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      1 /*
      2  * Licensed to the Apache Software Foundation (ASF) under one or more
      3  * contributor license agreements.  See the NOTICE file distributed with
      4  * this work for additional information regarding copyright ownership.
      5  * The ASF licenses this file to You under the Apache License, Version 2.0
      6  * (the "License"); you may not use this file except in compliance with
      7  * the License.  You may obtain a copy of the License at
      8  *
      9  *      http://www.apache.org/licenses/LICENSE-2.0
     10  *
     11  *  Unless required by applicable law or agreed to in writing, software
     12  *  distributed under the License is distributed on an "AS IS" BASIS,
     13  *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     14  *  See the License for the specific language governing permissions and
     15  *  limitations under the License.
     16  *
     17  */
     18 package org.apache.bcel.classfile;
     19 
     20 import java.io.DataInput;
     21 import java.io.DataOutputStream;
     22 import java.io.IOException;
     23 
     24 import org.apache.bcel.Const;
     25 
     26 /**
     27  * This class is derived from the abstract {@link Constant}
     28  * and represents a reference to a package.
     29  *
     30  * <p>Note: Early access Java 9 support- currently subject to change</p>
     31  *
     32  * @see     Constant
     33  * @since 6.1
     34  */
     35 public final class ConstantPackage extends Constant implements ConstantObject {
     36 
     37     private int name_index;
     38 
     39 
     40     /**
     41      * Initialize from another object.
     42      */
     43     public ConstantPackage(final ConstantPackage c) {
     44         this(c.getNameIndex());
     45     }
     46 
     47 
     48     /**
     49      * Initialize instance from file data.
     50      *
     51      * @param file Input stream
     52      * @throws IOException
     53      */
     54     ConstantPackage(final DataInput file) throws IOException {
     55         this(file.readUnsignedShort());
     56     }
     57 
     58 
     59     /**
     60      * @param name_index Name index in constant pool.  Should refer to a
     61      * ConstantUtf8.
     62      */
     63     public ConstantPackage(final int name_index) {
     64         super(Const.CONSTANT_Package);
     65         this.name_index = name_index;
     66     }
     67 
     68 
     69     /**
     70      * Called by objects that are traversing the nodes of the tree implicitely
     71      * defined by the contents of a Java class. I.e., the hierarchy of methods,
     72      * fields, attributes, etc. spawns a tree of objects.
     73      *
     74      * @param v Visitor object
     75      */
     76     @Override
     77     public void accept( final Visitor v ) {
     78         v.visitConstantPackage(this);
     79     }
     80 
     81 
     82     /**
     83      * Dump constant package to file stream in binary format.
     84      *
     85      * @param file Output file stream
     86      * @throws IOException
     87      */
     88     @Override
     89     public final void dump( final DataOutputStream file ) throws IOException {
     90         file.writeByte(super.getTag());
     91         file.writeShort(name_index);
     92     }
     93 
     94 
     95     /**
     96      * @return Name index in constant pool of package name.
     97      */
     98     public final int getNameIndex() {
     99         return name_index;
    100     }
    101 
    102 
    103     /**
    104      * @param name_index the name index in the constant pool of this Constant Package
    105      */
    106     public final void setNameIndex( final int name_index ) {
    107         this.name_index = name_index;
    108     }
    109 
    110 
    111     /** @return String object
    112      */
    113     @Override
    114     public Object getConstantValue( final ConstantPool cp ) {
    115         final Constant c = cp.getConstant(name_index, Const.CONSTANT_Utf8);
    116         return ((ConstantUtf8) c).getBytes();
    117     }
    118 
    119 
    120     /** @return dereferenced string
    121      */
    122     public String getBytes( final ConstantPool cp ) {
    123         return (String) getConstantValue(cp);
    124     }
    125 
    126 
    127     /**
    128      * @return String representation.
    129      */
    130     @Override
    131     public final String toString() {
    132         return super.toString() + "(name_index = " + name_index + ")";
    133     }
    134 }
    135