1 /*
2 * Copyright (c) 2005, 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 /*
27 *******************************************************************************
28 * (C) Copyright IBM Corp. 1996-2005 - All Rights Reserved *
29 * *
30 * The original version of this source code and documentation is copyrighted *
31 * and owned by IBM, These materials are provided under terms of a License *
32 * Agreement between IBM and Sun. This technology is protected by multiple *
33 * US and International patents. This notice and attribution to IBM may not *
34 * to removed. *
35 *******************************************************************************
36 */
37
38 /*
39 **********************************************************************
40 * Author: Alan Liu
41 * Created: September 23 2003
42 * Since: ICU 2.8
43 **********************************************************************
44 */
45
46 package sun.text.normalizer;
47
48 import java.text.ParsePosition;
49
50 /**
51 * An iterator that returns 32-bit code points. This class is deliberately
52 * <em>not</em> related to any of the JDK or ICU4J character iterator classes
53 * in order to minimize complexity.
54 * @author Alan Liu
55 * @since ICU 2.8
56 */
57 @SuppressWarnings("deprecation")
58 public class RuleCharacterIterator {
59
60 // TODO: Ideas for later. (Do not implement if not needed, lest the
61 // code coverage numbers go down due to unused methods.)
62 // 1. Add a copy constructor, equals() method, clone() method.
63 // 2. Rather than return DONE, throw an exception if the end
64 // is reached -- this is an alternate usage model, probably not useful.
65 // 3. Return isEscaped from next(). If this happens,
66 // don't keep an isEscaped member variable.
67
68 /**
69 * Text being iterated.
70 */
71 private String text;
72
73 /**
74 * Position of iterator.
75 */
76 private ParsePosition pos;
77
78 /**
79 * Symbol table used to parse and dereference variables. May be null.
80 */
81 private SymbolTable sym;
82
83 /**
84 * Current variable expansion, or null if none.
85 */
86 private char[] buf;
87
88 /**
89 * Position within buf[]. Meaningless if buf == null.
90 */
91 private int bufPos;
92
93 /**
94 * Flag indicating whether the last character was parsed from an escape.
95 */
96 private boolean isEscaped;
97
98 /**
99 * Value returned when there are no more characters to iterate.
100 */
101 public static final int DONE = -1;
102
103 /**
104 * Bitmask option to enable parsing of variable names. If (options &
105 * PARSE_VARIABLES) != 0, then an embedded variable will be expanded to
106 * its value. Variables are parsed using the SymbolTable API.
107 */
108 public static final int PARSE_VARIABLES = 1;
109
110 /**
111 * Bitmask option to enable parsing of escape sequences. If (options &
112 * PARSE_ESCAPES) != 0, then an embedded escape sequence will be expanded
113 * to its value. Escapes are parsed using Utility.unescapeAt().
114 */
115 public static final int PARSE_ESCAPES = 2;
116
117 /**
118 * Bitmask option to enable skipping of whitespace. If (options &
119 * SKIP_WHITESPACE) != 0, then whitespace characters will be silently
120 * skipped, as if they were not present in the input. Whitespace
121 * characters are defined by UCharacterProperty.isRuleWhiteSpace().
122 */
123 public static final int SKIP_WHITESPACE = 4;
124
125 /**
126 * Constructs an iterator over the given text, starting at the given
127 * position.
128 * @param text the text to be iterated
129 * @param sym the symbol table, or null if there is none. If sym is null,
130 * then variables will not be deferenced, even if the PARSE_VARIABLES
131 * option is set.
132 * @param pos upon input, the index of the next character to return. If a
133 * variable has been dereferenced, then pos will <em>not</em> increment as
134 * characters of the variable value are iterated.
135 */
136 public RuleCharacterIterator(String text, SymbolTable sym,
137 ParsePosition pos) {
138 if (text == null || pos.getIndex() > text.length()) {
139 throw new IllegalArgumentException();
140 }
141 this.text = text;
142 this.sym = sym;
143 this.pos = pos;
144 buf = null;
145 }
146
147 /**
148 * Returns true if this iterator has no more characters to return.
149 */
150 public boolean atEnd() {
151 return buf == null && pos.getIndex() == text.length();
152 }
153
154 /**
155 * Returns the next character using the given options, or DONE if there
156 * are no more characters, and advance the position to the next
157 * character.
158 * @param options one or more of the following options, bitwise-OR-ed
159 * together: PARSE_VARIABLES, PARSE_ESCAPES, SKIP_WHITESPACE.
160 * @return the current 32-bit code point, or DONE
161 */
162 public int next(int options) {
163 int c = DONE;
164 isEscaped = false;
165
166 for (;;) {
167 c = _current();
168 _advance(UTF16.getCharCount(c));
169
170 if (c == SymbolTable.SYMBOL_REF && buf == null &&
171 (options & PARSE_VARIABLES) != 0 && sym != null) {
172 String name = sym.parseReference(text, pos, text.length());
173 // If name == null there was an isolated SYMBOL_REF;
174 // return it. Caller must be prepared for this.
175 if (name == null) {
176 break;
177 }
178 bufPos = 0;
179 buf = sym.lookup(name);
180 if (buf == null) {
181 throw new IllegalArgumentException(
182 "Undefined variable: " + name);
183 }
184 // Handle empty variable value
185 if (buf.length == 0) {
186 buf = null;
187 }
188 continue;
189 }
190
191 if ((options & SKIP_WHITESPACE) != 0 &&
192 UCharacterProperty.isRuleWhiteSpace(c)) {
193 continue;
194 }
195
196 if (c == '\\' && (options & PARSE_ESCAPES) != 0) {
197 int offset[] = new int[] { 0 };
198 c = Utility.unescapeAt(lookahead(), offset);
199 jumpahead(offset[0]);
200 isEscaped = true;
201 if (c < 0) {
202 throw new IllegalArgumentException("Invalid escape");
203 }
204 }
205
206 break;
207 }
208
209 return c;
210 }
211
212 /**
213 * Returns true if the last character returned by next() was
214 * escaped. This will only be the case if the option passed in to
215 * next() included PARSE_ESCAPED and the next character was an
216 * escape sequence.
217 */
218 public boolean isEscaped() {
219 return isEscaped;
220 }
221
222 /**
223 * Returns true if this iterator is currently within a variable expansion.
224 */
225 public boolean inVariable() {
226 return buf != null;
227 }
228
229 /**
230 * Returns an object which, when later passed to setPos(), will
231 * restore this iterator's position. Usage idiom:
232 *
233 * RuleCharacterIterator iterator = ...;
234 * Object pos = iterator.getPos(null); // allocate position object
235 * for (;;) {
236 * pos = iterator.getPos(pos); // reuse position object
237 * int c = iterator.next(...);
238 * ...
239 * }
240 * iterator.setPos(pos);
241 *
242 * @param p a position object previously returned by getPos(),
243 * or null. If not null, it will be updated and returned. If
244 * null, a new position object will be allocated and returned.
245 * @return a position object which may be passed to setPos(),
246 * either `p,' or if `p' == null, a newly-allocated object
247 */
248 public Object getPos(Object p) {
249 if (p == null) {
250 return new Object[] {buf, new int[] {pos.getIndex(), bufPos}};
251 }
252 Object[] a = (Object[]) p;
253 a[0] = buf;
254 int[] v = (int[]) a[1];
255 v[0] = pos.getIndex();
256 v[1] = bufPos;
257 return p;
258 }
259
260 /**
261 * Restores this iterator to the position it had when getPos()
262 * returned the given object.
263 * @param p a position object previously returned by getPos()
264 */
265 public void setPos(Object p) {
266 Object[] a = (Object[]) p;
267 buf = (char[]) a[0];
268 int[] v = (int[]) a[1];
269 pos.setIndex(v[0]);
270 bufPos = v[1];
271 }
272
273 /**
274 * Skips ahead past any ignored characters, as indicated by the given
275 * options. This is useful in conjunction with the lookahead() method.
276 *
277 * Currently, this only has an effect for SKIP_WHITESPACE.
278 * @param options one or more of the following options, bitwise-OR-ed
279 * together: PARSE_VARIABLES, PARSE_ESCAPES, SKIP_WHITESPACE.
280 */
281 public void skipIgnored(int options) {
282 if ((options & SKIP_WHITESPACE) != 0) {
283 for (;;) {
284 int a = _current();
285 if (!UCharacterProperty.isRuleWhiteSpace(a)) break;
286 _advance(UTF16.getCharCount(a));
287 }
288 }
289 }
290
291 /**
292 * Returns a string containing the remainder of the characters to be
293 * returned by this iterator, without any option processing. If the
294 * iterator is currently within a variable expansion, this will only
295 * extend to the end of the variable expansion. This method is provided
296 * so that iterators may interoperate with string-based APIs. The typical
297 * sequence of calls is to call skipIgnored(), then call lookahead(), then
298 * parse the string returned by lookahead(), then call jumpahead() to
299 * resynchronize the iterator.
300 * @return a string containing the characters to be returned by future
301 * calls to next()
302 */
303 public String lookahead() {
304 if (buf != null) {
305 return new String(buf, bufPos, buf.length - bufPos);
306 } else {
307 return text.substring(pos.getIndex());
308 }
309 }
310
311 /**
312 * Advances the position by the given number of 16-bit code units.
313 * This is useful in conjunction with the lookahead() method.
314 * @param count the number of 16-bit code units to jump over
315 */
316 public void jumpahead(int count) {
317 if (count < 0) {
318 throw new IllegalArgumentException();
319 }
320 if (buf != null) {
321 bufPos += count;
322 if (bufPos > buf.length) {
323 throw new IllegalArgumentException();
324 }
325 if (bufPos == buf.length) {
326 buf = null;
327 }
328 } else {
329 int i = pos.getIndex() + count;
330 pos.setIndex(i);
331 if (i > text.length()) {
332 throw new IllegalArgumentException();
333 }
334 }
335 }
336
337 /**
338 * Returns the current 32-bit code point without parsing escapes, parsing
339 * variables, or skipping whitespace.
340 * @return the current 32-bit code point
341 */
342 private int _current() {
343 if (buf != null) {
344 return UTF16.charAt(buf, 0, buf.length, bufPos);
345 } else {
346 int i = pos.getIndex();
347 return (i < text.length()) ? UTF16.charAt(text, i) : DONE;
348 }
349 }
350
351 /**
352 * Advances the position by the given amount.
353 * @param count the number of 16-bit code units to advance past
354 */
355 private void _advance(int count) {
356 if (buf != null) {
357 bufPos += count;
358 if (bufPos == buf.length) {
359 buf = null;
360 }
361 } else {
362 pos.setIndex(pos.getIndex() + count);
363 if (pos.getIndex() > text.length()) {
364 pos.setIndex(text.length());
365 }
366 }
367 }
368 }