    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 */
    017package org.apache.bcel.classfile;
    018
    019import java.io.DataInput;
    020import java.io.DataOutputStream;
    021import java.io.IOException;
    022
    023import org.apache.bcel.Const;
    024
    025/**
    026 * This class represents the type of a local variable or item on stack used in the StackMap entries.
    027 *
    028 * @see StackMapEntry
    029 * @see StackMap
    030 * @see Const
    031 */
    032public final class StackMapType implements Node, Cloneable {
    033
    034    public static final StackMapType[] EMPTY_ARRAY = {}; // BCELifier code generator writes calls to constructor translating null to EMPTY_ARRAY
    035
    036    private byte type;
    037    private int index = -1; // Index to CONSTANT_Class or offset
    038    private ConstantPool constantPool;
    039
    040    /**
    041     * @param type type tag as defined in the Constants interface
    042     * @param index index to constant pool, or byte code offset
    043     */
    044    public StackMapType(final byte type, final int index, final ConstantPool constantPool) {
    045        this.type = checkType(type);
    046        this.index = index;
    047        this.constantPool = constantPool;
    048    }
    049
    050    /**
    051     * Constructs object from file stream.
    052     *
    053     * @param file Input stream
    054     * @throws IOException if an I/O error occurs.
    055     */
    056    StackMapType(final DataInput file, final ConstantPool constantPool) throws IOException {
    057        this(file.readByte(), -1, constantPool);
    058        if (hasIndex()) {
    059            this.index = file.readUnsignedShort();
    060        }
    061        this.constantPool = constantPool;
    062    }
    063
    064    /**
    065     * Called by objects that are traversing the nodes of the tree implicitly defined by the contents of a Java class.
    066     * I.e., the hierarchy of methods, fields, attributes, etc. spawns a tree of objects.
    067     *
    068     * @param v Visitor object
    069     * @since 6.8.0
    070     */
    071    @Override
    072    public void accept(final Visitor v) {
    073        v.visitStackMapType(this);
    074    }
    075
    076    private byte checkType(final byte type) {
    077        if (type < Const.ITEM_Bogus || type > Const.ITEM_NewObject) {
    078            throw new ClassFormatException("Illegal type for StackMapType: " + type);
    079        }
    080        return type;
    081    }
    082
    083    /**
    084     * @return deep copy of this object
    085     */
    086    public StackMapType copy() {
    087        try {
    088            return (StackMapType) clone();
    089        } catch (final CloneNotSupportedException e) {
    090            // TODO should this throw?
    091        }
    092        return null;
    093    }
    094
    095    /**
    096     * Dump type entries to file.
    097     *
    098     * @param file Output file stream
    099     * @throws IOException if an I/O error occurs.
    100     */
    101    public void dump(final DataOutputStream file) throws IOException {
    102        file.writeByte(type);
    103        if (hasIndex()) {
    104            file.writeShort(getIndex());
    105        }
    106    }
    107
    108    /**
    109     * Gets the class name of this StackMapType from the constant pool at index position.
    110     * @return the fully qualified name of the class for this StackMapType.
    111     * @since 6.8.0
    112     */
    113    public String getClassName() {
    114        return constantPool.constantToString(index, Const.CONSTANT_Class);
    115    }
    116
    117    /**
    118     * @return Constant pool used by this object.
    119     */
    120    public ConstantPool getConstantPool() {
    121        return constantPool;
    122    }
    123
    124    /**
    125     * @return index to constant pool if type == ITEM_Object, or offset in byte code, if type == ITEM_NewObject, and -1
    126     *         otherwise
    127     */
    128    public int getIndex() {
    129        return index;
    130    }
    131
    132    public byte getType() {
    133        return type;
    134    }
    135
    136    /**
    137     * @return true, if type is either ITEM_Object or ITEM_NewObject
    138     */
    139    public boolean hasIndex() {
    140        return type == Const.ITEM_Object || type == Const.ITEM_NewObject;
    141    }
    142
    143    private String printIndex() {
    144        if (type == Const.ITEM_Object) {
    145            if (index < 0) {
    146                return ", class=<unknown>";
    147            }
    148            return ", class=" + getClassName();
    149        }
    150        if (type == Const.ITEM_NewObject) {
    151            return ", offset=" + index;
    152        }
    153        return "";
    154    }
    155
    156    /**
    157     * @param constantPool Constant pool to be used for this object.
    158     */
    159    public void setConstantPool(final ConstantPool constantPool) {
    160        this.constantPool = constantPool;
    161    }
    162
    163    public void setIndex(final int index) {
    164        this.index = index;
    165    }
    166
    167    public void setType(final byte type) {
    168        this.type = checkType(type);
    169    }
    170
    171    /**
    172     * @return String representation
    173     */
    174    @Override
    175    public String toString() {
    176        return "(type=" + Const.getItemName(type) + printIndex() + ")";
    177    }
    178}