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      1 /* Copyright (C) 2003 Vladimir Roubtsov. All rights reserved.
      2  *
      3  * This program and the accompanying materials are made available under
      4  * the terms of the Common Public License v1.0 which accompanies this distribution,
      5  * and is available at http://www.eclipse.org/legal/cpl-v10.html
      6  *
      7  * $Id: Exception_info.java,v 1.1.1.1 2004/05/09 16:57:48 vlad_r Exp $
      8  */
      9 package com.vladium.jcd.cls.attribute;
     10 
     11 import java.io.IOException;
     12 
     13 import com.vladium.jcd.compiler.IClassFormatOutput;
     14 import com.vladium.jcd.lib.UDataInputStream;
     15 import com.vladium.jcd.lib.UDataOutputStream;
     16 
     17 // ----------------------------------------------------------------------------
     18 /**
     19  * An Exception_info is an entry layout format for {@link ExceptionHandlerTable}. Each
     20  * entry contains the following items:
     21  * <PRE>
     22  *    start_pc, end_pc
     23  * </PRE>
     24  * The values of the two items start_pc and end_pc indicate the ranges in the code
     25  * array at which the exception handler is active. The value of start_pc must be
     26  * a valid index into the code array of the opcode of an instruction. The value of
     27  * end_pc either must be a valid index into the code array of the opcode of an
     28  * instruction, or must be equal to code_length , the length of the code array.
     29  * The value of start_pc must be less than the value of end_pc.<P>
     30  *
     31  * The start_pc is inclusive and end_pc is exclusive; that is, the exception handler
     32  * must be active while the program counter is within the interval [start_pc, end_pc).
     33  * <PRE>
     34  *    handler_pc
     35  * </PRE>
     36  * The value of the handler_pc item indicates the start of the exception handler.
     37  * The value of the item must be a valid index into the code array, must be the index
     38  * of the opcode of an instruction, and must be less than the value of the code_length
     39  * item.
     40  * <PRE>
     41  *    catch_type
     42  * </PRE>
     43  * If the value of the catch_type item is nonzero, it must be a valid index into the
     44  * constant_pool table. The constant_pool entry at that index must be a
     45  * {@link com.vladium.jcd.cls.constant.CONSTANT_Class_info} structure representing
     46  * a class of exceptions that this exception handler is designated to catch.
     47  * This class must be the class Throwable or one of its subclasses. The exception
     48  * handler will be called only if the thrown exception is an instance of the given
     49  * class or one of its subclasses.<P>
     50  *
     51  * If the value of the catch_type item is zero, this exception handler is called for
     52  * all exceptions. This is used to implement finally.
     53  *
     54  * @author (C) 2001, Vlad Roubtsov
     55  */
     56 public
     57 final class Exception_info implements Cloneable, IClassFormatOutput
     58 {
     59     // public: ................................................................
     60 
     61 
     62     public int m_start_pc, m_end_pc, m_handler_pc, m_catch_type;
     63 
     64 
     65     public Exception_info (final int start_pc, final int end_pc,
     66                            final int handler_pc, final int catch_type)
     67     {
     68         m_start_pc = start_pc;
     69         m_end_pc = end_pc;
     70         m_handler_pc = handler_pc;
     71         m_catch_type = catch_type;
     72     }
     73 
     74 
     75     public String toString ()
     76     {
     77         return "exception_info: [start_pc/end_pc = " + m_start_pc + '/' + m_end_pc +
     78                ", handler_pc = " + m_handler_pc +
     79                ", catch_type = " + m_catch_type + ']';
     80     }
     81 
     82     // Cloneable:
     83 
     84     /**
     85      * Performs a deep copy.
     86      */
     87     public Object clone ()
     88     {
     89         try
     90         {
     91             return super.clone ();
     92         }
     93         catch (CloneNotSupportedException e)
     94         {
     95             throw new InternalError (e.toString ());
     96         }
     97     }
     98 
     99     // IClassFormatOutput:
    100 
    101     public void writeInClassFormat (final UDataOutputStream out) throws IOException
    102     {
    103         out.writeU2 (m_start_pc);
    104         out.writeU2 (m_end_pc);
    105         out.writeU2 (m_handler_pc);
    106         out.writeU2 (m_catch_type);
    107     }
    108 
    109     // protected: .............................................................
    110 
    111     // package: ...............................................................
    112 
    113 
    114     Exception_info (final UDataInputStream bytes) throws IOException
    115     {
    116         m_start_pc = bytes.readU2 ();
    117         m_end_pc = bytes.readU2 ();
    118         m_handler_pc = bytes.readU2 ();
    119         m_catch_type = bytes.readU2 ();
    120     }
    121 
    122     // private: ...............................................................
    123 
    124 } // end of class
    125 // ----------------------------------------------------------------------------
    126