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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 java.util.regex.Pattern;

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;
import edu.umd.cs.findbugs.TypeAnnotation;

/* Look for sequences of the form:
 *   ICONST_1
 ANEWARRAY int[]
 DUP
 ICONST_0
 ALOAD 1: a
 AASTORE
 INVOKESTATIC Arrays.asList(Object[]) : List
 */

public class VarArgsProblems extends BytecodeScanningDetector implements StatelessDetector {

    private final BugReporter bugReporter;

    private int state;

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

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

    public static final int SEEN_NOTHING = 0;

    public static final int SEEN_ICONST_1 = 1;

    public static final int SEEN_ANEWARRAY = 2;

    public static final int SEEN_DUP = 3;

    public static final int SEEN_ICONST_0 = 4;

    public static final int SEEN_ALOAD = 5;

    public static final int SEEN_AASTORE = 6;

    public static final int SEEN_GOTO = 7;

    Pattern primitiveArray = Pattern.compile("\\[[IJDFSCB]");

    String primitiveArraySig;

    @Override
    public void sawOpcode(int seen) {
        // System.out.println("State:" + state);
        if (seen == Const.GOTO && getBranchOffset() == 4) {
            state = SEEN_GOTO;
        } else {
            switch (state) {
            case SEEN_NOTHING:
                if ((seen == Const.ICONST_1)) {
                    state = SEEN_ICONST_1;
                }
                break;

            case SEEN_ICONST_1:
                if (seen == Const.ANEWARRAY && primitiveArray.matcher(getClassConstantOperand()).matches()) {
                    // System.out.println("Allocation of array of type " +
                    // getClassConstantOperand());
                    primitiveArraySig = getClassConstantOperand();
                    state = SEEN_ANEWARRAY;
                } else {
                    state = SEEN_NOTHING;
                }
                break;

            case SEEN_ANEWARRAY:
                if (seen == Const.DUP) {
                    state = SEEN_DUP;
                } else {
                    state = SEEN_NOTHING;
                }
                break;
            case SEEN_DUP:
                if (seen == Const.ICONST_0) {
                    state = SEEN_ICONST_0;
                } else {
                    state = SEEN_NOTHING;
                }
                break;
            case SEEN_ICONST_0:
                if (((seen >= Const.ALOAD_0) && (seen < Const.ALOAD_3)) || (seen == Const.ALOAD)) {
                    state = SEEN_ALOAD;
                } else {
                    state = SEEN_NOTHING;
                }
                break;

            case SEEN_ALOAD:
                if (seen == Const.AASTORE) {
                    state = SEEN_AASTORE;
                } else {
                    state = SEEN_NOTHING;
                }
                break;

            case SEEN_AASTORE:
                if (seen == Const.INVOKESTATIC || seen == Const.INVOKEINTERFACE || seen == Const.INVOKESPECIAL || seen == Const.INVOKEVIRTUAL) {
                    // System.out.println(getClassConstantOperand());
                    // System.out.println(getNameConstantOperand());
                    // System.out.println(getSigConstantOperand());
                    if (getSigConstantOperand().indexOf("Ljava/lang/Object;)") == -1) {
                        break;
                    }
                    int priority = NORMAL_PRIORITY;
                    if ("asList".equals(getNameConstantOperand()) && "java/util/Arrays".equals(getClassConstantOperand())) {
                        priority = HIGH_PRIORITY;
                    }
                    bugReporter.reportBug(new BugInstance(this, "VA_PRIMITIVE_ARRAY_PASSED_TO_OBJECT_VARARG", priority)
                            .addClassAndMethod(this).addType(primitiveArraySig).describe(TypeAnnotation.FOUND_ROLE)
                            .addCalledMethod(this).addSourceLine(this));
                }
                state = SEEN_NOTHING;
                break;

            case SEEN_GOTO:
                state = SEEN_NOTHING;
                break;
            default:
                throw new IllegalStateException("State " + state + " not expected");

            }
        }
    }
}