/*
 *  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.tomcat.util.bcel.classfile;

/**
 * Unknown (non-standard) attributes may be read via user-defined factory
 * objects that can be registered with the Attribute.addAttributeReader
 * method. These factory objects should implement this interface.

 * @see Attribute
 * @version $Id: AttributeReader.java 1181133 2011-10-10 18:49:14Z markt $
 * @author  <A HREF="mailto:m.dahm@gmx.de">M. Dahm</A>
 */
public interface AttributeReader {

    /**
     When this attribute reader is added via the static method
     Attribute.addAttributeReader, an attribute name is associated with it.
     As the class file parser parses attributes, it will call various
     AttributeReaders based on the name of the attributes it is
     constructing.

     @param name_index An index into the constant pool, indexing a
     ConstantUtf8 that represents the name of the attribute.

     @param length The length of the data contained in the attribute.  This
     is written into the constant pool and should agree with what the
     factory expects the length to be.

     @param file This is the data input stream that the factory needs to read
     its data from.

     @param constant_pool This is the constant pool associated with the
     Attribute that we are constructing.

     @return The user-defined AttributeReader should take this data and use
     it to construct an attribute.  In the case of errors, a null can be
     returned which will cause the parsing of the class file to fail.
     */
    Attribute createAttribute( int name_index, int length, java.io.DataInputStream file,
            ConstantPool constant_pool );
}
