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