1 /*
2 * Copyright (c) 2006, 2018, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 */
23
24 package jnlp.converter.parser.xml;
25
26 import java.io.ByteArrayInputStream;
27 import java.io.EOFException;
28 import java.io.InputStreamReader;
29 import java.io.IOException;
30 import java.io.Reader;
31 import java.io.UnsupportedEncodingException;
32
33 public class XMLEncoding {
34 /**
35 * Decodes a byte stream into a String by testing for a Byte Order Mark
36 * (BOM) or an XML declaration.
37 * <br />
38 * Detection begins by examining the first four octets of the stream for a
39 * BOM. If a BOM is not found, then an encoding declaration is looked for
40 * at the beginning of the stream. If the encoding still can not be
41 * determined at this point, then UTF-8 is assumed.
42 *
43 * @param data an array of bytes containing an encoded XML document.
44 *
45 * @return A string containing the decoded XML document.
46 */
47 public static String decodeXML(byte [] data) throws IOException {
48 int start = 0;
49 String encoding;
50
51 if (data.length < BOM_LENGTH) {
52 throw (new EOFException("encoding.error.not.xml"));
53 }
54 // no else required; successfully read stream
55 int firstFour = ((0xff000000 & ((int) data[0] << 24)) |
56 (0x00ff0000 & ((int) data[1] << 16)) |
57 (0x0000ff00 & ((int) data[2] << 8)) |
58 (0x000000ff & (int) data[3]));
59
60 // start by examining the first four bytes for a BOM
61 switch (firstFour) {
62 case EBCDIC:
63 // examine the encoding declaration
64 encoding = examineEncodingDeclaration(data, IBM037_ENC);
65 break;
66
67 case XML_DECLARATION:
68 // assume UTF-8, but examine the encoding declaration
69 encoding = examineEncodingDeclaration(data, UTF_8_ENC);
70 break;
71
72 case UTF_16BE:
73 encoding = UTF_16BE_ENC;
74 break;
75
76 case UTF_16LE:
77 encoding = UTF_16LE_ENC;
78 break;
79
80 case UNUSUAL_OCTET_1:
81 case UNUSUAL_OCTET_2:
82 throw (new UnsupportedEncodingException("encoding.error.unusual.octet"));
83
84 case UTF_32_BE_BOM:
85 case UTF_32_LE_BOM:
86 encoding = UTF_32_ENC;
87 break;
88
89 default:
90 int firstThree = firstFour & 0xffffff00;
91
92 switch (firstThree) {
93 case UTF_8_BOM:
94 // the InputStreamReader class doen't properly handle
95 // the Byte Order Mark (BOM) in UTF-8 streams, so don't
96 // putback those 3 bytes.
97 start = 3;
98 encoding = UTF_8_ENC;
99 break;
100
101 default:
102 int firstTwo = firstFour & 0xffff0000;
103
104 switch (firstTwo) {
105 case UTF_16_BE_BOM:
106 case UTF_16_LE_BOM:
107 encoding = UTF_16_ENC;
108 break;
109
110 default:
111 // this is probably UTF-8 without the encoding
112 // declaration
113 encoding = UTF_8_ENC;
114 break;
115 }
116 break;
117 }
118 break;
119 }
120
121 return (new String(data, start, data.length - start, encoding));
122 }
123
124 /**
125 * [3] S ::= ( #x20 | #x09 | #x0d | #x0a )
126 * [23] XMLDecl ::= '<?xml' VersionInfo EncodingDecl? SDDecl? S? '?>'
127 * [24] VersionInfo ::= S 'version' Eq ( '"' VersionNum '"' |
128 * "'" VersionNum "'" )
129 * [25] Eq ::= S? '=' S?
130 * [26] VersionNum ::= ([a-zA-Z0-9_.:] | '-')+
131 * [80] EncodingDecl ::= S 'encoding' Eq ( '"' EncName '"' |
132 * "'" EncName "'" )
133 * [81] EncName ::= [a-zA-Z] ([a-zA-Z0-9_.] | '-')*
134 */
135 private static String examineEncodingDeclaration(byte [] data,
136 String encoding) throws IOException {
137 boolean loop = false;
138 boolean recognized = false;
139 boolean almost = false;
140 boolean question = false;
141 boolean done = false;
142 boolean found = false;
143 int pos = 0;
144 int ch = -1;
145 Reader reader = null;
146 String result = ((encoding != null) ? encoding : UTF_8_ENC);
147
148 reader = new InputStreamReader(new ByteArrayInputStream(data), result);
149 ch = reader.read();
150
151 // if this is an XML declaration, it will start with the text '<?xml'
152 for (int i = 0; ((i < XML_DECL_START.length()) && (done == false)); i++) {
153 if (ch != XML_DECL_START.charAt(i)) {
154 // This doesn't look like an XML declaration. This method
155 // should only be called if the stream contains an XML
156 // declaration in the encoding that is passed into the method.
157 done = true;
158 break;
159 }
160 // no else required; still matches
161 ch = reader.read();
162 }
163
164 // there must be at least one whitespace character next.
165 loop = true;
166 while ((loop == true) && (done == false)) {
167 switch (ch) {
168 case SPACE:
169 case TAB: // intentional
170 case LINEFEED: // fall
171 case RETURN: // through
172 ch = reader.read();
173 break;
174
175 case -1:
176 // unexpected EOF
177 done = true;
178 break;
179
180 default:
181 // non-whitespace
182 loop = false;
183 break;
184 }
185 }
186
187 // now look for the text 'encoding', but if the end of the XML
188 // declaration (signified by the text '?>') comes first, then
189 // assume the encoding is UTF-8
190 loop = true;
191 while ((loop == true) && (done == false)) {
192 if (ch == -1) {
193 // unexpected EOF
194 done = true;
195 break;
196 } else if (recognized == true) {
197 // this is the encoding declaration as long as the next few
198 // characters are whitespace and/or the equals ('=') sign
199 switch (ch) {
200 case SPACE: // intentional
201 case TAB: // fall
202 case LINEFEED: // through
203 case RETURN:
204 // don't need to do anything
205 break;
206
207 case EQUAL:
208 if (almost == false) {
209 // got the equal, now find a quote
210 almost = true;
211 } else {
212 // this is not valid XML, so punt
213 recognized = false;
214 done = true;
215 }
216 break;
217
218 case DOUBLE_QUOTE: // intentional
219 case SINGLE_QUOTE: // fall through
220 if (almost == true) {
221 // got the quote, so move on to get the value
222 loop = false;
223 } else {
224 // got a quote before the equal; this is not valid
225 // XML, so punt
226 recognized = false;
227 done = true;
228 }
229 break;
230
231 default:
232 // non-whitespace
233 recognized = false;
234 if (almost == true) {
235 // this is not valid XML, so punt
236 done = true;
237 }
238 // no else required; this wasn't the encoding
239 // declaration
240 break;
241 }
242
243 if (recognized == false) {
244 // this isn't the encoding declaration, so go back to the
245 // top without reading the next character
246 pos = 0;
247 continue;
248 }
249 // no else required; still looking good
250 } else if (ch == ENCODING_DECL.charAt(pos++)) {
251 if (ENCODING_DECL.length() == pos) {
252 // this looks like the encoding declaration
253 recognized = true;
254 }
255 // no else required; this might be the encoding declaration
256 } else if (ch == '?') {
257 question = true;
258 pos = 0;
259 } else if ((ch == '>') && (question == true)) {
260 // there is no encoding declaration, so assume that the initial
261 // encoding guess was correct
262 done = true;
263 continue;
264 } else {
265 // still searching for the encoding declaration
266 pos = 0;
267 }
268
269 ch = reader.read();
270 }
271
272 if (done == false) {
273 StringBuilder buffer = new StringBuilder(MAX_ENC_NAME);
274
275 if (((ch >= 'a') && (ch <= 'z')) |
276 ((ch >= 'A') && (ch <= 'Z'))) {
277 // add the character to the result
278 buffer.append((char) ch);
279
280 loop = true;
281 while ((loop == true) && (done == false)) {
282 ch = reader.read();
283
284 if (((ch >= 'a') && (ch <= 'z')) ||
285 ((ch >= 'A') && (ch <= 'Z')) ||
286 ((ch >= '0') && (ch <= '9')) ||
287 (ch == '_') || (ch == '.') || (ch == '-')) {
288 // add the character to the result
289 buffer.append((char) ch);
290 } else if ((ch == DOUBLE_QUOTE) || (ch == SINGLE_QUOTE)) {
291 // finished!
292 found = true;
293 done = true;
294 result = buffer.toString();
295 } else {
296 // this is not a valid encoding name, so punt
297 done = true;
298 }
299 }
300 } else {
301 // this is not a valid encoding name, so punt
302 done = true;
303 }
304 }
305 // no else required; already failed to find the encoding somewhere else
306
307 return (result);
308 }
309
310 private static final int BOM_LENGTH = 4;
311 private static final int MAX_ENC_NAME = 512;
312
313 private static final int SPACE = 0x00000020;
314 private static final int TAB = 0x00000009;
315 private static final int LINEFEED = 0x0000000a;
316 private static final int RETURN = 0x0000000d;
317 private static final int EQUAL = '=';
318 private static final int DOUBLE_QUOTE = '\"';
319 private static final int SINGLE_QUOTE = '\'';
320
321 private static final int UTF_32_BE_BOM = 0x0000feff;
322 private static final int UTF_32_LE_BOM = 0xfffe0000;
323 private static final int UTF_16_BE_BOM = 0xfeff0000;
324 private static final int UTF_16_LE_BOM = 0xfffe0000;
325 private static final int UTF_8_BOM = 0xefbbbf00;
326 private static final int UNUSUAL_OCTET_1 = 0x00003c00;
327 private static final int UNUSUAL_OCTET_2 = 0x003c0000;
328 private static final int UTF_16BE = 0x003c003f;
329 private static final int UTF_16LE = 0x3c003f00;
330 private static final int EBCDIC = 0x4c6fa794;
331 private static final int XML_DECLARATION = 0x3c3f786d;
332
333 private static final String UTF_32_ENC = "UTF-32";
334 private static final String UTF_16_ENC = "UTF-16";
335 private static final String UTF_16BE_ENC = "UTF-16BE";
336 private static final String UTF_16LE_ENC = "UTF-16LE";
337 private static final String UTF_8_ENC = "UTF-8";
338 private static final String IBM037_ENC = "IBM037";
339
340 private static final String XML_DECL_START = "<?xml";
341 private static final String ENCODING_DECL = "encoding";
342 }