summaryrefslogtreecommitdiffhomepage
path: root/vendor/golang.org/x/text/internal/language/parse.go
blob: aad1e0acf77c8f33fc8f7ca84843f8ba8441ebd9 (plain) (blame)
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
595
596
597
598
599
600
601
602
603
604
605
606
607
608
// Copyright 2013 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package language

import (
	"bytes"
	"errors"
	"fmt"
	"sort"

	"golang.org/x/text/internal/tag"
)

// isAlpha returns true if the byte is not a digit.
// b must be an ASCII letter or digit.
func isAlpha(b byte) bool {
	return b > '9'
}

// isAlphaNum returns true if the string contains only ASCII letters or digits.
func isAlphaNum(s []byte) bool {
	for _, c := range s {
		if !('a' <= c && c <= 'z' || 'A' <= c && c <= 'Z' || '0' <= c && c <= '9') {
			return false
		}
	}
	return true
}

// ErrSyntax is returned by any of the parsing functions when the
// input is not well-formed, according to BCP 47.
// TODO: return the position at which the syntax error occurred?
var ErrSyntax = errors.New("language: tag is not well-formed")

// ErrDuplicateKey is returned when a tag contains the same key twice with
// different values in the -u section.
var ErrDuplicateKey = errors.New("language: different values for same key in -u extension")

// ValueError is returned by any of the parsing functions when the
// input is well-formed but the respective subtag is not recognized
// as a valid value.
type ValueError struct {
	v [8]byte
}

// NewValueError creates a new ValueError.
func NewValueError(tag []byte) ValueError {
	var e ValueError
	copy(e.v[:], tag)
	return e
}

func (e ValueError) tag() []byte {
	n := bytes.IndexByte(e.v[:], 0)
	if n == -1 {
		n = 8
	}
	return e.v[:n]
}

// Error implements the error interface.
func (e ValueError) Error() string {
	return fmt.Sprintf("language: subtag %q is well-formed but unknown", e.tag())
}

// Subtag returns the subtag for which the error occurred.
func (e ValueError) Subtag() string {
	return string(e.tag())
}

// scanner is used to scan BCP 47 tokens, which are separated by _ or -.
type scanner struct {
	b     []byte
	bytes [max99thPercentileSize]byte
	token []byte
	start int // start position of the current token
	end   int // end position of the current token
	next  int // next point for scan
	err   error
	done  bool
}

func makeScannerString(s string) scanner {
	scan := scanner{}
	if len(s) <= len(scan.bytes) {
		scan.b = scan.bytes[:copy(scan.bytes[:], s)]
	} else {
		scan.b = []byte(s)
	}
	scan.init()
	return scan
}

// makeScanner returns a scanner using b as the input buffer.
// b is not copied and may be modified by the scanner routines.
func makeScanner(b []byte) scanner {
	scan := scanner{b: b}
	scan.init()
	return scan
}

func (s *scanner) init() {
	for i, c := range s.b {
		if c == '_' {
			s.b[i] = '-'
		}
	}
	s.scan()
}

// restToLower converts the string between start and end to lower case.
func (s *scanner) toLower(start, end int) {
	for i := start; i < end; i++ {
		c := s.b[i]
		if 'A' <= c && c <= 'Z' {
			s.b[i] += 'a' - 'A'
		}
	}
}

func (s *scanner) setError(e error) {
	if s.err == nil || (e == ErrSyntax && s.err != ErrSyntax) {
		s.err = e
	}
}

// resizeRange shrinks or grows the array at position oldStart such that
// a new string of size newSize can fit between oldStart and oldEnd.
// Sets the scan point to after the resized range.
func (s *scanner) resizeRange(oldStart, oldEnd, newSize int) {
	s.start = oldStart
	if end := oldStart + newSize; end != oldEnd {
		diff := end - oldEnd
		var b []byte
		if n := len(s.b) + diff; n > cap(s.b) {
			b = make([]byte, n)
			copy(b, s.b[:oldStart])
		} else {
			b = s.b[:n]
		}
		copy(b[end:], s.b[oldEnd:])
		s.b = b
		s.next = end + (s.next - s.end)
		s.end = end
	}
}

// replace replaces the current token with repl.
func (s *scanner) replace(repl string) {
	s.resizeRange(s.start, s.end, len(repl))
	copy(s.b[s.start:], repl)
}

// gobble removes the current token from the input.
// Caller must call scan after calling gobble.
func (s *scanner) gobble(e error) {
	s.setError(e)
	if s.start == 0 {
		s.b = s.b[:+copy(s.b, s.b[s.next:])]
		s.end = 0
	} else {
		s.b = s.b[:s.start-1+copy(s.b[s.start-1:], s.b[s.end:])]
		s.end = s.start - 1
	}
	s.next = s.start
}

// deleteRange removes the given range from s.b before the current token.
func (s *scanner) deleteRange(start, end int) {
	s.b = s.b[:start+copy(s.b[start:], s.b[end:])]
	diff := end - start
	s.next -= diff
	s.start -= diff
	s.end -= diff
}

// scan parses the next token of a BCP 47 string.  Tokens that are larger
// than 8 characters or include non-alphanumeric characters result in an error
// and are gobbled and removed from the output.
// It returns the end position of the last token consumed.
func (s *scanner) scan() (end int) {
	end = s.end
	s.token = nil
	for s.start = s.next; s.next < len(s.b); {
		i := bytes.IndexByte(s.b[s.next:], '-')
		if i == -1 {
			s.end = len(s.b)
			s.next = len(s.b)
			i = s.end - s.start
		} else {
			s.end = s.next + i
			s.next = s.end + 1
		}
		token := s.b[s.start:s.end]
		if i < 1 || i > 8 || !isAlphaNum(token) {
			s.gobble(ErrSyntax)
			continue
		}
		s.token = token
		return end
	}
	if n := len(s.b); n > 0 && s.b[n-1] == '-' {
		s.setError(ErrSyntax)
		s.b = s.b[:len(s.b)-1]
	}
	s.done = true
	return end
}

// acceptMinSize parses multiple tokens of the given size or greater.
// It returns the end position of the last token consumed.
func (s *scanner) acceptMinSize(min int) (end int) {
	end = s.end
	s.scan()
	for ; len(s.token) >= min; s.scan() {
		end = s.end
	}
	return end
}

// Parse parses the given BCP 47 string and returns a valid Tag. If parsing
// failed it returns an error and any part of the tag that could be parsed.
// If parsing succeeded but an unknown value was found, it returns
// ValueError. The Tag returned in this case is just stripped of the unknown
// value. All other values are preserved. It accepts tags in the BCP 47 format
// and extensions to this standard defined in
// https://www.unicode.org/reports/tr35/#Unicode_Language_and_Locale_Identifiers.
func Parse(s string) (t Tag, err error) {
	// TODO: consider supporting old-style locale key-value pairs.
	if s == "" {
		return Und, ErrSyntax
	}
	defer func() {
		if recover() != nil {
			t = Und
			err = ErrSyntax
			return
		}
	}()
	if len(s) <= maxAltTaglen {
		b := [maxAltTaglen]byte{}
		for i, c := range s {
			// Generating invalid UTF-8 is okay as it won't match.
			if 'A' <= c && c <= 'Z' {
				c += 'a' - 'A'
			} else if c == '_' {
				c = '-'
			}
			b[i] = byte(c)
		}
		if t, ok := grandfathered(b); ok {
			return t, nil
		}
	}
	scan := makeScannerString(s)
	return parse(&scan, s)
}

func parse(scan *scanner, s string) (t Tag, err error) {
	t = Und
	var end int
	if n := len(scan.token); n <= 1 {
		scan.toLower(0, len(scan.b))
		if n == 0 || scan.token[0] != 'x' {
			return t, ErrSyntax
		}
		end = parseExtensions(scan)
	} else if n >= 4 {
		return Und, ErrSyntax
	} else { // the usual case
		t, end = parseTag(scan, true)
		if n := len(scan.token); n == 1 {
			t.pExt = uint16(end)
			end = parseExtensions(scan)
		} else if end < len(scan.b) {
			scan.setError(ErrSyntax)
			scan.b = scan.b[:end]
		}
	}
	if int(t.pVariant) < len(scan.b) {
		if end < len(s) {
			s = s[:end]
		}
		if len(s) > 0 && tag.Compare(s, scan.b) == 0 {
			t.str = s
		} else {
			t.str = string(scan.b)
		}
	} else {
		t.pVariant, t.pExt = 0, 0
	}
	return t, scan.err
}

// parseTag parses language, script, region and variants.
// It returns a Tag and the end position in the input that was parsed.
// If doNorm is true, then <lang>-<extlang> will be normalized to <extlang>.
func parseTag(scan *scanner, doNorm bool) (t Tag, end int) {
	var e error
	// TODO: set an error if an unknown lang, script or region is encountered.
	t.LangID, e = getLangID(scan.token)
	scan.setError(e)
	scan.replace(t.LangID.String())
	langStart := scan.start
	end = scan.scan()
	for len(scan.token) == 3 && isAlpha(scan.token[0]) {
		// From http://tools.ietf.org/html/bcp47, <lang>-<extlang> tags are equivalent
		// to a tag of the form <extlang>.
		if doNorm {
			lang, e := getLangID(scan.token)
			if lang != 0 {
				t.LangID = lang
				langStr := lang.String()
				copy(scan.b[langStart:], langStr)
				scan.b[langStart+len(langStr)] = '-'
				scan.start = langStart + len(langStr) + 1
			}
			scan.gobble(e)
		}
		end = scan.scan()
	}
	if len(scan.token) == 4 && isAlpha(scan.token[0]) {
		t.ScriptID, e = getScriptID(script, scan.token)
		if t.ScriptID == 0 {
			scan.gobble(e)
		}
		end = scan.scan()
	}
	if n := len(scan.token); n >= 2 && n <= 3 {
		t.RegionID, e = getRegionID(scan.token)
		if t.RegionID == 0 {
			scan.gobble(e)
		} else {
			scan.replace(t.RegionID.String())
		}
		end = scan.scan()
	}
	scan.toLower(scan.start, len(scan.b))
	t.pVariant = byte(end)
	end = parseVariants(scan, end, t)
	t.pExt = uint16(end)
	return t, end
}

var separator = []byte{'-'}

// parseVariants scans tokens as long as each token is a valid variant string.
// Duplicate variants are removed.
func parseVariants(scan *scanner, end int, t Tag) int {
	start := scan.start
	varIDBuf := [4]uint8{}
	variantBuf := [4][]byte{}
	varID := varIDBuf[:0]
	variant := variantBuf[:0]
	last := -1
	needSort := false
	for ; len(scan.token) >= 4; scan.scan() {
		// TODO: measure the impact of needing this conversion and redesign
		// the data structure if there is an issue.
		v, ok := variantIndex[string(scan.token)]
		if !ok {
			// unknown variant
			// TODO: allow user-defined variants?
			scan.gobble(NewValueError(scan.token))
			continue
		}
		varID = append(varID, v)
		variant = append(variant, scan.token)
		if !needSort {
			if last < int(v) {
				last = int(v)
			} else {
				needSort = true
				// There is no legal combinations of more than 7 variants
				// (and this is by no means a useful sequence).
				const maxVariants = 8
				if len(varID) > maxVariants {
					break
				}
			}
		}
		end = scan.end
	}
	if needSort {
		sort.Sort(variantsSort{varID, variant})
		k, l := 0, -1
		for i, v := range varID {
			w := int(v)
			if l == w {
				// Remove duplicates.
				continue
			}
			varID[k] = varID[i]
			variant[k] = variant[i]
			k++
			l = w
		}
		if str := bytes.Join(variant[:k], separator); len(str) == 0 {
			end = start - 1
		} else {
			scan.resizeRange(start, end, len(str))
			copy(scan.b[scan.start:], str)
			end = scan.end
		}
	}
	return end
}

type variantsSort struct {
	i []uint8
	v [][]byte
}

func (s variantsSort) Len() int {
	return len(s.i)
}

func (s variantsSort) Swap(i, j int) {
	s.i[i], s.i[j] = s.i[j], s.i[i]
	s.v[i], s.v[j] = s.v[j], s.v[i]
}

func (s variantsSort) Less(i, j int) bool {
	return s.i[i] < s.i[j]
}

type bytesSort struct {
	b [][]byte
	n int // first n bytes to compare
}

func (b bytesSort) Len() int {
	return len(b.b)
}

func (b bytesSort) Swap(i, j int) {
	b.b[i], b.b[j] = b.b[j], b.b[i]
}

func (b bytesSort) Less(i, j int) bool {
	for k := 0; k < b.n; k++ {
		if b.b[i][k] == b.b[j][k] {
			continue
		}
		return b.b[i][k] < b.b[j][k]
	}
	return false
}

// parseExtensions parses and normalizes the extensions in the buffer.
// It returns the last position of scan.b that is part of any extension.
// It also trims scan.b to remove excess parts accordingly.
func parseExtensions(scan *scanner) int {
	start := scan.start
	exts := [][]byte{}
	private := []byte{}
	end := scan.end
	for len(scan.token) == 1 {
		extStart := scan.start
		ext := scan.token[0]
		end = parseExtension(scan)
		extension := scan.b[extStart:end]
		if len(extension) < 3 || (ext != 'x' && len(extension) < 4) {
			scan.setError(ErrSyntax)
			end = extStart
			continue
		} else if start == extStart && (ext == 'x' || scan.start == len(scan.b)) {
			scan.b = scan.b[:end]
			return end
		} else if ext == 'x' {
			private = extension
			break
		}
		exts = append(exts, extension)
	}
	sort.Sort(bytesSort{exts, 1})
	if len(private) > 0 {
		exts = append(exts, private)
	}
	scan.b = scan.b[:start]
	if len(exts) > 0 {
		scan.b = append(scan.b, bytes.Join(exts, separator)...)
	} else if start > 0 {
		// Strip trailing '-'.
		scan.b = scan.b[:start-1]
	}
	return end
}

// parseExtension parses a single extension and returns the position of
// the extension end.
func parseExtension(scan *scanner) int {
	start, end := scan.start, scan.end
	switch scan.token[0] {
	case 'u': // https://www.ietf.org/rfc/rfc6067.txt
		attrStart := end
		scan.scan()
		for last := []byte{}; len(scan.token) > 2; scan.scan() {
			if bytes.Compare(scan.token, last) != -1 {
				// Attributes are unsorted. Start over from scratch.
				p := attrStart + 1
				scan.next = p
				attrs := [][]byte{}
				for scan.scan(); len(scan.token) > 2; scan.scan() {
					attrs = append(attrs, scan.token)
					end = scan.end
				}
				sort.Sort(bytesSort{attrs, 3})
				copy(scan.b[p:], bytes.Join(attrs, separator))
				break
			}
			last = scan.token
			end = scan.end
		}
		// Scan key-type sequences. A key is of length 2 and may be followed
		// by 0 or more "type" subtags from 3 to the maximum of 8 letters.
		var last, key []byte
		for attrEnd := end; len(scan.token) == 2; last = key {
			key = scan.token
			end = scan.end
			for scan.scan(); end < scan.end && len(scan.token) > 2; scan.scan() {
				end = scan.end
			}
			// TODO: check key value validity
			if bytes.Compare(key, last) != 1 || scan.err != nil {
				// We have an invalid key or the keys are not sorted.
				// Start scanning keys from scratch and reorder.
				p := attrEnd + 1
				scan.next = p
				keys := [][]byte{}
				for scan.scan(); len(scan.token) == 2; {
					keyStart := scan.start
					end = scan.end
					for scan.scan(); end < scan.end && len(scan.token) > 2; scan.scan() {
						end = scan.end
					}
					keys = append(keys, scan.b[keyStart:end])
				}
				sort.Stable(bytesSort{keys, 2})
				if n := len(keys); n > 0 {
					k := 0
					for i := 1; i < n; i++ {
						if !bytes.Equal(keys[k][:2], keys[i][:2]) {
							k++
							keys[k] = keys[i]
						} else if !bytes.Equal(keys[k], keys[i]) {
							scan.setError(ErrDuplicateKey)
						}
					}
					keys = keys[:k+1]
				}
				reordered := bytes.Join(keys, separator)
				if e := p + len(reordered); e < end {
					scan.deleteRange(e, end)
					end = e
				}
				copy(scan.b[p:], reordered)
				break
			}
		}
	case 't': // https://www.ietf.org/rfc/rfc6497.txt
		scan.scan()
		if n := len(scan.token); n >= 2 && n <= 3 && isAlpha(scan.token[1]) {
			_, end = parseTag(scan, false)
			scan.toLower(start, end)
		}
		for len(scan.token) == 2 && !isAlpha(scan.token[1]) {
			end = scan.acceptMinSize(3)
		}
	case 'x':
		end = scan.acceptMinSize(1)
	default:
		end = scan.acceptMinSize(2)
	}
	return end
}

// getExtension returns the name, body and end position of the extension.
func getExtension(s string, p int) (end int, ext string) {
	if s[p] == '-' {
		p++
	}
	if s[p] == 'x' {
		return len(s), s[p:]
	}
	end = nextExtension(s, p)
	return end, s[p:end]
}

// nextExtension finds the next extension within the string, searching
// for the -<char>- pattern from position p.
// In the fast majority of cases, language tags will have at most
// one extension and extensions tend to be small.
func nextExtension(s string, p int) int {
	for n := len(s) - 3; p < n; {
		if s[p] == '-' {
			if s[p+2] == '-' {
				return p
			}
			p += 3
		} else {
			p++
		}
	}
	return len(s)
}