/*
 * 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.
 * 
 * This file is a derivative of code released under the terms listed below.  
 *
 */
/**
 *
 * Copyright (c) 2009-2012,
 *
 *  Galois, Inc. (Aaron Tomb <atomb@galois.com>, 
 *                Rogan Creswick <creswick@galois.com>, 
 *                Adam Foltzer <acfoltzer@galois.com>)
 *  Steve Suh    <suhsteve@gmail.com>
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 * this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
 * and/or other materials provided with the distribution.
 *
 * 3. The names of the contributors may not be used to endorse or promote
 * products derived from this software without specific prior written
 * permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 *
 */
package org.scandroid.flow.functions;

import org.scandroid.domain.DomainElement;
import org.scandroid.domain.IFDSTaintDomain;
import org.scandroid.domain.LocalElement;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.ibm.wala.dataflow.IFDS.IUnaryFlowFunction;
import com.ibm.wala.ssa.ISSABasicBlock;
import com.ibm.wala.util.intset.IntSet;
import com.ibm.wala.util.intset.SparseIntSet;


/**
 * Flow function that only permits globals  - and the zero element - to flow through
 * 
 * @author creswick
 *
 */
public class GlobalIdentityFunction <E extends ISSABasicBlock>
    implements IUnaryFlowFunction {
	private static final Logger logger = LoggerFactory.getLogger(GlobalIdentityFunction.class);
	
	private final IFDSTaintDomain<E> domain;

	public GlobalIdentityFunction(IFDSTaintDomain<E> domain) {
		this.domain = domain;
	}

	/* (non-Javadoc)
	 * @see com.ibm.wala.dataflow.IFDS.IUnaryFlowFunction#getTargets(int)
	 */
	@Override
	public IntSet getTargets(int d1) {
		if (0 == d1) {
			return TaintTransferFunctions.ZERO_SET;
		}
		
		DomainElement de = domain.getMappedObject(d1);
		if( de.codeElement instanceof LocalElement ) {
			// if the query domain element is a local, then it is /not/ passed through.
			logger.trace("taking {} to emptyset", de);
			return TaintTransferFunctions.EMPTY_SET;
		} else {
			return SparseIntSet.singleton(d1);
		}
	}
}