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/*
 * FindBugs - Find bugs in Java programs
 * Copyright (C) 2005-2006 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
 */

package edu.umd.cs.findbugs.detect;

import java.util.BitSet;

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

import edu.umd.cs.findbugs.BugInstance;
import edu.umd.cs.findbugs.BugReporter;
import edu.umd.cs.findbugs.BytecodeScanningDetector;
import edu.umd.cs.findbugs.FieldAnnotation;
import edu.umd.cs.findbugs.LocalVariableAnnotation;
import edu.umd.cs.findbugs.StatelessDetector;
import edu.umd.cs.findbugs.ba.XClass;
import edu.umd.cs.findbugs.ba.XField;

public class FindLocalSelfAssignment2 extends BytecodeScanningDetector implements StatelessDetector {

    private final BugReporter bugReporter;

    private int previousLoadOf = -1;

    private int previousGotoTarget;

    private int gotoCount;

    public FindLocalSelfAssignment2(BugReporter bugReporter) {
        this.bugReporter = bugReporter;
    }

    private final BitSet previousStores = new BitSet();

    @Override
    public void visit(Code obj) {
        previousLoadOf = -1;
        previousGotoTarget = -1;
        gotoCount = 0;
        previousStores.clear();
        super.visit(obj);
    }

    @Override
    public void sawOpcode(int seen) {
        if (seen == Const.GOTO) {
            previousGotoTarget = getBranchTarget();
            gotoCount++;
            if (previousGotoTarget < getPC()) {
                previousLoadOf = -1;
            }
        } else {
            if (isRegisterLoad()) {
                previousLoadOf = getRegisterOperand();
            } else {
                if (isRegisterStore()) {
                    if (previousLoadOf == getRegisterOperand() && gotoCount < 2 && getPC() != previousGotoTarget) {
                        int priority = NORMAL_PRIORITY;
                        String methodName = getMethodName();
                        if (Const.CONSTRUCTOR_NAME.equals(methodName) || methodName.startsWith("set") && getCode().getCode().length <= 5
                                || !previousStores.get(getRegisterOperand())) {
                            priority = HIGH_PRIORITY;
                        }
                        previousStores.set(getRegisterOperand());
                        XClass c = getXClass();
                        LocalVariableAnnotation local = LocalVariableAnnotation.getLocalVariableAnnotation(getMethod(),
                                getRegisterOperand(), getPC(), getPC());
                        if ("?".equals(local.getName())) {
                            priority++;
                        } else {
                            for (XField f : c.getXFields()) {
                                if (f.getName().equals(local.getName()) && (f.isStatic() || !getMethod().isStatic())) {
                                    bugReporter.reportBug(new BugInstance(this, "SA_LOCAL_SELF_ASSIGNMENT_INSTEAD_OF_FIELD",
                                            priority).addClassAndMethod(this).add(local).addField(f)
                                            .describe(FieldAnnotation.DID_YOU_MEAN_ROLE).addSourceLine(this));
                                    return;

                                }
                            }
                        }

                        bugReporter.reportBug(new BugInstance(this, "SA_LOCAL_SELF_ASSIGNMENT", priority).addClassAndMethod(this)
                                .add(local).addSourceLine(this));
                    } else {
                        previousStores.set(getRegisterOperand());
                    }
                }

                previousLoadOf = -1;
                gotoCount = 0;
            }
        }
    }
}