summaryrefslogtreecommitdiff
path: root/fs/unicode/utf8-norm.c
blob: 768f8ab448b8f7372ffe001a0da82a71bf973926 (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
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (c) 2014 SGI.
 * All rights reserved.
 */

#include "utf8n.h"

int utf8version_is_supported(const struct unicode_map *um, unsigned int version)
{
	int i = um->tables->utf8agetab_size - 1;

	while (i >= 0 && um->tables->utf8agetab[i] != 0) {
		if (version == um->tables->utf8agetab[i])
			return 1;
		i--;
	}
	return 0;
}

/*
 * UTF-8 valid ranges.
 *
 * The UTF-8 encoding spreads the bits of a 32bit word over several
 * bytes. This table gives the ranges that can be held and how they'd
 * be represented.
 *
 * 0x00000000 0x0000007F: 0xxxxxxx
 * 0x00000000 0x000007FF: 110xxxxx 10xxxxxx
 * 0x00000000 0x0000FFFF: 1110xxxx 10xxxxxx 10xxxxxx
 * 0x00000000 0x001FFFFF: 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
 * 0x00000000 0x03FFFFFF: 111110xx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
 * 0x00000000 0x7FFFFFFF: 1111110x 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
 *
 * There is an additional requirement on UTF-8, in that only the
 * shortest representation of a 32bit value is to be used.  A decoder
 * must not decode sequences that do not satisfy this requirement.
 * Thus the allowed ranges have a lower bound.
 *
 * 0x00000000 0x0000007F: 0xxxxxxx
 * 0x00000080 0x000007FF: 110xxxxx 10xxxxxx
 * 0x00000800 0x0000FFFF: 1110xxxx 10xxxxxx 10xxxxxx
 * 0x00010000 0x001FFFFF: 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
 * 0x00200000 0x03FFFFFF: 111110xx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
 * 0x04000000 0x7FFFFFFF: 1111110x 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
 *
 * Actual unicode characters are limited to the range 0x0 - 0x10FFFF,
 * 17 planes of 65536 values.  This limits the sequences actually seen
 * even more, to just the following.
 *
 *          0 -     0x7F: 0                   - 0x7F
 *       0x80 -    0x7FF: 0xC2 0x80           - 0xDF 0xBF
 *      0x800 -   0xFFFF: 0xE0 0xA0 0x80      - 0xEF 0xBF 0xBF
 *    0x10000 - 0x10FFFF: 0xF0 0x90 0x80 0x80 - 0xF4 0x8F 0xBF 0xBF
 *
 * Within those ranges the surrogates 0xD800 - 0xDFFF are not allowed.
 *
 * Note that the longest sequence seen with valid usage is 4 bytes,
 * the same a single UTF-32 character.  This makes the UTF-8
 * representation of Unicode strictly smaller than UTF-32.
 *
 * The shortest sequence requirement was introduced by:
 *    Corrigendum #1: UTF-8 Shortest Form
 * It can be found here:
 *    http://www.unicode.org/versions/corrigendum1.html
 *
 */

/*
 * Return the number of bytes used by the current UTF-8 sequence.
 * Assumes the input points to the first byte of a valid UTF-8
 * sequence.
 */
static inline int utf8clen(const char *s)
{
	unsigned char c = *s;

	return 1 + (c >= 0xC0) + (c >= 0xE0) + (c >= 0xF0);
}

/*
 * Decode a 3-byte UTF-8 sequence.
 */
static unsigned int
utf8decode3(const char *str)
{
	unsigned int		uc;

	uc = *str++ & 0x0F;
	uc <<= 6;
	uc |= *str++ & 0x3F;
	uc <<= 6;
	uc |= *str++ & 0x3F;

	return uc;
}

/*
 * Encode a 3-byte UTF-8 sequence.
 */
static int
utf8encode3(char *str, unsigned int val)
{
	str[2] = (val & 0x3F) | 0x80;
	val >>= 6;
	str[1] = (val & 0x3F) | 0x80;
	val >>= 6;
	str[0] = val | 0xE0;

	return 3;
}

/*
 * utf8trie_t
 *
 * A compact binary tree, used to decode UTF-8 characters.
 *
 * Internal nodes are one byte for the node itself, and up to three
 * bytes for an offset into the tree.  The first byte contains the
 * following information:
 *  NEXTBYTE  - flag        - advance to next byte if set
 *  BITNUM    - 3 bit field - the bit number to tested
 *  OFFLEN    - 2 bit field - number of bytes in the offset
 * if offlen == 0 (non-branching node)
 *  RIGHTPATH - 1 bit field - set if the following node is for the
 *                            right-hand path (tested bit is set)
 *  TRIENODE  - 1 bit field - set if the following node is an internal
 *                            node, otherwise it is a leaf node
 * if offlen != 0 (branching node)
 *  LEFTNODE  - 1 bit field - set if the left-hand node is internal
 *  RIGHTNODE - 1 bit field - set if the right-hand node is internal
 *
 * Due to the way utf8 works, there cannot be branching nodes with
 * NEXTBYTE set, and moreover those nodes always have a righthand
 * descendant.
 */
typedef const unsigned char utf8trie_t;
#define BITNUM		0x07
#define NEXTBYTE	0x08
#define OFFLEN		0x30
#define OFFLEN_SHIFT	4
#define RIGHTPATH	0x40
#define TRIENODE	0x80
#define RIGHTNODE	0x40
#define LEFTNODE	0x80

/*
 * utf8leaf_t
 *
 * The leaves of the trie are embedded in the trie, and so the same
 * underlying datatype: unsigned char.
 *
 * leaf[0]: The unicode version, stored as a generation number that is
 *          an index into ->utf8agetab[].  With this we can filter code
 *          points based on the unicode version in which they were
 *          defined.  The CCC of a non-defined code point is 0.
 * leaf[1]: Canonical Combining Class. During normalization, we need
 *          to do a stable sort into ascending order of all characters
 *          with a non-zero CCC that occur between two characters with
 *          a CCC of 0, or at the begin or end of a string.
 *          The unicode standard guarantees that all CCC values are
 *          between 0 and 254 inclusive, which leaves 255 available as
 *          a special value.
 *          Code points with CCC 0 are known as stoppers.
 * leaf[2]: Decomposition. If leaf[1] == 255, then leaf[2] is the
 *          start of a NUL-terminated string that is the decomposition
 *          of the character.
 *          The CCC of a decomposable character is the same as the CCC
 *          of the first character of its decomposition.
 *          Some characters decompose as the empty string: these are
 *          characters with the Default_Ignorable_Code_Point property.
 *          These do affect normalization, as they all have CCC 0.
 *
 * The decompositions in the trie have been fully expanded, with the
 * exception of Hangul syllables, which are decomposed algorithmically.
 *
 * Casefolding, if applicable, is also done using decompositions.
 *
 * The trie is constructed in such a way that leaves exist for all
 * UTF-8 sequences that match the criteria from the "UTF-8 valid
 * ranges" comment above, and only for those sequences.  Therefore a
 * lookup in the trie can be used to validate the UTF-8 input.
 */
typedef const unsigned char utf8leaf_t;

#define LEAF_GEN(LEAF)	((LEAF)[0])
#define LEAF_CCC(LEAF)	((LEAF)[1])
#define LEAF_STR(LEAF)	((const char *)((LEAF) + 2))

#define MINCCC		(0)
#define MAXCCC		(254)
#define STOPPER		(0)
#define	DECOMPOSE	(255)

/* Marker for hangul syllable decomposition. */
#define HANGUL		((char)(255))
/* Size of the synthesized leaf used for Hangul syllable decomposition. */
#define UTF8HANGULLEAF	(12)

/*
 * Hangul decomposition (algorithm from Section 3.12 of Unicode 6.3.0)
 *
 * AC00;<Hangul Syllable, First>;Lo;0;L;;;;;N;;;;;
 * D7A3;<Hangul Syllable, Last>;Lo;0;L;;;;;N;;;;;
 *
 * SBase = 0xAC00
 * LBase = 0x1100
 * VBase = 0x1161
 * TBase = 0x11A7
 * LCount = 19
 * VCount = 21
 * TCount = 28
 * NCount = 588 (VCount * TCount)
 * SCount = 11172 (LCount * NCount)
 *
 * Decomposition:
 *   SIndex = s - SBase
 *
 * LV (Canonical/Full)
 *   LIndex = SIndex / NCount
 *   VIndex = (Sindex % NCount) / TCount
 *   LPart = LBase + LIndex
 *   VPart = VBase + VIndex
 *
 * LVT (Canonical)
 *   LVIndex = (SIndex / TCount) * TCount
 *   TIndex = (Sindex % TCount)
 *   LVPart = SBase + LVIndex
 *   TPart = TBase + TIndex
 *
 * LVT (Full)
 *   LIndex = SIndex / NCount
 *   VIndex = (Sindex % NCount) / TCount
 *   TIndex = (Sindex % TCount)
 *   LPart = LBase + LIndex
 *   VPart = VBase + VIndex
 *   if (TIndex == 0) {
 *          d = <LPart, VPart>
 *   } else {
 *          TPart = TBase + TIndex
 *          d = <LPart, TPart, VPart>
 *   }
 */

/* Constants */
#define SB	(0xAC00)
#define LB	(0x1100)
#define VB	(0x1161)
#define TB	(0x11A7)
#define LC	(19)
#define VC	(21)
#define TC	(28)
#define NC	(VC * TC)
#define SC	(LC * NC)

/* Algorithmic decomposition of hangul syllable. */
static utf8leaf_t *
utf8hangul(const char *str, unsigned char *hangul)
{
	unsigned int	si;
	unsigned int	li;
	unsigned int	vi;
	unsigned int	ti;
	unsigned char	*h;

	/* Calculate the SI, LI, VI, and TI values. */
	si = utf8decode3(str) - SB;
	li = si / NC;
	vi = (si % NC) / TC;
	ti = si % TC;

	/* Fill in base of leaf. */
	h = hangul;
	LEAF_GEN(h) = 2;
	LEAF_CCC(h) = DECOMPOSE;
	h += 2;

	/* Add LPart, a 3-byte UTF-8 sequence. */
	h += utf8encode3((char *)h, li + LB);

	/* Add VPart, a 3-byte UTF-8 sequence. */
	h += utf8encode3((char *)h, vi + VB);

	/* Add TPart if required, also a 3-byte UTF-8 sequence. */
	if (ti)
		h += utf8encode3((char *)h, ti + TB);

	/* Terminate string. */
	h[0] = '\0';

	return hangul;
}

/*
 * Use trie to scan s, touching at most len bytes.
 * Returns the leaf if one exists, NULL otherwise.
 *
 * A non-NULL return guarantees that the UTF-8 sequence starting at s
 * is well-formed and corresponds to a known unicode code point.  The
 * shorthand for this will be "is valid UTF-8 unicode".
 */
static utf8leaf_t *utf8nlookup(const struct unicode_map *um,
		enum utf8_normalization n, unsigned char *hangul, const char *s,
		size_t len)
{
	utf8trie_t	*trie = um->tables->utf8data + um->ntab[n]->offset;
	int		offlen;
	int		offset;
	int		mask;
	int		node;

	if (len == 0)
		return NULL;

	node = 1;
	while (node) {
		offlen = (*trie & OFFLEN) >> OFFLEN_SHIFT;
		if (*trie & NEXTBYTE) {
			if (--len == 0)
				return NULL;
			s++;
		}
		mask = 1 << (*trie & BITNUM);
		if (*s & mask) {
			/* Right leg */
			if (offlen) {
				/* Right node at offset of trie */
				node = (*trie & RIGHTNODE);
				offset = trie[offlen];
				while (--offlen) {
					offset <<= 8;
					offset |= trie[offlen];
				}
				trie += offset;
			} else if (*trie & RIGHTPATH) {
				/* Right node after this node */
				node = (*trie & TRIENODE);
				trie++;
			} else {
				/* No right node. */
				return NULL;
			}
		} else {
			/* Left leg */
			if (offlen) {
				/* Left node after this node. */
				node = (*trie & LEFTNODE);
				trie += offlen + 1;
			} else if (*trie & RIGHTPATH) {
				/* No left node. */
				return NULL;
			} else {
				/* Left node after this node */
				node = (*trie & TRIENODE);
				trie++;
			}
		}
	}
	/*
	 * Hangul decomposition is done algorithmically. These are the
	 * codepoints >= 0xAC00 and <= 0xD7A3. Their UTF-8 encoding is
	 * always 3 bytes long, so s has been advanced twice, and the
	 * start of the sequence is at s-2.
	 */
	if (LEAF_CCC(trie) == DECOMPOSE && LEAF_STR(trie)[0] == HANGUL)
		trie = utf8hangul(s - 2, hangul);
	return trie;
}

/*
 * Use trie to scan s.
 * Returns the leaf if one exists, NULL otherwise.
 *
 * Forwards to utf8nlookup().
 */
static utf8leaf_t *utf8lookup(const struct unicode_map *um,
		enum utf8_normalization n, unsigned char *hangul, const char *s)
{
	return utf8nlookup(um, n, hangul, s, (size_t)-1);
}

/*
 * Length of the normalization of s, touch at most len bytes.
 * Return -1 if s is not valid UTF-8 unicode.
 */
ssize_t utf8nlen(const struct unicode_map *um, enum utf8_normalization n,
		const char *s, size_t len)
{
	utf8leaf_t	*leaf;
	size_t		ret = 0;
	unsigned char	hangul[UTF8HANGULLEAF];

	while (len && *s) {
		leaf = utf8nlookup(um, n, hangul, s, len);
		if (!leaf)
			return -1;
		if (um->tables->utf8agetab[LEAF_GEN(leaf)] >
		    um->ntab[n]->maxage)
			ret += utf8clen(s);
		else if (LEAF_CCC(leaf) == DECOMPOSE)
			ret += strlen(LEAF_STR(leaf));
		else
			ret += utf8clen(s);
		len -= utf8clen(s);
		s += utf8clen(s);
	}
	return ret;
}

/*
 * Set up an utf8cursor for use by utf8byte().
 *
 *   u8c    : pointer to cursor.
 *   data   : const struct utf8data to use for normalization.
 *   s      : string.
 *   len    : length of s.
 *
 * Returns -1 on error, 0 on success.
 */
int utf8ncursor(struct utf8cursor *u8c, const struct unicode_map *um,
		enum utf8_normalization n, const char *s, size_t len)
{
	if (!s)
		return -1;
	u8c->um = um;
	u8c->n = n;
	u8c->s = s;
	u8c->p = NULL;
	u8c->ss = NULL;
	u8c->sp = NULL;
	u8c->len = len;
	u8c->slen = 0;
	u8c->ccc = STOPPER;
	u8c->nccc = STOPPER;
	/* Check we didn't clobber the maximum length. */
	if (u8c->len != len)
		return -1;
	/* The first byte of s may not be an utf8 continuation. */
	if (len > 0 && (*s & 0xC0) == 0x80)
		return -1;
	return 0;
}

/*
 * Get one byte from the normalized form of the string described by u8c.
 *
 * Returns the byte cast to an unsigned char on succes, and -1 on failure.
 *
 * The cursor keeps track of the location in the string in u8c->s.
 * When a character is decomposed, the current location is stored in
 * u8c->p, and u8c->s is set to the start of the decomposition. Note
 * that bytes from a decomposition do not count against u8c->len.
 *
 * Characters are emitted if they match the current CCC in u8c->ccc.
 * Hitting end-of-string while u8c->ccc == STOPPER means we're done,
 * and the function returns 0 in that case.
 *
 * Sorting by CCC is done by repeatedly scanning the string.  The
 * values of u8c->s and u8c->p are stored in u8c->ss and u8c->sp at
 * the start of the scan.  The first pass finds the lowest CCC to be
 * emitted and stores it in u8c->nccc, the second pass emits the
 * characters with this CCC and finds the next lowest CCC. This limits
 * the number of passes to 1 + the number of different CCCs in the
 * sequence being scanned.
 *
 * Therefore:
 *  u8c->p  != NULL -> a decomposition is being scanned.
 *  u8c->ss != NULL -> this is a repeating scan.
 *  u8c->ccc == -1   -> this is the first scan of a repeating scan.
 */
int utf8byte(struct utf8cursor *u8c)
{
	utf8leaf_t *leaf;
	int ccc;

	for (;;) {
		/* Check for the end of a decomposed character. */
		if (u8c->p && *u8c->s == '\0') {
			u8c->s = u8c->p;
			u8c->p = NULL;
		}

		/* Check for end-of-string. */
		if (!u8c->p && (u8c->len == 0 || *u8c->s == '\0')) {
			/* There is no next byte. */
			if (u8c->ccc == STOPPER)
				return 0;
			/* End-of-string during a scan counts as a stopper. */
			ccc = STOPPER;
			goto ccc_mismatch;
		} else if ((*u8c->s & 0xC0) == 0x80) {
			/* This is a continuation of the current character. */
			if (!u8c->p)
				u8c->len--;
			return (unsigned char)*u8c->s++;
		}

		/* Look up the data for the current character. */
		if (u8c->p) {
			leaf = utf8lookup(u8c->um, u8c->n, u8c->hangul, u8c->s);
		} else {
			leaf = utf8nlookup(u8c->um, u8c->n, u8c->hangul,
					   u8c->s, u8c->len);
		}

		/* No leaf found implies that the input is a binary blob. */
		if (!leaf)
			return -1;

		ccc = LEAF_CCC(leaf);
		/* Characters that are too new have CCC 0. */
		if (u8c->um->tables->utf8agetab[LEAF_GEN(leaf)] >
		    u8c->um->ntab[u8c->n]->maxage) {
			ccc = STOPPER;
		} else if (ccc == DECOMPOSE) {
			u8c->len -= utf8clen(u8c->s);
			u8c->p = u8c->s + utf8clen(u8c->s);
			u8c->s = LEAF_STR(leaf);
			/* Empty decomposition implies CCC 0. */
			if (*u8c->s == '\0') {
				if (u8c->ccc == STOPPER)
					continue;
				ccc = STOPPER;
				goto ccc_mismatch;
			}

			leaf = utf8lookup(u8c->um, u8c->n, u8c->hangul, u8c->s);
			if (!leaf)
				return -1;
			ccc = LEAF_CCC(leaf);
		}

		/*
		 * If this is not a stopper, then see if it updates
		 * the next canonical class to be emitted.
		 */
		if (ccc != STOPPER && u8c->ccc < ccc && ccc < u8c->nccc)
			u8c->nccc = ccc;

		/*
		 * Return the current byte if this is the current
		 * combining class.
		 */
		if (ccc == u8c->ccc) {
			if (!u8c->p)
				u8c->len--;
			return (unsigned char)*u8c->s++;
		}

		/* Current combining class mismatch. */
ccc_mismatch:
		if (u8c->nccc == STOPPER) {
			/*
			 * Scan forward for the first canonical class
			 * to be emitted.  Save the position from
			 * which to restart.
			 */
			u8c->ccc = MINCCC - 1;
			u8c->nccc = ccc;
			u8c->sp = u8c->p;
			u8c->ss = u8c->s;
			u8c->slen = u8c->len;
			if (!u8c->p)
				u8c->len -= utf8clen(u8c->s);
			u8c->s += utf8clen(u8c->s);
		} else if (ccc != STOPPER) {
			/* Not a stopper, and not the ccc we're emitting. */
			if (!u8c->p)
				u8c->len -= utf8clen(u8c->s);
			u8c->s += utf8clen(u8c->s);
		} else if (u8c->nccc != MAXCCC + 1) {
			/* At a stopper, restart for next ccc. */
			u8c->ccc = u8c->nccc;
			u8c->nccc = MAXCCC + 1;
			u8c->s = u8c->ss;
			u8c->p = u8c->sp;
			u8c->len = u8c->slen;
		} else {
			/* All done, proceed from here. */
			u8c->ccc = STOPPER;
			u8c->nccc = STOPPER;
			u8c->sp = NULL;
			u8c->ss = NULL;
			u8c->slen = 0;
		}
	}
}

#ifdef CONFIG_UNICODE_NORMALIZATION_SELFTEST_MODULE
EXPORT_SYMBOL_GPL(utf8version_is_supported);
EXPORT_SYMBOL_GPL(utf8nlen);
EXPORT_SYMBOL_GPL(utf8ncursor);
EXPORT_SYMBOL_GPL(utf8byte);
#endif