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 objects that can be registered with the
022 * Attribute.addAttributeReader method. These factory objects should implement this interface.
023 *
024 * @see Attribute
025 * @since 6.0
026 */
027public interface UnknownAttributeReader {
028
029    /**
030     * When this attribute reader is added via the static method Attribute.addAttributeReader, an attribute name is
031     * associated with it. As the class file parser parses attributes, it will call various AttributeReaders based on the
032     * name of the attributes it is constructing.
033     *
034     * @param nameIndex An index into the constant pool, indexing a ConstantUtf8 that represents the name of the attribute.
035     * @param length The length of the data contained in the attribute. This is written into the constant pool and should
036     *        agree with what the factory expects the length to be.
037     * @param file This is the data input that the factory needs to read its data from.
038     * @param constantPool This is the constant pool associated with the Attribute that we are constructing.
039     *
040     * @return The user-defined AttributeReader should take this data and use it to construct an attribute. In the case of
041     *         errors, a null can be returned which will cause the parsing of the class file to fail.
042     *
043     * @see Attribute#addAttributeReader(String, UnknownAttributeReader)
044     */
045    Attribute createAttribute(int nameIndex, int length, java.io.DataInput file, ConstantPool constantPool);
046}