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 import java.lang.ref.ReferenceQueue;
47 import java.lang.ref.SoftReference;
48
49 import org.eclipse.jgit.storage.pack.PackConfig;
50
51 class DeltaCache {
52 private final long size;
53
54 private final int entryLimit;
55
56 private final ReferenceQueue<byte[]> queue;
57
58 private long used;
59
60 DeltaCache(PackConfig pc) {
61 size = pc.getDeltaCacheSize();
62 entryLimit = pc.getDeltaCacheLimit();
63 queue = new ReferenceQueue<>();
64 }
65
66 boolean canCache(int length, ObjectToPack src, ObjectToPack res) {
67 // If the cache would overflow, don't store.
68 //
69 if (0 < size && size < used + length) {
70 checkForGarbageCollectedObjects();
71 if (0 < size && size < used + length)
72 return false;
73 }
74
75 if (length < entryLimit) {
76 used += length;
77 return true;
78 }
79
80 // If the combined source files are multiple megabytes but the delta
81 // is on the order of a kilobyte or two, this was likely costly to
82 // construct. Cache it anyway, even though its over the limit.
83 //
84 if (length >> 10 < (src.getWeight() >> 20) + (res.getWeight() >> 21)) {
85 used += length;
86 return true;
87 }
88
89 return false;
90 }
91
92 void credit(int reservedSize) {
93 used -= reservedSize;
94 }
95
96 Ref cache(byte[] data, int actLen, int reservedSize) {
97 // The caller may have had to allocate more space than is
98 // required. If we are about to waste anything, shrink it.
99 //
100 data = resize(data, actLen);
101
102 // When we reserved space for this item we did it for the
103 // inflated size of the delta, but we were just given the
104 // compressed version. Adjust the cache cost to match.
105 //
106 if (reservedSize != data.length) {
107 used -= reservedSize;
108 used += data.length;
109 }
110 return new Ref(data, queue);
111 }
112
113 byte[] resize(byte[] data, int actLen) {
114 if (data.length != actLen) {
115 byte[] nbuf = new byte[actLen];
116 System.arraycopy(data, 0, nbuf, 0, actLen);
117 data = nbuf;
118 }
119 return data;
120 }
121
122 private void checkForGarbageCollectedObjects() {
123 Ref r;
124 while ((r = (Ref) queue.poll()) != null)
125 used -= r.cost;
126 }
127
128 static class Ref extends SoftReference<byte[]> {
129 final int cost;
130
131 Ref(byte[] array, ReferenceQueue<byte[]> queue) {
132 super(array, queue);
133 cost = array.length;
134 }
135 }
136 }