org.apache.drill.exec.compile.RetargetableClassVisitor Maven / Gradle / Ivy
/*
* 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;
/**
* An ASM ClassVisitor that allows for a late-bound delegate.
*
* The ClassVisitor constructor takes an optional ClassVisitor argument
* to which all calls will be delegated. However, in some circumstances, ClassVisitor
* derivatives may not be able to specify the delegate until after they have called
* the ClassVisitor constructor themselves. In other words, they may not be able to
* specify the delegate until *after* they have called super(). This version of the
* ClassVisitor will support that via the use of the {@link #setDelegate} method.
*/
public class RetargetableClassVisitor extends ClassVisitor {
private boolean started;
/**
* See {@link org.objectweb.asm.ClassVisitor#ClassVisitor(int)}.
*/
public RetargetableClassVisitor(final int api) {
super(api);
}
/**
* See {@link org.objectweb.asm.ClassVisitor#ClassVisitor(int, ClassVisitor)}.
*/
public RetargetableClassVisitor(final int api, final ClassVisitor cv) {
super(api, cv);
}
/**
* Set the delegate for this ClassVisitor. Must be called before the visitor is
* used (i.e., before any other methods are called), and only once.
* @param cv the ClassVisitor to delegate calls to
*/
protected void setDelegate(final ClassVisitor cv) {
if (started) {
throw new IllegalStateException("can't change delegate after visitor has been used");
}
// This member was only protected, so we can take advantage of that to set it here.
this.cv = cv;
}
}