/*****************************************************************************
* Licensed to the Apache Software Foundation (ASF) under one *
* or more contributor license agreements. See the NOTICE file *
* distributed with this work for additional information *
* regarding copyright ownership. The ASF licenses this file *
* to you under the Apache License, Version 2.0 (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.apache.org/licenses/LICENSE-2.0 *
* *
* Unless required by applicable law or agreed to in writing, *
* software distributed under the License is distributed on an *
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY *
* KIND, either express or implied. See the License for the *
* specific language governing permissions and limitations *
* under the License. *
* *
* *
* This file is part of the BeanShell Java Scripting distribution. *
* Documentation and updates may be found at http://www.beanshell.org/ *
* Patrick Niemeyer (pat@pat.net) *
* Author of Learning Java, O'Reilly & Associates *
* *
*****************************************************************************/
package bsh;
import java.util.
Vector;
/**
A stack of NameSpaces representing the call path.
Each method invocation, for example, pushes a new NameSpace onto the stack.
The top of the stack is always the current namespace of evaluation.
<p>
This is used to support the this.caller magic reference and to print
script "stack traces" when evaluation errors occur.
<p>
Note: it would be awefully nice to use the java.util.Stack here.
Sigh... have to stay 1.1 compatible.
<p>
Note: How can this be thread safe, you might ask? Wouldn't a thread
executing various beanshell methods be mutating the callstack? Don't we
need one CallStack per Thread in the interpreter? The answer is that we do.
Any java.lang.Thread enters our script via an external (hard) Java
reference via a This type interface, e.g. the Runnable interface
implemented by This or an arbitrary interface implemented by XThis.
In that case the This invokeMethod() method (called by any interface that
it exposes) creates a new CallStack for each external call.
<p>
*/
public class
CallStack
{
private
Vector stack = new
Vector(2);
public
CallStack() { }
public
CallStack(
NameSpace namespace ) {
push(
namespace );
}
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();
}
/**
Occasionally we need to freeze the callstack for error reporting
purposes, etc.
*/
public
CallStack copy() {
CallStack cs = new
CallStack();
cs.
stack = (
Vector)this.
stack.
clone();
return
cs;
}
}