summaryrefslogtreecommitdiff
path: root/libjava/classpath/gnu/javax/swing/text/html/css/CSSParser.java
blob: 4be315e3727aa9ecb5bf69d47177b931dd65ea4f (plain)
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
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
/* CSSParser.java -- A parser for CSS stylesheets
   Copyright (C) 2006 Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.

GNU Classpath is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
General Public License for more details.

You should have received a copy of the GNU General Public License
along with GNU Classpath; see the file COPYING.  If not, write to the
Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301 USA.

Linking this library statically or dynamically with other modules is
making a combined work based on this library.  Thus, the terms and
conditions of the GNU General Public License cover the whole
combination.

As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
modules, and to copy and distribute the resulting executable under
terms of your choice, provided that you also meet, for each linked
independent module, the terms and conditions of the license of that
module.  An independent module is a module which is not derived from
or based on this library.  If you modify this library, you may extend
this exception to your version of the library, but you are not
obligated to do so.  If you do not wish to do so, delete this
exception statement from your version. */


package gnu.javax.swing.text.html.css;

import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.Reader;
import java.util.StringTokenizer;

/**
 * A parser for CSS stylesheets.
 *
 * This parser is based on the simple CSS grammar describe in
 *
 * http://www.w3.org/TR/CSS21/syndata.html .
 *
 * @author Roman Kennke (kennke@aicas.com)
 */
// TODO: Maybe use more restrictive grammar:
// http://www.w3.org/TR/CSS21/grammar.html#q1
public class CSSParser
{

  /**
   * The scanner used to read the input streams into more usable tokens.
   */
  private CSSScanner scanner;

  /**
   * The parser callback.
   */
  private CSSParserCallback callback;

  /**
   * One lookahead token.
   */
  private int lookahead;

  /**
   * The parse error.
   */
  private String error;

  /**
   * Creates a new CSSParser that parses the specified input.
   *
   * @param in the source to parse
   */
  public CSSParser(Reader in, CSSParserCallback cb)
  {
    scanner = new CSSScanner(in);
    callback = cb;
    lookahead = -1;
  }

  /**
   * Parses the input source specified in the constructor.
   *
   * @throws IOException if an IO or parse error occurs
   */
  public void parse()
    throws IOException
  {
    boolean success = parseStylesheet();
    if (! success)
      {
        throw new CSSParserException(error);
      }
  }

  /**
   * Parses a stylesheet.
   *
   * @return <code>true</code> if the stylesheet could be parsed successfully,
   *         <code>false</code> otherwise
   *
   * @throws IOException if an IO or parse error occurs
   */
  private boolean parseStylesheet()
    throws IOException
  {
    int token = peekToken();
    while (token != CSSScanner.EOF && (token == CSSScanner.CDC
           || token == CSSScanner.CDO || token == CSSScanner.S
           || parseStatement()))
      {
        if (token == CSSScanner.CDC || token == CSSScanner.CDO
            || token == CSSScanner.S)
          readToken();
        token = peekToken();
      }
    // Last token must be EOF for valid stylesheets, I'd think.
    return token == CSSScanner.EOF;
  }

  /**
   * Parses a CSS statement.
   * @return <code>true</code> if the stylesheet could be parsed successfully,
   *         <code>false</code> otherwise
   *
   * @throws IOException if an IO or parse error occurs
   */
  private boolean parseStatement()
    throws IOException
  {
    return parseRuleset() || parseAtRule();
  }

  /**
   * Parses a CSS rule set.
   *
   * @return <code>true</code> if the ruleset could be parsed successfully,
   *         <code>false</code> otherwise
   *
   * @throws IOException if an IO or parse error occurs
   */
  private boolean parseRuleset()
    throws IOException
  {
    StringBuilder selector = new StringBuilder();
    parseSelector(selector);
    StringTokenizer selSplitter =
      new StringTokenizer(selector.toString(), ",");
    Selector[] sels = new Selector[selSplitter.countTokens()];
    for (int i = 0; selSplitter.hasMoreTokens(); i++)
      {
        String sel = selSplitter.nextToken().trim();
        sels[i] = new Selector(sel);
      }
    callback.startStatement(sels);
    // Read any number of whitespace.
    int token;
    do
      {
        token = readToken();
      } while (token == CSSScanner.S);
    boolean ret = true;

    if (token == CSSScanner.CURLY_LEFT)
      {
        // Read any number of whitespace.
        do
          {
            token = readToken();
          } while (token == CSSScanner.S);
        lookahead = token;

        // Maybe read declaration.
        boolean decl = parseDeclaration();
        token = peekToken();
        while (token == CSSScanner.SEMICOLON)
          {
            readToken(); // Read the semicolon.
            // Read any number of whitespace.
            do
              {
                token = readToken();
              } while (token == CSSScanner.S);
            lookahead = token;

            // Maybe read declaration.
            parseDeclaration();
            token = peekToken();
          }
        if (token != CSSScanner.CURLY_RIGHT)
          {
            error = "Expected right curly brace";
            ret = false;
          }
        else
          {
            readToken();
            // Read any number of whitespace.
            do
              {
                token = readToken();
              } while (token == CSSScanner.S);
            lookahead = token;
            callback.endStatement();
          }
      }
    else
      {
        ret = false;
        error = "Expected left curly brace";
      }
    return ret;
  }

  /**
   * Parses a CSS declaration.
   *
   * @return <code>true</code> if the ruleset could be parsed successfully,
   *         <code>false</code> otherwise
   *
   * @throws IOException if an IO or parse error occurs
   */
  private boolean parseDeclaration()
   throws IOException
  {
    // Maybe fetch one DELIM.
    int token = readToken();
    if (token == CSSScanner.DELIM)
      token = readToken();

    boolean ret = true;

    // Parse property
    String property = null;
    if (token == CSSScanner.IDENT)
      {
        property = new String(scanner.parseBuffer, 0, scanner.tokenEnd);
        // Read any number of whitespace.
        do
          {
            token = readToken();
          } while (token == CSSScanner.S);

        // Read ':'.
        if (token == CSSScanner.DELIM && scanner.parseBuffer[0] == ':')
          {
            // Read any number of whitespace.
            do
              {
                token = readToken();
              } while (token == CSSScanner.S);
            lookahead = token;

            StringBuilder value = new StringBuilder();
            if (parseValue(value))
              {
                callback.declaration(property, value.toString().trim());
              }
            else
              {
                ret = false;
                error = "Error while reading the property value";
              }
          }
        else
          {
            ret = false;
            error = "Expected colon to separate property and value";
          }

      }
    else
      {
        lookahead = token;
        ret = false;
        error = "Expected IDENT token for property";
      }
    return ret;
  }

  /**
   * Parses a property value.
   *
   * @param s the string builder to read the value into
   *
   * @return <code>true</code> if the ruleset could be parsed successfully,
   *         <code>false</code> otherwise
   *
   * @throws IOException if an IO or parse error occurs
   */
  private boolean parseValue(StringBuilder s)
    throws IOException
  {
    // FIXME: Handle block and ATKEYWORD.
    boolean success = parseAny(s);
    while (parseAny(s))
      ;

    return success;
  }

  /**
   * Parses a selector.
   *
   * @param sel the string buffer to put the selector into
   *
   * @return <code>true</code> if the ruleset could be parsed successfully,
   *         <code>false</code> otherwise
   *
   * @throws IOException if an IO or parse error occurs
   */
  private boolean parseSelector(StringBuilder sel)
    throws IOException
  {
    // At least one any needs to be parsed.
    boolean ret = parseAny(sel);
    if (ret)
      {
        while (parseAny(sel))
          ;
      }
    return ret;
  }

  /**
   * Parses the any rule. If s is not null, then the contents of the
   * tokens is appended verbatim.
   *
   * @param s the string builder to append to
   *
   * @return <code>true</code> if the ruleset could be parsed successfully,
   *         <code>false</code> otherwise
   *
   * @throws IOException if an IO or parse error occurs
   */
  private boolean parseAny(StringBuilder s)
    throws IOException
  {
    int token = peekToken();
    boolean ret = false;
    if (token == CSSScanner.IDENT || token == CSSScanner.NUMBER
        || token == CSSScanner.PERCENTAGE || token == CSSScanner.DIMENSION
        || token == CSSScanner.STRING || token == CSSScanner.DELIM
        || token == CSSScanner.URI || token == CSSScanner.HASH
        || token == CSSScanner.UNICODE_RANGE || token == CSSScanner.INCLUDES
        || token == CSSScanner.DASHMATCH)
      {
        if (s != null)
          s.append(scanner.parseBuffer, 0, scanner.tokenEnd);
        readToken();
        ret = true;
      }
    else if (token == CSSScanner.FUNCTION)
      System.err.println("Implement parseAny for FUNCTION");
    else if (token == CSSScanner.PAREN_LEFT)
      System.err.println("Implement parseAny for (");
    else if (token == CSSScanner.BRACE_LEFT)
      System.err.println("Implement parseAny for [");

    // Parse any following whitespace too.
    token = peekToken();
    while (token == CSSScanner.S)
      {
        if (s != null)
          s.append(scanner.parseBuffer, 0, scanner.tokenEnd);
        readToken();
        token = peekToken();
      }
    return ret;
  }

  /**
   * Parses a CSS at-rule.
   *
   * @return <code>true</code> if the at-rule could be parsed successfully,
   *         <code>false</code> otherwise
   *
   * @throws IOException if an IO or parse error occurs
   */
  private boolean parseAtRule()
    throws IOException
  {
    // FIXME: Implement.
    return false;
  }

  /**
   * Reads the next token, and skips the comments.
   *
   * @return the next non-comment token
   */
  private int readToken()
    throws IOException
  {
    int token;
    if (lookahead == -1)
      {
        do
          {
            token = scanner.nextToken();
          } while (token == CSSScanner.COMMENT);
      }
    else
      {
        token = lookahead;
        lookahead = -1;
      }
    return token;
  }

  /**
   * Returns the next token to be read, without really reading it. The next
   * call to readToken() will return the same token again.
   *
   * @return the next token to be read, without really reading it
   */
  private int peekToken()
    throws IOException
  {
    int token;
    if (lookahead == -1)
      {
        do
          {
            token = scanner.nextToken();
          } while (token == CSSScanner.COMMENT);
        lookahead = token;
      }
    else
      token = lookahead;
    return token;
  }

  /**
   * For testing, we read in the default.css in javax/swing/text/html
   *
   * @param args
   */
  public static void main(String[] args)
  {
    try
      {
        InputStream in;
        if (args.length > 0)
          {
            File file = new File(args[0]);
            in = new FileInputStream(file);
          }
        else
          {
            String name = "/javax/swing/text/html/default.css";
            in = CSSScanner.class.getResourceAsStream(name);
          }
        BufferedInputStream bin = new BufferedInputStream(in);
        InputStreamReader r = new InputStreamReader(bin);
        CSSParserCallback cb = new CSSParserCallback()
        {
          public void startStatement(Selector[] selector)
          {
            System.out.print("startStatement: ");
            for (int i = 0; i < selector.length; i++)
              {
                System.out.print(selector[i]);
                if (i < selector.length - 1)
                  System.out.print(',');
                else
                  System.out.println();
              }
          }
          public void endStatement()
          {
            System.out.println("endStatement");
          }
          public void declaration(String property, String value)
          {
            System.out.println("declaration: " + property + ", " + value);
          }
        };
        CSSParser p = new CSSParser(r, cb);
        p.parse();
      }
    catch (IOException ex)
      {
        ex.printStackTrace();
      }
  }

}