CompactDataOutput.java revision 10a3ed3d5af2cbfbec2b35405d8d9420a9bf8776 
1/*******************************************************************************
2 * Copyright (c) Copyright (c) Copyright (c) 2009, 2012 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 CompactDataInput
22 */
23public class CompactDataOutput extends DataOutputStream {
24
25	/**
26	 * Creates a new {@link CompactDataOutput} instance that writes data to the
27	 * specified underlying output stream
28	 *
29	 * @param out
30	 *            underlying output stream
31	 */
32	public CompactDataOutput(final OutputStream out) {
33		super(out);
34	}
35
36	/**
37	 * Writes a variable length representation of an integer value that reduces
38	 * the number of written bytes for small positive values. Depending on the
39	 * given value 1 to 5 bytes will be written to the underlying stream.
40	 *
41	 * @param value
42	 *            value to write
43	 * @throws IOException
44	 */
45	public void writeVarInt(final int value) throws IOException {
46		if ((value & 0xFFFFFF80) == 0) {
47			writeByte(value);
48		} else {
49			writeByte(0x80 | (value & 0x7F));
50			writeVarInt(value >>> 7);
51		}
52	}
53
54	/**
55	 * Writes a boolean array. Internally a sequence of boolean values is packed
56	 * into single bits.
57	 *
58	 * @param value
59	 *            boolean array
60	 * @throws IOException
61	 */
62	public void writeBooleanArray(final boolean[] value) throws IOException {
63		writeVarInt(value.length);
64		int buffer = 0;
65		int bufferSize = 0;
66		for (final boolean b : value) {
67			if (b) {
68				buffer |= 0x01 << bufferSize;
69			}
70			if (++bufferSize == 8) {
71				writeByte(buffer);
72				buffer = 0;
73				bufferSize = 0;
74			}
75		}
76		if (bufferSize > 0) {
77			writeByte(buffer);
78		}
79	}
80
81}
82