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/*
 * FindBugs - Find bugs in Java programs
 * Copyright (C) 2005 Dave Brosius 
 * 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.detect;

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.StatelessDetector;

public class QuestionableBooleanAssignment extends BytecodeScanningDetector implements StatelessDetector {
    public static final int SEEN_NOTHING = 0;

    public static final int SEEN_ICONST_0_OR_1 = 1;

    public static final int SEEN_DUP = 2;

    public static final int SEEN_ISTORE = 3;

    public static final int SEEN_GOTO = 4;

    public static final int SEEN_IF = 5;

    private final BugReporter bugReporter;

    private int state;

    private BugInstance bug;

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

    @Override
    public void visitCode(Code obj) {
        state = SEEN_NOTHING;
        super.visitCode(obj);
        bug = null;
    }

    @Override
    public void sawOpcode(int seen) {
        if (seen == Const.GOTO && getBranchOffset() == 4) {
            state = SEEN_GOTO;
        } else {
            switch (state) {
            case SEEN_NOTHING:
                if ((seen == Const.ICONST_1) || (seen == Const.ICONST_0)) {
                    state = SEEN_ICONST_0_OR_1;
                }
                break;

            case SEEN_ICONST_0_OR_1:
                if (seen == Const.DUP) {
                    state = SEEN_DUP;
                } else {
                    state = SEEN_NOTHING;
                }
                break;

            case SEEN_DUP:
                if (((seen >= Const.ISTORE_0) && (seen <= Const.ISTORE_3)) || (seen == Const.ISTORE)) {
                    state = SEEN_ISTORE;
                } else {
                    state = SEEN_NOTHING;
                }
                break;

            case SEEN_ISTORE:
                if (seen == Const.IFEQ || seen == Const.IFNE) {
                    bug = new BugInstance(this, "QBA_QUESTIONABLE_BOOLEAN_ASSIGNMENT", HIGH_PRIORITY).addClassAndMethod(this)
                            .addSourceLine(this);
                    state = SEEN_IF;
                } else {
                    state = SEEN_NOTHING;
                }
                break;

            case SEEN_IF:
                state = SEEN_NOTHING;
                if (seen == Const.NEW) {
                    String cName = getClassConstantOperand();
                    if ("java/lang/AssertionError".equals(cName)) {
                        break;
                    }
                }
                bugReporter.reportBug(bug);
                break;
            case SEEN_GOTO:
                state = SEEN_NOTHING;
                break;
            default:
                break;
            }
        }
    }
}