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 */
021 package com.unboundid.asn1;
022
023
024
025
026 import static com.unboundid.asn1.ASN1Constants.*;
027 import static com.unboundid.asn1.ASN1Messages.*;
028 import static com.unboundid.util.Debug.*;
029 import static com.unboundid.util.StaticUtils.*;
030
031
032
033 /**
034 * This class provides an ASN.1 null element, which does not hold a value. Null
035 * elements are generally used as placeholders that can be substituted for other
036 * types of elements.
037 */
038 public final class ASN1Null
039 extends ASN1Element
040 {
041 /**
042 * A pre-allocated ASN.1 null element with the universal null BER type.
043 */
044 public static final ASN1Null UNIVERSAL_NULL_ELEMENT = new ASN1Null();
045
046
047
048 /**
049 * The serial version UID for this serializable class.
050 */
051 private static final long serialVersionUID = -3264450066845549348L;
052
053
054
055 /**
056 * Creates a new ASN.1 null element with the default BER type.
057 */
058 public ASN1Null()
059 {
060 super(UNIVERSAL_NULL_TYPE);
061 }
062
063
064
065 /**
066 * Creates a new ASN.1 null element with the specified BER type.
067 *
068 * @param type The BER type to use for this ASN.1 null element.
069 */
070 public ASN1Null(final byte type)
071 {
072 super(type);
073 }
074
075
076
077 /**
078 * Decodes the contents of the provided byte array as a null element.
079 *
080 * @param elementBytes The byte array to decode as an ASN.1 null element.
081 *
082 * @return The decoded ASN.1 null element.
083 *
084 * @throws ASN1Exception If the provided array cannot be decoded as a null
085 * element.
086 */
087 public static ASN1Null decodeAsNull(final byte[] elementBytes)
088 throws ASN1Exception
089 {
090 try
091 {
092 int valueStartPos = 2;
093 int length = (elementBytes[1] & 0x7F);
094 if (length != elementBytes[1])
095 {
096 final int numLengthBytes = length;
097
098 length = 0;
099 for (int i=0; i < numLengthBytes; i++)
100 {
101 length <<= 8;
102 length |= (elementBytes[valueStartPos++] & 0xFF);
103 }
104 }
105
106 if ((elementBytes.length - valueStartPos) != length)
107 {
108 throw new ASN1Exception(ERR_ELEMENT_LENGTH_MISMATCH.get(length,
109 (elementBytes.length - valueStartPos)));
110 }
111
112 if (length != 0)
113 {
114 throw new ASN1Exception(ERR_NULL_HAS_VALUE.get());
115 }
116
117 return new ASN1Null(elementBytes[0]);
118 }
119 catch (final ASN1Exception ae)
120 {
121 debugException(ae);
122 throw ae;
123 }
124 catch (final Exception e)
125 {
126 debugException(e);
127 throw new ASN1Exception(ERR_ELEMENT_DECODE_EXCEPTION.get(e), e);
128 }
129 }
130
131
132
133 /**
134 * Decodes the provided ASN.1 element as a null element.
135 *
136 * @param element The ASN.1 element to be decoded.
137 *
138 * @return The decoded ASN.1 null element.
139 *
140 * @throws ASN1Exception If the provided element cannot be decoded as a null
141 * element.
142 */
143 public static ASN1Null decodeAsNull(final ASN1Element element)
144 throws ASN1Exception
145 {
146 if (element.getValue().length != 0)
147 {
148 throw new ASN1Exception(ERR_NULL_HAS_VALUE.get());
149 }
150
151 return new ASN1Null(element.getType());
152 }
153
154
155
156 /**
157 * Appends a string representation of this ASN.1 element to the provided
158 * buffer.
159 *
160 * @param buffer The buffer to which to append the information.
161 */
162 @Override()
163 public void toString(final StringBuilder buffer)
164 {
165 buffer.append("ASN1Null(type=");
166 toHex(getType(), buffer);
167 buffer.append(')');
168 }
169 }