/***
 * ASM: a very small and fast Java bytecode manipulation framework
 * Copyright (c) 2000,2002,2003 INRIA, France Telecom 
 * 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. Neither the name of the copyright holders nor the names of its
 *    contributors may be used to endorse or promote products derived from
 *    this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND 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.
 */

package oracle.toplink.libraries.asm;

/**
 * A non standard class, field, method or code attribute.
 *
 * @author Eric Bruneton, Eugene Kuleshov
 */

public class Attribute {

  /**
   * The type of this attribute.
   */

  public final String type;

  /**
   * The next attribute in this attribute list. May be <tt>null</tt>.
   */

  public Attribute next;

  /**
   * Constructs a new empty attribute.
   *
   * @param type the type of the attribute.
   */

  protected Attribute (final String type) {
    this.type = type;
  }

  /**
   * Returns <tt>true</tt> if this type of attribute is unknown.
   *
   * @return <tt>true</tt> if the class of this object is equal to
   *      {@link Attribute}.
   */

  public boolean isUnknown () {
    return getClass().getName().equals("oracle.toplink.libraries.asm.Attribute");
  }

  /**
   * Returns the labels corresponding to this attribute.
   *
   * @return the labels corresponding to this attribute, or <tt>null</tt> if
   *      this attribute is not a code attribute that contains labels.
   */

  protected Label[] getLabels () {
    return null;
  }

  /**
   * Reads a {@link #type type} attribute. This method must return a <i>new</i>
   * {@link Attribute} object, of type {@link #type type}, corresponding to the
   * <tt>len</tt> bytes starting at the given offset, in the given class reader.
   *
   * @param cr the class that contains the attribute to be read.
   * @param off index of the first byte of the attribute's content in {@link
   *      ClassReader#b cr.b}. The 6 attribute header bytes, containing the type
   *      and the length of the attribute, are not taken into account here.
   * @param len the length of the attribute's content.
   * @param buf buffer to be used to call {@link ClassReader#readUTF8 readUTF8},
   *      {@link ClassReader#readClass(int,char[]) readClass} or {@link
   *      ClassReader#readConst readConst}.
   * @param codeOff index of the first byte of code's attribute content in
   *      {@link ClassReader#b cr.b}, or -1 if the attribute to be read is not a
   *      code attribute. The 6 attribute header bytes, containing the type and
   *      the length of the attribute, are not taken into account here.
   * @param labels the labels of the method's code, or <tt>null</tt> if the
   *      attribute to be read is not a code attribute.
   * @return a <i>new</i> {@link Attribute} object corresponding to the given
   *      bytes.
   */

  protected Attribute read (
    ClassReader cr, int off, int len, char[] buf, int codeOff, Label[] labels)
  {
    return new Attribute(type);
  }

  /**
   * Returns the byte array form of this attribute.
   *
   * @param cw the class to which this attribute must be added. This parameter
   *      can be used to add to the constant pool of this class the items that
   *      corresponds to this attribute.
   * @param code the bytecode of the method corresponding to this code
   *      attribute, or <tt>null</tt> if this attribute is not a code
   *      attributes.
   * @param len the length of the bytecode of the method corresponding to this
   *      code attribute, or <tt>null</tt> if this attribute is not a code
   *      attribute.
   * @param maxStack the maximum stack size of the method corresponding to this
   *      code attribute, or -1 if this attribute is not a code attribute.
   * @param maxLocals the maximum number of local variables of the method
   *      corresponding to this code attribute, or -1 if this attribute is not
   *      a code attribute.
   * @return the byte array form of this attribute.
   */

  protected ByteVector write (
    ClassWriter cw, byte[] code, int len, int maxStack, int maxLocals)
  {
    return new ByteVector();
  }

  /**
   * Returns the length of the attribute list that begins with this attribute.
   *
   * @return the length of the attribute list that begins with this attribute.
   */

  final int getCount () {
    int count = 0;
    Attribute attr = this;
    while (attr != null) {
      if (!attr.isUnknown()) {
        count += 1;
      }
      attr = attr.next;
    }
    return count;
  }

  /**
   * Returns the size of all the attributes in this attribute list.
   *
   * @param cw the class writer to be used to convert the attributes into byte
   *      arrays, with the {@link #write write} method.
   * @param code the bytecode of the method corresponding to these code
   *      attributes, or <tt>null</tt> if these attributes are not code
   *      attributes.
   * @param len the length of the bytecode of the method corresponding to these
   *      code attributes, or <tt>null</tt> if these attributes are not code
   *      attributes.
   * @param maxStack the maximum stack size of the method corresponding to these
   *      code attributes, or -1 if these attributes are not code attributes.
   * @param maxLocals the maximum number of local variables of the method
   *      corresponding to these code attributes, or -1 if these attributes are
   *      not code attributes.
   * @return the size of all the attributes in this attribute list. This size
   *      includes the size of the attribute headers.
   */

  final int getSize (
    final ClassWriter cw,
    final byte[] code,
    final int len,
    final int maxStack,
    final int maxLocals)
  {
    Attribute attr = this;
    int size = 0;
    while (attr != null) {
      if (!attr.isUnknown()) {
        cw.newUTF8(attr.type);
        size += attr.write(cw, code, len, maxStack, maxLocals).length + 6;
      }
      attr = attr.next;
    }
    return size;
  }

  /**
   * Writes all the attributes of this attribute list in the given byte vector.
   *
   * @param cw the class writer to be used to convert the attributes into byte
   *      arrays, with the {@link #write write} method.
   * @param code the bytecode of the method corresponding to these code
   *      attributes, or <tt>null</tt> if these attributes are not code
   *      attributes.
   * @param len the length of the bytecode of the method corresponding to these
   *      code attributes, or <tt>null</tt> if these attributes are not code
   *      attributes.
   * @param maxStack the maximum stack size of the method corresponding to these
   *      code attributes, or -1 if these attributes are not code attributes.
   * @param maxLocals the maximum number of local variables of the method
   *      corresponding to these code attributes, or -1 if these attributes are
   *      not code attributes.
   * @param out where the attributes must be written.
   */

  final void put (
    final ClassWriter cw,
    final byte[] code,
    final int len,
    final int maxStack,
    final int maxLocals,
    final ByteVector out)
  {
    if (next != null) {
      next.put(cw, code, len, maxStack, maxLocals, out);
    }
    if (isUnknown()) {
      if (cw.checkAttributes) {
        throw new IllegalArgumentException("Unknown attribute type " + type);
      }
    } else {
      ByteVector b = write(cw, code, len, maxStack, maxLocals);
      out.putShort(cw.newUTF8(type)).putInt(b.length);
      out.putByteArray(b.data, 0, b.length);
    }
  }
}
