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Java > Open Source Codes > org > apache > bcel > verifier > statics > LocalVariableInfo


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 JavaDoc;
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 JavaDoc types = new Hashtable JavaDoc();
37     /** The names database. KEY: String representing the offset integer. */
38     private Hashtable JavaDoc names = new Hashtable JavaDoc();
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 JavaDoc 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 JavaDoc getName(int offset){
75         return (String JavaDoc) (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 JavaDoc 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 JavaDoc 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 }
108
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