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The UnboundID LDAP SDK for Java is a fast, comprehensive, and easy-to-use Java API for communicating with LDAP directory servers and performing related tasks like reading and writing LDIF, encoding and decoding data using base64 and ASN.1 BER, and performing secure communication. This package contains the Standard Edition of the LDAP SDK, which is a complete, general-purpose library for communicating with LDAPv3 directory servers.

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/*
 * Copyright 2007-2018 Ping Identity Corporation
 * All Rights Reserved.
 */
/*
 * Copyright (C) 2008-2018 Ping Identity Corporation
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License (GPLv2 only)
 * or the terms of the GNU Lesser General Public License (LGPLv2.1 only)
 * as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, see .
 */
package com.unboundid.asn1;



import com.unboundid.util.Debug;
import com.unboundid.util.NotMutable;
import com.unboundid.util.StaticUtils;
import com.unboundid.util.ThreadSafety;
import com.unboundid.util.ThreadSafetyLevel;

import static com.unboundid.asn1.ASN1Messages.*;



/**
 * This class provides an ASN.1 null element, which does not hold a value.  Null
 * elements are generally used as placeholders that can be substituted for other
 * types of elements.
 */
@NotMutable()
@ThreadSafety(level=ThreadSafetyLevel.COMPLETELY_THREADSAFE)
public final class ASN1Null
       extends ASN1Element
{
  /**
   * A pre-allocated ASN.1 null element with the universal null BER type.
   */
  public static final ASN1Null UNIVERSAL_NULL_ELEMENT = new ASN1Null();



  /**
   * The serial version UID for this serializable class.
   */
  private static final long serialVersionUID = -3264450066845549348L;



  /**
   * Creates a new ASN.1 null element with the default BER type.
   */
  public ASN1Null()
  {
    super(ASN1Constants.UNIVERSAL_NULL_TYPE);
  }



  /**
   * Creates a new ASN.1 null element with the specified BER type.
   *
   * @param  type  The BER type to use for this ASN.1 null element.
   */
  public ASN1Null(final byte type)
  {
    super(type);
  }



  /**
   * Decodes the contents of the provided byte array as a null element.
   *
   * @param  elementBytes  The byte array to decode as an ASN.1 null element.
   *
   * @return  The decoded ASN.1 null element.
   *
   * @throws  ASN1Exception  If the provided array cannot be decoded as a null
   *                         element.
   */
  public static ASN1Null decodeAsNull(final byte[] elementBytes)
         throws ASN1Exception
  {
    try
    {
      int valueStartPos = 2;
      int length = (elementBytes[1] & 0x7F);
      if (length != elementBytes[1])
      {
        final int numLengthBytes = length;

        length = 0;
        for (int i=0; i < numLengthBytes; i++)
        {
          length <<= 8;
          length |= (elementBytes[valueStartPos++] & 0xFF);
        }
      }

      if ((elementBytes.length - valueStartPos) != length)
      {
        throw new ASN1Exception(ERR_ELEMENT_LENGTH_MISMATCH.get(length,
                                     (elementBytes.length - valueStartPos)));
      }

      if (length != 0)
      {
        throw new ASN1Exception(ERR_NULL_HAS_VALUE.get());
      }

      return new ASN1Null(elementBytes[0]);
    }
    catch (final ASN1Exception ae)
    {
      Debug.debugException(ae);
      throw ae;
    }
    catch (final Exception e)
    {
      Debug.debugException(e);
      throw new ASN1Exception(ERR_ELEMENT_DECODE_EXCEPTION.get(e), e);
    }
  }



  /**
   * Decodes the provided ASN.1 element as a null element.
   *
   * @param  element  The ASN.1 element to be decoded.
   *
   * @return  The decoded ASN.1 null element.
   *
   * @throws  ASN1Exception  If the provided element cannot be decoded as a null
   *                         element.
   */
  public static ASN1Null decodeAsNull(final ASN1Element element)
         throws ASN1Exception
  {
    if (element.getValue().length != 0)
    {
      throw new ASN1Exception(ERR_NULL_HAS_VALUE.get());
    }

    return new ASN1Null(element.getType());
  }



  /**
   * {@inheritDoc}
   */
  @Override()
  public void toString(final StringBuilder buffer)
  {
    buffer.append("ASN1Null(type=");
    StaticUtils.toHex(getType(), buffer);
    buffer.append(')');
  }
}