CompactDataOutput.java
1/*******************************************************************************
2 * Copyright (c) 2009, 2010 Mountainminds GmbH & Co. KG and Contributors
3 * All rights reserved. This program and the accompanying materials
4 * are made available under the terms of the Eclipse Public License v1.0
5 * which accompanies this distribution, and is available at
6 * http://www.eclipse.org/legal/epl-v10.html
7 *
8 * Contributors:
9 * Marc R. Hoffmann - initial API and implementation
10 *
11 *******************************************************************************/
12package org.jacoco.core.data;
13
14import java.io.DataOutputStream;
15import java.io.IOException;
16import java.io.OutputStream;
17
18/**
19 * Additional data output methods for compact storage of data structures.
20 *
21 * @see CompactDataOutput
22 * @author Marc R. Hoffmann
23 * @version 0.4.1.20101007204400
24 */
25public class CompactDataOutput extends DataOutputStream {
26
27 /**
28 * Creates a new {@link CompactDataOutput} instance that writes data to the
29 * specified underlying output stream
30 *
31 * @param out
32 * underlying output stream
33 */
34 public CompactDataOutput(final OutputStream out) {
35 super(out);
36 }
37
38 /**
39 * Writes a variable length representation of an integer value that reduces
40 * the number of written bytes for small positive values. Depending on the
41 * given value 1 to 5 bytes will be written to the underlying stream.
42 *
43 * @param value
44 * value to write
45 * @throws IOException
46 */
47 public void writeVarInt(final int value) throws IOException {
48 if ((value & 0xFFFFFF80) == 0) {
49 writeByte(value);
50 } else {
51 writeByte(0x80 | (value & 0x7F));
52 writeVarInt(value >>> 7);
53 }
54 }
55
56 /**
57 * Writes a boolean array. Internally a sequence of boolean values is packed
58 * into single bits.
59 *
60 * @param value
61 * boolean array
62 * @throws IOException
63 */
64 public void writeBooleanArray(final boolean[] value) throws IOException {
65 writeVarInt(value.length);
66 int buffer = 0;
67 int bufferSize = 0;
68 for (final boolean b : value) {
69 if (b) {
70 buffer |= 0x01 << bufferSize;
71 }
72 if (++bufferSize == 8) {
73 writeByte(buffer);
74 buffer = 0;
75 bufferSize = 0;
76 }
77 }
78 if (bufferSize > 0) {
79 writeByte(buffer);
80 }
81 }
82
83}