    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;
    023import java.util.Iterator;
    024import java.util.stream.Stream;
    025
    026import org.apache.bcel.Const;
    027import org.apache.bcel.util.Args;
    028
    029/**
    030 * This class represents colection of local variables in a method. This attribute is contained in the <em>Code</em>
    031 * attribute.
    032 *
    033 * @see Code
    034 * @see LocalVariable
    035 */
    036public class LocalVariableTable extends Attribute implements Iterable<LocalVariable> {
    037
    038    private static final LocalVariable[] EMPTY_ARRAY = {};
    039
    040    private LocalVariable[] localVariableTable; // variables
    041
    042    /**
    043     * Constructs object from input stream.
    044     *
    045     * @param nameIndex Index in constant pool
    046     * @param length Content length in bytes
    047     * @param input Input stream
    048     * @param constantPool Array of constants
    049     * @throws IOException if an I/O error occurs.
    050     */
    051    LocalVariableTable(final int nameIndex, final int length, final DataInput input, final ConstantPool constantPool) throws IOException {
    052        this(nameIndex, length, (LocalVariable[]) null, constantPool);
    053        final int localVariableTableLength = input.readUnsignedShort();
    054        localVariableTable = new LocalVariable[localVariableTableLength];
    055        for (int i = 0; i < localVariableTableLength; i++) {
    056            localVariableTable[i] = new LocalVariable(input, constantPool);
    057        }
    058    }
    059
    060    /**
    061     * @param nameIndex Index in constant pool to 'LocalVariableTable'
    062     * @param length Content length in bytes
    063     * @param localVariableTable Table of local variables
    064     * @param constantPool Array of constants
    065     */
    066    public LocalVariableTable(final int nameIndex, final int length, final LocalVariable[] localVariableTable, final ConstantPool constantPool) {
    067        super(Const.ATTR_LOCAL_VARIABLE_TABLE, nameIndex, length, constantPool);
    068        this.localVariableTable = localVariableTable != null ? localVariableTable : EMPTY_ARRAY;
    069        Args.requireU2(this.localVariableTable.length, "localVariableTable.length");
    070    }
    071
    072    /**
    073     * Initialize from another object. Note that both objects use the same references (shallow copy). Use copy() for a
    074     * physical copy.
    075     *
    076     * @param c Source to copy.
    077     */
    078    public LocalVariableTable(final LocalVariableTable c) {
    079        this(c.getNameIndex(), c.getLength(), c.getLocalVariableTable(), c.getConstantPool());
    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.visitLocalVariableTable(this);
    091    }
    092
    093    /**
    094     * @return deep copy of this attribute
    095     */
    096    @Override
    097    public Attribute copy(final ConstantPool constantPool) {
    098        final LocalVariableTable c = (LocalVariableTable) clone();
    099        c.localVariableTable = new LocalVariable[localVariableTable.length];
    100        Arrays.setAll(c.localVariableTable, i -> localVariableTable[i].copy());
    101        c.setConstantPool(constantPool);
    102        return c;
    103    }
    104
    105    /**
    106     * Dump local variable 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 final void dump(final DataOutputStream file) throws IOException {
    113        super.dump(file);
    114        file.writeShort(localVariableTable.length);
    115        for (final LocalVariable variable : localVariableTable) {
    116            variable.dump(file);
    117        }
    118    }
    119
    120    /**
    121     *
    122     * @param index the variable slot
    123     *
    124     * @return the first LocalVariable that matches the slot or null if not found
    125     *
    126     * @deprecated since 5.2 because multiple variables can share the same slot, use getLocalVariable(int index, int pc)
    127     *             instead.
    128     */
    129    @java.lang.Deprecated
    130    public final LocalVariable getLocalVariable(final int index) {
    131        for (final LocalVariable variable : localVariableTable) {
    132            if (variable.getIndex() == index) {
    133                return variable;
    134            }
    135        }
    136        return null;
    137    }
    138
    139    /**
    140     *
    141     * @param index the variable slot
    142     * @param pc the current pc that this variable is alive
    143     *
    144     * @return the LocalVariable that matches or null if not found
    145     */
    146    public final LocalVariable getLocalVariable(final int index, final int pc) {
    147        for (final LocalVariable variable : localVariableTable) {
    148            if (variable.getIndex() == index) {
    149                final int startPc = variable.getStartPC();
    150                final int endPc = startPc + variable.getLength();
    151                if (pc >= startPc && pc <= endPc) {
    152                    return variable;
    153                }
    154            }
    155        }
    156        return null;
    157    }
    158
    159    /**
    160     * @return Array of local variables of method.
    161     */
    162    public final LocalVariable[] getLocalVariableTable() {
    163        return localVariableTable;
    164    }
    165
    166    public final int getTableLength() {
    167        return localVariableTable.length;
    168    }
    169
    170    @Override
    171    public Iterator<LocalVariable> iterator() {
    172        return Stream.of(localVariableTable).iterator();
    173    }
    174
    175    public final void setLocalVariableTable(final LocalVariable[] localVariableTable) {
    176        this.localVariableTable = localVariableTable != null ? localVariableTable : EMPTY_ARRAY;
    177    }
    178
    179    /**
    180     * @return String representation.
    181     */
    182    @Override
    183    public final String toString() {
    184        final StringBuilder buf = new StringBuilder();
    185        for (int i = 0; i < localVariableTable.length; i++) {
    186            buf.append(localVariableTable[i]);
    187            if (i < localVariableTable.length - 1) {
    188                buf.append('\n');
    189            }
    190        }
    191        return buf.toString();
    192    }
    193}