codeattribute.java

已经移植好的java虚拟机

/*
 *  Copyright (c) 2000 Sun Microsystems, Inc., 901 San Antonio Road,
 *  Palo Alto, CA 94303, U.S.A.  All Rights Reserved.
 *
 *  Sun Microsystems, Inc. has intellectual property rights relating
 *  to the technology embodied in this software.  In particular, and
 *  without limitation, these intellectual property rights may include
 *  one or more U.S. patents, foreign patents, or pending
 *  applications.  Sun, Sun Microsystems, the Sun logo, Java, KJava,
 *  and all Sun-based and Java-based marks are trademarks or
 *  registered trademarks of Sun Microsystems, Inc.  in the United
 *  States and other countries.
 *
 *  This software is distributed under licenses restricting its use,
 *  copying, distribution, and decompilation.  No part of this
 *  software may be reproduced in any form by any means without prior
 *  written authorization of Sun and its licensors, if any.
 *
 *  FEDERAL ACQUISITIONS:  Commercial Software -- Government Users
 *  Subject to Standard License Terms and Conditions
 */
package kdp.classparser.attributes;

import kdp.classparser.attributes.*;
import kdp.classparser.constantpoolclasses.*;

import java.io.*;

/**
 * Encapsulates the Code attribute of a Java class file.
 *
 * @author 			Aaron Dietrich
 * @version			$Id: CodeAttribute.java,v 1.2 2000/08/14 19:49:11 zmm3876 Exp $
 *
 * Revision History
 *   $Log: CodeAttribute.java,v $
 *   Revision 1.2  2000/08/14 19:49:11  zmm3876
 *   *** empty log message ***
 *
 *   Revision 1.1  2000/08/09 15:51:44  zmm3876
 *   *** empty log message ***
 *
 *   Revision 1.1.1.1  2000/07/07 13:34:23  jrv
 *   Initial import of kdp code
 *
 *   Revision 1.1.1.1  2000/05/31 19:14:47  ritsun
 *   Initial import of kvmdt to CVS
 *
 *   Revision 1.1  2000/04/25 00:30:39  ritsun
 *   Initial revision
 *
 */
public class CodeAttribute extends Attribute
  {
   /** index into constant pool table containing the name 
       of this class */
   private int					attributeNameIndex;
   /** length of this attribute in bytes */
   private int					attributeLength;
   /** the maximum depth of the operand stack of this method */
   private int					maxStack;
   /** the number of local variables in the local variable 
       array allocated upon invocation of this method */
   private int					maxLocals;
   /** the number of bytes in the code array for this method */
   private int					codeLength;
   /** the bytes of Java virtual machine code that implement a method */
   private byte				code[];
   /** the number of entries in the exceptionTable table */
   private int					exceptionTableLength;
   /** each entry describes one exception handler in the code array */
   private ExceptionTable     	exceptionTable[];
   /** the number of attributes of the Code attribute */
   private int					attributesCount;
   /** array of attributes for this CodeAttribute */
   private AttributeInfo	          attributes[];

   /**
    * Constructor.  Reads the CodeAttribute attribute from
    * the class file.
    *
    * @param		iStream			the input stream on which to read
    *                                   the class file
    * @param		constantPool		constant pool of the class file
    * @param		attributeNameIndex	attributeNameIndex member of
    *							attribute structure.
    * @param		attributeLength	attributeLength member of
    *							attribute structure.
    *
    * @exception	IOException		pass IOExceptions up
    */
   public CodeAttribute (DataInputStream iStream,
                         final ConstantPoolInfo[] constantPool,
   					int attributeNameIndex, int attributeLength)
                                                            throws IOException
     {
      this.attributeNameIndex = attributeNameIndex;
      this.attributeLength = attributeLength;

      //read in the maxStack and maxLocals items
      maxStack = iStream.readUnsignedShort ();
      maxLocals = iStream.readUnsignedShort ();

      //read in the length of the code array
      codeLength = iStream.readInt ();
      
      //allocate space for and read in the code array
      code = new byte[codeLength];
      for (int lcv=0; lcv < codeLength; ++lcv)
        code[lcv] = iStream.readByte ();
      
      //read in the number of items in the exception table
      exceptionTableLength = iStream.readUnsignedShort ();

      //allocate space for and read in the exception table      
      exceptionTable = new ExceptionTable[exceptionTableLength];
      for (int lcv=0; lcv < exceptionTableLength; ++lcv)
        exceptionTable[lcv] = new ExceptionTable (iStream);
      
      //read in the number of attributes
      attributesCount = iStream.readUnsignedShort ();

      //allocate space for and read in the attributes
      attributes = new AttributeInfo[attributesCount];
      for (int lcv=0; lcv < attributesCount; ++lcv)
        attributes[lcv] = new AttributeInfo (iStream, constantPool);
     }

   /**
    * Retrieves the line number table of this code attribute
    *
    * @return       LineNumberTableAttribute      this code attribute's
    *                                             line number table.
    */
   public LineNumberTableAttribute getLineNumberTable ()
     {
      int           attrIndex = 0;
      boolean       found = false;

      //loop through this code attribute's attributes until the line number
      //table is found or there are no more to look through
      while ((!found) && (attrIndex < attributesCount))
        {
         if (attributes[attrIndex].getType () == AttributeInfo.ATTR_LINENUMBER)
           found = true;
         else
           ++attrIndex;
        }

      if (found)
        {//if we found the line number table return it
         AttributeInfo              attrInfo = attributes[attrIndex];
         LineNumberTableAttribute   lineNumberTable =
                                 (LineNumberTableAttribute) attrInfo.getInfo ();
         return lineNumberTable;
        }
      else
        return null; //did not find the line number table so return null
     }

   /**
    * Query this code attribute to see if it contains the source file
    * line number specified by lineNumber.
    *
    * @return       boolean        true if the line number is in this code
    *                              attribute, false otherwise
    */
   public boolean containsLine (int lineNumber)
     {
      //get the line number table
      LineNumberTableAttribute     lines = getLineNumberTable ();

      //if the line number table was found tell it to look up the line number
      if (lines != null)
        return (lines.containsLine (lineNumber));
      else
        return false; //could not find the line number table so return false
     }
     
   /**
    * Returns the byte code for the method 
    *
    * @return           byte[]       byte code
    */

   public byte[] getByteCodes() {
       byte[] ret = new byte[ code.length ];
       System.arraycopy( code, 0, ret, 0, code.length );
       return ret;
   }

   public int getCodeLength() {
       return code.length;
   }


   /**
    * Returns the CodeAttribute attribute in a nice easy to
    * read format as a string.
    *
    * @param		constantPool		constant pool of the class file
    *
    * @return 		String			the attribute as a nice easy to
    *							read String
    */
   public String toString (final ConstantPoolInfo[] constantPool)
     {
      ConstantUtf8Info			utf8Info;
      String					s = new String ("");

      utf8Info = (ConstantUtf8Info) constantPool[attributeNameIndex];
      s = s + utf8Info.toString ();

      for (int lcv = 0; lcv < attributesCount; ++lcv)
        s = s + "\n\t\t" + attributes[lcv].toString ();

      return s;
     }
     
     public AttributeInfo[] getAttributes(){
        return attributes;
     }
     
     public int getAttributeCount(){
        return attributesCount;
     }
  }