-
Notifications
You must be signed in to change notification settings - Fork 10
/
language.go
975 lines (893 loc) · 29.5 KB
/
language.go
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
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
// 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.
//go:generate go run maketables.go gen_common.go -output tables.go
//go:generate go run gen_index.go
// Package language implements BCP 47 language tags and related functionality.
//
// The Tag type, which is used to represent languages, is agnostic to the
// meaning of its subtags. Tags are not fully canonicalized to preserve
// information that may be valuable in certain contexts. As a consequence, two
// different tags may represent identical languages.
//
// Initializing language- or locale-specific components usually consists of
// two steps. The first step is to select a display language based on the
// preferred languages of the user and the languages supported by an application.
// The second step is to create the language-specific services based on
// this selection. Each is discussed in more details below.
//
// Matching preferred against supported languages
//
// An application may support various languages. This list is typically limited
// by the languages for which there exists translations of the user interface.
// Similarly, a user may provide a list of preferred languages which is limited
// by the languages understood by this user.
// An application should use a Matcher to find the best supported language based
// on the user's preferred list.
// Matchers are aware of the intricacies of equivalence between languages.
// The default Matcher implementation takes into account things such as
// deprecated subtags, legacy tags, and mutual intelligibility between scripts
// and languages.
//
// A Matcher for English, Australian English, Danish, and standard Mandarin can
// be defined as follows:
//
// var matcher = language.NewMatcher([]language.Tag{
// language.English, // The first language is used as fallback.
// language.MustParse("en-AU"),
// language.Danish,
// language.Chinese,
// })
//
// The following code selects the best match for someone speaking Spanish and
// Norwegian:
//
// preferred := []language.Tag{ language.Spanish, language.Norwegian }
// tag, _, _ := matcher.Match(preferred...)
//
// In this case, the best match is Danish, as Danish is sufficiently a match to
// Norwegian to not have to fall back to the default.
// See ParseAcceptLanguage on how to handle the Accept-Language HTTP header.
//
// Selecting language-specific services
//
// One should always use the Tag returned by the Matcher to create an instance
// of any of the language-specific services provided by the text repository.
// This prevents the mixing of languages, such as having a different language for
// messages and display names, as well as improper casing or sorting order for
// the selected language.
// Using the returned Tag also allows user-defined settings, such as collation
// order or numbering system to be transparently passed as options.
//
// If you have language-specific data in your application, however, it will in
// most cases suffice to use the index returned by the matcher to identify
// the user language.
// The following loop provides an alternative in case this is not sufficient:
//
// supported := map[language.Tag]data{
// language.English: enData,
// language.MustParse("en-AU"): enAUData,
// language.Danish: daData,
// language.Chinese: zhData,
// }
// tag, _, _ := matcher.Match(preferred...)
// for ; tag != language.Und; tag = tag.Parent() {
// if v, ok := supported[tag]; ok {
// return v
// }
// }
// return enData // should not reach here
//
// Repeatedly taking the Parent of the tag returned by Match will eventually
// match one of the tags used to initialize the Matcher.
//
// Canonicalization
//
// By default, only legacy and deprecated tags are converted into their
// canonical equivalent. All other information is preserved. This approach makes
// the confidence scores more accurate and allows matchers to distinguish
// between variants that are otherwise lost.
//
// As a consequence, two tags that should be treated as identical according to
// BCP 47 or CLDR, like "en-Latn" and "en", will be represented differently. The
// Matchers will handle such distinctions, though, and are aware of the
// equivalence relations. The CanonType type can be used to alter the
// canonicalization form.
//
// References
//
// BCP 47 - Tags for Identifying Languages
// http://tools.ietf.org/html/bcp47
package language
// TODO: Remove above NOTE after:
// - verifying that tables are dropped correctly (most notably matcher tables).
import (
"errors"
"fmt"
"strings"
)
const (
// maxCoreSize is the maximum size of a BCP 47 tag without variants and
// extensions. Equals max lang (3) + script (4) + max reg (3) + 2 dashes.
maxCoreSize = 12
// max99thPercentileSize is a somewhat arbitrary buffer size that presumably
// is large enough to hold at least 99% of the BCP 47 tags.
max99thPercentileSize = 32
// maxSimpleUExtensionSize is the maximum size of a -u extension with one
// key-type pair. Equals len("-u-") + key (2) + dash + max value (8).
maxSimpleUExtensionSize = 14
)
// Tag represents a BCP 47 language tag. It is used to specify an instance of a
// specific language or locale. All language tag values are guaranteed to be
// well-formed.
type Tag struct {
lang langID
region regionID
script scriptID
pVariant byte // offset in str, includes preceding '-'
pExt uint16 // offset of first extension, includes preceding '-'
// str is the string representation of the Tag. It will only be used if the
// tag has variants or extensions.
str string
}
// Make is a convenience wrapper for Parse that omits the error.
// In case of an error, a sensible default is returned.
func Make(s string) Tag {
return Default.Make(s)
}
// Make is a convenience wrapper for c.Parse that omits the error.
// In case of an error, a sensible default is returned.
func (c CanonType) Make(s string) Tag {
t, _ := c.Parse(s)
return t
}
// Raw returns the raw base language, script and region, without making an
// attempt to infer their values.
func (t Tag) Raw() (b Base, s Script, r Region) {
return Base{t.lang}, Script{t.script}, Region{t.region}
}
// equalTags compares language, script and region subtags only.
func (t Tag) equalTags(a Tag) bool {
return t.lang == a.lang && t.script == a.script && t.region == a.region
}
// IsRoot returns true if t is equal to language "und".
func (t Tag) IsRoot() bool {
if int(t.pVariant) < len(t.str) {
return false
}
return t.equalTags(und)
}
// private reports whether the Tag consists solely of a private use tag.
func (t Tag) private() bool {
return t.str != "" && t.pVariant == 0
}
// CanonType can be used to enable or disable various types of canonicalization.
type CanonType int
const (
// Replace deprecated base languages with their preferred replacements.
DeprecatedBase CanonType = 1 << iota
// Replace deprecated scripts with their preferred replacements.
DeprecatedScript
// Replace deprecated regions with their preferred replacements.
DeprecatedRegion
// Remove redundant scripts.
SuppressScript
// Normalize legacy encodings. This includes legacy languages defined in
// CLDR as well as bibliographic codes defined in ISO-639.
Legacy
// Map the dominant language of a macro language group to the macro language
// subtag. For example cmn -> zh.
Macro
// The CLDR flag should be used if full compatibility with CLDR is required.
// There are a few cases where language.Tag may differ from CLDR. To follow all
// of CLDR's suggestions, use All|CLDR.
CLDR
// Raw can be used to Compose or Parse without Canonicalization.
Raw CanonType = 0
// Replace all deprecated tags with their preferred replacements.
Deprecated = DeprecatedBase | DeprecatedScript | DeprecatedRegion
// All canonicalizations recommended by BCP 47.
BCP47 = Deprecated | SuppressScript
// All canonicalizations.
All = BCP47 | Legacy | Macro
// Default is the canonicalization used by Parse, Make and Compose. To
// preserve as much information as possible, canonicalizations that remove
// potentially valuable information are not included. The Matcher is
// designed to recognize similar tags that would be the same if
// they were canonicalized using All.
Default = Deprecated | Legacy
canonLang = DeprecatedBase | Legacy | Macro
// TODO: LikelyScript, LikelyRegion: suppress similar to ICU.
)
// canonicalize returns the canonicalized equivalent of the tag and
// whether there was any change.
func (t Tag) canonicalize(c CanonType) (Tag, bool) {
if c == Raw {
return t, false
}
changed := false
if c&SuppressScript != 0 {
if t.lang < langNoIndexOffset && uint8(t.script) == suppressScript[t.lang] {
t.script = 0
changed = true
}
}
if c&canonLang != 0 {
for {
if l, aliasType := normLang(t.lang); l != t.lang {
switch aliasType {
case langLegacy:
if c&Legacy != 0 {
if t.lang == _sh && t.script == 0 {
t.script = _Latn
}
t.lang = l
changed = true
}
case langMacro:
if c&Macro != 0 {
// We deviate here from CLDR. The mapping "nb" -> "no"
// qualifies as a typical Macro language mapping. However,
// for legacy reasons, CLDR maps "no", the macro language
// code for Norwegian, to the dominant variant "nb". This
// change is currently under consideration for CLDR as well.
// See http://unicode.org/cldr/trac/ticket/2698 and also
// http://unicode.org/cldr/trac/ticket/1790 for some of the
// practical implications. TODO: this check could be removed
// if CLDR adopts this change.
if c&CLDR == 0 || t.lang != _nb {
changed = true
t.lang = l
}
}
case langDeprecated:
if c&DeprecatedBase != 0 {
if t.lang == _mo && t.region == 0 {
t.region = _MD
}
t.lang = l
changed = true
// Other canonicalization types may still apply.
continue
}
}
} else if c&Legacy != 0 && t.lang == _no && c&CLDR != 0 {
t.lang = _nb
changed = true
}
break
}
}
if c&DeprecatedScript != 0 {
if t.script == _Qaai {
changed = true
t.script = _Zinh
}
}
if c&DeprecatedRegion != 0 {
if r := normRegion(t.region); r != 0 {
changed = true
t.region = r
}
}
return t, changed
}
// Canonicalize returns the canonicalized equivalent of the tag.
func (c CanonType) Canonicalize(t Tag) (Tag, error) {
t, changed := t.canonicalize(c)
if changed {
t.remakeString()
}
return t, nil
}
// Confidence indicates the level of certainty for a given return value.
// For example, Serbian may be written in Cyrillic or Latin script.
// The confidence level indicates whether a value was explicitly specified,
// whether it is typically the only possible value, or whether there is
// an ambiguity.
type Confidence int
const (
No Confidence = iota // full confidence that there was no match
Low // most likely value picked out of a set of alternatives
High // value is generally assumed to be the correct match
Exact // exact match or explicitly specified value
)
var confName = []string{"No", "Low", "High", "Exact"}
func (c Confidence) String() string {
return confName[c]
}
// remakeString is used to update t.str in case lang, script or region changed.
// It is assumed that pExt and pVariant still point to the start of the
// respective parts.
func (t *Tag) remakeString() {
if t.str == "" {
return
}
extra := t.str[t.pVariant:]
if t.pVariant > 0 {
extra = extra[1:]
}
if t.equalTags(und) && strings.HasPrefix(extra, "x-") {
t.str = extra
t.pVariant = 0
t.pExt = 0
return
}
var buf [max99thPercentileSize]byte // avoid extra memory allocation in most cases.
b := buf[:t.genCoreBytes(buf[:])]
if extra != "" {
diff := uint8(len(b)) - t.pVariant
b = append(b, '-')
b = append(b, extra...)
t.pVariant += diff
t.pExt += uint16(diff)
} else {
t.pVariant = uint8(len(b))
t.pExt = uint16(len(b))
}
t.str = string(b)
}
// genCoreBytes writes a string for the base languages, script and region tags
// to the given buffer and returns the number of bytes written. It will never
// write more than maxCoreSize bytes.
func (t *Tag) genCoreBytes(buf []byte) int {
n := t.lang.stringToBuf(buf[:])
if t.script != 0 {
n += copy(buf[n:], "-")
n += copy(buf[n:], t.script.String())
}
if t.region != 0 {
n += copy(buf[n:], "-")
n += copy(buf[n:], t.region.String())
}
return n
}
// String returns the canonical string representation of the language tag.
func (t Tag) String() string {
if t.str != "" {
return t.str
}
if t.script == 0 && t.region == 0 {
return t.lang.String()
}
buf := [maxCoreSize]byte{}
return string(buf[:t.genCoreBytes(buf[:])])
}
// Base returns the base language of the language tag. If the base language is
// unspecified, an attempt will be made to infer it from the context.
// It uses a variant of CLDR's Add Likely Subtags algorithm. This is subject to change.
func (t Tag) Base() (Base, Confidence) {
if t.lang != 0 {
return Base{t.lang}, Exact
}
c := High
if t.script == 0 && !(Region{t.region}).IsCountry() {
c = Low
}
if tag, err := addTags(t); err == nil && tag.lang != 0 {
return Base{tag.lang}, c
}
return Base{0}, No
}
// Script infers the script for the language tag. If it was not explicitly given, it will infer
// a most likely candidate.
// If more than one script is commonly used for a language, the most likely one
// is returned with a low confidence indication. For example, it returns (Cyrl, Low)
// for Serbian.
// If a script cannot be inferred (Zzzz, No) is returned. We do not use Zyyy (undetermined)
// as one would suspect from the IANA registry for BCP 47. In a Unicode context Zyyy marks
// common characters (like 1, 2, 3, '.', etc.) and is therefore more like multiple scripts.
// See http://www.unicode.org/reports/tr24/#Values for more details. Zzzz is also used for
// unknown value in CLDR. (Zzzz, Exact) is returned if Zzzz was explicitly specified.
// Note that an inferred script is never guaranteed to be the correct one. Latin is
// almost exclusively used for Afrikaans, but Arabic has been used for some texts
// in the past. Also, the script that is commonly used may change over time.
// It uses a variant of CLDR's Add Likely Subtags algorithm. This is subject to change.
func (t Tag) Script() (Script, Confidence) {
if t.script != 0 {
return Script{t.script}, Exact
}
sc, c := scriptID(_Zzzz), No
if t.lang < langNoIndexOffset {
if scr := scriptID(suppressScript[t.lang]); scr != 0 {
// Note: it is not always the case that a language with a suppress
// script value is only written in one script (e.g. kk, ms, pa).
if t.region == 0 {
return Script{scriptID(scr)}, High
}
sc, c = scr, High
}
}
if tag, err := addTags(t); err == nil {
if tag.script != sc {
sc, c = tag.script, Low
}
} else {
t, _ = (Deprecated | Macro).Canonicalize(t)
if tag, err := addTags(t); err == nil && tag.script != sc {
sc, c = tag.script, Low
}
}
return Script{sc}, c
}
// Region returns the region for the language tag. If it was not explicitly given, it will
// infer a most likely candidate from the context.
// It uses a variant of CLDR's Add Likely Subtags algorithm. This is subject to change.
func (t Tag) Region() (Region, Confidence) {
if t.region != 0 {
return Region{t.region}, Exact
}
if t, err := addTags(t); err == nil {
return Region{t.region}, Low // TODO: differentiate between high and low.
}
t, _ = (Deprecated | Macro).Canonicalize(t)
if tag, err := addTags(t); err == nil {
return Region{tag.region}, Low
}
return Region{_ZZ}, No // TODO: return world instead of undetermined?
}
// Variant returns the variants specified explicitly for this language tag.
// or nil if no variant was specified.
func (t Tag) Variants() []Variant {
v := []Variant{}
if int(t.pVariant) < int(t.pExt) {
for x, str := "", t.str[t.pVariant:t.pExt]; str != ""; {
x, str = nextToken(str)
v = append(v, Variant{x})
}
}
return v
}
// Parent returns the CLDR parent of t. In CLDR, missing fields in data for a
// specific language are substituted with fields from the parent language.
// The parent for a language may change for newer versions of CLDR.
func (t Tag) Parent() Tag {
if t.str != "" {
// Strip the variants and extensions.
t, _ = Raw.Compose(t.Raw())
if t.region == 0 && t.script != 0 && t.lang != 0 {
base, _ := addTags(Tag{lang: t.lang})
if base.script == t.script {
return Tag{lang: t.lang}
}
}
return t
}
if t.lang != 0 {
if t.region != 0 {
maxScript := t.script
if maxScript == 0 {
max, _ := addTags(t)
maxScript = max.script
}
for i := range parents {
if langID(parents[i].lang) == t.lang && scriptID(parents[i].maxScript) == maxScript {
for _, r := range parents[i].fromRegion {
if regionID(r) == t.region {
return Tag{
lang: t.lang,
script: scriptID(parents[i].script),
region: regionID(parents[i].toRegion),
}
}
}
}
}
// Strip the script if it is the default one.
base, _ := addTags(Tag{lang: t.lang})
if base.script != maxScript {
return Tag{lang: t.lang, script: maxScript}
}
return Tag{lang: t.lang}
} else if t.script != 0 {
// The parent for an base-script pair with a non-default script is
// "und" instead of the base language.
base, _ := addTags(Tag{lang: t.lang})
if base.script != t.script {
return und
}
return Tag{lang: t.lang}
}
}
return und
}
// returns token t and the rest of the string.
func nextToken(s string) (t, tail string) {
p := strings.Index(s[1:], "-")
if p == -1 {
return s[1:], ""
}
p++
return s[1:p], s[p:]
}
// Extension is a single BCP 47 extension.
type Extension struct {
s string
}
// String returns the string representation of the extension, including the
// type tag.
func (e Extension) String() string {
return e.s
}
// ParseExtension parses s as an extension and returns it on success.
func ParseExtension(s string) (e Extension, err error) {
scan := makeScannerString(s)
var end int
if n := len(scan.token); n != 1 {
return Extension{}, errSyntax
}
scan.toLower(0, len(scan.b))
end = parseExtension(&scan)
if end != len(s) {
return Extension{}, errSyntax
}
return Extension{string(scan.b)}, nil
}
// Type returns the one-byte extension type of e. It returns 0 for the zero
// exception.
func (e Extension) Type() byte {
if e.s == "" {
return 0
}
return e.s[0]
}
// Tokens returns the list of tokens of e.
func (e Extension) Tokens() []string {
return strings.Split(e.s, "-")
}
// Extension returns the extension of type x for tag t. It will return
// false for ok if t does not have the requested extension. The returned
// extension will be invalid in this case.
func (t Tag) Extension(x byte) (ext Extension, ok bool) {
for i := int(t.pExt); i < len(t.str)-1; {
var ext string
i, ext = getExtension(t.str, i)
if ext[0] == x {
return Extension{ext}, true
}
}
return Extension{string(x)}, false
}
// Extensions returns all extensions of t.
func (t Tag) Extensions() []Extension {
e := []Extension{}
for i := int(t.pExt); i < len(t.str)-1; {
var ext string
i, ext = getExtension(t.str, i)
e = append(e, Extension{ext})
}
return e
}
// TypeForKey returns the type associated with the given key, where key and type
// are of the allowed values defined for the Unicode locale extension ('u') in
// http://www.unicode.org/reports/tr35/#Unicode_Language_and_Locale_Identifiers.
// TypeForKey will traverse the inheritance chain to get the correct value.
func (t Tag) TypeForKey(key string) string {
if start, end, _ := t.findTypeForKey(key); end != start {
return t.str[start:end]
}
return ""
}
var (
errPrivateUse = errors.New("cannot set a key on a private use tag")
errInvalidArguments = errors.New("invalid key or type")
)
// SetTypeForKey returns a new Tag with the key set to type, where key and type
// are of the allowed values defined for the Unicode locale extension ('u') in
// http://www.unicode.org/reports/tr35/#Unicode_Language_and_Locale_Identifiers.
// An empty value removes an existing pair with the same key.
func (t Tag) SetTypeForKey(key, value string) (Tag, error) {
if t.private() {
return t, errPrivateUse
}
if len(key) != 2 {
return t, errInvalidArguments
}
// Remove the setting if value is "".
if value == "" {
start, end, _ := t.findTypeForKey(key)
if start != end {
// Remove key tag and leading '-'.
start -= 4
// Remove a possible empty extension.
if (end == len(t.str) || t.str[end+2] == '-') && t.str[start-2] == '-' {
start -= 2
}
if start == int(t.pVariant) && end == len(t.str) {
t.str = ""
t.pVariant, t.pExt = 0, 0
} else {
t.str = fmt.Sprintf("%s%s", t.str[:start], t.str[end:])
}
}
return t, nil
}
if len(value) < 3 || len(value) > 8 {
return t, errInvalidArguments
}
var (
buf [maxCoreSize + maxSimpleUExtensionSize]byte
uStart int // start of the -u extension.
)
// Generate the tag string if needed.
if t.str == "" {
uStart = t.genCoreBytes(buf[:])
buf[uStart] = '-'
uStart++
}
// Create new key-type pair and parse it to verify.
b := buf[uStart:]
copy(b, "u-")
copy(b[2:], key)
b[4] = '-'
b = b[:5+copy(b[5:], value)]
scan := makeScanner(b)
if parseExtensions(&scan); scan.err != nil {
return t, scan.err
}
// Assemble the replacement string.
if t.str == "" {
t.pVariant, t.pExt = byte(uStart-1), uint16(uStart-1)
t.str = string(buf[:uStart+len(b)])
} else {
s := t.str
start, end, hasExt := t.findTypeForKey(key)
if start == end {
if hasExt {
b = b[2:]
}
t.str = fmt.Sprintf("%s-%s%s", s[:start], b, s[end:])
} else {
t.str = fmt.Sprintf("%s%s%s", s[:start], value, s[end:])
}
}
return t, nil
}
// findKeyAndType returns the start and end position for the type corresponding
// to key or the point at which to insert the key-value pair if the type
// wasn't found. The hasExt return value reports whether an -u extension was present.
// Note: the extensions are typically very small and are likely to contain
// only one key-type pair.
func (t Tag) findTypeForKey(key string) (start, end int, hasExt bool) {
p := int(t.pExt)
if len(key) != 2 || p == len(t.str) || p == 0 {
return p, p, false
}
s := t.str
// Find the correct extension.
for p++; s[p] != 'u'; p++ {
if s[p] > 'u' {
p--
return p, p, false
}
if p = nextExtension(s, p); p == len(s) {
return len(s), len(s), false
}
}
// Proceed to the hyphen following the extension name.
p++
// curKey is the key currently being processed.
curKey := ""
// Iterate over keys until we get the end of a section.
for {
// p points to the hyphen preceding the current token.
if p3 := p + 3; s[p3] == '-' {
// Found a key.
// Check whether we just processed the key that was requested.
if curKey == key {
return start, p, true
}
// Set to the next key and continue scanning type tokens.
curKey = s[p+1 : p3]
if curKey > key {
return p, p, true
}
// Start of the type token sequence.
start = p + 4
// A type is at least 3 characters long.
p += 7 // 4 + 3
} else {
// Attribute or type, which is at least 3 characters long.
p += 4
}
// p points past the third character of a type or attribute.
max := p + 5 // maximum length of token plus hyphen.
if len(s) < max {
max = len(s)
}
for ; p < max && s[p] != '-'; p++ {
}
// Bail if we have exhausted all tokens or if the next token starts
// a new extension.
if p == len(s) || s[p+2] == '-' {
if curKey == key {
return start, p, true
}
return p, p, true
}
}
}
// CompactIndex returns an index, where 0 <= index < NumCompactTags, for tags
// for which data exists in the text repository. The index will change over time
// and should not be stored in persistent storage. Extensions, except for the
// 'va' type of the 'u' extension, are ignored. It will return 0, false if no
// compact tag exists, where 0 is the index for the root language (Und).
func CompactIndex(t Tag) (index int, ok bool) {
// TODO: perhaps give more frequent tags a lower index.
// TODO: we could make the indexes stable. This will excluded some
// possibilities for optimization, so don't do this quite yet.
b, s, r := t.Raw()
if len(t.str) > 0 {
if strings.HasPrefix(t.str, "x-") {
// We have no entries for user-defined tags.
return 0, false
}
if uint16(t.pVariant) != t.pExt {
// There are no tags with variants and an u-va type.
if t.TypeForKey("va") != "" {
return 0, false
}
t, _ = Raw.Compose(b, s, r, t.Variants())
} else if _, ok := t.Extension('u'); ok {
// Strip all but the 'va' entry.
variant := t.TypeForKey("va")
t, _ = Raw.Compose(b, s, r)
t, _ = t.SetTypeForKey("va", variant)
}
if len(t.str) > 0 {
// We have some variants.
for i, s := range specialTags {
if s == t {
return i + 1, true
}
}
return 0, false
}
}
// No variants specified: just compare core components.
// The key has the form lllssrrr, where l, s, and r are nibbles for
// respectively the langID, scriptID, and regionID.
key := uint32(b.langID) << (8 + 12)
key |= uint32(s.scriptID) << 12
key |= uint32(r.regionID)
x, ok := coreTags[key]
return int(x), ok
}
// Base is an ISO 639 language code, used for encoding the base language
// of a language tag.
type Base struct {
langID
}
// ParseBase parses a 2- or 3-letter ISO 639 code.
// It returns a ValueError if s is a well-formed but unknown language identifier
// or another error if another error occurred.
func ParseBase(s string) (Base, error) {
if n := len(s); n < 2 || 3 < n {
return Base{}, errSyntax
}
var buf [3]byte
l, err := getLangID(buf[:copy(buf[:], s)])
return Base{l}, err
}
// Script is a 4-letter ISO 15924 code for representing scripts.
// It is idiomatically represented in title case.
type Script struct {
scriptID
}
// ParseScript parses a 4-letter ISO 15924 code.
// It returns a ValueError if s is a well-formed but unknown script identifier
// or another error if another error occurred.
func ParseScript(s string) (Script, error) {
if len(s) != 4 {
return Script{}, errSyntax
}
var buf [4]byte
sc, err := getScriptID(script, buf[:copy(buf[:], s)])
return Script{sc}, err
}
// Region is an ISO 3166-1 or UN M.49 code for representing countries and regions.
type Region struct {
regionID
}
// EncodeM49 returns the Region for the given UN M.49 code.
// It returns an error if r is not a valid code.
func EncodeM49(r int) (Region, error) {
rid, err := getRegionM49(r)
return Region{rid}, err
}
// ParseRegion parses a 2- or 3-letter ISO 3166-1 or a UN M.49 code.
// It returns a ValueError if s is a well-formed but unknown region identifier
// or another error if another error occurred.
func ParseRegion(s string) (Region, error) {
if n := len(s); n < 2 || 3 < n {
return Region{}, errSyntax
}
var buf [3]byte
r, err := getRegionID(buf[:copy(buf[:], s)])
return Region{r}, err
}
// IsCountry returns whether this region is a country or autonomous area. This
// includes non-standard definitions from CLDR.
func (r Region) IsCountry() bool {
if r.regionID == 0 || r.IsGroup() || r.IsPrivateUse() && r.regionID != _XK {
return false
}
return true
}
// IsGroup returns whether this region defines a collection of regions. This
// includes non-standard definitions from CLDR.
func (r Region) IsGroup() bool {
if r.regionID == 0 {
return false
}
return int(regionInclusion[r.regionID]) < len(regionContainment)
}
// Contains returns whether Region c is contained by Region r. It returns true
// if c == r.
func (r Region) Contains(c Region) bool {
return r.regionID.contains(c.regionID)
}
func (r regionID) contains(c regionID) bool {
if r == c {
return true
}
g := regionInclusion[r]
if g >= nRegionGroups {
return false
}
m := regionContainment[g]
d := regionInclusion[c]
b := regionInclusionBits[d]
// A contained country may belong to multiple disjoint groups. Matching any
// of these indicates containment. If the contained region is a group, it
// must strictly be a subset.
if d >= nRegionGroups {
return b&m != 0
}
return b&^m == 0
}
var errNoTLD = errors.New("language: region is not a valid ccTLD")
// TLD returns the country code top-level domain (ccTLD). UK is returned for GB.
// In all other cases it returns either the region itself or an error.
//
// This method may return an error for a region for which there exists a
// canonical form with a ccTLD. To get that ccTLD canonicalize r first. The
// region will already be canonicalized it was obtained from a Tag that was
// obtained using any of the default methods.
func (r Region) TLD() (Region, error) {
// See http://en.wikipedia.org/wiki/Country_code_top-level_domain for the
// difference between ISO 3166-1 and IANA ccTLD.
if r.regionID == _GB {
r = Region{_UK}
}
if (r.typ() & ccTLD) == 0 {
return Region{}, errNoTLD
}
return r, nil
}
// Canonicalize returns the region or a possible replacement if the region is
// deprecated. It will not return a replacement for deprecated regions that
// are split into multiple regions.
func (r Region) Canonicalize() Region {
if cr := normRegion(r.regionID); cr != 0 {
return Region{cr}
}
return r
}
// Variant represents a registered variant of a language as defined by BCP 47.
type Variant struct {
variant string
}
// ParseVariant parses and returns a Variant. An error is returned if s is not
// a valid variant.
func ParseVariant(s string) (Variant, error) {
s = strings.ToLower(s)
if _, ok := variantIndex[s]; ok {
return Variant{s}, nil
}
return Variant{}, mkErrInvalid([]byte(s))
}
// String returns the string representation of the variant.
func (v Variant) String() string {
return v.variant
}