/jEdit/tags/jedit-4-0-pre3/bsh/CallStack.java

/*****************************************************************************
 *                                                                           *
 *  This file is part of the BeanShell Java Scripting distribution.          *
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 *  The contents of this file are subject to the Sun Public License Version  *
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 *  The Original Code is BeanShell. The Initial Developer of the Original    *
 *  Code is Pat Niemeyer. Portions created by Pat Niemeyer are Copyright     *
 *  (C) 2000.  All Rights Reserved.                                          *
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 *                                                                           *
 *  Patrick Niemeyer (pat@pat.net)                                           *
 *  Author of Learning Java, O'Reilly & Associates                           *
 *  http://www.pat.net/~pat/                                                 *
 *                                                                           *
 *****************************************************************************/

package bsh;

import java.util.Vector;

/**
	A stack of namespaces representing the call path.
	The top of the stack is always the current namespace of evaluation.

	This is necessary to support this this.caller magic reference and will
	also be used to provide additional debug/tracking and error reporting
	information in the future.

	Note: it would be awefully nice to use the java.util.Stack here.
	Sigh... have to stay 1.1 compatible.

	We don't want to serialize this, do we?  It should be ephemeral, like
	the interpreter reference I think.
*/
public class CallStack /*implements java.io.Serializable*/
{
	private Vector stack = new Vector(2);

	public void clear() {
		stack.removeAllElements();
	}

	public void push( NameSpace ns ) {
		stack.insertElementAt( ns, 0 );
	}

	public NameSpace top() {
		return get(0);
	}

	/**
		zero based.
	*/
	public NameSpace get(int depth) {
		if ( depth >= depth() )
			return NameSpace.JAVACODE;
		else
			return (NameSpace)(stack.elementAt(depth));
	}
	
	/**
		This is kind of crazy, but used by the setNameSpace command.
		zero based.
	*/
	public void set(int depth, NameSpace ns) {
		stack.setElementAt(ns, depth );
	}

	public NameSpace pop() {
		if ( depth() < 1 )
			throw new InterpreterError("pop on empty CallStack");
		NameSpace top = top();
		stack.removeElementAt(0);
		return top;
	}

	/**
		Swap in the value as the new top of the stack and return the old
		value.
	*/
	public NameSpace swap( NameSpace newTop ) {
		NameSpace oldTop = (NameSpace)(stack.elementAt(0));
		stack.setElementAt( newTop, 0 );
		return oldTop;
	}

	public int depth() {
		return stack.size();
	}

	public NameSpace [] toArray() {
		NameSpace [] nsa = new NameSpace [ depth() ];
		stack.copyInto( nsa );
		return nsa;
	}

	public String toString() {
		StringBuffer sb = new StringBuffer();
		sb.append("CallStack:\n");
		NameSpace [] nsa = toArray();
		for(int i=0; i<nsa.length; i++)
			sb.append("\t"+nsa[i]+"\n");

		return sb.toString();
	}
}