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* Licensed to the Apache Software Foundation (ASF) under one *
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* This file is part of the BeanShell Java Scripting distribution. *
* Documentation and updates may be found at http://www.beanshell.org/ *
* Patrick Niemeyer ([email protected]) *
* Author of Learning Java, O'Reilly & Associates *
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*****************************************************************************/
package bsh;
import java.io.Serializable;
import java.util.EmptyStackException;
import java.util.Stack;
/**
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.
This is used to support the this.caller magic reference and to print
script "stack traces" when evaluation errors occur.
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.
*/
public final class CallStack implements Serializable {
/** default serial version id */
private static final long serialVersionUID = 1L;
private final Stack stack = new Stack<>();
public SimpleNode node = null;
public CallStack() { }
public CallStack( NameSpace namespace ) {
push( namespace );
}
public void clear() {
stack.clear();
}
public void push( NameSpace ns ) {
stack.push( ns );
}
public NameSpace top() {
return stack.peek();
}
/**
zero based.
*/
public NameSpace get(int depth) {
int size = stack.size();
if ( depth >= size )
return NameSpace.JAVACODE;
return stack.toArray(new NameSpace[size])[size-1-depth];
}
/**
This is kind of crazy, but used by the setNameSpace command.
zero based.
*/
public synchronized void set(int depth, NameSpace ns) {
stack.set( stack.size()-1-depth, ns );
}
public NameSpace pop() {
try {
return stack.pop();
} catch(EmptyStackException e) {
throw new InterpreterError("pop on empty CallStack");
}
}
/**
Swap in the value as the new top of the stack and return the old
value.
*/
public NameSpace swap( NameSpace newTop ) {
NameSpace oldTop = stack.pop();
stack.push(newTop);
return oldTop;
}
public int depth() {
return stack.size();
}
/*
public NameSpace [] toArray() {
NameSpace [] nsa = new NameSpace [ depth() ];
stack.copyInto( nsa );
return nsa;
}
*/
public synchronized String toString() {
StringBuilder sb = new StringBuilder();
sb.append("CallStack:\n");
for( int i=stack.size()-1; i>=0; i-- )
sb.append("\t"+stack.get(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.addAll(this.stack);
return cs;
}
}