instructionfactory.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。

package org.apache.bcel.generic;

/* ====================================================================
 * 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",
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 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
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 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * 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;

/** 
 * Instances of this class may be used, e.g., to generate typed
 * versions of instructions. Its main purpose is to be used as the
 * byte code generating backend of a compiler. You can subclass it to
 * add your own create methods.
 *
 * @version $Id: InstructionFactory.java,v 1.2 2006/08/23 13:48:30 andos Exp $
 * @author <A HREF="mailto:[e-mail]">M. Dahm</A>
 * @see Constants
 */
public class InstructionFactory
  implements InstructionConstants, java.io.Serializable
{
  /**
	 * 
	 */
	private static final long serialVersionUID = 8039119527085435427L;
protected ClassGen        cg;
  protected ConstantPoolGen cp;

  public InstructionFactory(ClassGen cg, ConstantPoolGen cp) {
    this.cg = cg;
    this.cp = cp;
  }

  /** Initialize with ClassGen object
   */
  public InstructionFactory(ClassGen cg) {
    this(cg, cg.getConstantPool());
  }

  /** Initialize just with ConstantPoolGen object
   */
  public InstructionFactory(ConstantPoolGen cp) {
    this(null, cp);
  }

  /** Create an invoke instruction.
   *
   * @param class_name name of the called class
   * @param name name of the called method
   * @param ret_type return type of method
   * @param arg_types argument types of method
   * @param kind how to invoke, i.e., INVOKEINTERFACE, INVOKESTATIC, INVOKEVIRTUAL,
   * or INVOKESPECIAL
   * @see Constants
   */
  public InvokeInstruction createInvoke(String class_name, String name, Type ret_type,
					Type[] arg_types, short kind) {
    int    index;
    int    nargs      = 0;
    String signature  = Type.getMethodSignature(ret_type, arg_types);

    for(int i=0; i < arg_types.length; i++) // Count size of arguments
      nargs += arg_types[i].getSize();

    if(kind == Constants.INVOKEINTERFACE)
      index = cp.addInterfaceMethodref(class_name, name, signature);
    else
      index = cp.addMethodref(class_name, name, signature);

    switch(kind) {
    case Constants.INVOKESPECIAL:   return new INVOKESPECIAL(index);
    case Constants.INVOKEVIRTUAL:   return new INVOKEVIRTUAL(index);
    case Constants.INVOKESTATIC:    return new INVOKESTATIC(index);
    case Constants.INVOKEINTERFACE: return new INVOKEINTERFACE(index, nargs + 1);
    default:
      throw new RuntimeException("Oops: Unknown invoke kind:" + kind);
    }
  }

  /** Create a call to the most popular System.out.println() method.
   *
   * @param s the string to print
   */
  public InstructionList createPrintln(String s) {
    InstructionList il      = new InstructionList();
    int             out     = cp.addFieldref("java.lang.System", "out",
					     "Ljava/io/PrintStream;");
    int             println = cp.addMethodref("java.io.PrintStream", "println",
					      "(Ljava/lang/String;)V");

    il.append(new GETSTATIC(out));
    il.append(new PUSH(cp, s));
    il.append(new INVOKEVIRTUAL(println));

    return il;
  }

  /** Uses PUSH to push a constant value onto the stack.
   * @param value must be of type Number, Boolean, Character or String
   */
  public Instruction createConstant(Object value) {
    PUSH push;

    if(value instanceof Number)
      push = new PUSH(cp, (Number)value);
    else if(value instanceof String)
      push = new PUSH(cp, (String)value);
    else if(value instanceof Boolean)
      push = new PUSH(cp, (Boolean)value);
    else if(value instanceof Character)
      push = new PUSH(cp, (Character)value);
    else
      throw new ClassGenException("Illegal type: " + value.getClass());

    return push.getInstruction();
  }

  private static class MethodObject {
    Type[]   arg_types;
    Type     result_type;
    String[] arg_names;
    String   class_name;
    String   name;
    int      access;

    MethodObject(String c, String n, Type r, Type[] a, int acc) {
      class_name  = c;
      name        = n;
      result_type = r;
      arg_types   = a;
      access      = acc;
    }
  }

  private InvokeInstruction createInvoke(MethodObject m, short kind) {
    return createInvoke(m.class_name, m.name, m.result_type, m.arg_types, kind);
  }

  private static MethodObject[] append_mos = {
    new MethodObject("java.lang.StringBuffer", "append", Type.STRINGBUFFER,
		     new Type[] { Type.STRING }, Constants.ACC_PUBLIC),
    new MethodObject("java.lang.StringBuffer", "append", Type.STRINGBUFFER,
		     new Type[] { Type.OBJECT }, Constants.ACC_PUBLIC),
    null, null, // indices 2, 3
    new MethodObject("java.lang.StringBuffer", "append", Type.STRINGBUFFER,
		     new Type[] { Type.BOOLEAN }, Constants.ACC_PUBLIC),
    new MethodObject("java.lang.StringBuffer", "append", Type.STRINGBUFFER,
		     new Type[] { Type.CHAR }, Constants.ACC_PUBLIC),
    new MethodObject("java.lang.StringBuffer", "append", Type.STRINGBUFFER,
		     new Type[] { Type.FLOAT }, Constants.ACC_PUBLIC),
    new MethodObject("java.lang.StringBuffer", "append", Type.STRINGBUFFER,
		     new Type[] { Type.DOUBLE }, Constants.ACC_PUBLIC),
    new MethodObject("java.lang.StringBuffer", "append", Type.STRINGBUFFER,
		     new Type[] { Type.INT }, Constants.ACC_PUBLIC),
    new MethodObject("java.lang.StringBuffer", "append", Type.STRINGBUFFER, // No append(byte)
		     new Type[] { Type.INT }, Constants.ACC_PUBLIC),
    new MethodObject("java.lang.StringBuffer", "append", Type.STRINGBUFFER, // No append(short)
		     new Type[] { Type.INT }, Constants.ACC_PUBLIC),
    new MethodObject("java.lang.StringBuffer", "append", Type.STRINGBUFFER,
		     new Type[] { Type.LONG }, Constants.ACC_PUBLIC)    
  };

  private static final boolean isString(Type type) {
    return ((type instanceof ObjectType) && 
            ((ObjectType)type).getClassName().equals("java.lang.String"));
  }

  public Instruction createAppend(Type type) {
    byte t = type.getType();

    if(isString(type))
      return createInvoke(append_mos[0], Constants.INVOKEVIRTUAL);

    switch(t) {
    case Constants.T_BOOLEAN:
    case Constants.T_CHAR: 
    case Constants.T_FLOAT:
    case Constants.T_DOUBLE:
    case Constants.T_BYTE:
    case Constants.T_SHORT:
    case Constants.T_INT:
    case Constants.T_LONG
      :   return createInvoke(append_mos[t], Constants.INVOKEVIRTUAL);
    case Constants.T_ARRAY:
    case Constants.T_OBJECT:
      return createInvoke(append_mos[1], Constants.INVOKEVIRTUAL);
    default:
      throw new RuntimeException("Oops: No append for this type? " + type);
    }
  }

  /** Create a field instruction.
   *
   * @param class_name name of the accessed class
   * @param name name of the referenced field
   * @param type  type of field
   * @param kind how to access, i.e., GETFIELD, PUTFIELD, GETSTATIC, PUTSTATIC
   * @see Constants
   */
  public FieldInstruction createFieldAccess(String class_name, String name, Type type, short kind) {
    int    index;
    String signature  = type.getSignature();

    index = cp.addFieldref(class_name, name, signature);

    switch(kind) {
    case Constants.GETFIELD:  return new GETFIELD(index);
    case Constants.PUTFIELD:  return new PUTFIELD(index);
    case Constants.GETSTATIC: return new GETSTATIC(index);
    case Constants.PUTSTATIC: return new PUTSTATIC(index);

    default:
      throw new RuntimeException("Oops: Unknown getfield kind:" + kind);
    }
  }

  /** Create reference to `this'
   */
  public static Instruction createThis() {
    return new ALOAD(0);
  }

  /** Create typed return
   */
  public static ReturnInstruction createReturn(Type type) {
    switch(type.getType()) {
    case Constants.T_ARRAY:
    case Constants.T_OBJECT:  return ARETURN;
    case Constants.T_INT:
    case Constants.T_SHORT:
    case Constants.T_BOOLEAN:
    case Constants.T_CHAR: 
    case Constants.T_BYTE:    return IRETURN;
    case Constants.T_FLOAT:   return FRETURN;
    case Constants.T_DOUBLE:  return DRETURN;
    case Constants.T_LONG:    return LRETURN;
    case Constants.T_VOID:    return RETURN;

    default:
      throw new RuntimeException("Invalid type: " + type);
    }
  }
  
  private static final ArithmeticInstruction createBinaryIntOp(char first, String op) {
    switch(first) {
    case '-' : return ISUB;
    case '+' : return IADD;
    case '%' : return IREM;
    case '*' : return IMUL;
    case '/' : return IDIV;
    case '&' : return IAND;
    case '|' : return IOR;
    case '^' : return IXOR;
    case '<' : return ISHL;
    case '>' : return op.equals(">>>")? (ArithmeticInstruction)IUSHR :
      (ArithmeticInstruction)ISHR;
    default: throw new RuntimeException("Invalid operand " + op);
    }
  }

  private static final ArithmeticInstruction createBinaryLongOp(char first, String op) {
    switch(first) {
    case '-' : return LSUB;
    case '+' : return LADD;
    case '%' : return LREM;