001/*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *   https://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing,
013 * software distributed under the License is distributed on an
014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015 * KIND, either express or implied.  See the License for the
016 * specific language governing permissions and limitations
017 * under the License.
018 */
019
020package org.apache.bcel.classfile;
021
022import java.io.DataInput;
023import java.io.DataOutputStream;
024import java.io.IOException;
025
026import org.apache.bcel.Const;
027import org.apache.bcel.util.Args;
028
029/**
030 * This class is derived from <em>Attribute</em> and records the nest host of the nest to which the current class or
031 * interface claims to belong. There may be at most one NestHost attribute in a ClassFile structure.
032 *
033 * @see Attribute
034 */
035public final class NestHost extends Attribute {
036
037    private int hostClassIndex;
038
039    /**
040     * Constructs object from input stream.
041     *
042     * @param nameIndex Index in constant pool.
043     * @param length Content length in bytes.
044     * @param input Input stream.
045     * @param constantPool Array of constants.
046     * @throws IOException Thrown if an I/O error occurs.
047     */
048    NestHost(final int nameIndex, final int length, final DataInput input, final ConstantPool constantPool) throws IOException {
049        this(nameIndex, length, 0, constantPool);
050        hostClassIndex = input.readUnsignedShort();
051    }
052
053    /**
054     * Constructs a new NestHost.
055     *
056     * @param nameIndex Index in constant pool.
057     * @param length Content length in bytes.
058     * @param hostClassIndex Host class index.
059     * @param constantPool Array of constants.
060     */
061    public NestHost(final int nameIndex, final int length, final int hostClassIndex, final ConstantPool constantPool) {
062        super(Const.ATTR_NEST_HOST, nameIndex, length, constantPool);
063        this.hostClassIndex = Args.requireU2(hostClassIndex, "hostClassIndex");
064    }
065
066    /**
067     * Initializes from another object. Note that both objects use the same references (shallow copy). Use copy() for a
068     * physical copy.
069     *
070     * @param c Source to copy.
071     */
072    public NestHost(final NestHost c) {
073        this(c.getNameIndex(), c.getLength(), c.getHostClassIndex(), c.getConstantPool());
074    }
075
076    /**
077     * Called by objects that are traversing the nodes of the tree implicitly defined by the contents of a Java class.
078     * I.e., the hierarchy of methods, fields, attributes, etc. spawns a tree of objects.
079     *
080     * @param v Visitor object.
081     */
082    @Override
083    public void accept(final Visitor v) {
084        v.visitNestHost(this);
085    }
086
087    /**
088     * @return deep copy of this attribute.
089     */
090    @Override
091    public Attribute copy(final ConstantPool constantPool) {
092        final NestHost c = (NestHost) clone();
093        c.setConstantPool(constantPool);
094        return c;
095    }
096
097    /**
098     * Dumps NestHost attribute to file stream in binary format.
099     *
100     * @param file Output file stream.
101     * @throws IOException Thrown if an I/O error occurs.
102     */
103    @Override
104    public void dump(final DataOutputStream file) throws IOException {
105        super.dump(file);
106        file.writeShort(hostClassIndex);
107    }
108
109    /**
110     * Gets the host class index.
111     *
112     * @return index into constant pool of host class name.
113     */
114    public int getHostClassIndex() {
115        return hostClassIndex;
116    }
117
118    /**
119     * Sets the host class index.
120     *
121     * @param hostClassIndex The host class index.
122     */
123    public void setHostClassIndex(final int hostClassIndex) {
124        this.hostClassIndex = hostClassIndex;
125    }
126
127    /**
128     * @return String representation.
129     */
130    @Override
131    public String toString() {
132        final StringBuilder buf = new StringBuilder();
133        buf.append("NestHost: ");
134        final String className = super.getConstantPool().getConstantString(hostClassIndex, Const.CONSTANT_Class);
135        buf.append(Utility.compactClassName(className, false));
136        return buf.toString();
137    }
138}