KickJava   Java API By Example, From Geeks To Geeks.

Java > Open Source Codes > bsh > BSHBlock


1 /*****************************************************************************
2  * *
3  * This file is part of the BeanShell Java Scripting distribution. *
4  * Documentation and updates may be found at http://www.beanshell.org/ *
5  * *
6  * Sun Public License Notice: *
7  * *
8  * The contents of this file are subject to the Sun Public License Version *
9  * 1.0 (the "License"); you may not use this file except in compliance with *
10  * the License. A copy of the License is available at http://www.sun.com *
11  * *
12  * The Original Code is BeanShell. The Initial Developer of the Original *
13  * Code is Pat Niemeyer. Portions created by Pat Niemeyer are Copyright *
14  * (C) 2000. All Rights Reserved. *
15  * *
16  * GNU Public License Notice: *
17  * *
18  * Alternatively, the contents of this file may be used under the terms of *
19  * the GNU Lesser General Public License (the "LGPL"), in which case the *
20  * provisions of LGPL are applicable instead of those above. If you wish to *
21  * allow use of your version of this file only under the terms of the LGPL *
22  * and not to allow others to use your version of this file under the SPL, *
23  * indicate your decision by deleting the provisions above and replace *
24  * them with the notice and other provisions required by the LGPL. If you *
25  * do not delete the provisions above, a recipient may use your version of *
26  * this file under either the SPL or the LGPL. *
27  * *
28  * Patrick Niemeyer (pat@pat.net) *
29  * Author of Learning Java, O'Reilly & Associates *
30  * http://www.pat.net/~pat/ *
31  * *
32  *****************************************************************************/
33
34
35 package bsh;
36
37 class BSHBlock extends SimpleNode
38 {
39     public boolean isSynchronized = false;
40
41     BSHBlock(int id) { super(id); }
42
43     public Object JavaDoc eval( CallStack callstack, Interpreter interpreter)
44         throws EvalError
45     {
46         return eval( callstack, interpreter, false );
47     }
48
49     /**
50         @param overrideNamespace if set to true the block will be executed
51         in the current namespace (not a subordinate one).
52         <p>
53         If true *no* new BlockNamespace will be swapped onto the stack and
54         the eval will happen in the current
55         top namespace. This is used by BshMethod, TryStatement, etc.
56         which must intialize the block first and also for those that perform
57         multiple passes in the same block.
58     */
59     public Object JavaDoc eval(
60         CallStack callstack, Interpreter interpreter,
61         boolean overrideNamespace )
62         throws EvalError
63     {
64         Object JavaDoc syncValue = null;
65         if ( isSynchronized )
66         {
67             // First node is the expression on which to sync
68 SimpleNode exp = ((SimpleNode)jjtGetChild(0));
69             syncValue = exp.eval(callstack, interpreter);
70         }
71
72         Object JavaDoc ret;
73         if ( isSynchronized ) // Do the actual synchronization
74 synchronized( syncValue )
75             {
76                 ret = evalBlock(
77                     callstack, interpreter, overrideNamespace, null/*filter*/);
78             }
79         else
80                 ret = evalBlock(
81                     callstack, interpreter, overrideNamespace, null/*filter*/ );
82
83         return ret;
84     }
85
86     Object JavaDoc evalBlock(
87         CallStack callstack, Interpreter interpreter,
88         boolean overrideNamespace, NodeFilter nodeFilter )
89         throws EvalError
90     {
91         Object JavaDoc ret = Primitive.VOID;
92         NameSpace enclosingNameSpace = null;
93         if ( !overrideNamespace )
94         {
95             enclosingNameSpace= callstack.top();
96             BlockNameSpace bodyNameSpace =
97                 new BlockNameSpace( enclosingNameSpace );
98
99             callstack.swap( bodyNameSpace );
100         }
101
102         int startChild = isSynchronized ? 1 : 0;
103         int numChildren = jjtGetNumChildren();
104
105         try {
106             /*
107                 Evaluate block in two passes:
108                 First do class declarations then do everything else.
109             */
110             for(int i=startChild; i<numChildren; i++)
111             {
112                 SimpleNode node = ((SimpleNode)jjtGetChild(i));
113
114                 if ( nodeFilter != null && !nodeFilter.isVisible( node ) )
115                     continue;
116
117                 if ( node instanceof BSHClassDeclaration )
118                     node.eval( callstack, interpreter );
119             }
120             for(int i=startChild; i<numChildren; i++)
121             {
122                 SimpleNode node = ((SimpleNode)jjtGetChild(i));
123                 if ( node instanceof BSHClassDeclaration )
124                     continue;
125
126                 // filter nodes
127 if ( nodeFilter != null && !nodeFilter.isVisible( node ) )
128                     continue;
129
130                 ret = node.eval( callstack, interpreter );
131
132                 // statement or embedded block evaluated a return statement
133 if ( ret instanceof ReturnControl )
134                     break;
135             }
136         } finally {
137             // make sure we put the namespace back when we leave.
138 if ( !overrideNamespace )
139                 callstack.swap( enclosingNameSpace );
140         }
141         return ret;
142     }
143
144     public interface NodeFilter {
145         public boolean isVisible( SimpleNode node );
146     }
147
148 }
149
150
Popular Tags