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Unknown.java

package de.fub.bytecode.classfile;

import de.fub.bytecode.Constants;
import java.io.*;
import java.util.*;

/**
 * This class is derived from <em>Attribute</em> and represents a reference to an
 * unknown (i.e. unimplemented) attribute of this class.
 * It is instantiated from the <em>Attribute.readAttribute()</em> method.
 *
 * @version $Id: Unknown.java,v 1.1.1.1 2002/01/24 03:44:00 pserver Exp $
 * @author  <A HREF="http://www.inf.fu-berlin.de/~dahm">M. Dahm</A>
 * @see     Attribute
 */
public final class Unknown extends Attribute {
  private byte[] bytes;
  private String name;

  private static Hashtable unknown_attributes = new Hashtable();

  /**
   * Create a non-standard attribute.
   *
   * @param name_index Index in constant pool
   * @param length Content length in bytes
   * @param bytes Attribute contents
   * @param constant_pool Array of constants
   */
  public Unknown(int name_index, int length, byte[] bytes,
         ConstantPool constant_pool)
  {
    super(ATTR_UNKNOWN, name_index, length, constant_pool);
    this.bytes = bytes;

    name = ((ConstantUtf8)constant_pool.getConstant(name_index,
                            CONSTANT_Utf8)).getBytes();
    unknown_attributes.put(name, this);
  }  
  /**
   * Construct object from file stream.
   * @param name_index Index in constant pool
   * @param length Content length in bytes
   * @param file Input stream
   * @param constant_pool Array of constants
   * @throw IOException
   */
  Unknown(int name_index, int length, DataInputStream file,
      ConstantPool constant_pool)
       throws IOException
  {
    this(name_index, length, (byte [])null, constant_pool);

    if(length > 0) {
      bytes = new byte[length];
      file.readFully(bytes);
    }
  }  
  /**
   * Initialize from another object. Note that both objects use the same
   * references (shallow copy). Use clone() for a physical copy.
   */
  public Unknown(Unknown c) {
    this(c.getNameIndex(), c.getLength(), c.getBytes(), c.getConstantPool());
  }  
  /**
   * 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.visitUnknown(this);
  }  
  /**
   * @return deep copy of this attribute
   */
  public Attribute copy(ConstantPool constant_pool) {
    Unknown c = (Unknown)clone();

    if(bytes != null)
      c.bytes = (byte[])bytes.clone();

    c.constant_pool = constant_pool;
    return c;
  }  
  /**
   * Dump unknown bytes to file stream.
   *
   * @param file Output file stream
   * @throw IOException
   */ 
  public final void dump(DataOutputStream file) throws IOException
  {
    super.dump(file);
    if(length > 0)
      file.write(bytes, 0, length);
  }  
  /**
   * @return data bytes.
   */  
  public final byte[] getBytes() { return bytes; }  
  /**
   * @return name of attribute.
   */  
  public final String getName() { return name; }  
  /** @return array of unknown attributes, but just one for each kind.
   */
  static Unknown[] getUnknownAttributes() {
    Unknown[]   unknowns = new Unknown[unknown_attributes.size()];
    Enumeration entries  = unknown_attributes.elements();

    for(int i=0; entries.hasMoreElements(); i++)
      unknowns[i] = (Unknown)entries.nextElement();

    unknown_attributes = new Hashtable();
    return unknowns;
  }  
  /**
   * @param bytes.
   */
  public final void setBytes(byte[] bytes) {
    this.bytes = bytes;
  }  
  /**
   * @return String representation.
   */ 
  public final String toString() {
    if(length == 0 || bytes == null)
      return "(Unknown attribute " + name + ")";

    String hex;
    if(length > 10) {
      byte[] tmp = new byte[10];
      System.arraycopy(bytes, 0, tmp, 0, 10);
      hex = Utility.toHexString(tmp) + "... (truncated)";
    }
    else
      hex = Utility.toHexString(bytes);

    return "(Unknown attribute " + name + ": " + hex + ")";
  }  
}

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