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/* -*- Mode: C; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
*
* The contents of this file are subject to the Netscape Public
* License Version 1.1 (the "License"); you may not use this file
* except in compliance with the License. You may obtain a copy of
* the License at http://www.mozilla.org/NPL/
*
* Software distributed under the License is distributed on an "AS
* IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
* implied. See the License for the specific language governing
* rights and limitations under the License.
*
* The Original Code is mozilla.org code.
*
* The Initial Developer of the Original Code is Netscape
* Communications Corporation. Portions created by Netscape are
* Copyright (C) 1998 Netscape Communications Corporation. All
* Rights Reserved.
*
* Contributor(s):
*/
package netscape.jsdebug;
/**
* This interface provides access to the execution stack of a thread.
* It has several subclasses to distinguish between different kinds of
* stack frames: these currently include activations of Java methods
* or JavaScript functions.
* It is possible that synchronize blocks and try blocks deserve their own
* stack frames - to allow for later extensions a debugger should skip over
* stack frames it doesn't understand.
* Note that this appears very Java-specific. However, multiple threads and
* exceptions are relevant to JavaScript as well because of its
* interoperation with Java.
*
* @author John Bandhauer
* @author Nick Thompson
* @version 1.0
* @since 1.0
*/
public abstract class StackFrameInfo {
ThreadStateBase threadState;
StackFrameInfo caller;
protected StackFrameInfo(ThreadStateBase threadState) {
this.threadState = threadState;
}
/**
* Return true if this stack frame is still valid. Stack frames
* may become invalid when the thread is resumed (this is more
* conservative than invalidating the frame only when it actually
* returns).
*/
public boolean isValid() {
return threadState.isValid();
}
/**
* Get the stack frame where this one was built, or null for the
* start of the stack.
*/
public synchronized StackFrameInfo getCaller()
throws InvalidInfoException {
if (caller == null)
caller = getCaller0();
if (!isValid())
throw new InvalidInfoException("invalid StackFrameInfo");
return caller;
}
protected abstract StackFrameInfo getCaller0()
throws InvalidInfoException;
/**
* Get the thread that this stack frame is a part of.
*/
public Thread getThread() {
return threadState.getThread();
}
/**
* Get the 'enclosing' thread state
*/
public ThreadStateBase getThreadState() {
return threadState;
}
/**
* Get the current program counter value. Note that the
* class JavaPC supports the getMethod() operation.
*/
public abstract PC getPC()
throws InvalidInfoException;
}
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