# CompactDataInput.java

    /*******************************************************************************
     * Copyright (c) 2009, 2013 Mountainminds GmbH & Co. KG and Contributors
     * All rights reserved. This program and the accompanying materials
     * are made available under the terms of the Eclipse Public License v1.0
     * which accompanies this distribution, and is available at
     * http://www.eclipse.org/legal/epl-v10.html
     *
     * Contributors:
     *    Marc R. Hoffmann - initial API and implementation
     *
     *******************************************************************************/
    package org.jacoco.core.internal.data;

    import java.io.DataInputStream;
    import java.io.IOException;
    import java.io.InputStream;

    /**
     * Additional data input methods for compact storage of data structures.
     *
     * @see CompactDataOutput
     */
    public class CompactDataInput extends DataInputStream {

    	/**
    	 * Creates a new {@link CompactDataInput} that uses the specified underlying
    	 * input stream.
    	 *
    	 * @param in
    	 *            underlying input stream
    	 */
    	public CompactDataInput(final InputStream in) {
    		super(in);
    	}

    	/**
    	 * Reads a variable length representation of an integer value.
    	 *
    	 * @return read value
    	 * @throws IOException
    	 *             if thrown by the underlying stream
    	 */
    	public int readVarInt() throws IOException {
    		final int value = 0xFF & readByte();
    		if ((value & 0x80) == 0) {
    			return value;
    		}
    		return (value & 0x7F) | (readVarInt() << 7);
    	}

    	/**
    	 * Reads a boolean array.
    	 *
    	 * @return boolean array
    	 * @throws IOException
    	 *             if thrown by the underlying stream
    	 */
    	public boolean[] readBooleanArray() throws IOException {
    		final boolean[] value = new boolean[readVarInt()];
    		int buffer = 0;
    		for (int i = 0; i < value.length; i++) {
    			if ((i % 8) == 0) {
    				buffer = readByte();
    			}
    			value[i] = (buffer & 0x01) != 0;
    			buffer >>>= 1;
    		}
    		return value;
    	}

    }