    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;
    024import org.apache.bcel.Constants;
    025import org.apache.bcel.util.Args;
    026
    027/**
    028 * This class represents an entry in the exception table of the <em>Code</em> attribute and is used only there. It
    029 * contains a range in which a particular exception handler is active.
    030 *
    031 * <pre>
    032 * Code_attribute {
    033 *   u2 attribute_name_index;
    034 *   u4 attribute_length;
    035 *   u2 max_stack;
    036 *   u2 max_locals;
    037 *   u4 code_length;
    038 *   u1 code[code_length];
    039 *   u2 exception_table_length;
    040 *   {
    041 *     u2 start_pc;
    042 *     u2 end_pc;
    043 *     u2 handler_pc;
    044 *     u2 catch_type;
    045 *   } exception_table[exception_table_length];
    046 *   u2 attributes_count;
    047 *   attribute_info attributes[attributes_count];
    048 * }
    049 * </pre>
    050 *
    051 * @see Code
    052 */
    053public final class CodeException implements Cloneable, Node, Constants {
    054
    055    /**
    056     * Empty array.
    057     */
    058    static final CodeException[] EMPTY_CODE_EXCEPTION_ARRAY = {};
    059
    060    /** Range in the code the exception handler. */
    061    private int startPc;
    062
    063    /** Active. startPc is inclusive, endPc exclusive. */
    064    private int endPc;
    065
    066    /**
    067     * Starting address of exception handler, i.e., an offset from start of code.
    068     */
    069    private int handlerPc;
    070
    071    /*
    072     * If this is zero the handler catches any exception, otherwise it points to the exception class which is to be caught.
    073     */
    074    private int catchType;
    075
    076    /**
    077     * Constructs a new instance from another instance.
    078     *
    079     * @param c Source for copying.
    080     */
    081    public CodeException(final CodeException c) {
    082        this(c.getStartPC(), c.getEndPC(), c.getHandlerPC(), c.getCatchType());
    083    }
    084
    085    /**
    086     * Constructs a new instance from a DataInput.
    087     *
    088     * @param file Input stream
    089     * @throws IOException if an I/O error occurs.
    090     */
    091    CodeException(final DataInput file) throws IOException {
    092        this(file.readUnsignedShort(), file.readUnsignedShort(), file.readUnsignedShort(), file.readUnsignedShort());
    093    }
    094
    095    /**
    096     * Constructs a new instance.
    097     *
    098     * @param startPc Range in the code the exception handler is active, startPc is inclusive while
    099     * @param endPc is exclusive
    100     * @param handlerPc Starting address of exception handler, i.e., an offset from start of code.
    101     * @param catchType If zero the handler catches any exception, otherwise it points to the exception class which is to be
    102     *        caught.
    103     */
    104    public CodeException(final int startPc, final int endPc, final int handlerPc, final int catchType) {
    105        this.startPc = Args.requireU2(startPc, "startPc");
    106        this.endPc = Args.requireU2(endPc, "endPc");
    107        this.handlerPc = Args.requireU2(handlerPc, "handlerPc");
    108        this.catchType = Args.requireU2(catchType, "catchType");
    109    }
    110
    111    /**
    112     * Called by objects that are traversing the nodes of the tree implicitly defined by the contents of a Java class.
    113     * I.e., the hierarchy of methods, fields, attributes, etc. spawns a tree of objects.
    114     *
    115     * @param v Visitor object
    116     */
    117    @Override
    118    public void accept(final Visitor v) {
    119        v.visitCodeException(this);
    120    }
    121
    122    /**
    123     * @return deep copy of this object
    124     */
    125    public CodeException copy() {
    126        try {
    127            return (CodeException) clone();
    128        } catch (final CloneNotSupportedException e) {
    129            // TODO should this throw?
    130        }
    131        return null;
    132    }
    133
    134    /**
    135     * Dumps code exception to file stream in binary format.
    136     *
    137     * @param file Output file stream
    138     * @throws IOException if an I/O error occurs.
    139     */
    140    public void dump(final DataOutputStream file) throws IOException {
    141        file.writeShort(startPc);
    142        file.writeShort(endPc);
    143        file.writeShort(handlerPc);
    144        file.writeShort(catchType);
    145    }
    146
    147    /**
    148     * @return 0, if the handler catches any exception, otherwise it points to the exception class which is to be caught.
    149     */
    150    public int getCatchType() {
    151        return catchType;
    152    }
    153
    154    /**
    155     * @return Exclusive end index of the region where the handler is active.
    156     */
    157    public int getEndPC() {
    158        return endPc;
    159    }
    160
    161    /**
    162     * @return Starting address of exception handler, relative to the code.
    163     */
    164    public int getHandlerPC() {
    165        return handlerPc;
    166    }
    167
    168    /**
    169     * @return Inclusive start index of the region where the handler is active.
    170     */
    171    public int getStartPC() {
    172        return startPc;
    173    }
    174
    175    /**
    176     * @param catchType the type of exception that is caught
    177     */
    178    public void setCatchType(final int catchType) {
    179        this.catchType = catchType;
    180    }
    181
    182    /**
    183     * @param endPc end of handled block
    184     */
    185    public void setEndPC(final int endPc) {
    186        this.endPc = endPc;
    187    }
    188
    189    /**
    190     * @param handlerPc where the actual code is
    191     */
    192    public void setHandlerPC(final int handlerPc) { // TODO unused
    193        this.handlerPc = handlerPc;
    194    }
    195
    196    /**
    197     * @param startPc start of handled block
    198     */
    199    public void setStartPC(final int startPc) { // TODO unused
    200        this.startPc = startPc;
    201    }
    202
    203    /**
    204     * @return String representation.
    205     */
    206    @Override
    207    public String toString() {
    208        return "CodeException(startPc = " + startPc + ", endPc = " + endPc + ", handlerPc = " + handlerPc + ", catchType = " + catchType + ")";
    209    }
    210
    211    public String toString(final ConstantPool cp) {
    212        return toString(cp, true);
    213    }
    214
    215    /**
    216     * @param cp constant pool source.
    217     * @param verbose Output more if true.
    218     * @return String representation.
    219     */
    220    public String toString(final ConstantPool cp, final boolean verbose) {
    221        String str;
    222        if (catchType == 0) {
    223            str = "<Any exception>(0)";
    224        } else {
    225            str = Utility.compactClassName(cp.getConstantString(catchType, Const.CONSTANT_Class), false) + (verbose ? "(" + catchType + ")" : "");
    226        }
    227        return startPc + "\t" + endPc + "\t" + handlerPc + "\t" + str;
    228    }
    229}