    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 */
    019package org.apache.commons.compress.harmony.unpack200.bytecode;
    020
    021import java.io.DataOutputStream;
    022import java.io.IOException;
    023
    024/**
    025 * The abstract superclass for all types of class file entries.
    026 */
    027public abstract class ClassFileEntry {
    028
    029    /**
    030     * An empty ClassFileEntry array.
    031     */
    032    protected static final ClassFileEntry[] NONE = {};
    033    private boolean resolved;
    034
    035    /**
    036     * Writes this instance to the output stream.
    037     *
    038     * @param dos the output stream.
    039     * @throws IOException if an I/O error occurs.
    040     */
    041    protected abstract void doWrite(DataOutputStream dos) throws IOException;
    042
    043    @Override
    044    public abstract boolean equals(Object arg0);
    045
    046    /**
    047     * Returns an empty array.
    048     *
    049     * @return an empty array.
    050     */
    051    protected ClassFileEntry[] getNestedClassFileEntries() {
    052        return NONE;
    053    }
    054
    055    @Override
    056    public abstract int hashCode();
    057
    058    /**
    059     * Delegates to super {@link #hashCode}.
    060     *
    061     * @return super {@link #hashCode}.
    062     */
    063    protected int objectHashCode() {
    064        return super.hashCode();
    065    }
    066
    067    /**
    068     * Allows the constant pool entries to resolve their nested entries.
    069     *
    070     * @param pool The class constant pool.
    071     */
    072    protected void resolve(final ClassConstantPool pool) {
    073        resolved = true;
    074    }
    075
    076    @Override
    077    public abstract String toString();
    078
    079    /**
    080     * Writes this instance to the output stream.
    081     *
    082     * @param dos the output stream.
    083     * @throws IOException if an I/O error occurs.
    084     */
    085    public final void write(final DataOutputStream dos) throws IOException {
    086        if (!resolved) {
    087            throw new IllegalStateException("Entry has not been resolved");
    088        }
    089        doWrite(dos);
    090    }
    091
    092}