AbstractClosure.java

/*******************************************************************************
 * Copyright (c) 2011 Andr� Arnold and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *******************************************************************************/
package org.eclipse.xtend.backend.lib;

import java.util.List;

import org.eclipse.xtend.backend.common.BackendType;
import org.eclipse.xtend.backend.common.ExecutionContext;
import org.eclipse.xtend.backend.common.FunctionDefContext;
import org.eclipse.xtend.backend.common.LocalVarContext;
import org.eclipse.xtend.backend.functions.AbstractFunction;

/**
 * @author Andr� Arnold - Initial contribution and API
 */
public abstract class AbstractClosure extends AbstractFunction {
    private final LocalVarContext _lvcAtDefinitionTime;
    private final FunctionDefContext _fdcAtDefinitionTime;

    private final List<String> _paramNames;
    
    public AbstractClosure (LocalVarContext lvcAtDefinitionTime, FunctionDefContext fdcAtDefinitionTime, List<String> paramNames, List<? extends BackendType> paramTypes) {
        super (null, paramTypes, null, false);
        
        //freeze local variables at definition time so they will be available in a different context at evaluation time
        _lvcAtDefinitionTime = new LocalVarContext();
        _lvcAtDefinitionTime.getLocalVars().putAll (lvcAtDefinitionTime.getLocalVars());

        _fdcAtDefinitionTime = fdcAtDefinitionTime;
        _paramNames = paramNames;
    }
    
    public Object invoke (ExecutionContext ctx, Object[] params) {
        if (_fdcAtDefinitionTime == ctx.getFunctionDefContext())
            return invokeWithExistingFdc (ctx, params);
        else {
            final FunctionDefContext oldFdc = ctx.getFunctionDefContext ();
            try {
                ctx.setFunctionDefContext (_fdcAtDefinitionTime);
                return invokeWithExistingFdc(ctx, params);
            }
            finally {
                ctx.setFunctionDefContext (oldFdc);
            }
        }
    }
    
    protected abstract Object apply (ExecutionContext ctx);
    
    private Object invokeWithExistingFdc (ExecutionContext ctx, Object... params) {
        // potential local variables that are hidden by parameters are not restored - but they will never be visible anyway
        final LocalVarContext lvc = _lvcAtDefinitionTime; 
        for (int i=0; i<_paramNames.size(); i++) {
            lvc.getLocalVars().put(_paramNames.get(i), params[i]);
        }
        
        final LocalVarContext oldLvc = ctx.getLocalVarContext();
        try {
            ctx.setLocalVarContext(lvc);
            return apply (ctx);
        }
        finally {
            ctx.setLocalVarContext(oldLvc);
        }
    }
    
    @Override
    public void setFunctionDefContext (FunctionDefContext fdc) {
        throw new UnsupportedOperationException ();
    }
    
    @Override
    public FunctionDefContext getFunctionDefContext () {
        return _fdcAtDefinitionTime;
    }

    @Override
	public BackendType getReturnType () {
        throw new UnsupportedOperationException ();
    }
}