1 /*
2 * Copyright (C) 2012, 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.file;
45
46 import java.util.Arrays;
47
48 import com.googlecode.javaewah.EWAHCompressedBitmap;
49
50 /**
51 * A random access BitSet to supports efficient conversions to
52 * EWAHCompressedBitmap.
53 */
54 final class BitSet {
55
56 private long[] words;
57
58 BitSet(int initialCapacity) {
59 words = new long[block(initialCapacity) + 1];
60 }
61
62 final void clear() {
63 Arrays.fill(words, 0);
64 }
65
66 final void set(int position) {
67 int block = block(position);
68 if (block >= words.length) {
69 long[] buf = new long[2 * block(position)];
70 System.arraycopy(words, 0, buf, 0, words.length);
71 words = buf;
72 }
73 words[block] |= mask(position);
74 }
75
76 final void clear(int position) {
77 int block = block(position);
78 if (block < words.length)
79 words[block] &= ~mask(position);
80 }
81
82 final boolean get(int position) {
83 int block = block(position);
84 return block < words.length && (words[block] & mask(position)) != 0;
85 }
86
87 final EWAHCompressedBitmap toEWAHCompressedBitmap() {
88 EWAHCompressedBitmap compressed = new EWAHCompressedBitmap(
89 words.length);
90 int runningEmptyWords = 0;
91 long lastNonEmptyWord = 0;
92 for (long word : words) {
93 if (word == 0) {
94 runningEmptyWords++;
95 continue;
96 }
97
98 if (lastNonEmptyWord != 0)
99 compressed.addWord(lastNonEmptyWord);
100
101 if (runningEmptyWords > 0) {
102 compressed.addStreamOfEmptyWords(false, runningEmptyWords);
103 runningEmptyWords = 0;
104 }
105
106 lastNonEmptyWord = word;
107 }
108 int bitsThatMatter = 64 - Long.numberOfLeadingZeros(lastNonEmptyWord);
109 if (bitsThatMatter > 0)
110 compressed.addWord(lastNonEmptyWord, bitsThatMatter);
111 return compressed;
112 }
113
114 private static final int block(int position) {
115 return position >> 6;
116 }
117
118 private static final long mask(int position) {
119 return 1L << position;
120 }
121 }