/*

***** BEGIN LICENSE BLOCK *****

* Version: EPL 1.0/GPL 2.0/LGPL 2.1

*

* The contents of this file are subject to the Eclipse Public

* License Version 1.0 (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.eclipse.org/legal/epl-v10.html

*

* Software distributed under the License is distributed on an "AS

* IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or

* implied. See the License for the specific language governing

* rights and limitations under the License.

*

* Copyright (C) 2001-2002 Jan Arne Petersen <jpetersen@uni-bonn.de>

* Copyright (C) 2001-2002 Benoit Cerrina <b.cerrina@wanadoo.fr>

* Copyright (C) 2002-2004 Anders Bengtsson <ndrsbngtssn@yahoo.se>

* Copyright (C) 2004 Thomas E Enebo <enebo@acm.org>

*

* Alternatively, the contents of this file may be used under the terms of

* either of the GNU General Public License Version 2 or later (the "GPL"),

* or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),

* in which case the provisions of the GPL or the LGPL are applicable instead

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package org.jruby.ast;

import java.util.List;

import org.jruby.Ruby;

import org.jruby.RubyString;

import org.jruby.ast.types.INameNode;

import org.jruby.ast.visitor.NodeVisitor;

import org.jruby.lexer.yacc.ISourcePosition;

import org.jruby.runtime.Block;

import org.jruby.runtime.ThreadContext;

import org.jruby.runtime.builtin.IRubyObject;

import org.jruby.util.ByteList;

import org.jruby.util.DefinedMessage;

/**

* The access to a Constant.

*/

public class ConstNode extends Node implements INameNode {

private String name;

private volatile transient IRubyObject cachedValue = null;

private Object generation = -1;

public ConstNode(ISourcePosition position, String name) {

super(position);

this.name = name;

}

public NodeType getNodeType() {

return NodeType.CONSTNODE;

}

/**

* Accept for the visitor pattern.

* @param iVisitor the visitor

**/

public Object accept(NodeVisitor iVisitor) {

return iVisitor.visitConstNode(this);

}

/**

* Gets the name.

* @return Returns a String

*/

public String getName() {

return name;

}

public List<Node> childNodes() {

return EMPTY_LIST;

}

public void setName(String name) {

this.name = name;

}

@Override

public IRubyObject interpret(Ruby runtime, ThreadContext context, IRubyObject self, Block aBlock) {

IRubyObject value = getValue(context);

// We can callsite cache const_missing if we want

return value != null ? value :

context.getCurrentScope().getStaticScope().getModule().callMethod(context, "const_missing", runtime.fastNewSymbol(name));

}

@Override

public RubyString definition(Ruby runtime, ThreadContext context, IRubyObject self, Block aBlock) {

return context.getCurrentStaticScope().isConstantDefined(name) ? runtime.getDefinedMessage(DefinedMessage.CONSTANT) : null;

}

public IRubyObject getValue(ThreadContext context) {

IRubyObject value = cachedValue; // Store to temp so it does null out on us mid-stream

return isCached(context, value) ? value : reCache(context, name);

}

private boolean isCached(ThreadContext context, IRubyObject value) {

return value != null && generation == context.runtime.getConstantInvalidator().getData();

}

public IRubyObject reCache(ThreadContext context, String name) {

Object newGeneration = context.runtime.getConstantInvalidator().getData();

IRubyObject value = context.getCurrentStaticScope().getConstant(name);

cachedValue = value;

if (value != null) generation = newGeneration;

return value;

}

}