commons-bcel-master/src/main/java/org/apache/bcel/classfile/StackMapType.java
/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */
package org.apache.bcel.classfile;

import java.io.DataInput;
import java.io.DataOutputStream;
import java.io.IOException;

import org.apache.bcel.Const;

/**
 * This class represents the type of a local variable or item on stack used in the StackMap entries.
 *
 * @see StackMapEntry
 * @see StackMap
 * @see Const
 */
public final class StackMapType implements Node, Cloneable {

    public static final StackMapType[] EMPTY_ARRAY = {}; // BCELifier code generator writes calls to constructor translating null to EMPTY_ARRAY

    private byte type;
    private int index = -1; // Index to CONSTANT_Class or offset
    private ConstantPool constantPool;

    /**
     * @param type type tag as defined in the Constants interface
     * @param index index to constant pool, or byte code offset
     */
    public StackMapType(final byte type, final int index, final ConstantPool constantPool) {
        this.type = checkType(type);
        this.index = index;
        this.constantPool = constantPool;
    }

    /**
     * Construct object from file stream.
     *
     * @param file Input stream
     * @throws IOException if an I/O error occurs.
     */
    StackMapType(final DataInput file, final ConstantPool constantPool) throws IOException {
        this(file.readByte(), -1, constantPool);
        if (hasIndex()) {
            this.index = file.readUnsignedShort();
        }
        this.constantPool = constantPool;
    }

    /**
     * Called by objects that are traversing the nodes of the tree implicitly defined by the contents of a Java class.
     * I.e., the hierarchy of methods, fields, attributes, etc. spawns a tree of objects.
     *
     * @param v Visitor object
     * @since 6.8.0
     */
    @Override
    public void accept(final Visitor v) {
        v.visitStackMapType(this);
    }

    private byte checkType(final byte type) {
        if (type < Const.ITEM_Bogus || type > Const.ITEM_NewObject) {
            throw new ClassFormatException("Illegal type for StackMapType: " + type);
        }
        return type;
    }

    /**
     * @return deep copy of this object
     */
    public StackMapType copy() {
        try {
            return (StackMapType) clone();
        } catch (final CloneNotSupportedException e) {
            // TODO should this throw?
        }
        return null;
    }

    /**
     * Dump type entries to file.
     *
     * @param file Output file stream
     * @throws IOException if an I/O error occurs.
     */
    public void dump(final DataOutputStream file) throws IOException {
        file.writeByte(type);
        if (hasIndex()) {
            file.writeShort(getIndex());
        }
    }

    /**
     * Gets the class name of this StackMapType from the constant pool at index position.
     * @return the fully qualified name of the class for this StackMapType.
     * @since 6.8.0
     */
    public String getClassName() {
        return constantPool.constantToString(index, Const.CONSTANT_Class);
    }

    /**
     * @return Constant pool used by this object.
     */
    public ConstantPool getConstantPool() {
        return constantPool;
    }

    /**
     * @return index to constant pool if type == ITEM_Object, or offset in byte code, if type == ITEM_NewObject, and -1
     *         otherwise
     */
    public int getIndex() {
        return index;
    }

    public byte getType() {
        return type;
    }

    /**
     * @return true, if type is either ITEM_Object or ITEM_NewObject
     */
    public boolean hasIndex() {
        return type == Const.ITEM_Object || type == Const.ITEM_NewObject;
    }

    private String printIndex() {
        if (type == Const.ITEM_Object) {
            if (index < 0) {
                return ", class=<unknown>";
            }
            return ", class=" + getClassName();
        }
        if (type == Const.ITEM_NewObject) {
            return ", offset=" + index;
        }
        return "";
    }

    /**
     * @param constantPool Constant pool to be used for this object.
     */
    public void setConstantPool(final ConstantPool constantPool) {
        this.constantPool = constantPool;
    }

    public void setIndex(final int index) {
        this.index = index;
    }

    public void setType(final byte type) {
        this.type = checkType(type);
    }

    /**
     * @return String representation
     */
    @Override
    public String toString() {
        return "(type=" + Const.getItemName(type) + printIndex() + ")";
    }
}
