classnewinstancechecker.java

ProGuard 是一个免费的 Java类文件的压缩

/*
 * ProGuard -- shrinking, optimization, obfuscation, and preverification
 *             of Java bytecode.
 *
 * Copyright (c) 2002-2007 Eric Lafortune ([e-mail])
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the Free
 * Software Foundation; either version 2 of the License, or (at your option)
 * any later version.
 *
 * This program 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 General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */
package proguard.classfile.util;

import proguard.classfile.*;
import proguard.classfile.constant.*;
import proguard.classfile.constant.visitor.ConstantVisitor;


/**
 * This class can check whether method references point to
 * <code>Class.newInstance</code>.
 *
 * @author Eric Lafortune
 */
class      ClassNewInstanceChecker
extends    SimplifiedVisitor
implements ConstantVisitor
{
    // This field acts as a return variable for the ConstantVisitor.
    private boolean isClassNewInstanceInvocation;


    /**
     * Creates a new ClassNewInstanceChecker.
     */
    public ClassNewInstanceChecker()
    {
    }


    /**
     * Checks whether the specified method reference points to
     * <code>Class.newInstance</code>.
     * @param clazz                  the class in which the method reference
     *                               is located.
     * @param methodrefConstantIndex the index of the method reference in the
     *                               constant pool.
     * @return a boolean that indicates whether the reference points to the
     *         method.
     */
    public boolean check(Clazz clazz, int methodrefConstantIndex)
    {
        isClassNewInstanceInvocation = false;

        clazz.constantPoolEntryAccept(methodrefConstantIndex, this);

        return isClassNewInstanceInvocation;
    }


    // Implementations for ConstantVisitor.

    /**
     * Checks whether the given method reference points to
     * <code>Class.newInstance</code>.
     */
    public void visitMethodrefConstant(Clazz clazz, MethodrefConstant methodrefConstant)
    {
        String className  = methodrefConstant.getClassName(clazz);
        String methodName = methodrefConstant.getName(clazz);
        String methodType = methodrefConstant.getType(clazz);

        // Is it a reference to "Object Class.newInstance()"?
        isClassNewInstanceInvocation =
            className .equals(ClassConstants.INTERNAL_CLASS_NAME_JAVA_LANG_CLASS) &&
            methodName.equals(ClassConstants.INTERNAL_METHOD_NAME_NEW_INSTANCE)   &&
            methodType.equals(ClassConstants.INTERNAL_METHOD_TYPE_NEW_INSTANCE);
    }
}