/jEdit/tags/jedit-4-1-pre5/bsh/CallStack.java

  1/*****************************************************************************
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  3 *  This file is part of the BeanShell Java Scripting distribution.          *
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 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.                                          *
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 16 *  GNU Public License Notice:                                               *
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 27 *                                                                           *
 28 *  Patrick Niemeyer (pat@pat.net)                                           *
 29 *  Author of Learning Java, O'Reilly & Associates                           *
 30 *  http://www.pat.net/~pat/                                                 *
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 32 *****************************************************************************/
 33
 34package bsh;
 35
 36import java.util.Vector;
 37
 38/**
 39	A stack of namespaces representing the call path.
 40	The top of the stack is always the current namespace of evaluation.
 41	<p>
 42
 43	This is necessary to support this this.caller magic reference and will
 44	also be used to provide additional debug/tracking and error reporting
 45	information in the future.
 46	<p>
 47
 48	Note: it would be awefully nice to use the java.util.Stack here.
 49	Sigh... have to stay 1.1 compatible.
 50	<p>
 51
 52	Note: How can this be thread safe, you might ask?  Wouldn't
 53	a thread executing various beanshell methods be mutating the callstack?
 54	Don't we need one CallStack per Thread in the interpreter?
 55	The answer is that we do.  java.lang.Thread executes our script via the
 56	Runnable interface through an external (hard) Java reference via
 57	bsh.XThis.  In that case XThis creates a new CallStack for each external
 58	call...
 59	<p>
 60
 61*/
 62public class CallStack 
 63{
 64	private Vector stack = new Vector(2);
 65
 66	public void clear() {
 67		stack.removeAllElements();
 68	}
 69
 70	public void push( NameSpace ns ) {
 71		stack.insertElementAt( ns, 0 );
 72	}
 73
 74	public NameSpace top() {
 75		return get(0);
 76	}
 77
 78	/**
 79		zero based.
 80	*/
 81	public NameSpace get(int depth) {
 82		if ( depth >= depth() )
 83			return NameSpace.JAVACODE;
 84		else
 85			return (NameSpace)(stack.elementAt(depth));
 86	}
 87	
 88	/**
 89		This is kind of crazy, but used by the setNameSpace command.
 90		zero based.
 91	*/
 92	public void set(int depth, NameSpace ns) {
 93		stack.setElementAt(ns, depth );
 94	}
 95
 96	public NameSpace pop() {
 97		if ( depth() < 1 )
 98			throw new InterpreterError("pop on empty CallStack");
 99		NameSpace top = top();
100		stack.removeElementAt(0);
101		return top;
102	}
103
104	/**
105		Swap in the value as the new top of the stack and return the old
106		value.
107	*/
108	public NameSpace swap( NameSpace newTop ) {
109		NameSpace oldTop = (NameSpace)(stack.elementAt(0));
110		stack.setElementAt( newTop, 0 );
111		return oldTop;
112	}
113
114	public int depth() {
115		return stack.size();
116	}
117
118	public NameSpace [] toArray() {
119		NameSpace [] nsa = new NameSpace [ depth() ];
120		stack.copyInto( nsa );
121		return nsa;
122	}
123
124	public String toString() {
125		StringBuffer sb = new StringBuffer();
126		sb.append("CallStack:\n");
127		NameSpace [] nsa = toArray();
128		for(int i=0; i<nsa.length; i++)
129			sb.append("\t"+nsa[i]+"\n");
130
131		return sb.toString();
132	}
133}