1 /*****************************************************************************
2  * Licensed to the Apache Software Foundation (ASF) under one                *
3  * or more contributor license agreements.  See the NOTICE file              *
4  * distributed with this work for additional information                     *
5  * regarding copyright ownership.  The ASF licenses this file                *
6  * to you under the Apache License, Version 2.0 (the                         *
7  * "License"); you may not use this file except in compliance                *
8  * with the License.  You may obtain a copy of the License at                *
9  *                                                                           *
10  *     http://www.apache.org/licenses/LICENSE-2.0                            *
11  *                                                                           *
12  * Unless required by applicable law or agreed to in writing,                *
13  * software distributed under the License is distributed on an               *
14  * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY                    *
15  * KIND, either express or implied.  See the License for the                 *
16  * specific language governing permissions and limitations                   *
17  * under the License.                                                        *
18  *                                                                           *
19  * This file is part of the BeanShell Java Scripting distribution.           *
20  * Documentation and updates may be found at http://www.beanshell.org/       *
21  * Patrick Niemeyer (pat@pat.net)                                            *
22  * Author of Learning Java, O'Reilly & Associates                            *
23  *                                                                           *
24  *****************************************************************************/
25 
26 
27 package bsh;
28 
29 /**
30 	Implementation of the for(;;) statement.
31 */
32 class BSHForStatement extends SimpleNode implements ParserConstants
33 {
34     public boolean hasForInit;
35     public boolean hasExpression;
36     public boolean hasForUpdate;
37 
38     private SimpleNode forInit;
39     private SimpleNode expression;
40     private SimpleNode forUpdate;
41     private SimpleNode statement;
42 
43     private boolean parsed;
44 
BSHForStatement(int id)45     BSHForStatement(int id) { super(id); }
46 
eval(CallStack callstack , Interpreter interpreter)47     public Object eval(CallStack callstack , Interpreter interpreter)
48 		throws EvalError
49     {
50         int i = 0;
51         if(hasForInit)
52             forInit = ((SimpleNode)jjtGetChild(i++));
53         if(hasExpression)
54             expression = ((SimpleNode)jjtGetChild(i++));
55         if(hasForUpdate)
56             forUpdate = ((SimpleNode)jjtGetChild(i++));
57         if(i < jjtGetNumChildren()) // should normally be
58             statement = ((SimpleNode)jjtGetChild(i));
59 
60 		NameSpace enclosingNameSpace= callstack.top();
61 		BlockNameSpace forNameSpace = new BlockNameSpace( enclosingNameSpace );
62 
63 		/*
64 			Note: some interesting things are going on here.
65 
66 			1) We swap instead of push...  The primary mode of operation
67 			acts like we are in the enclosing namespace...  (super must be
68 			preserved, etc.)
69 
70 			2) We do *not* call the body block eval with the namespace
71 			override.  Instead we allow it to create a second subordinate
72 			BlockNameSpace child of the forNameSpace.  Variable propagation
73 			still works through the chain, but the block's child cleans the
74 			state between iteration.
75 			(which is correct Java behavior... see forscope4.bsh)
76 		*/
77 
78 		// put forNameSpace it on the top of the stack
79 		// Note: it's important that there is only one exit point from this
80 		// method so that we can swap back the namespace.
81 		callstack.swap( forNameSpace );
82 
83         // Do the for init
84         if ( hasForInit )
85             forInit.eval( callstack, interpreter );
86 
87 		Object returnControl = Primitive.VOID;
88         while(true)
89         {
90             if ( hasExpression )
91 			{
92 				boolean cond = BSHIfStatement.evaluateCondition(
93 					expression, callstack, interpreter );
94 
95 				if ( !cond )
96 					break;
97 			}
98 
99             boolean breakout = false; // switch eats a multi-level break here?
100             if ( statement != null ) // not empty statement
101             {
102 				// do *not* invoke special override for block... (see above)
103                 Object ret = statement.eval( callstack, interpreter );
104 
105                 if (ret instanceof ReturnControl)
106                 {
107                     switch(((ReturnControl)ret).kind)
108                     {
109                         case RETURN:
110 							returnControl = ret;
111 							breakout = true;
112                             break;
113 
114                         case CONTINUE:
115                             break;
116 
117                         case BREAK:
118                             breakout = true;
119                             break;
120                     }
121                 }
122             }
123 
124             if ( breakout )
125                 break;
126 
127             if ( hasForUpdate )
128                 forUpdate.eval( callstack, interpreter );
129         }
130 
131 		callstack.swap( enclosingNameSpace );  // put it back
132         return returnControl;
133     }
134 
135 }
136