Source: language.go in package golang.org/x/text/internal/language/compact

go:generate go run gen.go gen_index.go -output tables.gogo:generate go run gen_parents.go


package compact

TODO: Remove above NOTE after: - verifying that tables are dropped correctly (most notably matcher tables).


import (
	"strings"

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

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.

NOTE: exported tags will become part of the public API.

	language ID
	locale   ID
	full     fullTag // always a language.Tag for now.
}

const _und = 0

type fullTag interface {
	IsRoot() bool
	Parent() language.Tag
}

Make a compact Tag from a fully specified internal language Tag.

func Make(t language.Tag) (tag Tag) {
	if region := t.TypeForKey("rg"); len(region) == 6 && region[2:] == "zzzz" {
		if r, err := language.ParseRegion(region[:2]); err == nil {
			tFull := t

TODO: should we not consider "va" for the language tag?

			var exact1, exact2 bool
			tag.language, exact1 = FromTag(t)
			t.RegionID = r
			tag.locale, exact2 = FromTag(t)
			if !exact1 || !exact2 {
				tag.full = tFull
			}
			return tag
		}
	}
	lang, ok := FromTag(t)
	tag.language = lang
	tag.locale = lang
	if !ok {
		tag.full = t
	}
	return tag
}

Tag returns an internal language Tag version of this tag.

func (t Tag) Tag() language.Tag {
	if t.full != nil {
		return t.full.(language.Tag)
	}
	tag := t.language.Tag()
	if t.language != t.locale {
		loc := t.locale.Tag()
		tag, _ = tag.SetTypeForKey("rg", strings.ToLower(loc.RegionID.String())+"zzzz")
	}
	return tag
}

IsCompact reports whether this tag is fully defined in terms of ID.

func (t *Tag) IsCompact() bool {
	return t.full == nil
}

MayHaveVariants reports whether a tag may have variants. If it returns false it is guaranteed the tag does not have variants.

func (t Tag) MayHaveVariants() bool {
	return t.full != nil || int(t.language) >= len(coreTags)
}

MayHaveExtensions reports whether a tag may have extensions. If it returns false it is guaranteed the tag does not have them.

func (t Tag) MayHaveExtensions() bool {
	return t.full != nil ||
		int(t.language) >= len(coreTags) ||
		t.language != t.locale
}

IsRoot returns true if t is equal to language "und".

func (t Tag) IsRoot() bool {
	if t.full != nil {
		return t.full.IsRoot()
	}
	return t.language == _und
}

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.full != nil {
		return Make(t.full.Parent())
	}

Simulate stripping -u-rg-xxxxxx

		return Tag{language: t.language, locale: t.language}

TODO: use parent lookup table once cycle from internal package is removed. Probably by internalizing the table and declaring this fast enough. lang := compactID(internal.Parent(uint16(t.language)))

	lang, _ := FromTag(t.language.Tag().Parent())
	return Tag{language: lang, locale: lang}
}

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:]
}

LanguageID 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. If t does not match a compact index, exact will be false and the compact index will be returned for the first match after repeatedly taking the Parent of t.

func LanguageID(t Tag) (id ID, exact bool) {
	return t.language, t.full == nil
}

RegionalID returns the ID for the regional variant of this tag. This index is used to indicate region-specific overrides, such as default currency, default calendar and week data, default time cycle, and default measurement system and unit preferences. For instance, the tag en-GB-u-rg-uszzzz specifies British English with US settings for currency, number formatting, etc. The CompactIndex for this tag will be that for en-GB, while the RegionalID will be the one corresponding to en-US.

func RegionalID(t Tag) (id ID, exact bool) {
	return t.locale, t.full == nil
}

LanguageTag returns t stripped of regional variant indicators. At the moment this means it is stripped of a regional and variant subtag "rg" and "va" in the "u" extension.

func (t Tag) LanguageTag() Tag {
	if t.full == nil {
		return Tag{language: t.language, locale: t.language}
	}
	tt := t.Tag()
	tt.SetTypeForKey("rg", "")
	tt.SetTypeForKey("va", "")
	return Make(tt)
}

RegionalTag returns the regional variant of the tag. At the moment this means that the region is set from the regional subtag "rg" in the "u" extension.

func (t Tag) RegionalTag() Tag {
	rt := Tag{language: t.locale, locale: t.locale}
	if t.full == nil {
		return rt
	}
	b := language.Builder{}

tag, _ = tag.SetTypeForKey("rg", "")

	b.SetTag(t.locale.Tag())
	if v := tag.Variants(); v != "" {
		for _, v := range strings.Split(v, "-") {
			b.AddVariant(v)
		}
	}
	for _, e := range tag.Extensions() {
		b.AddExt(e)
	}
	return t
}

FromTag reports closest matching ID for an internal language Tag.

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.

	exact = true

	b, s, r := t.Raw()
	if t.HasString() {

We have no entries for user-defined tags.

			return 0, false
		}
		hasExtra := false
		if t.HasVariants() {
			if t.HasExtensions() {
				build := language.Builder{}
				build.SetTag(language.Tag{LangID: b, ScriptID: s, RegionID: r})
				build.AddVariant(t.Variants())
				exact = false
				t = build.Make()
			}
			hasExtra = true

TODO: va may mean something else. Consider not considering it. Strip all but the 'va' entry.

			old := t
			variant := t.TypeForKey("va")
			t = language.Tag{LangID: b, ScriptID: s, RegionID: r}
			if variant != "" {
				t, _ = t.SetTypeForKey("va", variant)
				hasExtra = true
			}
			exact = old == t
		} else {
			exact = false
		}

We have some variants.

			for i, s := range specialTags {
				if s == t {
					return ID(i + len(coreTags)), exact
				}
			}
			exact = false
		}
	}
	if x, ok := getCoreIndex(t); ok {
		return x, exact
	}
	exact = false

Deal with cases where an extra script is inserted for the region.

		t, _ := t.Maximize()
		if x, ok := getCoreIndex(t); ok {
			return x, exact
		}
	}

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.

		if x, ok := getCoreIndex(t); ok {
			return x, exact
		}
	}
	return 0, exact
}