--- /dev/null
+// Copyright 2015 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 colltab contains functionality related to collation tables.
+// It is only to be used by the collate and search packages.
+package colltab // import "golang.org/x/text/internal/colltab"
+
+import (
+ "sort"
+
+ "golang.org/x/text/language"
+)
+
+// MatchLang finds the index of t in tags, using a matching algorithm used for
+// collation and search. tags[0] must be language.Und, the remaining tags should
+// be sorted alphabetically.
+//
+// Language matching for collation and search is different from the matching
+// defined by language.Matcher: the (inferred) base language must be an exact
+// match for the relevant fields. For example, "gsw" should not match "de".
+// Also the parent relation is different, as a parent may have a different
+// script. So usually the parent of zh-Hant is und, whereas for MatchLang it is
+// zh.
+func MatchLang(t language.Tag, tags []language.Tag) int {
+ // Canonicalize the values, including collapsing macro languages.
+ t, _ = language.All.Canonicalize(t)
+
+ base, conf := t.Base()
+ // Estimate the base language, but only use high-confidence values.
+ if conf < language.High {
+ // The root locale supports "search" and "standard". We assume that any
+ // implementation will only use one of both.
+ return 0
+ }
+
+ // Maximize base and script and normalize the tag.
+ if _, s, r := t.Raw(); (r != language.Region{}) {
+ p, _ := language.Raw.Compose(base, s, r)
+ // Taking the parent forces the script to be maximized.
+ p = p.Parent()
+ // Add back region and extensions.
+ t, _ = language.Raw.Compose(p, r, t.Extensions())
+ } else {
+ // Set the maximized base language.
+ t, _ = language.Raw.Compose(base, s, t.Extensions())
+ }
+
+ // Find start index of the language tag.
+ start := 1 + sort.Search(len(tags)-1, func(i int) bool {
+ b, _, _ := tags[i+1].Raw()
+ return base.String() <= b.String()
+ })
+ if start < len(tags) {
+ if b, _, _ := tags[start].Raw(); b != base {
+ return 0
+ }
+ }
+
+ // Besides the base language, script and region, only the collation type and
+ // the custom variant defined in the 'u' extension are used to distinguish a
+ // locale.
+ // Strip all variants and extensions and add back the custom variant.
+ tdef, _ := language.Raw.Compose(t.Raw())
+ tdef, _ = tdef.SetTypeForKey("va", t.TypeForKey("va"))
+
+ // First search for a specialized collation type, if present.
+ try := []language.Tag{tdef}
+ if co := t.TypeForKey("co"); co != "" {
+ tco, _ := tdef.SetTypeForKey("co", co)
+ try = []language.Tag{tco, tdef}
+ }
+
+ for _, tx := range try {
+ for ; tx != language.Und; tx = parent(tx) {
+ for i, t := range tags[start:] {
+ if b, _, _ := t.Raw(); b != base {
+ break
+ }
+ if tx == t {
+ return start + i
+ }
+ }
+ }
+ }
+ return 0
+}
+
+// parent computes the structural parent. This means inheritance may change
+// script. So, unlike the CLDR parent, parent(zh-Hant) == zh.
+func parent(t language.Tag) language.Tag {
+ if t.TypeForKey("va") != "" {
+ t, _ = t.SetTypeForKey("va", "")
+ return t
+ }
+ result := language.Und
+ if b, s, r := t.Raw(); (r != language.Region{}) {
+ result, _ = language.Raw.Compose(b, s, t.Extensions())
+ } else if (s != language.Script{}) {
+ result, _ = language.Raw.Compose(b, t.Extensions())
+ } else if (b != language.Base{}) {
+ result, _ = language.Raw.Compose(t.Extensions())
+ }
+ return result
+}
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