/*
* Bytecode Analysis Framework
* Copyright (C) 2003,2004 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;
import org.apache.bcel.Constants;
import org.apache.bcel.generic.Instruction;
import org.apache.bcel.generic.InstructionHandle;
import org.apache.bcel.generic.InvokeInstruction;
import org.apache.bcel.generic.MethodGen;
import org.apache.bcel.generic.ReturnInstruction;
import edu.umd.cs.findbugs.SystemProperties;
import edu.umd.cs.findbugs.ba.vna.ValueNumber;
import edu.umd.cs.findbugs.ba.vna.ValueNumberAnalysis;
import edu.umd.cs.findbugs.ba.vna.ValueNumberDataflow;
import edu.umd.cs.findbugs.ba.vna.ValueNumberFrame;
/**
* Analysis to determine where particular values are locked in a method.
* The dataflow values are maps of value numbers to the number of times
* those values are locked.
*
* @author David Hovemeyer
* @see ValueNumberAnalysis
*/
public class LockAnalysis extends ForwardDataflowAnalysis<LockSet> {
private static final boolean DEBUG = SystemProperties.getBoolean("la.debug");
private MethodGen methodGen;
private ValueNumberDataflow vnaDataflow;
private ValueNumberAnalysis vna;
private boolean isSynchronized;
private boolean isStatic;
public LockAnalysis(MethodGen methodGen, ValueNumberDataflow vnaDataflow, DepthFirstSearch dfs) {
super(dfs);
this.methodGen = methodGen;
this.vnaDataflow = vnaDataflow;
this.vna = vnaDataflow.getAnalysis();
this.isSynchronized = methodGen.isSynchronized();
this.isStatic = methodGen.isStatic();
if (DEBUG) System.out.println("Analyzing Locks in " + methodGen.getClassName() + "." + methodGen.getName());
}
public LockSet createFact() {
return new LockSet();
}
public void copy(LockSet source, LockSet dest) {
dest.copyFrom(source);
}
public void initEntryFact(LockSet result) {
result.clear();
result.setDefaultLockCount(0);
if (isSynchronized && !isStatic) {
ValueNumber thisValue = vna.getThisValue();
result.setLockCount(thisValue.getNumber(), 1);
} else if (isSynchronized && isStatic) {
ValueNumber thisValue = vna.getClassObjectValue(methodGen.getClassName());
result.setLockCount(thisValue.getNumber(), 1);
}
}
public void makeFactTop(LockSet fact) {
fact.clear();
fact.setDefaultLockCount(LockSet.TOP);
}
public boolean isTop(LockSet fact) {
return fact.isTop();
}
public boolean same(LockSet fact1, LockSet fact2) {
return fact1.sameAs(fact2);
}
public void meetInto(LockSet fact, Edge edge, LockSet result) throws DataflowAnalysisException {
result.meetWith(fact);
}
@Override
public void transferInstruction(InstructionHandle handle, BasicBlock basicBlock, LockSet fact)
throws DataflowAnalysisException {
Instruction ins = handle.getInstruction();
short opcode = ins.getOpcode();
if (opcode == Constants.MONITORENTER || opcode == Constants.MONITOREXIT) {
ValueNumberFrame frame = vnaDataflow.getFactAtLocation(new Location(handle, basicBlock));
modifyLock(frame, fact, opcode == Constants.MONITORENTER ? 1 : -1);
} else if (opcode == Constants.INVOKEVIRTUAL || opcode == Constants.INVOKEINTERFACE) {
InvokeInstruction inv = (InvokeInstruction) ins;
String name = inv.getMethodName(methodGen.getConstantPool());
String sig = inv.getSignature(methodGen.getConstantPool());
ValueNumberFrame frame = vnaDataflow.getFactAtLocation(new Location(handle, basicBlock));
if (sig.equals("()V") && ( name.equals("lock") || name.equals("lockInterruptibly")))
modifyLock(frame, fact, 1);
else if (sig.equals("()V") && ( name.equals("unlock") ))
modifyLock(frame, fact, -1);
} else if ((ins instanceof ReturnInstruction) && isSynchronized && !isStatic) {
lockOp(fact, vna.getThisValue().getNumber(), -1);
}
}
private void modifyLock(ValueNumberFrame frame, LockSet fact, int delta) throws DataflowAnalysisException {
if (frame.isValid()) {
int lockNumber = frame.getTopValue().getNumber();
lockOp(fact, lockNumber, delta);
}
}
private void lockOp(LockSet fact, int lockNumber, int delta) {
int value = fact.getLockCount(lockNumber);
if (value < 0) // can't modify TOP or BOTTOM value
return;
value += delta;
if (value < 0)
value = LockSet.BOTTOM;
if (DEBUG) System.out.println("Setting " + lockNumber + " to " + value + " in " + methodGen.getClassName() + "." + methodGen.getName());
fact.setLockCount(lockNumber, value);
}
@Override
public boolean isFactValid(LockSet fact) {
return true;
}
// public static void main(String[] argv) throws Exception {
// if (argv.length != 1) {
// System.err.println("Usage: " + LockAnalysis.class.getName() + " <classfile>");
// System.exit(1);
// }
//
// DataflowTestDriver<LockSet, LockAnalysis> driver = new DataflowTestDriver<LockSet, LockAnalysis>() {
// @Override
// public Dataflow<LockSet, LockAnalysis> createDataflow(ClassContext classContext, Method method)
// throws CFGBuilderException, DataflowAnalysisException {
// return classContext.getLockDataflow(method);
// }
// };
//
// driver.execute(argv[0]);
// }
}
// vim:ts=4