soot.dexpler.AbstractNullTransformer Maven / Gradle / Ivy
package soot.dexpler;
/*-
* #%L
* Soot - a J*va Optimization Framework
* %%
* Copyright (C) 1997 - 2018 Raja Vallée-Rai and others
* %%
* 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 soot.RefLikeType;
import soot.Type;
import soot.Unit;
import soot.Value;
import soot.jimple.AssignStmt;
import soot.jimple.ConditionExpr;
import soot.jimple.EqExpr;
import soot.jimple.IfStmt;
import soot.jimple.InstanceFieldRef;
import soot.jimple.IntConstant;
import soot.jimple.LongConstant;
import soot.jimple.NeExpr;
import soot.jimple.NullConstant;
/**
* Abstract base class for {@link DexNullTransformer} and {@link DexIfTransformer}.
*
* @author Steven Arzt
*/
public abstract class AbstractNullTransformer extends DexTransformer {
/**
* Examine expr if it is a comparison with 0.
*
* @param expr
* the ConditionExpr to examine
*/
protected boolean isZeroComparison(ConditionExpr expr) {
if (expr instanceof EqExpr || expr instanceof NeExpr) {
if (expr.getOp2() instanceof IntConstant && ((IntConstant) expr.getOp2()).value == 0) {
return true;
}
if (expr.getOp2() instanceof LongConstant && ((LongConstant) expr.getOp2()).value == 0) {
return true;
}
}
return false;
}
/**
* Replace 0 with null in the given unit.
*
* @param u
* the unit where 0 will be replaced with null.
*/
protected void replaceWithNull(Unit u) {
if (u instanceof IfStmt) {
ConditionExpr expr = (ConditionExpr) ((IfStmt) u).getCondition();
if (isZeroComparison(expr)) {
expr.setOp2(NullConstant.v());
}
} else if (u instanceof AssignStmt) {
AssignStmt s = (AssignStmt) u;
Value v = s.getRightOp();
if ((v instanceof IntConstant && ((IntConstant) v).value == 0)
|| (v instanceof LongConstant && ((LongConstant) v).value == 0)) {
// If this is a field assignment, double-check the type. We
// might have a.f = 2 with a being a null candidate, but a.f
// being an int.
if (!(s.getLeftOp() instanceof InstanceFieldRef)
|| ((InstanceFieldRef) s.getLeftOp()).getFieldRef().type() instanceof RefLikeType) {
s.setRightOp(NullConstant.v());
}
}
}
}
protected static boolean isObject(Type t) {
return t instanceof RefLikeType;
}
}