1 // Copyright 2015 The Go Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style
3 // license that can be found in the LICENSE file.
5 // Package colltab contains functionality related to collation tables.
6 // It is only to be used by the collate and search packages.
7 package colltab // import "golang.org/x/text/internal/colltab"
12 "golang.org/x/text/language"
15 // MatchLang finds the index of t in tags, using a matching algorithm used for
16 // collation and search. tags[0] must be language.Und, the remaining tags should
17 // be sorted alphabetically.
19 // Language matching for collation and search is different from the matching
20 // defined by language.Matcher: the (inferred) base language must be an exact
21 // match for the relevant fields. For example, "gsw" should not match "de".
22 // Also the parent relation is different, as a parent may have a different
23 // script. So usually the parent of zh-Hant is und, whereas for MatchLang it is
25 func MatchLang(t language.Tag, tags []language.Tag) int {
26 // Canonicalize the values, including collapsing macro languages.
27 t, _ = language.All.Canonicalize(t)
29 base, conf := t.Base()
30 // Estimate the base language, but only use high-confidence values.
31 if conf < language.High {
32 // The root locale supports "search" and "standard". We assume that any
33 // implementation will only use one of both.
37 // Maximize base and script and normalize the tag.
38 if _, s, r := t.Raw(); (r != language.Region{}) {
39 p, _ := language.Raw.Compose(base, s, r)
40 // Taking the parent forces the script to be maximized.
42 // Add back region and extensions.
43 t, _ = language.Raw.Compose(p, r, t.Extensions())
45 // Set the maximized base language.
46 t, _ = language.Raw.Compose(base, s, t.Extensions())
49 // Find start index of the language tag.
50 start := 1 + sort.Search(len(tags)-1, func(i int) bool {
51 b, _, _ := tags[i+1].Raw()
52 return base.String() <= b.String()
54 if start < len(tags) {
55 if b, _, _ := tags[start].Raw(); b != base {
60 // Besides the base language, script and region, only the collation type and
61 // the custom variant defined in the 'u' extension are used to distinguish a
63 // Strip all variants and extensions and add back the custom variant.
64 tdef, _ := language.Raw.Compose(t.Raw())
65 tdef, _ = tdef.SetTypeForKey("va", t.TypeForKey("va"))
67 // First search for a specialized collation type, if present.
68 try := []language.Tag{tdef}
69 if co := t.TypeForKey("co"); co != "" {
70 tco, _ := tdef.SetTypeForKey("co", co)
71 try = []language.Tag{tco, tdef}
74 for _, tx := range try {
75 for ; tx != language.Und; tx = parent(tx) {
76 for i, t := range tags[start:] {
77 if b, _, _ := t.Raw(); b != base {
89 // parent computes the structural parent. This means inheritance may change
90 // script. So, unlike the CLDR parent, parent(zh-Hant) == zh.
91 func parent(t language.Tag) language.Tag {
92 if t.TypeForKey("va") != "" {
93 t, _ = t.SetTypeForKey("va", "")
96 result := language.Und
97 if b, s, r := t.Raw(); (r != language.Region{}) {
98 result, _ = language.Raw.Compose(b, s, t.Extensions())
99 } else if (s != language.Script{}) {
100 result, _ = language.Raw.Compose(b, t.Extensions())
101 } else if (b != language.Base{}) {
102 result, _ = language.Raw.Compose(t.Extensions())