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A Java Optimization Framework
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package soot.toolkits.scalar;

/*-
 * #%L
 * Soot - a J*va Optimization Framework
 * %%
 * Copyright (C) 1997 - 1999 Raja Vallee-Rai
 * %%
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation, either version 2.1 of the
 * License, or (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Lesser Public License for more details.
 * 
 * You should have received a copy of the GNU General Lesser Public
 * License along with this program.  If not, see
 * .
 * #L%
 */

import java.util.Collections;
import java.util.IdentityHashMap;
import java.util.Map;

import soot.options.Options;
import soot.toolkits.graph.DirectedGraph;
import soot.toolkits.graph.interaction.InteractionHandler;

/**
 * An abstract class providing a meta-framework for carrying out dataflow analysis. This class provides common methods and
 * fields required by the BranchedFlowAnalysis and FlowAnalysis abstract classes.
 *
 * @param 
 *          node type of the directed graph
 * @param 
 *          abstraction type
 */
public abstract class AbstractFlowAnalysis {

  /** The graph being analysed. */
  protected final DirectedGraph graph;

  /** Maps graph nodes to IN sets. */
  protected final Map unitToBeforeFlow;

  /** Filtered: Maps graph nodes to IN sets. */
  protected Map filterUnitToBeforeFlow;

  /** Constructs a flow analysis on the given DirectedGraph. */
  public AbstractFlowAnalysis(DirectedGraph graph) {
    this.graph = graph;
    this.unitToBeforeFlow = new IdentityHashMap(graph.size() * 2 + 1);
    this.filterUnitToBeforeFlow = Collections.emptyMap();
    if (Options.v().interactive_mode()) {
      InteractionHandler.v().handleCfgEvent(graph);
    }
  }

  /**
   * Returns the flow object corresponding to the initial values for each graph node.
   */
  protected abstract A newInitialFlow();

  /**
   * Returns the initial flow value for entry/exit graph nodes.
   *
   * This is equal to {@link #newInitialFlow()}
   */
  protected A entryInitialFlow() {
    return newInitialFlow();
  }

  /**
   * Determines whether entryInitialFlow() is applied to trap handlers.
   */
  protected boolean treatTrapHandlersAsEntries() {
    return false;
  }

  /** Returns true if this analysis is forwards. */
  protected abstract boolean isForward();

  /**
   * Compute the merge of the in1 and in2 sets, putting the result into out. The
   * behavior of this function depends on the implementation ( it may be necessary to check whether in1 and
   * in2 are equal or aliased ). Used by the doAnalysis method.
   */
  protected abstract void merge(A in1, A in2, A out);

  /**
   * Merges in1 and in2 into out, just before node succNode. By default, this method just calls merge(A,A,A), ignoring the
   * node.
   */
  protected void merge(N succNode, A in1, A in2, A out) {
    merge(in1, in2, out);
  }

  /** Creates a copy of the source flow object in dest. */
  protected abstract void copy(A source, A dest);

  /**
   * Carries out the actual flow analysis. Typically called from a concrete FlowAnalysis's constructor.
   */
  protected abstract void doAnalysis();

  /** Accessor function returning value of IN set for s. */
  public A getFlowBefore(N s) {
    return unitToBeforeFlow.get(s);
  }

  /**
   * Merges in into inout, just before node succNode.
   */
  protected void mergeInto(N succNode, A inout, A in) {
    A tmp = newInitialFlow();
    merge(succNode, inout, in, tmp);
    copy(tmp, inout);
  }
}