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/*
 * FindBugs - Find bugs in Java programs
 * Copyright (C) 2004-2005 Dave Brosius 
 * Copyright (C) 2004-2005 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 java.util.BitSet;
import java.util.Collections;

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

import edu.umd.cs.findbugs.BugInstance;
import edu.umd.cs.findbugs.BugReporter;
import edu.umd.cs.findbugs.BytecodeScanningDetector;
import edu.umd.cs.findbugs.StatelessDetector;
import edu.umd.cs.findbugs.ba.ClassContext;

/**
 * looks for calls to Thread.interrupted from a non static context, especially
 * when that context is not 'currentThread()'.
 */
public class SuspiciousThreadInterrupted extends BytecodeScanningDetector implements StatelessDetector {
    public static final int SEEN_NOTHING = 0;

    public static final int SEEN_CURRENTTHREAD = 1;

    public static final int SEEN_POP_AFTER_CURRENTTHREAD = 2;

    public static final int SEEN_UNKNOWNCONTEXT_POP = 3;

    public static final int SEEN_POSSIBLE_THREAD = 4;

    private final BugReporter bugReporter;

    private BitSet localsWithCurrentThreadValue;

    private int state;

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

    @Override
    public void visitClassContext(ClassContext classContext) {
        if (hasInterestingClass(classContext.getJavaClass().getConstantPool(), Collections.singleton("java/lang/Thread"))) {
            super.visitClassContext(classContext);
        }
    }

    @Override
    public void visit(Method obj) {
        localsWithCurrentThreadValue = new BitSet();
        state = SEEN_NOTHING;
        super.visit(obj);
    }

    @Override
    public void sawOpcode(int seen) {

        if (state == SEEN_POSSIBLE_THREAD) {
            if (seen == Const.POP) {
                state = SEEN_UNKNOWNCONTEXT_POP;
                return;
            } else {
                state = SEEN_NOTHING;
            }
        }
        switch (state) {
        case SEEN_NOTHING:
            if ((seen == Const.INVOKESTATIC) && "java/lang/Thread".equals(getClassConstantOperand())
                    && "currentThread".equals(getNameConstantOperand()) && "()Ljava/lang/Thread;".equals(getSigConstantOperand())) {
                state = SEEN_CURRENTTHREAD;
            } else if ((seen == Const.INVOKESTATIC || seen == Const.INVOKEINTERFACE || seen == Const.INVOKEVIRTUAL || seen == Const.INVOKESPECIAL)
                    && getSigConstantOperand().endsWith("Ljava/lang/Thread;")) {
                state = SEEN_POSSIBLE_THREAD;
            } else if (seen == Const.ALOAD) {
                if (localsWithCurrentThreadValue.get(getRegisterOperand())) {
                    state = SEEN_CURRENTTHREAD;
                } else {
                    state = SEEN_POSSIBLE_THREAD;
                }
            } else if ((seen >= Const.ALOAD_0) && (seen <= Const.ALOAD_3)) {
                if (localsWithCurrentThreadValue.get(seen - Const.ALOAD_0)) {
                    state = SEEN_CURRENTTHREAD;
                } else {
                    state = SEEN_POSSIBLE_THREAD;
                }
            } else if ((seen == Const.GETFIELD || seen == Const.GETSTATIC) && "Ljava/lang/Thread;".equals(getSigConstantOperand())) {
                state = SEEN_POSSIBLE_THREAD;
            }
            break;

        case SEEN_CURRENTTHREAD:
            if (seen == Const.POP) {
                state = SEEN_POP_AFTER_CURRENTTHREAD;
            } else if (seen == Const.ASTORE) {
                localsWithCurrentThreadValue.set(getRegisterOperand());
                state = SEEN_NOTHING;
            } else if ((seen >= Const.ASTORE_0) && (seen <= Const.ASTORE_3)) {
                localsWithCurrentThreadValue.set(seen - Const.ASTORE_0);
                state = SEEN_NOTHING;
            } else {
                state = SEEN_NOTHING;
            }
            break;

        default:
            if ((seen == Const.INVOKESTATIC) && "java/lang/Thread".equals(getClassConstantOperand())
                    && "interrupted".equals(getNameConstantOperand()) && "()Z".equals(getSigConstantOperand())) {
                if (state == SEEN_POP_AFTER_CURRENTTHREAD) {
                    bugReporter.reportBug(new BugInstance(this, "STI_INTERRUPTED_ON_CURRENTTHREAD", LOW_PRIORITY)
                            .addClassAndMethod(this).addSourceLine(this));
                } else if (state == SEEN_UNKNOWNCONTEXT_POP) {
                    bugReporter.reportBug(new BugInstance(this, "STI_INTERRUPTED_ON_UNKNOWNTHREAD", NORMAL_PRIORITY)
                            .addClassAndMethod(this).addSourceLine(this));
                }
            }
            state = SEEN_NOTHING;
            break;
        }
    }
}