/*

 * reserved comment block

 * DO NOT REMOVE OR ALTER!

 */

package com.sun.org.apache.bcel.internal.classfile;

/* ====================================================================

 * 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:

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 * 1. Redistributions of source code must retain the above copyright

 *    notice, this list of conditions and the following disclaimer.

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 *    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.

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 *    "Apache BCEL" must not be used to endorse or promote products

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 * 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 com.sun.org.apache.bcel.internal.Constants;

import java.io.*;

import java.util.HashMap;

/**

 * Abstract super class for <em>Attribute</em> objects. Currently the

 * <em>ConstantValue</em>, <em>SourceFile</em>, <em>Code</em>,

 * <em>Exceptiontable</em>, <em>LineNumberTable</em>,

 * <em>LocalVariableTable</em>, <em>InnerClasses</em> and

 * <em>Synthetic</em> attributes are supported. The

 * <em>Unknown</em> attribute stands for non-standard-attributes.

 *

 * @author  <A HREF="mailto:markus.dahm@berlin.de">M. Dahm</A>

 * @see     ConstantValue

 * @see     SourceFile

 * @see     Code

 * @see     Unknown

 * @see     ExceptionTable

 * @see     LineNumberTable

 * @see     LocalVariableTable

 * @see     InnerClasses

 * @see     Synthetic

 * @see     Deprecated

 * @see     Signature

*/

public abstract class Attribute implements Cloneable, Node, Serializable {

  protected int          name_index; // Points to attribute name in constant pool

  protected int          length;     // Content length of attribute field

  protected byte         tag;        // Tag to distiguish subclasses

  protected ConstantPool constant_pool;

  protected Attribute(byte tag, int name_index, int length,

                      ConstantPool constant_pool) {

    this.tag           = tag;

    this.name_index    = name_index;

    this.length        = length;

    this.constant_pool = constant_pool;

  }

  /**

   * 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 abstract void accept(Visitor v);

  /**

   * Dump attribute to file stream in binary format.

   *

   * @param file Output file stream

   * @throws IOException

   */

  public void dump(DataOutputStream file) throws IOException

  {

    file.writeShort(name_index);

    file.writeInt(length);

  }

  private static HashMap readers = new HashMap();

  /** Add an Attribute reader capable of parsing (user-defined) attributes

   * named "name". You should not add readers for the standard attributes

   * such as "LineNumberTable", because those are handled internally.

   *

   * @param name the name of the attribute as stored in the class file

   * @param r the reader object

   */

  public static void addAttributeReader(String name, AttributeReader r) {

    readers.put(name, r);

  }

  /** Remove attribute reader

   *

   * @param name the name of the attribute as stored in the class file

   */

  public static void removeAttributeReader(String name) {

    readers.remove(name);

  }

  /* Class method reads one attribute from the input data stream.

   * This method must not be accessible from the outside.  It is

   * called by the Field and Method constructor methods.

   *

   * @see    Field

   * @see    Method

   * @param  file Input stream

   * @param  constant_pool Array of constants

   * @return Attribute

   * @throws  IOException

   * @throws  ClassFormatException

   */

  public static final Attribute readAttribute(DataInputStream file,

                                              ConstantPool constant_pool)

    throws IOException, ClassFormatException

  {

    ConstantUtf8 c;

    String       name;

    int          name_index;

    int          length;

    byte         tag = Constants.ATTR_UNKNOWN; // Unknown attribute

    // Get class name from constant pool via `name_index' indirection

    name_index = (int)file.readUnsignedShort();

    c          = (ConstantUtf8)constant_pool.getConstant(name_index,

                                                         Constants.CONSTANT_Utf8);

    name       = c.getBytes();

    // Length of data in bytes

    length = file.readInt();

    // Compare strings to find known attribute

    for(byte i=0; i < Constants.KNOWN_ATTRIBUTES; i++) {

      if(name.equals(Constants.ATTRIBUTE_NAMES[i])) {

        tag = i; // found!

        break;

      }

    }

    // Call proper constructor, depending on `tag'

    switch(tag) {

    case Constants.ATTR_UNKNOWN:

      AttributeReader r = (AttributeReader)readers.get(name);

      if(r != null)

        return r.createAttribute(name_index, length, file, constant_pool);

      else

        return new Unknown(name_index, length, file, constant_pool);

    case Constants.ATTR_CONSTANT_VALUE:

      return new ConstantValue(name_index, length, file, constant_pool);

    case Constants.ATTR_SOURCE_FILE:

      return new SourceFile(name_index, length, file, constant_pool);

    case Constants.ATTR_CODE:

      return new Code(name_index, length, file, constant_pool);

    case Constants.ATTR_EXCEPTIONS:

      return new ExceptionTable(name_index, length, file, constant_pool);

    case Constants.ATTR_LINE_NUMBER_TABLE:

      return new LineNumberTable(name_index, length, file, constant_pool);

    case Constants.ATTR_LOCAL_VARIABLE_TABLE:

      return new LocalVariableTable(name_index, length, file, constant_pool);

    case Constants.ATTR_INNER_CLASSES:

      return new InnerClasses(name_index, length, file, constant_pool);

    case Constants.ATTR_SYNTHETIC:

      return new Synthetic(name_index, length, file, constant_pool);

    case Constants.ATTR_DEPRECATED:

      return new Deprecated(name_index, length, file, constant_pool);

    case Constants.ATTR_PMG:

      return new PMGClass(name_index, length, file, constant_pool);

    case Constants.ATTR_SIGNATURE:

      return new Signature(name_index, length, file, constant_pool);

    case Constants.ATTR_STACK_MAP:

      return new StackMap(name_index, length, file, constant_pool);

    default: // Never reached

      throw new IllegalStateException("Ooops! default case reached.");

    }

  }

  /**

   * @return Length of attribute field in bytes.

   */

  public final int   getLength()    { return length; }

  /**

   * @param Attribute length in bytes.

   */

  public final void setLength(int length) {

    this.length = length;

  }

  /**

   * @param name_index of attribute.

   */

  public final void setNameIndex(int name_index) {

    this.name_index = name_index;

  }

  /**

   * @return Name index in constant pool of attribute name.

   */

  public final int getNameIndex() { return name_index; }

  /**

   * @return Tag of attribute, i.e., its type. Value may not be altered, thus

   * there is no setTag() method.

   */

  public final byte  getTag()       { return tag; }

  /**

   * @return Constant pool used by this object.

   * @see ConstantPool

   */

  public final ConstantPool getConstantPool() { return constant_pool; }

  /**

   * @param constant_pool Constant pool to be used for this object.

   * @see ConstantPool

   */

  public final void setConstantPool(ConstantPool constant_pool) {

    this.constant_pool = constant_pool;

  }

  /**

   * Use copy() if you want to have a deep copy(), i.e., with all references

   * copied correctly.

   *

   * @return shallow copy of this attribute

   */

  public Object clone() {

    Object o = null;

    try {

      o = super.clone();

    } catch(CloneNotSupportedException e) {

      e.printStackTrace(); // Never occurs

    }

    return o;

  }

  /**

   * @return deep copy of this attribute

   */

  public abstract Attribute copy(ConstantPool constant_pool);

  /**

   * @return attribute name.

   */

  public String toString() {

    return Constants.ATTRIBUTE_NAMES[tag];

  }

}