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/*
 * FindBugs - Find bugs in Java programs
 * Copyright (C) 2004-2006 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
 *
 * Daniel Hakim
 *
 */

package edu.umd.cs.findbugs.detect;

import org.apache.bcel.Const;
import org.apache.bcel.classfile.Code;
import org.apache.bcel.classfile.Field;
import org.apache.bcel.classfile.Method;

import edu.umd.cs.findbugs.BugAccumulator;
import edu.umd.cs.findbugs.BugInstance;
import edu.umd.cs.findbugs.BugReporter;
import edu.umd.cs.findbugs.BytecodeScanningDetector;

public class FinalizerNullsFields extends BytecodeScanningDetector {

    final BugReporter bugReporter;

    final BugAccumulator bugAccumulator;

    int state = 0;

    boolean sawAnythingElse;

    public FinalizerNullsFields(BugReporter bugReporter) {
        this.bugReporter = bugReporter;
        this.bugAccumulator = new BugAccumulator(bugReporter);
    }

    boolean inFinalize;

    boolean sawFieldNulling;

    @Override
    public void visit(Method obj) {
        if ("finalize".equals(obj.getName())) {
            inFinalize = true;
        } else {
            inFinalize = false;
        }
    }

    @Override
    public void visit(Field obj) {

    }

    @Override
    public void visit(Code obj) {
        state = 0;
        sawAnythingElse = false;
        sawFieldNulling = false;
        if (inFinalize) {
            super.visit(obj);
            bugAccumulator.reportAccumulatedBugs();
            if (!sawAnythingElse && sawFieldNulling) {
                BugInstance bug = new BugInstance(this, "FI_FINALIZER_ONLY_NULLS_FIELDS", HIGH_PRIORITY).addClassAndMethod(this);
                bugReporter.reportBug(bug);
            }
        }
    }

    @Override
    public void sawOpcode(int seen) {
        if (state == 0 && seen == Const.ALOAD_0) {
            state++;
        } else if (state == 1 && seen == Const.ACONST_NULL) {
            state++;
        } else if (state == 2 && seen == Const.PUTFIELD) {
            bugAccumulator.accumulateBug(
                    new BugInstance(this, "FI_FINALIZER_NULLS_FIELDS", NORMAL_PRIORITY).addClassAndMethod(this)
                            .addReferencedField(this), this);
            sawFieldNulling = true;
            state = 0;
        } else if (seen == Const.RETURN) {
            state = 0;
        } else {
            state = 0;
            sawAnythingElse = true;
        }
    }
}