/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License, Version 1.0 only
 * (the "License").  You may not use this file except in compliance
 * with the License.
 *
 * You can obtain a copy of the license at
 * trunk/opends/resource/legal-notices/OpenDS.LICENSE
 * or https://OpenDS.dev.java.net/OpenDS.LICENSE.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at
 * trunk/opends/resource/legal-notices/OpenDS.LICENSE.  If applicable,
 * add the following below this CDDL HEADER, with the fields enclosed
 * by brackets "[]" replaced with your own identifying information:
 *      Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 *
 *
 *      Copyright 2010 Sun Microsystems, Inc.
 */
package org.opends.sdk.controls;



import org.opends.sdk.ByteString;



/**
 * Controls provide a mechanism whereby the semantics and arguments of existing
 * LDAP operations may be extended. One or more controls may be attached to a
 * single LDAP message. A control only affects the semantics of the message it
 * is attached to. Controls sent by clients are termed 'request controls', and
 * those sent by servers are termed 'response controls'.
 *
 * @see <a href="http://tools.ietf.org/html/rfc4511">RFC 4511 - Lightweight
 *      Directory Access Protocol (LDAP): The Protocol </a>
 */
public interface Control
{

  /**
   * Returns the numeric OID associated with this control.
   *
   * @return The numeric OID associated with this control.
   */
  String getOID();



  /**
   * Returns the value, if any, associated with this control. Its format is
   * defined by the specification of this control.
   *
   * @return The value associated with this control, or {@code null} if there is
   *         no value.
   */
  ByteString getValue();



  /**
   * Returns {@code true} if this control has a value. In some circumstances it
   * may be useful to determine if a control has a value, without actually
   * calculating the value and incurring any performance costs.
   *
   * @return {@code true} if this control has a value, or {@code false} if there
   *         is no value.
   */
  boolean hasValue();



  /**
   * Returns {@code true} if it is unacceptable to perform the operation without
   * applying the semantics of this control.
   * <p>
   * The criticality field only has meaning in controls attached to request
   * messages (except UnbindRequest). For controls attached to response messages
   * and the UnbindRequest, the criticality field SHOULD be {@code false}, and
   * MUST be ignored by the receiving protocol peer. A value of {@code true}
   * indicates that it is unacceptable to perform the operation without applying
   * the semantics of the control.
   *
   * @return {@code true} if this control must be processed by the Directory
   *         Server, or {@code false} if it can be ignored.
   */
  boolean isCritical();

}