1 /*
2 * Copyright (c) 1998, 2000, 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. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package javax.swing.text.html.parser;
27
28 /**
29 * A content model state. This is basically a list of pointers to
30 * the BNF expression representing the model (the ContentModel).
31 * Each element in a DTD has a content model which describes the
32 * elements that may occur inside, and the order in which they can
33 * occur.
34 * <p>
35 * Each time a token is reduced a new state is created.
36 * <p>
37 * See Annex H on page 556 of the SGML handbook for more information.
38 *
39 * @see Parser
40 * @see DTD
41 * @see Element
42 * @see ContentModel
43 * @author Arthur van Hoff
44 */
45 class ContentModelState {
46 ContentModel model;
47 long value;
48 ContentModelState next;
49
50 /**
51 * Create a content model state for a content model.
52 */
53 public ContentModelState(ContentModel model) {
54 this(model, null, 0);
55 }
56
57 /**
58 * Create a content model state for a content model given the
59 * remaining state that needs to be reduce.
60 */
61 ContentModelState(Object content, ContentModelState next) {
62 this(content, next, 0);
63 }
64
65 /**
66 * Create a content model state for a content model given the
67 * remaining state that needs to be reduce.
68 */
69 ContentModelState(Object content, ContentModelState next, long value) {
70 this.model = (ContentModel)content;
71 this.next = next;
72 this.value = value;
73 }
74
75 /**
76 * Return the content model that is relevant to the current state.
77 */
78 public ContentModel getModel() {
79 ContentModel m = model;
80 for (int i = 0; i < value; i++) {
81 if (m.next != null) {
82 m = m.next;
83 } else {
84 return null;
85 }
86 }
87 return m;
88 }
89
90 /**
91 * Check if the state can be terminated. That is there are no more
92 * tokens required in the input stream.
93 * @return true if the model can terminate without further input
94 */
95 @SuppressWarnings("fallthrough")
96 public boolean terminate() {
97 switch (model.type) {
98 case '+':
99 if ((value == 0) && !(model).empty()) {
100 return false;
101 }
102 // Fall through okay?
103 case '*':
104 case '?':
105 return (next == null) || next.terminate();
106
107 case '|':
108 for (ContentModel m = (ContentModel)model.content ; m != null ; m = m.next) {
109 if (m.empty()) {
110 return (next == null) || next.terminate();
111 }
112 }
113 return false;
114
115 case '&': {
116 ContentModel m = (ContentModel)model.content;
117
118 for (int i = 0 ; m != null ; i++, m = m.next) {
119 if ((value & (1L << i)) == 0) {
120 if (!m.empty()) {
121 return false;
122 }
123 }
124 }
125 return (next == null) || next.terminate();
126 }
127
128 case ',': {
129 ContentModel m = (ContentModel)model.content;
130 for (int i = 0 ; i < value ; i++, m = m.next);
131
132 for (; (m != null) && m.empty() ; m = m.next);
133 if (m != null) {
134 return false;
135 }
136 return (next == null) || next.terminate();
137 }
138
139 default:
140 return false;
141 }
142 }
143
144 /**
145 * Check if the state can be terminated. That is there are no more
146 * tokens required in the input stream.
147 * @return the only possible element that can occur next
148 */
149 public Element first() {
150 switch (model.type) {
151 case '*':
152 case '?':
153 case '|':
154 case '&':
155 return null;
156
157 case '+':
158 return model.first();
159
160 case ',': {
161 ContentModel m = (ContentModel)model.content;
162 for (int i = 0 ; i < value ; i++, m = m.next);
163 return m.first();
164 }
165
166 default:
167 return model.first();
168 }
169 }
170
171 /**
172 * Advance this state to a new state. An exception is thrown if the
173 * token is illegal at this point in the content model.
174 * @return next state after reducing a token
175 */
176 public ContentModelState advance(Object token) {
177 switch (model.type) {
178 case '+':
179 if (model.first(token)) {
180 return new ContentModelState(model.content,
181 new ContentModelState(model, next, value + 1)).advance(token);
182 }
183 if (value != 0) {
184 if (next != null) {
185 return next.advance(token);
186 } else {
187 return null;
188 }
189 }
190 break;
191
192 case '*':
193 if (model.first(token)) {
194 return new ContentModelState(model.content, this).advance(token);
195 }
196 if (next != null) {
197 return next.advance(token);
198 } else {
199 return null;
200 }
201
202 case '?':
203 if (model.first(token)) {
204 return new ContentModelState(model.content, next).advance(token);
205 }
206 if (next != null) {
207 return next.advance(token);
208 } else {
209 return null;
210 }
211
212 case '|':
213 for (ContentModel m = (ContentModel)model.content ; m != null ; m = m.next) {
214 if (m.first(token)) {
215 return new ContentModelState(m, next).advance(token);
216 }
217 }
218 break;
219
220 case ',': {
221 ContentModel m = (ContentModel)model.content;
222 for (int i = 0 ; i < value ; i++, m = m.next);
223
224 if (m.first(token) || m.empty()) {
225 if (m.next == null) {
226 return new ContentModelState(m, next).advance(token);
227 } else {
228 return new ContentModelState(m,
229 new ContentModelState(model, next, value + 1)).advance(token);
230 }
231 }
232 break;
233 }
234
235 case '&': {
236 ContentModel m = (ContentModel)model.content;
237 boolean complete = true;
238
239 for (int i = 0 ; m != null ; i++, m = m.next) {
240 if ((value & (1L << i)) == 0) {
241 if (m.first(token)) {
242 return new ContentModelState(m,
243 new ContentModelState(model, next, value | (1L << i))).advance(token);
244 }
245 if (!m.empty()) {
246 complete = false;
247 }
248 }
249 }
250 if (complete) {
251 if (next != null) {
252 return next.advance(token);
253 } else {
254 return null;
255 }
256 }
257 break;
258 }
259
260 default:
261 if (model.content == token) {
262 if (next == null && (token instanceof Element) &&
263 ((Element)token).content != null) {
264 return new ContentModelState(((Element)token).content);
265 }
266 return next;
267 }
268 // PENDING: Currently we don't correctly deal with optional start
269 // tags. This can most notably be seen with the 4.01 spec where
270 // TBODY's start and end tags are optional.
271 // Uncommenting this and the PENDING in ContentModel will
272 // correctly skip the omit tags, but the delegate is not notified.
273 // Some additional API needs to be added to track skipped tags,
274 // and this can then be added back.
275 /*
276 if ((model.content instanceof Element)) {
277 Element e = (Element)model.content;
278
279 if (e.omitStart() && e.content != null) {
280 return new ContentModelState(e.content, next).advance(
281 token);
282 }
283 }
284 */
285 }
286
287 // We used to throw this exception at this point. However, it
288 // was determined that throwing this exception was more expensive
289 // than returning null, and we could not justify to ourselves why
290 // it was necessary to throw an exception, rather than simply
291 // returning null. I'm leaving it in a commented out state so
292 // that it can be easily restored if the situation ever arises.
293 //
294 // throw new IllegalArgumentException("invalid token: " + token);
295 return null;
296 }
297 }