/*
 * 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.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
 * @since 6.0
 */
public interface UnknownAttributeReader {

    /**
     * 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 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.
     *
     * @see Attribute#addAttributeReader(String, UnknownAttributeReader)
     */
    Attribute createAttribute( int name_index, int length, java.io.DataInput file, ConstantPool constant_pool );
}
