001/*
002 * Copyright 2007-2014 UnboundID Corp.
003 * All Rights Reserved.
004 */
005/*
006 * Copyright (C) 2008-2014 UnboundID Corp.
007 *
008 * This program is free software; you can redistribute it and/or modify
009 * it under the terms of the GNU General Public License (GPLv2 only)
010 * or the terms of the GNU Lesser General Public License (LGPLv2.1 only)
011 * as published by the Free Software Foundation.
012 *
013 * This program is distributed in the hope that it will be useful,
014 * but WITHOUT ANY WARRANTY; without even the implied warranty of
015 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
016 * GNU General Public License for more details.
017 *
018 * You should have received a copy of the GNU General Public License
019 * along with this program; if not, see <http://www.gnu.org/licenses>.
020 */
021package com.unboundid.asn1;
022
023
024
025import com.unboundid.util.NotMutable;
026import com.unboundid.util.ThreadSafety;
027import com.unboundid.util.ThreadSafetyLevel;
028
029import static com.unboundid.asn1.ASN1Constants.*;
030import static com.unboundid.asn1.ASN1Messages.*;
031import static com.unboundid.util.Debug.*;
032import static com.unboundid.util.StaticUtils.*;
033
034
035
036/**
037 * This class provides an ASN.1 null element, which does not hold a value.  Null
038 * elements are generally used as placeholders that can be substituted for other
039 * types of elements.
040 */
041@NotMutable()
042@ThreadSafety(level=ThreadSafetyLevel.COMPLETELY_THREADSAFE)
043public final class ASN1Null
044       extends ASN1Element
045{
046  /**
047   * A pre-allocated ASN.1 null element with the universal null BER type.
048   */
049  public static final ASN1Null UNIVERSAL_NULL_ELEMENT = new ASN1Null();
050
051
052
053  /**
054   * The serial version UID for this serializable class.
055   */
056  private static final long serialVersionUID = -3264450066845549348L;
057
058
059
060  /**
061   * Creates a new ASN.1 null element with the default BER type.
062   */
063  public ASN1Null()
064  {
065    super(UNIVERSAL_NULL_TYPE);
066  }
067
068
069
070  /**
071   * Creates a new ASN.1 null element with the specified BER type.
072   *
073   * @param  type  The BER type to use for this ASN.1 null element.
074   */
075  public ASN1Null(final byte type)
076  {
077    super(type);
078  }
079
080
081
082  /**
083   * Decodes the contents of the provided byte array as a null element.
084   *
085   * @param  elementBytes  The byte array to decode as an ASN.1 null element.
086   *
087   * @return  The decoded ASN.1 null element.
088   *
089   * @throws  ASN1Exception  If the provided array cannot be decoded as a null
090   *                         element.
091   */
092  public static ASN1Null decodeAsNull(final byte[] elementBytes)
093         throws ASN1Exception
094  {
095    try
096    {
097      int valueStartPos = 2;
098      int length = (elementBytes[1] & 0x7F);
099      if (length != elementBytes[1])
100      {
101        final int numLengthBytes = length;
102
103        length = 0;
104        for (int i=0; i < numLengthBytes; i++)
105        {
106          length <<= 8;
107          length |= (elementBytes[valueStartPos++] & 0xFF);
108        }
109      }
110
111      if ((elementBytes.length - valueStartPos) != length)
112      {
113        throw new ASN1Exception(ERR_ELEMENT_LENGTH_MISMATCH.get(length,
114                                     (elementBytes.length - valueStartPos)));
115      }
116
117      if (length != 0)
118      {
119        throw new ASN1Exception(ERR_NULL_HAS_VALUE.get());
120      }
121
122      return new ASN1Null(elementBytes[0]);
123    }
124    catch (final ASN1Exception ae)
125    {
126      debugException(ae);
127      throw ae;
128    }
129    catch (final Exception e)
130    {
131      debugException(e);
132      throw new ASN1Exception(ERR_ELEMENT_DECODE_EXCEPTION.get(e), e);
133    }
134  }
135
136
137
138  /**
139   * Decodes the provided ASN.1 element as a null element.
140   *
141   * @param  element  The ASN.1 element to be decoded.
142   *
143   * @return  The decoded ASN.1 null element.
144   *
145   * @throws  ASN1Exception  If the provided element cannot be decoded as a null
146   *                         element.
147   */
148  public static ASN1Null decodeAsNull(final ASN1Element element)
149         throws ASN1Exception
150  {
151    if (element.getValue().length != 0)
152    {
153      throw new ASN1Exception(ERR_NULL_HAS_VALUE.get());
154    }
155
156    return new ASN1Null(element.getType());
157  }
158
159
160
161  /**
162   * Appends a string representation of this ASN.1 element to the provided
163   * buffer.
164   *
165   * @param  buffer  The buffer to which to append the information.
166   */
167  @Override()
168  public void toString(final StringBuilder buffer)
169  {
170    buffer.append("ASN1Null(type=");
171    toHex(getType(), buffer);
172    buffer.append(')');
173  }
174}