zorg/vendor/golang.org/x/text/language/language.go

908 lines
26 KiB
Go

// 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 gen.go gen_common.go -output tables.go
//go:generate go run gen_index.go
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
// TODO: we will soon run out of positions for script. Idea: instead of
// storing lang, region, and script codes, store only the compact index and
// have a lookup table from this code to its expansion. This greatly speeds
// up table lookup, speed up common variant cases.
// This will also immediately free up 3 extra bytes. Also, the pVariant
// field can now be moved to the lookup table, as the compact index uniquely
// determines the offset of a possible variant.
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 := len(b) - int(t.pVariant)
b = append(b, '-')
b = append(b, extra...)
t.pVariant = uint8(int(t.pVariant) + diff)
t.pExt = uint16(int(t.pExt) + 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[:])])
}
// MarshalText implements encoding.TextMarshaler.
func (t Tag) MarshalText() (text []byte, err error) {
if t.str != "" {
text = append(text, t.str...)
} else if t.script == 0 && t.region == 0 {
text = append(text, t.lang.String()...)
} else {
buf := [maxCoreSize]byte{}
text = buf[:t.genCoreBytes(buf[:])]
}
return text, nil
}
// UnmarshalText implements encoding.TextUnmarshaler.
func (t *Tag) UnmarshalText(text []byte) error {
tag, err := Raw.Parse(string(text))
*t = tag
return err
}
// 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{}, 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
}