org.apache.drill.exec.compile.InnerClassAccessStripper.java Source code

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Here is the source code for org.apache.drill.exec.compile.InnerClassAccessStripper.java

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/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.drill.exec.compile;

import org.objectweb.asm.ClassVisitor;
import org.objectweb.asm.Opcodes;

/**
 * An ASM ClassVisitor that strips class the access bits that are only possible
 * on inner classes (ACC_PROTECTED, ACC_PRIVATE, and ACC_FINAL). These bits are
 * only stripped from the class' visit() call if the class' name contains a
 * '$'.
 *
 * <p>This visitor is meant to be used on classes that will undergo validation
 * with CheckClassAdapter. CheckClassAdapter assumes it will only be called on
 * non-inner classes, and throws an IllegalArgumentException if the class is
 * protected, private, or final. However, once classes are compiled, they appear
 * in their class files alone, and these options may be present, with no way
 * for an outside observer to tell if they were originally inner classes.
 */
public class InnerClassAccessStripper extends ClassVisitor {
    private int originalClassAccess;
    private boolean accessCaptured;

    /**
     * See {@link org.objectweb.asm.ClassVisitor#ClassVisitor(int)}.
     */
    public InnerClassAccessStripper(final int api) {
        super(api);
    }

    /**
     * See {@link org.objectweb.asm.ClassVisitor#ClassVisitor(int, ClassVisitor)}.
     */
    public InnerClassAccessStripper(final int api, final ClassVisitor cv) {
        super(api, cv);
    }

    /**
     * Return the original class' access bits.
     *
     * <p>This may only be called after {@link ClassVisitor#visit(int, int, String, String, String, String[])}
     * has been called; that's where the bits are stripped and captured.
     *
     * @return the original class bits
     * @throws IllegalStateException if visit() hasn't been called yet
     */
    public int getOriginalAccess() {
        if (!accessCaptured) {
            throw new IllegalStateException("can't get original access before it is captured");
        }

        return originalClassAccess;
    }

    @Override
    public void visit(final int version, final int access, final String name, final String signature,
            final String superName, final String[] interfaces) {
        /*
         * Record the original access bits so we can restore them before the next
         * link in the visitor chain.
         */
        originalClassAccess = access;
        accessCaptured = true;

        // If we're checking an inner class, suppress access bits that ASM chokes on.
        int checkClassAccess = access;
        if (name.indexOf('$') >= 0) {
            checkClassAccess &= ~(Opcodes.ACC_PROTECTED | Opcodes.ACC_PRIVATE | Opcodes.ACC_STATIC);
        }
        super.visit(version, checkClassAccess, name, signature, superName, interfaces);
    }
}