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jlechner |
/* VMStackWalker.java -- Reference implementation of VM hooks for stack access
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Copyright (C) 2005 Free Software Foundation
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This file is part of GNU Classpath.
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GNU Classpath is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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GNU Classpath is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GNU Classpath; see the file COPYING. If not, write to the
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Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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02110-1301 USA.
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Linking this library statically or dynamically with other modules is
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making a combined work based on this library. Thus, the terms and
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conditions of the GNU General Public License cover the whole
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combination.
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As a special exception, the copyright holders of this library give you
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permission to link this library with independent modules to produce an
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executable, regardless of the license terms of these independent
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modules, and to copy and distribute the resulting executable under
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terms of your choice, provided that you also meet, for each linked
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independent module, the terms and conditions of the license of that
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module. An independent module is a module which is not derived from
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or based on this library. If you modify this library, you may extend
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this exception to your version of the library, but you are not
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obligated to do so. If you do not wish to do so, delete this
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exception statement from your version. */
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package gnu.classpath;
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/**
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* This class provides access to the classes on the Java stack
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* for reflection and security purposes.
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*
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* <p>
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* This class is only available to privileged code (i.e., code loaded
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* by the bootstrap loader).
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*
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* @author John Keiser
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* @author Eric Blake <ebb9@email.byu.edu>
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* @author Archie Cobbs
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*/
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public final class VMStackWalker
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{
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/**
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* Get a list of all the classes currently executing methods on the
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* Java stack. <code>getClassContext()[0]</code> is the class associated
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* with the currently executing method, i.e., the method that called
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* <code>VMStackWalker.getClassContext()</code> (possibly through
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* reflection). So you may need to pop off these stack frames from
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* the top of the stack:
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* <ul>
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* <li><code>VMStackWalker.getClassContext()</code>
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* <li><code>Method.invoke()</code>
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* </ul>
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*
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* @return an array of the declaring classes of each stack frame
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*/
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public static native Class[] getClassContext();
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/**
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* Get the class associated with the method invoking the method
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* invoking this method, or <code>null</code> if the stack is not
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* that deep (e.g., invoked via JNI invocation API). This method
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* is an optimization for the expression <code>getClassContext()[1]</code>
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* and should return the same result.
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*
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* <p>
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* VM implementers are encouraged to provide a more efficient
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* version of this method.
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*/
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public static Class getCallingClass()
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{
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Class[] ctx = getClassContext();
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if (ctx.length < 3)
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return null;
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return ctx[2];
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}
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/**
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* Get the class loader associated with the Class returned by
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* <code>getCallingClass()</code>, or <code>null</code> if no such class
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* exists or it is the boot loader. This method is an optimization for the
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* expression <code>VMStackWalker.getClassLoader(getClassContext()[1])</code>
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* and should return the same result.
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*
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* <p>
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* VM implementers are encouraged to provide a more efficient
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* version of this method.
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*/
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public static ClassLoader getCallingClassLoader()
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{
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Class[] ctx = getClassContext();
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if (ctx.length < 3)
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return null;
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return getClassLoader(ctx[2]);
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}
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/**
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* Retrieve the class's ClassLoader, or <code>null</code> if loaded
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* by the bootstrap loader. I.e., this should return the same thing
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* as {@link java.lang.VMClass#getClassLoader}. This duplicate version
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* is here to work around access permissions.
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*/
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public static native ClassLoader getClassLoader(Class cl);
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}
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