KickJava   Java API By Example, From Geeks To Geeks.

Java > Open Source Codes > org > apache > bcel > verifier > structurals > Frame


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.structurals;
18
19
20
21 /**
22  * This class represents a JVM execution frame; that means,
23  * a local variable array and an operand stack.
24  *
25  * @version $Id: Frame.java 386056 2006-03-15 11:31:56Z tcurdt $
26  * @author Enver Haase
27  */
28  
29 public class Frame{
30
31     /**
32      * For instance initialization methods, it is important to remember
33      * which instance it is that is not initialized yet. It will be
34      * initialized invoking another constructor later.
35      * NULL means the instance already *is* initialized.
36      */
37     protected static UninitializedObjectType _this;
38
39     /**
40      *
41      */
42     private LocalVariables locals;
43
44     /**
45      *
46      */
47     private OperandStack stack;
48
49     /**
50      *
51      */
52     public Frame(int maxLocals, int maxStack){
53         locals = new LocalVariables(maxLocals);
54         stack = new OperandStack(maxStack);
55     }
56
57     /**
58      *
59      */
60     public Frame(LocalVariables locals, OperandStack stack){
61         this.locals = locals;
62         this.stack = stack;
63     }
64
65     /**
66      *
67      */
68     protected Object JavaDoc clone(){
69         Frame f = new Frame(locals.getClone(), stack.getClone());
70         return f;
71     }
72
73     /**
74      *
75      */
76     public Frame getClone(){
77         return (Frame) clone();
78     }
79
80     /**
81      *
82      */
83     public LocalVariables getLocals(){
84         return locals;
85     }
86
87     /**
88      *
89      */
90     public OperandStack getStack(){
91         return stack;
92     }
93
94     /** @return a hash code value for the object.
95      */
96     public int hashCode() { return stack.hashCode() ^ locals.hashCode(); }
97
98     /**
99      *
100      */
101     public boolean equals(Object JavaDoc o){
102         if (!(o instanceof Frame)) {
103             return false; // implies "null" is non-equal.
104 }
105         Frame f = (Frame) o;
106         return this.stack.equals(f.stack) && this.locals.equals(f.locals);
107     }
108
109     /**
110      * Returns a String representation of the Frame instance.
111      */
112     public String JavaDoc toString(){
113         String JavaDoc s="Local Variables:\n";
114         s += locals;
115         s += "OperandStack:\n";
116         s += stack;
117         return s;
118     }
119 }
120
Popular Tags