Source code: gnu/classpath/VMStackWalker.java
1 /* VMStackWalker.java -- Reference implementation of VM hooks for stack access
2 Copyright (C) 2005 Free Software Foundation
3
4 This file is part of GNU Classpath.
5
6 GNU Classpath is free software; you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 2, or (at your option)
9 any later version.
10
11 GNU Classpath is distributed in the hope that it will be useful, but
12 WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 General Public License for more details.
15
16 You should have received a copy of the GNU General Public License
17 along with GNU Classpath; see the file COPYING. If not, write to the
18 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
19 02110-1301 USA.
20
21 Linking this library statically or dynamically with other modules is
22 making a combined work based on this library. Thus, the terms and
23 conditions of the GNU General Public License cover the whole
24 combination.
25
26 As a special exception, the copyright holders of this library give you
27 permission to link this library with independent modules to produce an
28 executable, regardless of the license terms of these independent
29 modules, and to copy and distribute the resulting executable under
30 terms of your choice, provided that you also meet, for each linked
31 independent module, the terms and conditions of the license of that
32 module. An independent module is a module which is not derived from
33 or based on this library. If you modify this library, you may extend
34 this exception to your version of the library, but you are not
35 obligated to do so. If you do not wish to do so, delete this
36 exception statement from your version. */
37
38 package gnu.classpath;
39
40 /**
41 * This class provides access to the classes on the Java stack
42 * for reflection and security purposes.
43 *
44 * <p>
45 * This class is only available to privileged code (i.e., code loaded
46 * by the bootstrap loader).
47 *
48 * @author John Keiser
49 * @author Eric Blake <ebb9@email.byu.edu>
50 * @author Archie Cobbs
51 */
52 public final class VMStackWalker
53 {
54 /**
55 * Get a list of all the classes currently executing methods on the
56 * Java stack. <code>getClassContext()[0]</code> is the class associated
57 * with the currently executing method, i.e., the method that called
58 * <code>VMStackWalker.getClassContext()</code> (possibly through
59 * reflection). So you may need to pop off these stack frames from
60 * the top of the stack:
61 * <ul>
62 * <li><code>VMStackWalker.getClassContext()</code>
63 * <li><code>Method.invoke()</code>
64 * </ul>
65 *
66 * @return an array of the declaring classes of each stack frame
67 */
68 public static native Class[] getClassContext();
69
70 /**
71 * Get the class associated with the method invoking the method
72 * invoking this method, or <code>null</code> if the stack is not
73 * that deep (e.g., invoked via JNI invocation API). This method
74 * is an optimization for the expression <code>getClassContext()[1]</code>
75 * and should return the same result.
76 *
77 * <p>
78 * VM implementers are encouraged to provide a more efficient
79 * version of this method.
80 */
81 public static Class getCallingClass()
82 {
83 Class[] ctx = getClassContext();
84 if (ctx.length < 3)
85 return null;
86 return ctx[2];
87 }
88
89 /**
90 * Get the class loader associated with the Class returned by
91 * <code>getCallingClass()</code>, or <code>null</code> if no
92 * such class exists or it is the boot loader. This method is an optimization
93 * for the expression <code>getClassContext()[1].getClassLoader()</code>
94 * and should return the same result.
95 *
96 * <p>
97 * VM implementers are encouraged to provide a more efficient
98 * version of this method.
99 */
100 public static ClassLoader getCallingClassLoader()
101 {
102 Class[] ctx = getClassContext();
103 if (ctx.length < 3)
104 return null;
105 return ctx[2].getClassLoader();
106 }
107 }
108