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/jEdit/tags/jedit-4-2-pre4/bsh/CallStack.java

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Java | 149 lines | 61 code | 17 blank | 71 comment | 3 complexity | 97f69a9729d8872ddc5c98ae80de8fbe MD5 | raw file
  1/*****************************************************************************
  2 *                                                                           *
  3 *  This file is part of the BeanShell Java Scripting distribution.          *
  4 *  Documentation and updates may be found at http://www.beanshell.org/      *
  5 *                                                                           *
  6 *  Sun Public License Notice:                                               *
  7 *                                                                           *
  8 *  The contents of this file are subject to the Sun Public License Version  *
  9 *  1.0 (the "License"); you may not use this file except in compliance with *
 10 *  the License. A copy of the License is available at http://www.sun.com    * 
 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.                                          *
 15 *                                                                           *
 16 *  GNU Public License Notice:                                               *
 17 *                                                                           *
 18 *  Alternatively, the contents of this file may be used under the terms of  *
 19 *  the GNU Lesser General Public License (the "LGPL"), in which case the    *
 20 *  provisions of LGPL are applicable instead of those above. If you wish to *
 21 *  allow use of your version of this file only under the  terms of the LGPL *
 22 *  and not to allow others to use your version of this file under the SPL,  *
 23 *  indicate your decision by deleting the provisions above and replace      *
 24 *  them with the notice and other provisions required by the LGPL.  If you  *
 25 *  do not delete the provisions above, a recipient may use your version of  *
 26 *  this file under either the SPL or the LGPL.                              *
 27 *                                                                           *
 28 *  Patrick Niemeyer (pat@pat.net)                                           *
 29 *  Author of Learning Java, O'Reilly & Associates                           *
 30 *  http://www.pat.net/~pat/                                                 *
 31 *                                                                           *
 32 *****************************************************************************/
 33
 34package bsh;
 35
 36import java.util.Vector;
 37
 38/**
 39	A stack of NameSpaces representing the call path.
 40	Each method invocation, for example, pushes a new NameSpace onto the stack.
 41	The top of the stack is always the current namespace of evaluation.
 42	<p>
 43
 44	This is used to support the this.caller magic reference and to print
 45	script "stack traces" when evaluation errors occur.
 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 a thread 
 53	executing various beanshell methods be mutating the callstack?  Don't we 
 54	need one CallStack per Thread in the interpreter?  The answer is that we do.
 55	Any java.lang.Thread enters our script via an external (hard) Java 
 56	reference via a This type interface, e.g.  the Runnable interface 
 57	implemented by This or an arbitrary interface implemented by XThis.  
 58	In that case the This invokeMethod() method (called by any interface that 
 59	it exposes) creates a new CallStack for each external call.
 60	<p>
 61*/
 62public class CallStack 
 63{
 64	private Vector stack = new Vector(2);
 65
 66	public CallStack() { }
 67
 68	public CallStack( NameSpace namespace ) { 
 69		push( namespace );
 70	}
 71
 72	public void clear() {
 73		stack.removeAllElements();
 74	}
 75
 76	public void push( NameSpace ns ) {
 77		stack.insertElementAt( ns, 0 );
 78	}
 79
 80	public NameSpace top() {
 81		return get(0);
 82	}
 83
 84	/**
 85		zero based.
 86	*/
 87	public NameSpace get(int depth) {
 88		if ( depth >= depth() )
 89			return NameSpace.JAVACODE;
 90		else
 91			return (NameSpace)(stack.elementAt(depth));
 92	}
 93	
 94	/**
 95		This is kind of crazy, but used by the setNameSpace command.
 96		zero based.
 97	*/
 98	public void set(int depth, NameSpace ns) {
 99		stack.setElementAt(ns, depth );
100	}
101
102	public NameSpace pop() {
103		if ( depth() < 1 )
104			throw new InterpreterError("pop on empty CallStack");
105		NameSpace top = top();
106		stack.removeElementAt(0);
107		return top;
108	}
109
110	/**
111		Swap in the value as the new top of the stack and return the old
112		value.
113	*/
114	public NameSpace swap( NameSpace newTop ) {
115		NameSpace oldTop = (NameSpace)(stack.elementAt(0));
116		stack.setElementAt( newTop, 0 );
117		return oldTop;
118	}
119
120	public int depth() {
121		return stack.size();
122	}
123
124	public NameSpace [] toArray() {
125		NameSpace [] nsa = new NameSpace [ depth() ];
126		stack.copyInto( nsa );
127		return nsa;
128	}
129
130	public String toString() {
131		StringBuffer sb = new StringBuffer();
132		sb.append("CallStack:\n");
133		NameSpace [] nsa = toArray();
134		for(int i=0; i<nsa.length; i++)
135			sb.append("\t"+nsa[i]+"\n");
136
137		return sb.toString();
138	}
139
140	/**
141		Occasionally we need to freeze the callstack for error reporting
142		purposes, etc.
143	*/
144	public CallStack copy() {
145		CallStack cs = new CallStack();
146		cs.stack = (Vector)this.stack.clone();
147		return cs;
148	}
149}