exec/java-exec/src/main/java/org/apache/drill/exec/compile/TemplateClassDefinition.java

/*
 * 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 java.util.concurrent.atomic.AtomicLong;

import org.apache.drill.exec.compile.sig.SignatureHolder;

/**
 * Defines a code generation "template" which consist of:
 * <ul>
 * <li>An interface that defines the generated class.</li>
 * <li>A template class which implements the interface to provide
 * "generic" methods that need not be generated.</li>
 * <li>A signature that lists the methods and vector holders used
 * by the template.</li>
 * </ul>
 *
 * @param <T> The template interface
 */

public class TemplateClassDefinition<T>{

  static final org.slf4j.Logger logger = org.slf4j.LoggerFactory.getLogger(TemplateClassDefinition.class);

  private final Class<T> iface;
  private final Class<? extends T> template;
  private final SignatureHolder signature;
  private static final AtomicLong classNumber = new AtomicLong(0);

  public <X extends T> TemplateClassDefinition(Class<T> iface, Class<X> template) {
    super();
    this.iface = iface;
    this.template = template;
    SignatureHolder holder = null;
    try{
      holder = SignatureHolder.getHolder(template);
    }catch(Exception ex){
      logger.error("Failure while trying to build signature holder for signature. {}", template.getName(), ex);
    }
    this.signature = holder;
  }

  public long getNextClassNumber(){
    return classNumber.getAndIncrement();
  }

  public Class<T> getExternalInterface() {
    return iface;
  }

  public Class<? extends T> getTemplateClass() {
    return template;
  }

  public String getTemplateClassName() {
    return template.getName();
  }

  public SignatureHolder getSignature(){
    return signature;
  }

  @Override
  public String toString() {
    StringBuilder buf = new StringBuilder();
    buf.append("TemplateClassDefinition [interface=");
    buf.append((iface == null) ? "null" : iface.getName());
    buf.append(", template=");
    buf.append((template == null) ? "null" : template.getName());
    buf.append(", signature=\n");
    buf.append(signature);
    buf.append("]");
    return buf.toString();
  }
}