package soot.toolkits.scalar;

/*-
 * #%L
 * Soot - a J*va Optimization Framework
 * %%
 * Copyright (C) 2004 Ganesh Sittampalam
 * Copyright (C) 2007 Eric Bodden
 * %%
 * 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
 * <http://www.gnu.org/licenses/lgpl-2.1.html>.
 * #L%
 */

import soot.Local;
import soot.Unit;
import soot.Value;
import soot.ValueBox;
import soot.toolkits.graph.DirectedBodyGraph;

/**
 * An analysis to check whether or not local variables have been initialised.
 * 
 * @author Ganesh Sittampalam
 * @author Eric Bodden
 */
public class InitAnalysis extends ForwardFlowAnalysis<Unit, FlowSet<Local>> {

  protected final FlowSet<Local> allLocals = new ArraySparseSet<Local>();

  public InitAnalysis(DirectedBodyGraph<Unit> g) {
    super(g);

    FlowSet<Local> allLocalsRef = this.allLocals;
    for (Local loc : g.getBody().getLocals()) {
      allLocalsRef.add(loc);
    }

    doAnalysis();
  }

  @Override
  protected FlowSet<Local> entryInitialFlow() {
    return new ArraySparseSet<Local>();
  }

  @Override
  protected FlowSet<Local> newInitialFlow() {
    FlowSet<Local> ret = new ArraySparseSet<Local>();
    allLocals.copy(ret);
    return ret;
  }

  @Override
  protected void flowThrough(FlowSet<Local> in, Unit unit, FlowSet<Local> out) {
    in.copy(out);

    for (ValueBox defBox : unit.getDefBoxes()) {
      Value lhs = defBox.getValue();
      if (lhs instanceof Local) {
        out.add((Local) lhs);
      }
    }
  }

  @Override
  protected void merge(FlowSet<Local> in1, FlowSet<Local> in2, FlowSet<Local> out) {
    in1.intersection(in2, out);
  }

  @Override
  protected void copy(FlowSet<Local> source, FlowSet<Local> dest) {
    source.copy(dest);
  }
}
