constantpoolgen.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。

    utf8_table.put(n, new Index(ret));

    return ret;
  }

  /** 
   * Look for ConstantLong in ConstantPool.
   *
   * @param n Long number to look for
   * @return index on success, -1 otherwise
   */
  public int lookupLong(long n) {
    for(int i=1; i < index; i++) {
      if(constants[i] instanceof ConstantLong) {
	ConstantLong c = (ConstantLong)constants[i];

	if(c.getBytes() == n)
	  return i;
      }
    }

    return -1;
  }

  /**
   * Add a new long constant to the ConstantPool, if it is not already in there.
   *
   * @param n Long number to add
   * @return index of entry
   */
  public int addLong(long n) {
    int  ret;

    if((ret = lookupLong(n)) != -1)
      return ret; // Already in CP

    adjustSize();

    ret = index;
    constants[index] = new ConstantLong(n);
    index += 2;   // Wastes one entry according to spec

    return ret;
  }

  /** 
   * Look for ConstantDouble in ConstantPool.
   *
   * @param n Double number to look for
   * @return index on success, -1 otherwise
   */
  public int lookupDouble(double n) {
    long bits = Double.doubleToLongBits(n);

    for(int i=1; i < index; i++) {
      if(constants[i] instanceof ConstantDouble) {
	ConstantDouble c = (ConstantDouble)constants[i];
	
	if(Double.doubleToLongBits(c.getBytes()) == bits)
	  return i;
      }
    }

    return -1;
  }

  /**
   * Add a new double constant to the ConstantPool, if it is not already in there.
   *
   * @param n Double number to add
   * @return index of entry
   */
  public int addDouble(double n) {
    int  ret;

    if((ret = lookupDouble(n)) != -1)
      return ret; // Already in CP

    adjustSize();

    ret = index;
    constants[index] = new ConstantDouble(n);
    index += 2;   // Wastes one entry according to spec

    return ret;
  }

  private HashMap<String, Index> n_a_t_table = new HashMap<String, Index>();

  /** 
   * Look for ConstantNameAndType in ConstantPool.
   *
   * @param name of variable/method
   * @param signature of variable/method
   * @return index on success, -1 otherwise
   */
  public int lookupNameAndType(String name, String signature) {
    Index index = (Index)n_a_t_table.get(name + NAT_DELIM + signature);
    return (index != null)? index.index : -1;
  }

  /**
   * Add a new NameAndType constant to the ConstantPool if it is not already 
   * in there.
   *
   * @param n NameAndType string to add
   * @return index of entry
   */
  public int addNameAndType(String name, String signature) {
    int  ret;
    int  name_index, signature_index;

    if((ret = lookupNameAndType(name, signature)) != -1)
      return ret; // Already in CP

    adjustSize();

    name_index      = addUtf8(name);
    signature_index = addUtf8(signature);
    ret = index;
    constants[index++] = new ConstantNameAndType(name_index, signature_index);

    n_a_t_table.put(name + NAT_DELIM + signature, new Index(ret));
    return ret;
  }

  private HashMap<String, Index> cp_table = new HashMap<String, Index>();

  /** 
   * Look for ConstantMethodref in ConstantPool.
   *
   * @param class_name Where to find method
   * @param method_name Guess what
   * @param signature return and argument types
   * @return index on success, -1 otherwise
   */
  public int lookupMethodref(String class_name, String method_name, String signature) {
    Index index = (Index)cp_table.get(class_name + METHODREF_DELIM + method_name +
				      METHODREF_DELIM + signature);
    return (index != null)? index.index : -1;
  }

  public int lookupMethodref(MethodGen method) {
    return lookupMethodref(method.getClassName(), method.getName(),
			  method.getSignature());
  }

  /**
   * Add a new Methodref constant to the ConstantPool, if it is not already 
   * in there.
   *
   * @param n Methodref string to add
   * @return index of entry
   */
  public int addMethodref(String class_name, String method_name, String signature) {
    int  ret, class_index, name_and_type_index;

    if((ret = lookupMethodref(class_name, method_name, signature)) != -1)
      return ret; // Already in CP

    adjustSize();

    name_and_type_index = addNameAndType(method_name, signature);
    class_index         = addClass(class_name);
    ret = index;
    constants[index++] = new ConstantMethodref(class_index, name_and_type_index);

    cp_table.put(class_name + METHODREF_DELIM + method_name +
		 METHODREF_DELIM + signature, new Index(ret));

    return ret;
  }

  public int addMethodref(MethodGen method) {
    return addMethodref(method.getClassName(), method.getName(),
			method.getSignature());
  }

  /** 
   * Look for ConstantInterfaceMethodref in ConstantPool.
   *
   * @param class_name Where to find method
   * @param method_name Guess what
   * @param signature return and argument types
   * @return index on success, -1 otherwise
   */
  public int lookupInterfaceMethodref(String class_name, String method_name, String signature) {
    Index index = (Index)cp_table.get(class_name + IMETHODREF_DELIM + method_name +
				      IMETHODREF_DELIM + signature);
    return (index != null)? index.index : -1;
  }

  public int lookupInterfaceMethodref(MethodGen method) {
    return lookupInterfaceMethodref(method.getClassName(), method.getName(),
				    method.getSignature());
  }

  /**
   * Add a new InterfaceMethodref constant to the ConstantPool, if it is not already 
   * in there.
   *
   * @param n InterfaceMethodref string to add
   * @return index of entry
   */
  public int addInterfaceMethodref(String class_name, String method_name, String signature) {
    int ret, class_index, name_and_type_index;

    if((ret = lookupInterfaceMethodref(class_name, method_name, signature)) != -1)
      return ret; // Already in CP

    adjustSize();

    class_index         = addClass(class_name);
    name_and_type_index = addNameAndType(method_name, signature);
    ret = index;
    constants[index++] = new ConstantInterfaceMethodref(class_index, name_and_type_index);

    cp_table.put(class_name + IMETHODREF_DELIM + method_name +
		 IMETHODREF_DELIM + signature, new Index(ret));

    return ret;
  }

  public int addInterfaceMethodref(MethodGen method) {
    return addInterfaceMethodref(method.getClassName(), method.getName(),
				 method.getSignature());
  }

  /** 
   * Look for ConstantFieldref in ConstantPool.
   *
   * @param class_name Where to find method
   * @param field_name Guess what
   * @param signature return and argument types
   * @return index on success, -1 otherwise
   */
  public int lookupFieldref(String class_name, String field_name, String signature) {
    Index index = (Index)cp_table.get(class_name + FIELDREF_DELIM + field_name +
				      FIELDREF_DELIM + signature);
    return (index != null)? index.index : -1;
  }

  /**
   * Add a new Fieldref constant to the ConstantPool, if it is not already 
   * in there.
   *
   * @param n Fieldref string to add
   * @return index of entry
   */
  public int addFieldref(String class_name, String field_name, String signature) {
    int  ret;
    int  class_index, name_and_type_index;

    if((ret = lookupFieldref(class_name, field_name, signature)) != -1)
      return ret; // Already in CP

    adjustSize();

    class_index         = addClass(class_name);
    name_and_type_index = addNameAndType(field_name, signature);
    ret = index;
    constants[index++] = new ConstantFieldref(class_index, name_and_type_index);

    cp_table.put(class_name + FIELDREF_DELIM + field_name + FIELDREF_DELIM + signature, new Index(ret));

    return ret;
  }

  /**
   * @param i index in constant pool
   * @return constant pool entry at index i
   */
  public Constant getConstant(int i) { return constants[i]; }

  /**
   * Use with care!
   *
   * @param i index in constant pool
   * @param c new constant pool entry at index i
   */
  public void setConstant(int i, Constant c) { constants[i] = c; }

  /**
   * @return intermediate constant pool
   */
  public ConstantPool getConstantPool() {
    return new ConstantPool(constants);
  }

  /**
   * @return current size of constant pool
   */
  public int getSize() {
    return index;
  }

  /**
   * @return constant pool with proper length
   */
  public ConstantPool getFinalConstantPool() { 
    Constant[] cs = new Constant[index];
    
    System.arraycopy(constants, 0, cs, 0, index);

    return new ConstantPool(cs); 
  }

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

    for(int i=1; i < index; i++)
      buf.append(i + ")" + constants[i] + "\n");

    return buf.toString();
  }

  /** Import constant from another ConstantPool and return new index.
   */
  public int addConstant(Constant c, ConstantPoolGen cp) {
    Constant[] constants = cp.getConstantPool().getConstantPool();

    switch(c.getTag()) {
    case Constants.CONSTANT_String: {
      ConstantString s  = (ConstantString)c;
      ConstantUtf8   u8 = (ConstantUtf8)constants[s.getStringIndex()];

      return addString(u8.getBytes());
    }

    case Constants.CONSTANT_Class: {
      ConstantClass s  = (ConstantClass)c;
      ConstantUtf8  u8 = (ConstantUtf8)constants[s.getNameIndex()];

      return addClass(u8.getBytes());
    }

    case Constants.CONSTANT_NameAndType: {
      ConstantNameAndType n    = (ConstantNameAndType)c;
      ConstantUtf8        u8   = (ConstantUtf8)constants[n.getNameIndex()];
      ConstantUtf8        u8_2 = (ConstantUtf8)constants[n.getSignatureIndex()];

      return addNameAndType(u8.getBytes(), u8_2.getBytes());
    }

    case Constants.CONSTANT_Utf8:
      return addUtf8(((ConstantUtf8)c).getBytes());

    case Constants.CONSTANT_Double:
      return addDouble(((ConstantDouble)c).getBytes());

    case Constants.CONSTANT_Float:
      return addFloat(((ConstantFloat)c).getBytes());

    case Constants.CONSTANT_Long:
      return addLong(((ConstantLong)c).getBytes());

    case Constants.CONSTANT_Integer:
      return addInteger(((ConstantInteger)c).getBytes());

    case Constants.CONSTANT_InterfaceMethodref: case Constants.CONSTANT_Methodref:
    case Constants.CONSTANT_Fieldref: {
      ConstantCP          m     = (ConstantCP)c;
      ConstantClass       clazz = (ConstantClass)constants[m.getClassIndex()];
      ConstantNameAndType n     = (ConstantNameAndType)constants[m.getNameAndTypeIndex()];
      ConstantUtf8 u8           = (ConstantUtf8)constants[clazz.getNameIndex()];
      String       class_name   = u8.getBytes().replace('/', '.');

      u8 = (ConstantUtf8)constants[n.getNameIndex()];
      String name = u8.getBytes();

      u8 = (ConstantUtf8)constants[n.getSignatureIndex()];
      String signature = u8.getBytes();

      switch(c.getTag()) {
      case Constants.CONSTANT_InterfaceMethodref:
	return addInterfaceMethodref(class_name, name, signature);

      case Constants.CONSTANT_Methodref:
	return addMethodref(class_name, name, signature);

      case Constants.CONSTANT_Fieldref:
	return addFieldref(class_name, name, signature);

      default: // Never reached
	throw new RuntimeException("Unknown constant type " + c);
      }
    }

    default: // Never reached
      throw new RuntimeException("Unknown constant type " + c);
    }
  }
}