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