1 /*
2 * Copyright (C) 2010, Google Inc.
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.internal.storage.pack;
45
46 final class DeltaWindowEntry {
47 DeltaWindowEntry prev;
48 DeltaWindowEntry next;
49 ObjectToPack object;
50
51 /** Complete contents of this object. Lazily loaded. */
52 byte[] buffer;
53
54 /** Index of this object's content, to encode other deltas. Lazily loaded. */
55 DeltaIndex index;
56
57 final void set(ObjectToPack object) {
58 this.object = object;
59 this.index = null;
60 this.buffer = null;
61 }
62
63 /** @return current delta chain depth of this object. */
64 final int depth() {
65 return object.getDeltaDepth();
66 }
67
68 /** @return type of the object in this window entry. */
69 final int type() {
70 return object.getType();
71 }
72
73 /** @return estimated unpacked size of the object, in bytes . */
74 final int size() {
75 return object.getWeight();
76 }
77
78 /** @return true if there is no object stored in this entry. */
79 final boolean empty() {
80 return object == null;
81 }
82
83 final void makeNext(DeltaWindowEntry e) {
84 // Disconnect e from the chain.
85 e.prev.next = e.next;
86 e.next.prev = e.prev;
87
88 // Insert e after this.
89 e.next = next;
90 e.prev = this;
91 next.prev = e;
92 next = e;
93 }
94
95 static DeltaWindowEntry createWindow(int cnt) {
96 // C Git increases the window size supplied by the user by 1.
97 // We don't know why it does this, but if the user asks for
98 // window=10, it actually processes with window=11. Because
99 // the window size has the largest direct impact on the final
100 // pack file size, we match this odd behavior here to give us
101 // a better chance of producing a similar sized pack as C Git.
102 //
103 // We would prefer to directly honor the user's request since
104 // PackWriter has a minimum of 2 for the window size, but then
105 // users might complain that JGit is creating a bigger pack file.
106 DeltaWindowEntry res = new DeltaWindowEntry();
107 DeltaWindowEntry p = res;
108 for (int i = 0; i < cnt; i++) {
109 DeltaWindowEntry e = new DeltaWindowEntry();
110 e.prev = p;
111 p.next = e;
112 p = e;
113 }
114 p.next = res;
115 res.prev = p;
116 return res;
117 }
118 }