codehtml.java

Java Bytecode Editor 是一个 JAVA 的字节码反汇编和修改器。它可以很方便的修改已经编译成 Class 文件的 JAVA 文件。

      }
      // Attach return type
      buf.append("):" + Class2HTML.referenceType(type));

      break;
		
      /* Operands are references to items in constant pool
       */
    case LDC_W: case LDC2_W:
      index = bytes.readShort();

      buf.append("<A HREF=\"" + class_name + "_cp.html#cp" + index + 
		 "\" TARGET=\"ConstantPool\">" +
		 Class2HTML.toHTML(constant_pool.constantToString(index, 
								  constant_pool.
								  getConstant(index).getTag()))+
		 "</a>");
      break;

    case LDC:
      index = bytes.readUnsignedByte();
      buf.append("<A HREF=\"" + class_name + "_cp.html#cp" + index + 
		 "\" TARGET=\"ConstantPool\">" +
		 Class2HTML.toHTML(constant_pool.constantToString(index, 
								  constant_pool.
								  getConstant(index).getTag()))+
		 "</a>");
      break;
	
      /* Array of references.
       */
    case ANEWARRAY:
      index = bytes.readShort();
	  
      buf.append(constant_html.referenceConstant(index));
      break;
	
      /* Multidimensional array of references.
       */
    case MULTIANEWARRAY:
      index = bytes.readShort();
      int dimensions = bytes.readByte();
      buf.append(constant_html.referenceConstant(index) + ":" + dimensions + "-dimensional");
      break;

      /* Increment local variable.
       */
    case IINC:
      if(wide) {
	vindex   = bytes.readShort();
	constant = bytes.readShort();
	wide     = false;
      }
      else {
	vindex   = bytes.readUnsignedByte();
	constant = bytes.readByte();
      }
      buf.append("%" + vindex + " " + constant);
      break;

    default:
      if(NO_OF_OPERANDS[opcode] > 0) {
	for(int i=0; i < TYPE_OF_OPERANDS[opcode].length; i++) {
	  switch(TYPE_OF_OPERANDS[opcode][i]) {
	  case T_BYTE:
	    buf.append(bytes.readUnsignedByte());
	    break;

	  case T_SHORT: // Either branch or index
	    buf.append(bytes.readShort());
	    break;

	  case T_INT:
	    buf.append(bytes.readInt());
	    break;
					      
	  default: // Never reached
	    System.err.println("Unreachable default case reached!");
	    System.exit(-1);
	  }
	  buf.append("&nbsp;");
	}
      }
    }

    buf.append("</TD>");
    return buf.toString();
  }

  /**
   * Find all target addresses in code, so that they can be marked
   * with &lt;A NAME = ...&gt;. Target addresses are kept in an BitSet object.
   */
  private final void findGotos(ByteSequence bytes, Method method, Code code) 
       throws IOException
  {
    int index;
    goto_set = new BitSet(bytes.available());
    int opcode;

    /* First get Code attribute from method and the exceptions handled
     * (try .. catch) in this method. We only need the line number here.
     */
	
    if(code != null) {
      CodeException[] ce  = code.getExceptionTable();
      int             len = ce.length;

      for(int i=0; i < len; i++) {
	goto_set.set(ce[i].getStartPC());
	goto_set.set(ce[i].getEndPC());
	goto_set.set(ce[i].getHandlerPC());
      }

      // Look for local variables and their range
      Attribute[] attributes = code.getAttributes();
      for(int i=0; i < attributes.length; i++) {
	if(attributes[i].getTag() == ATTR_LOCAL_VARIABLE_TABLE) {
	  LocalVariable[] vars = ((LocalVariableTable)attributes[i]).getLocalVariableTable();

	  for(int j=0; j < vars.length; j++) {
	    int  start = vars[j].getStartPC();
	    int  end   = (int)(start + vars[j].getLength());
	    goto_set.set(start);
	    goto_set.set(end);
	  }
	  break;
	}
      }
    }

    // Get target addresses from GOTO, JSR, TABLESWITCH, etc.
    for(int i=0; bytes.available() > 0; i++) {
      opcode = bytes.readUnsignedByte();
      //System.out.println(OPCODE_NAMES[opcode]);
      switch(opcode) {
      case TABLESWITCH: case LOOKUPSWITCH:
	//bytes.readByte(); // Skip already read byte

	int remainder = bytes.getIndex() % 4;
	int no_pad_bytes  = (remainder == 0)? 0 : 4 - remainder;
	int default_offset, offset;

	for(int j=0; j < no_pad_bytes; j++)
	  bytes.readByte();

	// Both cases have a field default_offset in common
	default_offset = bytes.readInt();

	if(opcode == TABLESWITCH) {
	  int low = bytes.readInt();
	  int high = bytes.readInt();

	  offset = bytes.getIndex() - 12 - no_pad_bytes - 1;
	  default_offset += offset;
	  goto_set.set(default_offset);

	  for(int j=0; j < (high - low + 1); j++) {
	    index = offset + bytes.readInt();
	    goto_set.set(index);
	  }
	}
	else { // LOOKUPSWITCH
	  int npairs = bytes.readInt();

	  offset = bytes.getIndex() - 8 - no_pad_bytes - 1;
	  default_offset += offset;
	  goto_set.set(default_offset);

	  for(int j=0; j < npairs; j++) {
//	    int match = bytes.readInt();

	    index = offset + bytes.readInt();
	    goto_set.set(index);
	  }
	}
	break;
	
      case GOTO:      case IFEQ:      case IFGE:      case IFGT:
      case IFLE:      case IFLT:
      case IFNE:      case IFNONNULL: case IFNULL:    case IF_ACMPEQ:
      case IF_ACMPNE: case IF_ICMPEQ: case IF_ICMPGE: case IF_ICMPGT:
      case IF_ICMPLE: case IF_ICMPLT: case IF_ICMPNE: case JSR:
	//bytes.readByte(); // Skip already read byte
	index = bytes.getIndex() + bytes.readShort() - 1;
	  
	goto_set.set(index);
	break;

      case GOTO_W: case JSR_W:
	//bytes.readByte(); // Skip already read byte
	index = bytes.getIndex() + bytes.readInt() - 1;
	goto_set.set(index);
	break;

      default:
	bytes.unreadByte();
	codeToHTML(bytes, 0); // Ignore output
      }
    }
  }    

  /**
   * Write a single method with the byte code associated with it.
   */
  private void writeMethod(Method method, int method_number)
       throws IOException
  {
    // Get raw signature
    String       signature = method.getSignature();
    // Get array of strings containing the argument types
    String[]     args      = Utility.methodSignatureArgumentTypes(signature, false);
    // Get return type string
    String       type      = Utility.methodSignatureReturnType(signature, false);
    // Get method name
    String       name      = method.getName();
    String    	 html_name = Class2HTML.toHTML(name);
    // Get method's access flags
    String       access    = Utility.accessToString(method.getAccessFlags());
    access = Utility.replace(access, " ", "&nbsp;");
    // Get the method's attributes, the Code Attribute in particular
    Attribute[]  attributes= method.getAttributes();	

    file.print("<P><B><FONT COLOR=\"#FF0000\">" + access + "</FONT>&nbsp;" +
	       "<A NAME=method" + method_number + ">" + Class2HTML.referenceType(type) +
	       "</A>&nbsp<A HREF=\"" + class_name + "_methods.html#method" + method_number +
	       "\" TARGET=Methods>" + html_name + "</A>(");

    for(int i=0; i < args.length; i++) {
      file.print(Class2HTML.referenceType(args[i]));
      if(i < args.length - 1)
	file.print(",&nbsp;");
    }

    file.println(")</B></P>");
		
    Code c=null;
    byte[] code=null;

    if(attributes.length > 0) {
      file.print("<H4>Attributes</H4><UL>\n");
      for(int i=0; i < attributes.length; i++) {
	byte tag = attributes[i].getTag();

	if(tag != ATTR_UNKNOWN)
	  file.print("<LI><A HREF=\"" + class_name + "_attributes.html#method" + method_number + "@" + i +
		     "\" TARGET=Attributes>" + ATTRIBUTE_NAMES[tag] + "</A></LI>\n");
	else
	  file.print("<LI>" + attributes[i] + "</LI>");

	if(tag == ATTR_CODE) {
	  c = (Code)attributes[i];
	  Attribute[] attributes2 = c.getAttributes();
	  code 								= c.getCode();
					
	  file.print("<UL>");
	  for(int j=0; j < attributes2.length; j++) {
	    tag = attributes2[j].getTag();
	    file.print("<LI><A HREF=\"" + class_name + "_attributes.html#" +
		       "method" + method_number + "@" + i + "@" + j + "\" TARGET=Attributes>" +
		       ATTRIBUTE_NAMES[tag] + "</A></LI>\n");

	  }
	  file.print("</UL>");
	}
      }
      file.println("</UL>");
    }

    if(code != null) { // No code, an abstract method, e.g.
      //System.out.println(name + "\n" + Utility.codeToString(code, constant_pool, 0, -1));

      // Print the byte code
      ByteSequence stream = new ByteSequence(code);
      stream.mark(stream.available());
      findGotos(stream, method, c);
      stream.reset();

      file.println("<TABLE BORDER=0><TR><TH ALIGN=LEFT>Byte<BR>offset</TH>" +
		   "<TH ALIGN=LEFT>Instruction</TH><TH ALIGN=LEFT>Argument</TH>");

      for(int i=0; stream.available() > 0; i++) {
	int offset = stream.getIndex();
	String str = codeToHTML(stream, method_number);
	String anchor = "";

	/* Set an anchor mark if this line is targetted by a goto, jsr, etc.
	 * Defining an anchor for every line is very inefficient!
	 */
	if(goto_set.get(offset))
	  anchor = "<A NAME=code" + method_number + "@" + offset +  "></A>";

	String anchor2;
	if(stream.getIndex() == code.length) // last loop
	  anchor2 = "<A NAME=code" + method_number + "@" + code.length + ">" + offset + "</A>";
	else
	  anchor2 = "" + offset;

	file.println("<TR VALIGN=TOP><TD>" + anchor2 + "</TD><TD>" + anchor + str + "</TR>");
      }
      
      // Mark last line, may be targetted from Attributes window
      file.println("<TR><TD> </A></TD></TR>");
      file.println("</TABLE>");
    }

  }                          
}