linenumbertable.java

该开源工具主要用于class文件的操作

package org.apache.bcel.classfile;

/* ====================================================================
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 2001 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Apache" and "Apache Software Foundation" and
 *    "Apache BCEL" must not be used to endorse or promote products
 *    derived from this software without prior written permission. For
 *    written permission, please contact [e-mail].
 *
 * 5. Products derived from this software may not be called "Apache",
 *    "Apache BCEL", nor may "Apache" appear in their name, without
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 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
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 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 */

import  org.apache.bcel.Constants;
import  java.io.*;

/**
 * This class represents a table of line numbers for debugging
 * purposes. This attribute is used by the <em>Code</em> attribute. It
 * contains pairs of PCs and line numbers.
 *
 * @version $Id: LineNumberTable.java,v 1.1.1.1 2001/10/29 20:00:02 jvanzyl Exp $
 * @author  <A HREF="mailto:[e-mail]">M. Dahm</A>
 * @see     Code
 * @see LineNumber
 */
public final class LineNumberTable extends Attribute {
  private int          line_number_table_length;
  private LineNumber[] line_number_table; // Table of line/numbers pairs

  /*
   * Initialize from another object. Note that both objects use the same
   * references (shallow copy). Use copy() for a physical copy.
   */
  public LineNumberTable(LineNumberTable c) {
    this(c.getNameIndex(), c.getLength(), c.getLineNumberTable(),
	 c.getConstantPool());
  }

  /*
   * @param name_index Index of name
   * @param length Content length in bytes
   * @param line_number_table Table of line/numbers pairs
   * @param constant_pool Array of constants
   */
  public LineNumberTable(int name_index, int length,
			 LineNumber[] line_number_table,
			 ConstantPool constant_pool)
  {
    super(Constants.ATTR_LINE_NUMBER_TABLE, name_index, length, constant_pool);
    setLineNumberTable(line_number_table);
  }
   
  /**
   * Construct object from file stream.
   * @param name_index Index of name
   * @param length Content length in bytes
   * @param file Input stream
   * @throw IOException
   * @param constant_pool Array of constants
   */
  LineNumberTable(int name_index, int length, DataInputStream file,
		  ConstantPool constant_pool) throws IOException
  {
    this(name_index, length, (LineNumber[])null, constant_pool);
    line_number_table_length = (file.readUnsignedShort());
    line_number_table = new LineNumber[line_number_table_length];

    for(int i=0; i < line_number_table_length; i++)
      line_number_table[i] = new LineNumber(file);
  }    
  /**
   * Called by objects that are traversing the nodes of the tree implicitely
   * defined by the contents of a Java class. I.e., the hierarchy of methods,
   * fields, attributes, etc. spawns a tree of objects.
   *
   * @param v Visitor object
   */
  public void accept(Visitor v) {
    v.visitLineNumberTable(this);
  }    
  /**
   * Dump line number table attribute to file stream in binary format.
   *
   * @param file Output file stream
   * @throw IOException
   */ 
  public final void dump(DataOutputStream file) throws IOException
  {
    super.dump(file);
    file.writeShort(line_number_table_length);
    for(int i=0; i < line_number_table_length; i++)
      line_number_table[i].dump(file);
  }    
   
  /**
   * @return Array of (pc offset, line number) pairs.
   */  
  public final LineNumber[] getLineNumberTable() { return line_number_table; }    

  /**
   * @param line_number_table.
   */
  public final void setLineNumberTable(LineNumber[] line_number_table) {
    this.line_number_table = line_number_table;

    line_number_table_length = (line_number_table == null)? 0 :
      line_number_table.length;
  }

  /**
   * @return String representation.
   */ 
  public final String toString() {
    StringBuffer buf  = new StringBuffer();
    StringBuffer line = new StringBuffer();

    for(int i=0; i < line_number_table_length; i++) {
      line.append(line_number_table[i].toString());

      if(i < line_number_table_length - 1)
	line.append(", ");

      if(line.length() > 72) {
	line.append('\n');
	buf.append(line);
	line.setLength(0);
      }
    }

    buf.append(line);

    return buf.toString();    
  }

  /**
   * Map byte code positions to source code lines.
   *
   * @param pos byte code offset
   * @return corresponding line in source code
   */
  public int getSourceLine(int pos) {
    int l = 0, r = line_number_table_length-1;

    if(r < 0) // array is empty
      return -1;

    int min_index = -1, min=-1;
    
    /* Do a binary search since the array is ordered.
     */
    do {
      int i = (l + r) / 2;
      int j = line_number_table[i].getStartPC();

      if(j == pos)
	return line_number_table[i].getLineNumber();
      else if(pos < j) // else constrain search area
	r = i - 1;
      else // pos > j
	l = i + 1;

      /* If exact match can't be found (which is the most common case)
       * return the line number that corresponds to the greatest index less
       * than pos.
       */
      if(j < pos && j > min) {
        min       = j;
        min_index = i;
      }
    } while(l <= r);

    return line_number_table[min_index].getLineNumber();
  }

  /**
   * @return deep copy of this attribute
   */
  public Attribute copy(ConstantPool constant_pool) {
    LineNumberTable c = (LineNumberTable)clone();

    c.line_number_table = new LineNumber[line_number_table_length];
    for(int i=0; i < line_number_table_length; i++)
      c.line_number_table[i] = line_number_table[i].copy();

    c.constant_pool = constant_pool;
    return c;
  }

  public final int getTableLength() { return line_number_table_length; }
}