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  /*
   * Copyright (C) 2015 The Pennsylvania State University and the University of Wisconsin
   * Systems and Internet Infrastructure Security Laboratory
   *
   * Author: Damien Octeau
   *
   * Licensed under the Apache License, Version 2.0 (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.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
 package edu.psu.cse.siis.coal;
 
 import java.util.List;
 
 
 import soot.Local;
 import soot.Scene;
 import soot.Value;
Utility functions for edge function and flow function factories.
 
 public class FunctionFactoryUtils {
   private static final Logger logger = LoggerFactory.getLogger(FunctionFactoryUtils.class);
 
   private static PointsToAnalysis pointsToAnalysis = null;

  
Gets the points-to set for a given value. The value can be, for example, a variable or a field.

Parameters:
value A value.
Returns:
The points-to set for the input value.
 
   public static PointsToSet getPointsToSetForValue(Value value) {
     if ( == null) {
        = Scene.v().getPointsToAnalysis();
     }
 
     if (value instanceof Local) {
       return .reachingObjects((Localvalue);
     } else if (value instanceof InstanceFieldRef) {
       InstanceFieldRef sootFieldRef = (InstanceFieldRefvalue;
       PointsToSet refPointsToSet = .reachingObjects((LocalsootFieldRef.getBase());
 
       return .reachingObjects(refPointsToSetsootFieldRef.getField());
     } else if (value instanceof StaticFieldRef) {
       StaticFieldRef sootFieldRef = (StaticFieldRefvalue;
 
       return .reachingObjects(sootFieldRef.getField());
     } else if (value instanceof ArrayRef) {
       ArrayRef arrayRef = (ArrayRefvalue;
       PointsToSet arrayPointsToSet = .reachingObjects((LocalarrayRef.getBase());
 
       return .reachingObjectsOfArrayElement(arrayPointsToSet);
     } else {
       return EmptyPointsToSet.v();
     }
   }

  
Determines if a value potentially points to the same location as one of the values in a list. This is useful for example to determine if a variable should be propagated through the boundaries of a called method.

Parameters:
source The reference value.
arguments A list of value.
Returns:
The index of the element in the list that the reference value is pointing to, or -1 if no common heap location is found.
 
   public static int shouldPropagateSource(Value sourceList<Valuearguments) {
     if (.isDebugEnabled()) {
       .debug("**Source: " + source);
     }
     for (int i = 0; i < arguments.size(); ++i) {
       if (.isDebugEnabled()) {
         .debug("**Argument: " + arguments.get(i));
       }
       if (sourcePointsToArgument(sourcearguments.get(i))) {
         return i;
       }
     }
    return -1;
  }

  
Determines if an instance field should be propagated through a method call. This method only checks propagation rule for the field base. It does not check if the field points to an argument, which should be done outside this method.

Parameters:
instanceFieldRef An instance field reference.
invokeExpr An invoke expression for the called method.
Returns:
True if the field should be propagated.
  public static boolean shouldPropagateInstanceField(InstanceFieldRef instanceFieldRef,
      InvokeExpr invokeExpr) {
    Value fieldBase = instanceFieldRef.getBase();
    List<ValueargList = invokeExpr.getArgs();
    // A field reference should be propagated if the base of the field points to a method argument.
    for (int i = 0; i < argList.size(); ++i) {
      if (sourcePointsToArgument(fieldBaseargList.get(i))) {
        return true;
      }
    }
    // A field reference should be propagated if the base of the field points to the base of the
    // method call for an instance call.
    if (invokeExpr instanceof InstanceInvokeExpr) {
      Value invokeExprBase = ((InstanceInvokeExprinvokeExpr).getBase();
      if (sourcePointsToArgument(fieldBaseinvokeExprBase)) {
        return true;
      }
    }
    return false;
  }

  
Check if a source value points to an argument value. This includes source values that are field references.

Parameters:
source A value.
argument Another value.
Returns:
True if the source and the argument values point to the same location.
  private static boolean sourcePointsToArgument(Value sourceValue argument) {
    PointsToSet sourcePointsToSet = FunctionFactoryUtils.getPointsToSetForValue(source);
    PointsToSet argumentPointsToSet = FunctionFactoryUtils.getPointsToSetForValue(argument);
    if (.isDebugEnabled()) {
      .debug(source + " " + argument + ": " + source.equivTo(argument) + " - "
          + sourcePointsToSet.hasNonEmptyIntersection(argumentPointsToSet));
    }
    return source.equivTo(argument)
        || sourcePointsToSet.hasNonEmptyIntersection(argumentPointsToSet);
  }
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