    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one or more
    003 * contributor license agreements.  See the NOTICE file distributed with
    004 * this work for additional information regarding copyright ownership.
    005 * The ASF licenses this file to You under the Apache License, Version 2.0
    006 * (the "License"); you may not use this file except in compliance with
    007 * the License.  You may obtain a copy of the License at
    008 *
    009 *      http://www.apache.org/licenses/LICENSE-2.0
    010 *
    011 *  Unless required by applicable law or agreed to in writing, software
    012 *  distributed under the License is distributed on an "AS IS" BASIS,
    013 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014 *  See the License for the specific language governing permissions and
    015 *  limitations under the License.
    016 */
    017
    018package org.apache.bcel.classfile;
    019
    020/**
    021 * Unknown (non-standard) attributes may be read via user-defined factory
    022 * objects that can be registered with the Attribute.addAttributeReader
    023 * method. These factory objects should implement this interface.
    024 *
    025 * @see Attribute
    026 * @since 6.0
    027 */
    028public interface UnknownAttributeReader {
    029
    030    /**
    031     * When this attribute reader is added via the static method Attribute.addAttributeReader,
    032     * an attribute name is associated with it. As the class file parser parses attributes,
    033     * it will call various AttributeReaders based on the name of the attributes it is constructing.
    034     *
    035     * @param name_index    An index into the constant pool, indexing a ConstantUtf8
    036     *                      that represents the name of the attribute.
    037     * @param length        The length of the data contained in the attribute. This is written
    038     *                      into the constant pool and should agree with what the factory expects the length to be.
    039     * @param file          This is the data input that the factory needs to read its data from.
    040     * @param constant_pool This is the constant pool associated with the Attribute that we are constructing.
    041     *
    042     * @return The user-defined AttributeReader should take this data and use
    043     * it to construct an attribute.  In the case of errors, a null can be
    044     * returned which will cause the parsing of the class file to fail.
    045     *
    046     * @see Attribute#addAttributeReader(String, UnknownAttributeReader)
    047     */
    048    Attribute createAttribute( int name_index, int length, java.io.DataInput file, ConstantPool constant_pool );
    049}