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1   /*
2    * Copyright  2000-2004 The Apache Software Foundation
3    *
4    *  Licensed under the Apache License, Version 2.0 (the "License"); 
5    *  you may not use this file except in compliance with the License.
6    *  You may obtain a copy of the License at
7    *
8    *      http://www.apache.org/licenses/LICENSE-2.0
9    *
10   *  Unless required by applicable law or agreed to in writing, software
11   *  distributed under the License is distributed on an "AS IS" BASIS,
12   *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13   *  See the License for the specific language governing permissions and
14   *  limitations under the License. 
15   *
16   */ 
17  package org.apache.bcel.verifier.statics;
18  
19  
20  import java.util.Hashtable;
21  import org.apache.bcel.generic.Type;
22  import org.apache.bcel.verifier.exc.LocalVariableInfoInconsistentException;
23  
24  /***
25   * A utility class holding the information about
26   * the name and the type of a local variable in
27   * a given slot (== index). This information
28   * often changes in course of byte code offsets.
29   *
30   * @version $Id: LocalVariableInfo.java 371539 2006-01-23 14:08:00Z tcurdt $
31   * @author Enver Haase
32   */
33  public class LocalVariableInfo{
34  
35  	/*** The types database. KEY: String representing the offset integer. */
36  	private Hashtable types = new Hashtable();
37  	/*** The names database. KEY: String representing the offset integer. */
38  	private Hashtable names = new Hashtable();
39  
40  	/***
41  	 * Adds a name of a local variable and a certain slot to our 'names'
42  	 * (Hashtable) database.
43  	 */
44  	private void setName(int offset, String name){
45  		names.put( ((Integer.toString(offset))), name);
46  	}
47  	/***
48  	 * Adds a type of a local variable and a certain slot to our 'types'
49  	 * (Hashtable) database.
50  	 */
51  	private void setType(int offset, Type t){
52  		types.put( ((Integer.toString(offset))), t);
53  	}
54  
55  	/***
56  	 * Returns the type of the local variable that uses this local
57  	 * variable slot at the given bytecode offset.
58  	 * Care for legal bytecode offsets yourself, otherwise the return value
59  	 * might be wrong.
60  	 * May return 'null' if nothing is known about the type of this local
61  	 * variable slot at the given bytecode offset.
62  	 */
63  	public Type getType(int offset){
64  		return (Type) types.get(Integer.toString(offset));
65  	}
66  	/***
67  	 * Returns the name of the local variable that uses this local
68  	 * variable slot at the given bytecode offset.
69  	 * Care for legal bytecode offsets yourself, otherwise the return value
70  	 * might be wrong.
71  	 * May return 'null' if nothing is known about the type of this local
72  	 * variable slot at the given bytecode offset.
73  	 */
74  	public String getName(int offset){
75  		return (String) (names.get(Integer.toString(offset)));
76  	}
77  	/***
78  	 * Adds some information about this local variable (slot).
79  	 * @throws LocalVariableInfoInconsistentException if the new information conflicts
80  	 *         with already gathered information.
81  	 */
82  	public void add(String name, int startpc, int length, Type t) throws LocalVariableInfoInconsistentException{
83  		for (int i=startpc; i<=startpc+length; i++){ // incl/incl-notation!
84  			add(i,name,t);
85  		}
86  	}
87  
88  	/***
89  	 * Adds information about name and type for a given offset.
90  	 * @throws LocalVariableInfoInconsistentException if the new information conflicts
91  	 *         with already gathered information.
92  	 */
93  	private void add(int offset, String name, Type t) throws LocalVariableInfoInconsistentException{
94  		if (getName(offset) != null){
95  			if (! getName(offset).equals(name)){
96  				throw new LocalVariableInfoInconsistentException("At bytecode offset '"+offset+"' a local variable has two different names: '"+getName(offset)+"' and '"+name+"'.");
97  			}
98  		}
99  		if (getType(offset) != null){
100 			if (! getType(offset).equals(t)){
101 				throw new LocalVariableInfoInconsistentException("At bytecode offset '"+offset+"' a local variable has two different types: '"+getType(offset)+"' and '"+t+"'.");
102 			}
103 		}
104 		setName(offset, name);
105 		setType(offset, t);
106 	}
107 }