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
020import java.io.DataInput;
021import java.io.DataOutputStream;
022import java.io.IOException;
023
024import org.apache.bcel.Const;
025import org.apache.bcel.util.Args;
026
027/**
028 * This class is derived from <em>Attribute</em> and records the nest host of the nest to which the current class or
029 * interface claims to belong. There may be at most one NestHost attribute in a ClassFile structure.
030 *
031 * @see Attribute
032 */
033public final class NestHost extends Attribute {
034
035    private int hostClassIndex;
036
037    /**
038     * Constructs object from input stream.
039     *
040     * @param nameIndex Index in constant pool
041     * @param length Content length in bytes
042     * @param input Input stream
043     * @param constantPool Array of constants
044     * @throws IOException if an I/O error occurs.
045     */
046    NestHost(final int nameIndex, final int length, final DataInput input, final ConstantPool constantPool) throws IOException {
047        this(nameIndex, length, 0, constantPool);
048        hostClassIndex = input.readUnsignedShort();
049    }
050
051    /**
052     * @param nameIndex Index in constant pool
053     * @param length Content length in bytes
054     * @param hostClassIndex Host class index
055     * @param constantPool Array of constants
056     */
057    public NestHost(final int nameIndex, final int length, final int hostClassIndex, final ConstantPool constantPool) {
058        super(Const.ATTR_NEST_MEMBERS, nameIndex, length, constantPool);
059        this.hostClassIndex = Args.requireU2(hostClassIndex, "hostClassIndex");
060    }
061
062    /**
063     * Initializes from another object. Note that both objects use the same references (shallow copy). Use copy() for a
064     * physical copy.
065     *
066     * @param c Source to copy.
067     */
068    public NestHost(final NestHost c) {
069        this(c.getNameIndex(), c.getLength(), c.getHostClassIndex(), c.getConstantPool());
070    }
071
072    /**
073     * Called by objects that are traversing the nodes of the tree implicitly defined by the contents of a Java class.
074     * I.e., the hierarchy of methods, fields, attributes, etc. spawns a tree of objects.
075     *
076     * @param v Visitor object
077     */
078    @Override
079    public void accept(final Visitor v) {
080        v.visitNestHost(this);
081    }
082
083    /**
084     * @return deep copy of this attribute
085     */
086    @Override
087    public Attribute copy(final ConstantPool constantPool) {
088        final NestHost c = (NestHost) clone();
089        c.setConstantPool(constantPool);
090        return c;
091    }
092
093    /**
094     * Dumps NestHost attribute to file stream in binary format.
095     *
096     * @param file Output file stream
097     * @throws IOException if an I/O error occurs.
098     */
099    @Override
100    public void dump(final DataOutputStream file) throws IOException {
101        super.dump(file);
102        file.writeShort(hostClassIndex);
103    }
104
105    /**
106     * @return index into constant pool of host class name.
107     */
108    public int getHostClassIndex() {
109        return hostClassIndex;
110    }
111
112    /**
113     * @param hostClassIndex the host class index
114     */
115    public void setHostClassIndex(final int hostClassIndex) {
116        this.hostClassIndex = hostClassIndex;
117    }
118
119    /**
120     * @return String representation
121     */
122    @Override
123    public String toString() {
124        final StringBuilder buf = new StringBuilder();
125        buf.append("NestHost: ");
126        final String className = super.getConstantPool().getConstantString(hostClassIndex, Const.CONSTANT_Class);
127        buf.append(Utility.compactClassName(className, false));
128        return buf.toString();
129    }
130}