1 /*
2 * Copyright (C) 2011, 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 import java.io.IOException;
47
48 /** Describes a pack file {@link ObjectReuseAsIs} can append onto a stream. */
49 public abstract class CachedPack {
50 /**
51 * Get the number of objects in this pack.
52 *
53 * @return the total object count for the pack.
54 * @throws IOException
55 * if the object count cannot be read.
56 */
57 public abstract long getObjectCount() throws IOException;
58
59 /**
60 * Get the number of delta objects stored in this pack.
61 * <p>
62 * This is an optional method, not every cached pack storage system knows
63 * the precise number of deltas stored within the pack. This number must be
64 * smaller than {@link #getObjectCount()} as deltas are not supposed to span
65 * across pack files.
66 * <p>
67 * This method must be fast, if the only way to determine delta counts is to
68 * scan the pack file's contents one object at a time, implementors should
69 * return 0 and avoid the high cost of the scan.
70 *
71 * @return the number of deltas; 0 if the number is not known or there are
72 * no deltas.
73 * @throws IOException
74 * if the delta count cannot be read.
75 */
76 public long getDeltaCount() throws IOException {
77 return 0;
78 }
79
80 /**
81 * Determine if this pack contains the object representation given.
82 * <p>
83 * PackWriter uses this method during the finding sources phase to prune
84 * away any objects from the leading thin-pack that already appear within
85 * this pack and should not be sent twice.
86 * <p>
87 * Implementors are strongly encouraged to rely on looking at {@code rep}
88 * only and using its internal state to decide if this object is within this
89 * pack. Implementors should ensure a representation from this cached pack
90 * is tested as part of
91 * {@link ObjectReuseAsIs#selectObjectRepresentation(PackWriter, org.eclipse.jgit.lib.ProgressMonitor, Iterable)}
92 * , ensuring this method would eventually return true if the object would
93 * be included by this cached pack.
94 *
95 * @param obj
96 * the object being packed. Can be used as an ObjectId.
97 * @param rep
98 * representation from the {@link ObjectReuseAsIs} instance that
99 * originally supplied this CachedPack.
100 * @return true if this pack contains this object.
101 */
102 public abstract boolean hasObject(ObjectToPack obj,
103 StoredObjectRepresentation rep);
104 }