src/main/java/org/apache/bcel/classfile/UnknownAttributeReader.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
 *
 *   https://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 nameIndex 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 constantPool 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 nameIndex, int length, java.io.DataInput file, ConstantPool constantPool);
}