1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
|
/* -*- Mode: Java; tab-width: 4 -*-
*
* Copyright (c) 2004 Apple Computer, Inc. All rights reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
To do:
- implement remove()
- fix set() to replace existing values
*/
package com.apple.dnssd;
/**
Object used to construct and parse DNS-SD format TXT records.
For more info see <a href="http://files.dns-sd.org/draft-cheshire-dnsext-dns-sd.txt">DNS-Based Service Discovery</a>, section 6.
*/
public class TXTRecord
{
/*
DNS-SD specifies that a TXT record corresponding to an SRV record consist of
a packed array of bytes, each preceded by a length byte. Each string
is an attribute-value pair.
The TXTRecord object stores the entire TXT data as a single byte array, traversing it
as need be to implement its various methods.
*/
static final protected byte kAttrSep = '=';
protected byte[] fBytes;
/** Constructs a new, empty TXT record. */
public TXTRecord()
{ fBytes = new byte[0]; }
/** Constructs a new TXT record from a byte array in the standard format. */
public TXTRecord( byte[] initBytes)
{ fBytes = (byte[]) initBytes.clone(); }
/** Set a key/value pair in the TXT record. Setting an existing key will replace its value.<P>
@param key
The key name. Must be ASCII, with no '=' characters.
<P>
@param value
Value to be encoded into bytes using the default platform character set.
*/
public void set( String key, String value)
{
byte[] valBytes = (value != null) ? value.getBytes() : null;
this.set( key, valBytes);
}
/** Set a key/value pair in the TXT record. Setting an existing key will replace its value.<P>
@param key
The key name. Must be ASCII, with no '=' characters.
<P>
@param value
Binary representation of the value.
*/
public void set( String key, byte[] value)
{
byte[] keyBytes;
int valLen = (value != null) ? value.length : 0;
try {
keyBytes = key.getBytes( "US-ASCII");
}
catch ( java.io.UnsupportedEncodingException uee) {
throw new IllegalArgumentException();
}
for ( int i=0; i < keyBytes.length; i++)
if ( keyBytes[i] == '=')
throw new IllegalArgumentException();
if ( keyBytes.length + valLen >= 255)
throw new ArrayIndexOutOfBoundsException();
int prevLoc = this.remove( key);
if ( prevLoc == -1)
prevLoc = this.size();
this.insert( keyBytes, value, prevLoc);
}
protected void insert( byte[] keyBytes, byte[] value, int index)
// Insert a key-value pair at index
{
byte[] oldBytes = fBytes;
int valLen = (value != null) ? value.length : 0;
int insertion = 0;
int newLen, avLen;
// locate the insertion point
for ( int i=0; i < index && insertion < fBytes.length; i++)
insertion += (0xFF & (fBytes[ insertion] + 1));
avLen = keyBytes.length + valLen + (value != null ? 1 : 0);
newLen = avLen + oldBytes.length + 1;
fBytes = new byte[ newLen];
System.arraycopy( oldBytes, 0, fBytes, 0, insertion);
int secondHalfLen = oldBytes.length - insertion;
System.arraycopy( oldBytes, insertion, fBytes, newLen - secondHalfLen, secondHalfLen);
fBytes[ insertion] = ( byte) avLen;
System.arraycopy( keyBytes, 0, fBytes, insertion + 1, keyBytes.length);
if ( value != null)
{
fBytes[ insertion + 1 + keyBytes.length] = kAttrSep;
System.arraycopy( value, 0, fBytes, insertion + keyBytes.length + 2, valLen);
}
}
/** Remove a key/value pair from the TXT record. Returns index it was at, or -1 if not found. */
public int remove( String key)
{
int avStart = 0;
for ( int i=0; avStart < fBytes.length; i++)
{
int avLen = fBytes[ avStart];
if ( key.length() <= avLen &&
( key.length() == avLen || fBytes[ avStart + key.length() + 1] == kAttrSep))
{
String s = new String( fBytes, avStart + 1, key.length());
if ( 0 == key.compareToIgnoreCase( s))
{
byte[] oldBytes = fBytes;
fBytes = new byte[ oldBytes.length - avLen - 1];
System.arraycopy( oldBytes, 0, fBytes, 0, avStart);
System.arraycopy( oldBytes, avStart + avLen + 1, fBytes, avStart, oldBytes.length - avStart - avLen - 1);
return i;
}
}
avStart += (0xFF & (avLen + 1));
}
return -1;
}
/** Return the number of keys in the TXT record. */
public int size()
{
int i, avStart;
for ( i=0, avStart=0; avStart < fBytes.length; i++)
avStart += (0xFF & (fBytes[ avStart] + 1));
return i;
}
/** Return true if key is present in the TXT record, false if not. */
public boolean contains( String key)
{
String s = null;
for ( int i=0; null != ( s = this.getKey( i)); i++)
if ( 0 == key.compareToIgnoreCase( s))
return true;
return false;
}
/** Return a key in the TXT record by zero-based index. Returns null if index exceeds the total number of keys. */
public String getKey( int index)
{
int avStart = 0;
for ( int i=0; i < index && avStart < fBytes.length; i++)
avStart += fBytes[ avStart] + 1;
if ( avStart < fBytes.length)
{
int avLen = fBytes[ avStart];
int aLen = 0;
for ( aLen=0; aLen < avLen; aLen++)
if ( fBytes[ avStart + aLen + 1] == kAttrSep)
break;
return new String( fBytes, avStart + 1, aLen);
}
return null;
}
/**
Look up a key in the TXT record by zero-based index and return its value. <P>
Returns null if index exceeds the total number of keys.
Returns null if the key is present with no value.
*/
public byte[] getValue( int index)
{
int avStart = 0;
byte[] value = null;
for ( int i=0; i < index && avStart < fBytes.length; i++)
avStart += fBytes[ avStart] + 1;
if ( avStart < fBytes.length)
{
int avLen = fBytes[ avStart];
int aLen = 0;
for ( aLen=0; aLen < avLen; aLen++)
{
if ( fBytes[ avStart + aLen + 1] == kAttrSep)
{
value = new byte[ avLen - aLen - 1];
System.arraycopy( fBytes, avStart + aLen + 2, value, 0, avLen - aLen - 1);
break;
}
}
}
return value;
}
/** Converts the result of getValue() to a string in the platform default character set. */
public String getValueAsString( int index)
{
byte[] value = this.getValue( index);
return value != null ? new String( value) : null;
}
/** Get the value associated with a key. Will be null if the key is not defined.
Array will have length 0 if the key is defined with an = but no value.<P>
@param forKey
The left-hand side of the key-value pair.
<P>
@return The binary representation of the value.
*/
public byte[] getValue( String forKey)
{
String s = null;
int i;
for ( i=0; null != ( s = this.getKey( i)); i++)
if ( 0 == forKey.compareToIgnoreCase( s))
return this.getValue( i);
return null;
}
/** Converts the result of getValue() to a string in the platform default character set.<P>
@param forKey
The left-hand side of the key-value pair.
<P>
@return The value represented in the default platform character set.
*/
public String getValueAsString( String forKey)
{
byte[] val = this.getValue( forKey);
return val != null ? new String( val) : null;
}
/** Return the contents of the TXT record as raw bytes. */
public byte[] getRawBytes() { return (byte[]) fBytes.clone(); }
/** Return a string representation of the object. */
public String toString()
{
String a, result = null;
for ( int i=0; null != ( a = this.getKey( i)); i++)
{
String av = String.valueOf( i) + "={" + a;
String val = this.getValueAsString( i);
if ( val != null)
av += "=" + val + "}";
else
av += "}";
if ( result == null)
result = av;
else
result = result + ", " + av;
}
return result != null ? result : "";
}
}
|