/*
 * 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>)
 *  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 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.MutableSparseIntSet;
import java.util.List;
import org.scandroid.domain.CodeElement;
import org.scandroid.domain.DomainElement;
import org.scandroid.domain.IFDSTaintDomain;

final class PairBasedFlowFunction<E extends ISSABasicBlock> implements IUnaryFlowFunction {
  //	private static final Logger logger =
  //			LoggerFactory.getLogger(PairBasedFlowFunction.class);

  private final List<UseDefPair> useToDefList;
  private final IFDSTaintDomain<E> domain;

  public PairBasedFlowFunction(IFDSTaintDomain<E> domain, List<UseDefPair> useToDefList) {
    this.domain = domain;
    this.useToDefList = useToDefList;
  }

  @Override
  public IntSet getTargets(int d) {
    // logger.debug("getTargets("+d+")");
    if (0 == d) {
      // logger.debug("getTargets("+d+"): {0}");
      return TaintTransferFunctions.ZERO_SET;
    }

    MutableSparseIntSet set = MutableSparseIntSet.makeEmpty();

    DomainElement de = domain.getMappedObject(d);
    // Here we list what facts we pass through. If a fact was true
    // before executing this instruction, it'll be true after,
    // unless we created a new definition of its associated
    // CodeElement.

    // see if D is still true; if so, pass it through:
    // (this corresponds to the vertical 'pass through' arrows in the RHS paper)
    // we actually assume that D passes through, unless there
    // is evidence to the contrary.  Because of this, instructions will
    // 'default' to propagating taints that were not relevant to that
    // instruction, which is what we want.
    set.add(d);
    for (UseDefPair udPair : useToDefList) {
      CodeElement def = udPair.getDef();

      if (def.equals(de.codeElement)) {
        // this instruction redefined D, so we
        // do *not* pass it through - this conditional has
        // contradicted our assumption that D should be passed through,
        // so remove it from the set:
        set.remove(d);
        break;
      }
    }

    ////////////////////////////////////////////////////////////////
    // see if the taints associated with D also flow through to any
    // other domain elements:

    for (UseDefPair udPair : useToDefList) {
      CodeElement use = udPair.getUse();

      if (use.equals(de.codeElement)) {
        // ok, the d element flows to the def, so we add that def
        // and keep looking.
        DomainElement newDE = new DomainElement(udPair.getDef(), de.taintSource);
        set.add(domain.getMappedIndex(newDE));
      }
    }
    // logger.debug("getTargets("+d+"): "+set);
    return set;
  }
}
