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FieldGen.java

package de.fub.bytecode.generic;

import de.fub.bytecode.Constants;
import de.fub.bytecode.classfile.*;
import java.util.Vector;
import java.util.Enumeration;

/** 
 * Template class for building up a field.  The only extraordinary thing
 * one can do is to add a constant value attribute to a field (which must of
 * course be compatible with to the declared type).
 *
 * @version $Id: FieldGen.java,v 1.1.1.1 2002/01/24 03:41:39 pserver Exp $
 * @author  <A HREF="http://www.inf.fu-berlin.de/~dahm">M. Dahm</A>
 * @see Field
 */
public class FieldGen extends FieldGenOrMethodGen {
  private int    index = -1;
  private Vector attributes;

  private Vector observers;

  /**
   * Declare a field. If it is static (isStatic() == true) and has a
   * basic type like int or String it may have an initial value
   * associated with it as defined by setInitValue().
   *
   * @param access_flags access qualifiers
   * @param type  field type
   * @param name field name
   * @param cp constant pool
   */
  public FieldGen(int access_flags, Type type, String name, ConstantPoolGen cp) {
    setAccessFlags(access_flags);
    setType(type);
    setName(name);
    setConstantPool(cp);
  }  
  /**
   * Instantiate from existing method.
   *
   * @param field Field object
   * @param cp constant pool (must contain the same entries as the field's constant pool)
   */
  public FieldGen(Field field, ConstantPoolGen cp) {
    this(field.getAccessFlags(), Type.getType(field.getSignature()), field.getName(), cp);

    Attribute[] attrs = field.getAttributes();

    for(int i=0; i < attrs.length; i++) {
      if(attrs[i] instanceof ConstantValue)
    index = ((ConstantValue)attrs[i]).getConstantValueIndex();
      else
    addAttribute(attrs[i]);
    }
  }  
  /** Add observer for this object.
   */
  public void addObserver(FieldObserver o) {
    if(observers == null)
      observers = new Vector();

    observers.add(o);
  }  
  /** Remove any initial value.
   */
  public void cancelInitValue() {
    index = -1;
  }  
  private void checkType(Type atype) {
    if(type == null)
      throw new ClassGenException("You haven't defined the type of the field yet");
    
    if(!isStatic())
      throw new ClassGenException("Only static fields may have an initial value!");

    if(!type.equals(atype))
      throw new ClassGenException("Types are not compatible: " + type + " vs. " + atype);
  }  
  /**
   * Get field object after having set up all necessary values.
   */
  public Field getField() {
    String      signature       = getSignature();
    int         name_index      = cp.addUtf8(name);
    int         signature_index = cp.addUtf8(signature);

    if(index > 0) {
      checkType(type);
      addAttribute(new ConstantValue(cp.addUtf8("ConstantValue"),
                     2, index, cp.getConstantPool()));
    }

    return new Field(access_flags, name_index, signature_index, getAttributes(),
             cp.getConstantPool());
  }  
  public String getInitValue() {
    if(index > 0) {
      Constant c = cp.getConstant(index);
      return cp.getConstantPool().constantToString(c);
    } else
      return null;
  }  
  public String  getSignature()  { return type.getSignature(); }  
  /** Remove observer for this object.
   */
  public void removeObserver(FieldObserver o) {
    if(observers != null)
      observers.removeElement(o);
  }  
  public void setInitValue(byte b) {
    checkType(Type.BYTE);

    if(b != 0)
      index = cp.addInteger(b);
  }  
  public void setInitValue(char c) {
    checkType(Type.CHAR);

    if(c != 0)
      index = cp.addInteger(c);
  }  
  public void setInitValue(double d) {
    checkType(Type.DOUBLE);

    if(d != 0.0)
      index = cp.addDouble(d);
  }  
  public void setInitValue(float f) {
    checkType(Type.FLOAT);

    if(f != 0.0)
      index = cp.addFloat(f);
  }  
  public void setInitValue(int i) {
    checkType(Type.INT);

    if(i != 0)
      index = cp.addInteger(i);
  }  
  public void setInitValue(long l) {
    checkType(Type.LONG);

    if(l != 0L)
      index = cp.addLong(l);
  }  
  /**
   * Set (optional) initial value of field, otherwise it will be set to null/0/false
   * by the JVM automatically.
   */
  public void setInitValue(String str) {
    checkType(new ObjectType("java.lang.String"));

    if(str != null)
      index = cp.addString(str);
  }  
  public void setInitValue(short s) {
    checkType(Type.SHORT);

    if(s != 0)
      index = cp.addInteger(s);
  }  
  public void setInitValue(boolean b) {
    checkType(Type.BOOLEAN);

    if(b)
      index = cp.addInteger(1);
  }  
  /**
   * Return string representation close to declaration format,
   * `public static final short MAX = 100', e.g..
   *
   * @return String representation of field
   */
  public final String toString() {
    String name, signature, access; // Short cuts to constant pool

    access    = Utility.accessToString(access_flags);
    access    = access.equals("")? "" : (access + " ");
    signature = type.toString();
    name      = getName();

    StringBuffer buf = new StringBuffer(access + signature + " " + name);
    String value = getInitValue();

    if(value != null)
      buf.append(" = " + value);

    return buf.toString();
  }  
  /** Call notify() method on all observers. This method is not called
   * automatically whenever the state has changed, but has to be
   * called by the user after he has finished editing the object.
   */
  public void update() {
    if(observers != null)
      for(Enumeration e = observers.elements(); e.hasMoreElements(); )
    ((FieldObserver)e.nextElement()).notify(this);
  }  
}

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