/*
* Bytecode Analysis Framework
* Copyright (C) 2005, University of Maryland
*
* This library 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 library 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
package edu.umd.cs.findbugs.ba.constant;
import org.apache.bcel.generic.InstructionHandle;
import org.apache.bcel.generic.MethodGen;
import edu.umd.cs.findbugs.ba.BasicBlock;
import edu.umd.cs.findbugs.ba.DataflowAnalysisException;
import edu.umd.cs.findbugs.ba.DepthFirstSearch;
import edu.umd.cs.findbugs.ba.Edge;
import edu.umd.cs.findbugs.ba.FrameDataflowAnalysis;
import edu.umd.cs.findbugs.ba.Location;
/**
* Dataflow analysis to find constant values.
*
* @see edu.umd.cs.findbugs.ba.constant.Constant
* @author David Hovemeyer
*/
public class ConstantAnalysis extends FrameDataflowAnalysis<Constant, ConstantFrame> {
private final MethodGen methodGen;
private final ConstantFrameModelingVisitor visitor;
public ConstantAnalysis(MethodGen methodGen, DepthFirstSearch dfs) {
super(dfs);
this.methodGen = methodGen;
this.visitor = new ConstantFrameModelingVisitor(methodGen.getConstantPool());
}
@Override
public ConstantFrame createFact() {
return new ConstantFrame(methodGen.getMaxLocals());
}
@Override
public void initEntryFact(ConstantFrame frame) {
frame.setValid();
frame.clearStack();
int numSlots = frame.getNumSlots();
for (int i = 0; i < numSlots; ++i) {
frame.setValue(i, Constant.NOT_CONSTANT);
}
}
@Override
public void transferInstruction(InstructionHandle handle, BasicBlock basicBlock, ConstantFrame frame)
throws DataflowAnalysisException {
visitor.setFrameAndLocation(frame, new Location(handle, basicBlock));
visitor.analyzeInstruction(handle.getInstruction());
}
@Override
public void meetInto(ConstantFrame fact, Edge edge, ConstantFrame result) throws DataflowAnalysisException {
if (fact.isValid()) {
ConstantFrame tmpFact = null;
if (edge.isExceptionEdge()) {
tmpFact = modifyFrame(fact, null);
tmpFact.clearStack();
tmpFact.pushValue(Constant.NOT_CONSTANT);
}
if (tmpFact != null) {
fact = tmpFact;
}
}
mergeInto(fact, result);
}
@Override
protected void mergeValues(ConstantFrame otherFrame, ConstantFrame resultFrame, int slot) throws DataflowAnalysisException {
Constant value = Constant.merge(resultFrame.getValue(slot), otherFrame.getValue(slot));
resultFrame.setValue(slot, value);
}
// /*
// * Test driver.
// */
// public static void main(String[] argv) throws Exception {
// if (argv.length != 1) {
// System.err.println("Usage: " + ConstantAnalysis.class.getName() +
// " <class file>");
// System.exit(1);
// }
//
// DataflowTestDriver<ConstantFrame, ConstantAnalysis> driver =
// new DataflowTestDriver<ConstantFrame, ConstantAnalysis>() {
// @Override
// public Dataflow<ConstantFrame, ConstantAnalysis> createDataflow(
// ClassContext classContext,
// Method method) throws CFGBuilderException, DataflowAnalysisException {
// return classContext.getConstantDataflow(method);
// }
// };
//
// driver.execute(argv[0]);
// }
}