--- /dev/null
+// Copyright 2014 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 (
+ "fmt"
+ "sort"
+)
+
+// The Coverage interface is used to define the level of coverage of an
+// internationalization service. Note that not all types are supported by all
+// services. As lists may be generated on the fly, it is recommended that users
+// of a Coverage cache the results.
+type Coverage interface {
+ // Tags returns the list of supported tags.
+ Tags() []Tag
+
+ // BaseLanguages returns the list of supported base languages.
+ BaseLanguages() []Base
+
+ // Scripts returns the list of supported scripts.
+ Scripts() []Script
+
+ // Regions returns the list of supported regions.
+ Regions() []Region
+}
+
+var (
+ // Supported defines a Coverage that lists all supported subtags. Tags
+ // always returns nil.
+ Supported Coverage = allSubtags{}
+)
+
+// TODO:
+// - Support Variants, numbering systems.
+// - CLDR coverage levels.
+// - Set of common tags defined in this package.
+
+type allSubtags struct{}
+
+// Regions returns the list of supported regions. As all regions are in a
+// consecutive range, it simply returns a slice of numbers in increasing order.
+// The "undefined" region is not returned.
+func (s allSubtags) Regions() []Region {
+ reg := make([]Region, numRegions)
+ for i := range reg {
+ reg[i] = Region{regionID(i + 1)}
+ }
+ return reg
+}
+
+// Scripts returns the list of supported scripts. As all scripts are in a
+// consecutive range, it simply returns a slice of numbers in increasing order.
+// The "undefined" script is not returned.
+func (s allSubtags) Scripts() []Script {
+ scr := make([]Script, numScripts)
+ for i := range scr {
+ scr[i] = Script{scriptID(i + 1)}
+ }
+ return scr
+}
+
+// BaseLanguages returns the list of all supported base languages. It generates
+// the list by traversing the internal structures.
+func (s allSubtags) BaseLanguages() []Base {
+ base := make([]Base, 0, numLanguages)
+ for i := 0; i < langNoIndexOffset; i++ {
+ // We included "und" already for the value 0.
+ if i != nonCanonicalUnd {
+ base = append(base, Base{langID(i)})
+ }
+ }
+ i := langNoIndexOffset
+ for _, v := range langNoIndex {
+ for k := 0; k < 8; k++ {
+ if v&1 == 1 {
+ base = append(base, Base{langID(i)})
+ }
+ v >>= 1
+ i++
+ }
+ }
+ return base
+}
+
+// Tags always returns nil.
+func (s allSubtags) Tags() []Tag {
+ return nil
+}
+
+// coverage is used used by NewCoverage which is used as a convenient way for
+// creating Coverage implementations for partially defined data. Very often a
+// package will only need to define a subset of slices. coverage provides a
+// convenient way to do this. Moreover, packages using NewCoverage, instead of
+// their own implementation, will not break if later new slice types are added.
+type coverage struct {
+ tags func() []Tag
+ bases func() []Base
+ scripts func() []Script
+ regions func() []Region
+}
+
+func (s *coverage) Tags() []Tag {
+ if s.tags == nil {
+ return nil
+ }
+ return s.tags()
+}
+
+// bases implements sort.Interface and is used to sort base languages.
+type bases []Base
+
+func (b bases) Len() int {
+ return len(b)
+}
+
+func (b bases) Swap(i, j int) {
+ b[i], b[j] = b[j], b[i]
+}
+
+func (b bases) Less(i, j int) bool {
+ return b[i].langID < b[j].langID
+}
+
+// BaseLanguages returns the result from calling s.bases if it is specified or
+// otherwise derives the set of supported base languages from tags.
+func (s *coverage) BaseLanguages() []Base {
+ if s.bases == nil {
+ tags := s.Tags()
+ if len(tags) == 0 {
+ return nil
+ }
+ a := make([]Base, len(tags))
+ for i, t := range tags {
+ a[i] = Base{langID(t.lang)}
+ }
+ sort.Sort(bases(a))
+ k := 0
+ for i := 1; i < len(a); i++ {
+ if a[k] != a[i] {
+ k++
+ a[k] = a[i]
+ }
+ }
+ return a[:k+1]
+ }
+ return s.bases()
+}
+
+func (s *coverage) Scripts() []Script {
+ if s.scripts == nil {
+ return nil
+ }
+ return s.scripts()
+}
+
+func (s *coverage) Regions() []Region {
+ if s.regions == nil {
+ return nil
+ }
+ return s.regions()
+}
+
+// NewCoverage returns a Coverage for the given lists. It is typically used by
+// packages providing internationalization services to define their level of
+// coverage. A list may be of type []T or func() []T, where T is either Tag,
+// Base, Script or Region. The returned Coverage derives the value for Bases
+// from Tags if no func or slice for []Base is specified. For other unspecified
+// types the returned Coverage will return nil for the respective methods.
+func NewCoverage(list ...interface{}) Coverage {
+ s := &coverage{}
+ for _, x := range list {
+ switch v := x.(type) {
+ case func() []Base:
+ s.bases = v
+ case func() []Script:
+ s.scripts = v
+ case func() []Region:
+ s.regions = v
+ case func() []Tag:
+ s.tags = v
+ case []Base:
+ s.bases = func() []Base { return v }
+ case []Script:
+ s.scripts = func() []Script { return v }
+ case []Region:
+ s.regions = func() []Region { return v }
+ case []Tag:
+ s.tags = func() []Tag { return v }
+ default:
+ panic(fmt.Sprintf("language: unsupported set type %T", v))
+ }
+ }
+ return s
+}
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