    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.bcel.classfile;
    020
    021import java.io.DataInput;
    022import java.io.DataOutputStream;
    023import java.io.IOException;
    024import java.util.Arrays;
    025
    026import org.apache.bcel.Const;
    027import org.apache.bcel.util.Args;
    028
    029/**
    030 * This class represents a stack map attribute used for preverification of Java classes for the
    031 * <a href="https://java.sun.com/j2me/"> Java 2 Micro Edition</a> (J2ME). This attribute is used by the
    032 * <a href="https://java.sun.com/products/cldc/">KVM</a> and contained within the Code attribute of a method. See CLDC
    033 * specification �5.3.1.2
    034 *
    035 * <pre>
    036 * StackMapTable_attribute {
    037 *   u2              attribute_name_index;
    038 *   u4              attribute_length;
    039 *   u2              number_of_entries;
    040 *   stack_map_frame entries[number_of_entries];
    041 * }
    042 * </pre>
    043 *
    044 * @see Code
    045 * @see StackMapEntry
    046 * @see StackMapType
    047 */
    048public final class StackMap extends Attribute {
    049
    050    private StackMapEntry[] table; // Table of stack map entries
    051
    052    /**
    053     * Constructs object from input stream.
    054     *
    055     * @param nameIndex Index of name.
    056     * @param length Content length in bytes.
    057     * @param dataInput Input stream.
    058     * @param constantPool Array of constants.
    059     * @throws IOException if an I/O error occurs.
    060     */
    061    StackMap(final int nameIndex, final int length, final DataInput dataInput, final ConstantPool constantPool) throws IOException {
    062        this(nameIndex, length, (StackMapEntry[]) null, constantPool);
    063        final int mapLength = dataInput.readUnsignedShort();
    064        table = new StackMapEntry[mapLength];
    065        for (int i = 0; i < mapLength; i++) {
    066            table[i] = new StackMapEntry(dataInput, constantPool);
    067        }
    068    }
    069
    070    /*
    071     * @param nameIndex Index of name.
    072     * @param length Content length in bytes.
    073     * @param map Table of stack map entries.
    074     * @param constantPool Array of constants.
    075     */
    076    public StackMap(final int nameIndex, final int length, final StackMapEntry[] table, final ConstantPool constantPool) {
    077        super(Const.ATTR_STACK_MAP, nameIndex, length, constantPool);
    078        this.table = table != null ? table : StackMapEntry.EMPTY_ARRAY;
    079        Args.requireU2(this.table.length, "table.length");
    080    }
    081
    082    /**
    083     * Called by objects that are traversing the nodes of the tree implicitly defined by the contents of a Java class.
    084     * I.e., the hierarchy of methods, fields, attributes, etc. spawns a tree of objects.
    085     *
    086     * @param v Visitor object.
    087     */
    088    @Override
    089    public void accept(final Visitor v) {
    090        v.visitStackMap(this);
    091    }
    092
    093    /**
    094     * @return deep copy of this attribute.
    095     */
    096    @Override
    097    public Attribute copy(final ConstantPool constantPool) {
    098        final StackMap c = (StackMap) clone();
    099        c.table = new StackMapEntry[table.length];
    100        Arrays.setAll(c.table, i -> table[i].copy());
    101        c.setConstantPool(constantPool);
    102        return c;
    103    }
    104
    105    /**
    106     * Dumps stack map table attribute to file stream in binary format.
    107     *
    108     * @param file Output file stream.
    109     * @throws IOException if an I/O error occurs.
    110     */
    111    @Override
    112    public void dump(final DataOutputStream file) throws IOException {
    113        super.dump(file);
    114        file.writeShort(table.length);
    115        for (final StackMapEntry entry : table) {
    116            entry.dump(file);
    117        }
    118    }
    119
    120    public int getMapLength() {
    121        return table.length;
    122    }
    123
    124    /**
    125     * @return Array of stack map entries.
    126     */
    127    public StackMapEntry[] getStackMap() {
    128        return table;
    129    }
    130
    131    /**
    132     * @param table Array of stack map entries.
    133     */
    134    public void setStackMap(final StackMapEntry[] table) {
    135        this.table = table != null ? table : StackMapEntry.EMPTY_ARRAY;
    136        int len = 2; // Length of 'number_of_entries' field prior to the array of stack maps
    137        for (final StackMapEntry element : this.table) {
    138            len += element.getMapEntrySize();
    139        }
    140        setLength(len);
    141    }
    142
    143    /**
    144     * @return String representation.
    145     */
    146    @Override
    147    public String toString() {
    148        final StringBuilder buf = new StringBuilder("StackMap(");
    149        int runningOffset = -1; // no +1 on first entry
    150        for (int i = 0; i < table.length; i++) {
    151            runningOffset = table[i].getByteCodeOffset() + runningOffset + 1;
    152            buf.append(String.format("%n@%03d %s", runningOffset, table[i]));
    153            if (i < table.length - 1) {
    154                buf.append(", ");
    155            }
    156        }
    157        buf.append(')');
    158        return buf.toString();
    159    }
    160}