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1   /*
2    * @(#) IFNONNULL.java Jan 8, 2004
3    * 
4    * Copyright (c) 2003 Delft University of Technology Jaffalaan 5, 2628 BX Delft,
5    * the Netherlands All rights reserved.
6    * 
7    * This software is proprietary information of Delft University of Technology
8    * The code is published under the General Public License
9    */
10  package nl.tudelft.simulation.dsol.interpreter.operations;
11  
12  import java.io.DataInput;
13  import java.io.IOException;
14  
15  import nl.tudelft.simulation.dsol.interpreter.LocalVariable;
16  import nl.tudelft.simulation.dsol.interpreter.OperandStack;
17  import nl.tudelft.simulation.dsol.interpreter.classfile.Constant;
18  
19  /***
20   * The IFNULL operation as defined in <a
21   * href="http://java.sun.com/docs/books/vmspec/2nd-edition/html/Instructions2.doc6.html">
22   * http://java.sun.com/docs/books/vmspec/2nd-edition/html/Instructions2.doc6.html
23   * </a>.
24   * <p>
25   * (c) copyright 2003 <a href="http://www.simulation.tudelft.nl">Delft
26   * University of Technology </a>, the Netherlands. <br>
27   * See for project information <a
28   * href="http://www.simulation.tudelft.nl">www.simulation.tudelft.nl </a> <br>
29   * License of use: <a href="http://www.gnu.org/copyleft/gpl.html">General Public
30   * License (GPL) </a>, no warranty <br>
31   * 
32   * @author <a href="http://www.tbm.tudelft.nl/webstaf/peterja/index.htm">Peter
33   *         Jacobs </a><a
34   *         href="http://www.tbm.tudelft.nl/webstaf/alexandv/index.htm">Alexander
35   *         Verbraeck </a>
36   * @version 1.3 Apr 6, 2004
37   * @since 1.4
38   */
39  public class IFNULL extends JumpOperation
40  {
41  	/*** OP refers to the operand code */
42  	public static final int OP = 198;
43  
44  	/*** the index to load */
45  	private int offset = -1;
46  
47  	/***
48  	 * constructs a new IFNONNULL
49  	 * 
50  	 * @param dataInput the dataInput
51  	 * @throws IOException on IOfailure
52  	 */
53  	public IFNULL(final DataInput dataInput) throws IOException
54  	{
55  		super();
56  		this.offset = dataInput.readShort();
57  	}
58  
59  	/***
60  	 * @see nl.tudelft.simulation.dsol.interpreter.operations.JumpOperation
61  	 *      #execute(nl.tudelft.simulation.dsol.interpreter.OperandStack,
62  	 *      nl.tudelft.simulation.dsol.interpreter.classfile.Constant[],
63  	 *      nl.tudelft.simulation.dsol.interpreter.LocalVariable[])
64  	 */
65  	public int execute(final OperandStack stack, final Constant[] constantPool,
66  			final LocalVariable[] localVariables)
67  	{
68  		if (stack.pop() == null)
69  		{
70  			return this.offset;
71  		}
72  		return this.getByteLength();
73  	}
74  
75  	/***
76  	 * @see nl.tudelft.simulation.dsol.interpreter.Operation#getByteLength()
77  	 */
78  	public int getByteLength()
79  	{
80  		return OPCODE_BYTE_LENGTH + 2;
81  	}
82  
83  	/***
84  	 * @see nl.tudelft.simulation.dsol.interpreter.Operation#getOpcode()
85  	 */
86  	public int getOpcode()
87  	{
88  		return IFNULL.OP;
89  	}
90  }