    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;
    022import java.util.Arrays;
    023
    024import org.apache.bcel.Const;
    025import org.apache.bcel.util.Args;
    026
    027/**
    028 * This class represents a stack map attribute used for preverification of Java classes for the
    029 * <a href="https://java.sun.com/j2me/"> Java 2 Micro Edition</a> (J2ME). This attribute is used by the
    030 * <a href="https://java.sun.com/products/cldc/">KVM</a> and contained within the Code attribute of a method. See CLDC
    031 * specification �5.3.1.2
    032 *
    033 * <pre>
    034 * StackMapTable_attribute {
    035 *   u2              attribute_name_index;
    036 *   u4              attribute_length;
    037 *   u2              number_of_entries;
    038 *   stack_map_frame entries[number_of_entries];
    039 * }
    040 * </pre>
    041 *
    042 * @see Code
    043 * @see StackMapEntry
    044 * @see StackMapType
    045 */
    046public final class StackMap extends Attribute {
    047
    048    private StackMapEntry[] table; // Table of stack map entries
    049
    050    /**
    051     * Constructs object from input stream.
    052     *
    053     * @param nameIndex Index of name
    054     * @param length Content length in bytes
    055     * @param dataInput Input stream
    056     * @param constantPool Array of constants
    057     * @throws IOException if an I/O error occurs.
    058     */
    059    StackMap(final int nameIndex, final int length, final DataInput dataInput, final ConstantPool constantPool) throws IOException {
    060        this(nameIndex, length, (StackMapEntry[]) null, constantPool);
    061        final int mapLength = dataInput.readUnsignedShort();
    062        table = new StackMapEntry[mapLength];
    063        for (int i = 0; i < mapLength; i++) {
    064            table[i] = new StackMapEntry(dataInput, constantPool);
    065        }
    066    }
    067
    068    /*
    069     * @param nameIndex Index of name
    070     *
    071     * @param length Content length in bytes
    072     *
    073     * @param map Table of stack map entries
    074     *
    075     * @param constantPool Array of constants
    076     */
    077    public StackMap(final int nameIndex, final int length, final StackMapEntry[] table, final ConstantPool constantPool) {
    078        super(Const.ATTR_STACK_MAP, nameIndex, length, constantPool);
    079        this.table = table != null ? table : StackMapEntry.EMPTY_ARRAY;
    080        Args.requireU2(this.table.length, "table.length");
    081    }
    082
    083    /**
    084     * Called by objects that are traversing the nodes of the tree implicitly defined by the contents of a Java class.
    085     * I.e., the hierarchy of methods, fields, attributes, etc. spawns a tree of objects.
    086     *
    087     * @param v Visitor object
    088     */
    089    @Override
    090    public void accept(final Visitor v) {
    091        v.visitStackMap(this);
    092    }
    093
    094    /**
    095     * @return deep copy of this attribute
    096     */
    097    @Override
    098    public Attribute copy(final ConstantPool constantPool) {
    099        final StackMap c = (StackMap) clone();
    100        c.table = new StackMapEntry[table.length];
    101        Arrays.setAll(c.table, i -> table[i].copy());
    102        c.setConstantPool(constantPool);
    103        return c;
    104    }
    105
    106    /**
    107     * Dump stack map table attribute to file stream in binary format.
    108     *
    109     * @param file Output file stream
    110     * @throws IOException if an I/O error occurs.
    111     */
    112    @Override
    113    public void dump(final DataOutputStream file) throws IOException {
    114        super.dump(file);
    115        file.writeShort(table.length);
    116        for (final StackMapEntry entry : table) {
    117            entry.dump(file);
    118        }
    119    }
    120
    121    public int getMapLength() {
    122        return table.length;
    123    }
    124
    125    /**
    126     * @return Array of stack map entries
    127     */
    128    public StackMapEntry[] getStackMap() {
    129        return table;
    130    }
    131
    132    /**
    133     * @param table Array of stack map entries
    134     */
    135    public void setStackMap(final StackMapEntry[] table) {
    136        this.table = table != null ? table : StackMapEntry.EMPTY_ARRAY;
    137        int len = 2; // Length of 'number_of_entries' field prior to the array of stack maps
    138        for (final StackMapEntry element : this.table) {
    139            len += element.getMapEntrySize();
    140        }
    141        setLength(len);
    142    }
    143
    144    /**
    145     * @return String representation.
    146     */
    147    @Override
    148    public String toString() {
    149        final StringBuilder buf = new StringBuilder("StackMap(");
    150        int runningOffset = -1; // no +1 on first entry
    151        for (int i = 0; i < table.length; i++) {
    152            runningOffset = table[i].getByteCodeOffset() + runningOffset + 1;
    153            buf.append(String.format("%n@%03d %s", runningOffset, table[i]));
    154            if (i < table.length - 1) {
    155                buf.append(", ");
    156            }
    157        }
    158        buf.append(')');
    159        return buf.toString();
    160    }
    161}