CompactDataOutput.java revision d620fbe772969e4ecf214cc65eb1bf5aa424f6e1 
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.internal.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 $qualified.bundle.version$
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}
84