1 /*
2 * Copyright (C) 2008, Google Inc.
3 * Copyright (C) 2006-2008, 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.lib;
46
47 import java.util.zip.Inflater;
48
49 /** Creates zlib based inflaters as necessary for object decompression. */
50 public class InflaterCache {
51 private static final int SZ = 4;
52
53 private static final Inflater[] inflaterCache;
54
55 private static int openInflaterCount;
56
57 static {
58 inflaterCache = new Inflater[SZ];
59 }
60
61 /**
62 * Obtain an Inflater for decompression.
63 * <p>
64 * Inflaters obtained through this cache should be returned (if possible) by
65 * {@link #release(Inflater)} to avoid garbage collection and reallocation.
66 *
67 * @return an available inflater. Never null.
68 */
69 public static Inflater get() {
70 final Inflater r = getImpl();
71 return r != null ? r : new Inflater(false);
72 }
73
74 private synchronized static Inflater getImpl() {
75 if (openInflaterCount > 0) {
76 final Inflater r = inflaterCache[--openInflaterCount];
77 inflaterCache[openInflaterCount] = null;
78 return r;
79 }
80 return null;
81 }
82
83 /**
84 * Release an inflater previously obtained from this cache.
85 *
86 * @param i
87 * the inflater to return. May be null, in which case this method
88 * does nothing.
89 */
90 public static void release(final Inflater i) {
91 if (i != null) {
92 i.reset();
93 if (releaseImpl(i))
94 i.end();
95 }
96 }
97
98 private static synchronized boolean releaseImpl(final Inflater i) {
99 if (openInflaterCount < SZ) {
100 inflaterCache[openInflaterCount++] = i;
101 return false;
102 }
103 return true;
104 }
105
106 private InflaterCache() {
107 throw new UnsupportedOperationException();
108 }
109 }