. */
52 class TopoSortGenerator extends Generator {
53 private static final int TOPO_DELAY = RevWalk.TOPO_DELAY;
54
55 private final FIFORevQueue pending;
56
57 private final int outputType;
58
59 /**
60 * Create a new sorter and completely spin the generator.
61 * <p>
62 * When the constructor completes the supplied generator will have no
63 * commits remaining, as all of the commits will be held inside of this
64 * generator's internal buffer.
65 *
66 * @param s
67 * generator to pull all commits out of, and into this buffer.
68 * @throws MissingObjectException
69 * @throws IncorrectObjectTypeException
70 * @throws IOException
71 */
72 TopoSortGenerator(Generator s) throws MissingObjectException,
73 IncorrectObjectTypeException, IOException {
74 pending = new FIFORevQueue();
75 outputType = s.outputType() | SORT_TOPO;
76 s.shareFreeList(pending);
77 for (;;) {
78 final RevCommit c = s.next();
79 if (c == null)
80 break;
81 for (RevCommit p : c.parents)
82 p.inDegree++;
83 pending.add(c);
84 }
85 }
86
87 @Override
88 int outputType() {
89 return outputType;
90 }
91
92 @Override
93 void shareFreeList(BlockRevQueue q) {
94 q.shareFreeList(pending);
95 }
96
97 @Override
98 RevCommit next() throws MissingObjectException,
99 IncorrectObjectTypeException, IOException {
100 for (;;) {
101 final RevCommit c = pending.next();
102 if (c == null)
103 return null;
104
105 if (c.inDegree > 0) {
106 // At least one of our children is missing. We delay
107 // production until all of our children are output.
108 //
109 c.flags |= TOPO_DELAY;
110 continue;
111 }
112
113 // All of our children have already produced,
114 // so it is OK for us to produce now as well.
115 //
116 for (RevCommit p : c.parents) {
117 if (--p.inDegree == 0 && (p.flags & TOPO_DELAY) != 0) {
118 // This parent tried to come before us, but we are
119 // his last child. unpop the parent so it goes right
120 // behind this child.
121 //
122 p.flags &= ~TOPO_DELAY;
123 pending.unpop(p);
124 }
125 }
126 return c;
127 }
128 }
129 }